MSc Dissertation, UOW London

Displacement ventilation for energy efficiency in museums and art galleries

University Of Westminster

College of Design, Creative and Digital Industries

School Of Architecture and Cities

MSc Architecture and Environmental Design, 2022/2023

7AEVD008: Thesis Project

Srush� Pawade W1923937

Acknowledgement

To everyone who helped me during my research and thesis comple�on, I would like to offer my sincere gra�tude. Without the unflagging support, inspira�on, and encouragement from several people and organisa�ons, this project would not have been feasible. This ini�a�ve would not have been possible without the steadfast assistance, inspira�on, and support of several people and organisa�ons.

I want to express my sincere gra�tude to my thesis adviser, Juan Vallejo, for their excellent advice, knowledge, and unfailing support during this study journey. I am deeply apprecia�ve of the collabora�on on this thesis project with ARUP and express my gra�tude to Vera Sarioglu for her invaluable assistance as my advisor.

Furthermore, I extend my hear�elt thanks to Dr. Rosa Schiano-Phan, Kar�keya Rajput, and Amedeo Scofone for their unwavering advice, diligent efforts, and steadfast support

I am apprecia�ve to my friends and my family who offered insigh�ul feedback, helpful cri�cism, and moral support throughout the course of this thesis. You all played a vital part in making this research a reality, and for that, I truly thank you all.

Abstract

To increase energy efficiency, this thesis abstract inves�gates the use of displacement ven�la�on in museum galleries. To protect their collec�ons, museums need a stable environment, and HVAC systems are essen�al for preserving the air's purity. An innova�ve technology called displacement ven�la�on can increase energy efficiency while maintaining air quality. The abstract discusses the significance of ven�la�on in museums, museum design standards, and cu�ng-edge HVAC systems u�lised in museums. The study simulates the characteris�cs of the organisa�on of the air in a shoe box model. To increase energy economy while maintaining air quality, displacement ven�la�on design recommenda�ons can be created using the findings of this study and applied to museum galleries.

The study aims to evaluate the effec�veness of displacement ven�la�on in enhancing energy efficiency, indoor air quality, and thermal comfort in museum galleries. A case study of a museum gallery in London is conducted, where both mixed ven�la�on and displacement ven�la�on systems are implemented and analysed.

The CFD analysis is u�lized to simulate and analyse the airflow paterns, temperature distribu�on, and indoor air quality in the gallery spaces. The results of the CFD analysis provide insights into the effec�veness of both ven�la�on systems in terms of air distribu�on and thermal comfort. Addi�onally, TPLP analysis is employed to quan�fy the total primary energy consump�on of each ven�la�on system, considering all energy inputs.

The findings of this research contribute to a beter understanding of the energy efficiency of museum galleries with displacement ven�la�on. The comparison between mixed ven�la�on and displacement ven�la�on, based on CFD and TPLP analysis, provides valuable insights for op�mizing the design and opera�on of ven�la�on systems in museum galleries. The results inform future museum gallery designs, aiming to achieve improved energy efficiency, indoor air quality, and thermal comfort while preserving artwork and ar�facts.

1 Overview

To op�mise the design and the ven�la�on system opera�on, the thesis intends to assess the energy efficiency of displacement ven�la�on in museum galleries. The evalua�on of the literature focuses on the drawbacks of conven�onal ven�la�on techniques and the poten�al benefits of displacement ven�la�on to boost energy efficiency. The case studies present proof in favour of displacement ven�la�on's efficiency in regula�ng interior climate and ataining energy savings. The effec�veness of the ven�la�on system can be understood as well as poten�al areas for improvement thanks to CFD analysis, which makes it possible to thoroughly examine airflow paterns and thermal performance within the gallery space. The thermal performance of the ven�la�on system, including heat transfer coefficients and thermal resistance, is assessed using TPLP analysis. To assess the energy efficiency of displacement ven�la�on in museum galleries and make recommenda�ons for improvement, the thesis uses CFD and TPLP analysis. Its goal is to advance our understanding of displacement ven�la�on and its use in museum galleries. Given that the op�misa�on strategies and newfound knowledge can also be used to design other types of buildings, the conclusions and sugges�ons drawn from this analysis may have wider significance for sustainable building design prac�ses.

1.1 Introduc�on

The preserva�on of artefacts and the crea�on of a welcoming environment for visitors both depend heavily on the energy efficiency and indoor climate management of museum galleries. For achieving these objec�ves, displacement ven�la�on has emerged as a poten�al method. With the use of the analysis methods of Computa�onal Fluid Dynamics (CFD) and Thermal Performance of Buildings (TPLP), this thesis inves�gates how displacement ven�la�on can be used to increase the energy efficiency of museum galleries. Previous research has inves�gated the applica�on of CFD analysis to the design and op�misa�on of displacement ven�la�on systems. CFD simula�ons enable the examina�on of airflow paterns and thermal performance through the modelling of the museum gallery and the ven�la�on system. This makes it possible to comprehend in detail how successful the current ven�la�on system and the suggested displacement ven�la�on system are. The thermal performance of the ven�la�on systems is also assessed using TPLP analysis. TPLP analysis yields informa�on about the total thermal performance of the building envelope by calcula�ng variables like heat transfer coefficients and thermal resistance.

1.2 Research Ques�ons:

How does displacement ven�la�on affect the energy use in museum galleries?

How does indoor air quality in museum galleries differ when displacement ven�la�on is used?

In comparison to alterna�ve ven�la�on systems in museum galleries, what are the energy-saving poten�al and effec�veness of displacement ven�la�on?

What variables affect displacement ven�la�on's effec�veness in terms of energy efficiency in museum galleries?

How do displacement ven�la�on systems' layout and design affect how energy-efficient they are in museum galleries?

1.3 Hypothesis:

When compared to other ven�la�on systems, displacement ven�la�on will consume less energy in museum galleries.

By successfully elimina�ng impuri�es and providing improved air circula�on, displacement ven�la�on would enhance the indoor air quality in museum galleries.

Compared to other ven�la�on systems, displacement ven�la�on systems have the poten�al to deliver significant energy savings in museum galleries.

The design of the space, human traffic paterns, and the outside environment all have an impact on displacement ven�la�on's energy-efficient performance in museum galleries.

Displacement ven�la�on systems' energy efficiency in museum galleries can be increased by op�mal design and configura�on, resul�ng in addi�onal energy savings.

These research inquiries and conjectures can establish the groundwork for examining how displacement ven�la�on contributes to augmen�ng the energy efficiency of museum galleries. Addi�onal research and analysis have the poten�al to offer valuable insights into the efficacy and possible advantages of employing displacement ven�la�on systems within this context

1.4 Aims and objec�ves.

Aim: The aim is to increase the museum galleries' energy efficiency while safeguarding the ideal indoor clima�c condi�ons for the preserva�on of artefacts and crea�ng a comfortable environment for visitors.

Objec�ves:

Examining, with a focus on energy efficiency, the performance of displacement ven�la�on in managing the local preserva�on environment for artefacts in museums galleries.

Conduct a thorough literature review to comprehend the principles and applica�ons of displacement ven�la�on in the context of museums, paying par�cular aten�on to energy efficiency and indoor climate management.

Consider issues including air distribu�on, temperature stra�fica�on, and pollu�on dispersion when using CFD simula�ons to examine the airflow paterns and thermal performance of displacement ven�la�on systems in museum galleries.

Examine the effects of various design factors on the energy efficiency and interior climate condi�ons atained by displacement ven�la�on systems in museum galleries, such as supply air temperature, velocity of supply air, and diffuser placement.

Consider challenges like controlling rela�ve humidity and removing pollutants when you assess the success of displacement ven�la�on in managing the local preserva�on environment for artefacts in museums galleries.

Compare displacement ven�la�on technology's poten�al for energy conserva�on to other ven�la�on techniques frequently employed in museum galleries, such as mixed flow ven�la�on.

To increase energy efficiency and the indoor environment, provide recommenda�ons and guidance for the design and op�misa�on of displacement ven�la�on systems in museum galleries based on the results of CFD simula�ons and TPLP analyses

2 Methodology

An extensive review of the literature was done on indoor climate management, energy efficiency, and displacement ven�la�on in museum galleries. Studies on the fundamentals of displacement ven�la�on, its efficiency in regula�ng indoor climate, and its poten�al for energy conserva�on were among those covered.

By measuring and keeping track of the indoor environment condi�ons in the museum gallery, informa�on on the current ven�la�on system, including air dispersion, temperature, and humidity levels, was gathered.

Data from the measurements was used to assess the performance of the current ven�la�on system and to pinpoint areas that needed improvement.

The airflow paterns and thermal performance of both the mixed ven�la�on system and the suggested displacement ven�la�on system were examined using CFD simula�ons. This required modelling the museum gallery and the ven�la�on system, as well as employing CFD so�ware to reproduce the temperature distribu�on and airflow. The efficacy of the current ven�la�on system was assessed using CFD simula�ons, and flaws in the system were noted.

The thermal efficiency of both the mixed ven�la�on system and the suggested displacement ven�la�on system were assessed using TPLP analysis. This required calcula�ng various parameters that the thermal performance of the building envelope, including heat transfer coefficients, thermal resistance, and others.

The displacement ven�la�on system's design was op�mised to increase energy efficiency and indoor climate control based on the findings from the TPLP analysis and CFD simula�on results. This involved modifying variables including diffuser placement, supply air temperature, and supply air velocity to create the ideal indoor atmosphere. By contras�ng them with the measured data from the museum exhibit, the outcomes of the TPLP analysis and CFD simula�ons were found to be valid. This required confirming the simula�on models' accuracy and evalua�ng the planned displacement ven�la�on system's effec�veness

3 Interpreta�ve Approach

3.1 Introduc�on

To assess the effect of displacement ven�la�on on energy efficiency in museum galleries, the interpre�ve approach employed in the thesis combines literature review, case studies, and CFD analysis. As a poten�al technique for airing museum galleries, displacement ven�la�on also ensures the preserva�on of artefacts and uses less energy.{1}

3.2 Types Of Museums

3.3 Energy consump�on in museums

A tourist is more likely to spend more �me in a museum if they feel comfortable. This might lead to a richer experience and a beter comprehension of the presenta�ons.

To maintain an environment inside those safeguards and preserves their collec�ons, museums need a lot of energy. Systems for hea�ng, cooling, ligh�ng, and ven�la�on are included. A heritage scien�st and researcher claim that museums typically use around 300 kWh per m2 annually. For larger museums, this may translate into annual energy use in the millions of kWh.{2}

The greatest energy consumers in museums are ligh�ng and HVAC systems, which can be split down by end use. The amount of energy used in museum galleries can be greatly decreased by implemen�ng energy-saving measures like LED ligh�ng and effec�ve HVAC systems. Studies on the rela�onship between indoor air quality and energy efficiency in museums have a par�cular focus on reducing energy use without sacrificing indoor air quality. {3}

Figure 1 source: (pdf) a computa�onal method for the design explora�on and op�miza�on of dayligh�ng performance of museum buildings (researchgate.net)

3.4 Need for energy efficiency.

The total gas and electricity used in the UK's arts and culture sector in 2020–2021 was examined in a report published in April 2022.A total of 24.55 million kilowat hours of gas and 22.93 million kilowat hours of electricity were used by museums between April 2020 and March 2021, making them the industry with the highest gas and electricity consump�on.{4}

3.5 Standards and comparison

Design specifica�ons for ven�la�on are necessary at museums to preserve the air's purity and guard against harm to the artefacts.

Museums store priceless collec�ons that might be harmed by changes in humidity and temperature. The preserva�on of collec�ons requires a stable environment, which proper ven�la�on helps to maintain.

By maintaining air movement and allowing enough air to pass through high-efficiency filters, proper ven�la�on can help prevent the spread of mould. To borrow collec�ons from other museums, museums must maintain interior environmental condi�ons within certain limits. To �ghtly regulate the internal condi�ons, an air�ght container and an effec�ve mechanical system are required.By providing adequate interior air quality, ven�la�on ensures the staff's and visitors' health and well-being. By minimising the hea�ng and cooling load, proper ven�la�on can cut energy usage. Some museums have installed cu�ng-edge HVAC systems that might set a new benchmark for museums and related applica�ons.{5}

To prevent damage to the collec�ons they house, facili�es used for the display or storage of items, books, and papers that require long-term preserva�on must be maintained in the proper rela�ve humidity and temperature ranges around the clock.

Making provisions in the design for modifying the space's characteris�cs to accommodate shi�ing needs is crucial. This needs to be in line with good energy-efficient procedures. Different environmental condi�ons may be required depending on the specific physical state of certain things or groups of objects. Human breathing requires fresh air ven�la�on, and it's possible that historic materials likewise need air replenishment to lower the concentra�on of toxins from off-gassing compounds. Par�cle and gaseous filtra�on are advised for historic materials that are suscep�ble to environmental contaminants that are expected to be present in high concentra�ons in metropolitan areas if mechanical ven�la�on is installed. Paper, parchment, tex�les, leather, and wood are examples of materials that can be preserved within the general range of 40% to 65%. RH should be kept below 50% for metals and minerals and below 40% for bronze and glass.

While most materials may be good for a person's RH range of 40% to 60% in se�ngs where many people may congregate, those that need drier condi�ons might require to be shown or stored within microclimates. Requirements for ven�la�on and air condi�oning for historical items, the range of 18 to 24 °C, which is suitable for human comfort, is appropriate. Since people rarely detect varia�ons in rela�ve humidity, facili�es housing historical artefacts ought to be ou�ited with temperature and rela�ve humidity monitoring equipment.

Figure 2 Source: Energy consump�on of UK arts industries 2021 | Sta�sta

According to ASHRAE, Solu�ons that can improve the local external climate should be inves�gated first in accordance with the interna�onal demand for lowering energy use and researching alterna�ve renewable energy sources. It can be challenging to understand what all of this implies for the museum, but for many ins�tu�ons, it may call for:

• keeping daily fluctua�ons to 3%, permi�ng seasonal varia�ons between the two extremes, and maintaining throughout the year, a rela�ve humidity of between 40% and 55%.

• keeping the 65-to-75-degree Fahrenheit range in temperature throughout the year, allowing seasonal swings between the two extremes but limi�ng daily fluctua�ons to no more than 5 degrees Fahrenheit.

• designed filtra�on using the ASHRAE Dust Spot Efficiency Test to remove at least 50% of the par�cles.

• Using area filtra�on as required or construc�ng gaseous filtra�on to ensure preserva�on standards throughout the plant.

• appropriate ven�la�on to prevent stagnant air pockets, "dead" areas at range endpoints and stack corners, and other issues that favour the development of mould and mildew.

3.6 Space Types in Museums

Climate zone and projected changes in the climate, the site macro context and morphology, the building and its orienta�on, current environmental control techniques, and monitoring data on each risk (temperature, rela�ve humidity, pollutants, and light) both indoors and outdoors are all per�nent informa�on to comprehending how the environment affects the building, collec�on, and people.

Analy�cal informa�on that has already been acquired is evaluated to determine what se�ngs can realis�cally be reached in a specific climate zone using current control techniques, or the an�cipated effects of suggested changes to the building envelope or kind of environmental management.

4 Literature Analysis

4.1 Ven�la�on

To improve thermal comfort, be sa�sfied with other aspects of the indoor environment, or achieve other goals, ven�la�on involves delivering and withdrawing air from a place to regulate indoor air quality, temperature, humidity, and air mo�on. Ven�la�on can be done naturally or ar�ficially, and it can be purposeful or accidental. Ven�la�on is necessary to hydrate metabolic impuri�es (odour and carbon dioxide) and supply oxygen for metabolism. By dilu�on and removal of contaminants released within a room, ven�la�on is essen�al for ensuring acceptable indoor air quality. Ven�la�on can also be u�lised to remove heat and smoke from a burning structure and to maintain high indoor air quality.

3 source : Applied Sciences | Free Full-Text | The Interplay between Air Quality and Energy Efficiency in Museums, a Review (mdpi.com)

• To provide improved indoor air quality for collec�on care and human comfort, museum buildings, whether they are historic or modern, must create a balanced interior environment.

• To ensure the stability and safety of the artefacts it is aiming to preserve and safeguard, a museum needs to adhere to several precise guidelines, layouts, and other considera�ons.

• The use of mechanical ven�la�on systems is said to produce a beter indoor climate that is healthy and conducive to both human comfort and collec�on care.

• Indoor pollutant concentra�ons in naturally ven�lated structures are nearly on level with outdoor numbers. However, buildings with HVAC systems that feature gas-phase filtra�on minimise the entry of pollutants, bringing the level indoors down to as litle as 5% of the concentra�on outside.

Figure

4.2

Thermal Comfort

Due to its poten�al to impact both the visitor experience and the preserva�on of artwork and artefacts, thermal comfort is a crucial component in museum gallery design. Thermal comfort guidelines have been developed for museum environments through research. In its conclusion, the study developed temperature limita�ons that fall within a 90% comfort range.{6}

The indoor environment is me�culously maintained at a steady 20°C temperature and a rela�ve humidity level of 50%. Nonetheless, this specific indoor climate consumes a notable amount of energy, as highlighted by Maas et al. in their 2014 study. Studies indicate that fluctua�ons in temperature pose less risk to the preserva�on of the art collec�on compared to varia�ons in rela�ve humidity. To assess the thermal comfort of museum designs, simula�on has been employed. The goal is to facilitate reflec�on on the architecture of museum buildings and roads.

If the temperature is within a comfortable range, guests are more likely to enjoy their visit. Visitors may feel uncomfortable and become disoriented if the temperature is too hot or cold, which might ruin their experience. For the protec�on of artwork and artefacts, a correct thermal condi�on must always be maintained. The tourist experience may suffer if the temperature is too hot or too low since it could harm the displays.{7}

A sa�sfying temperature sense is required for an enjoyable museum visit. If visitors are relaxed and able to concentrate on the exhibits rather than their discomfort, they are more likely to enjoy their visit. Their level of thermal comfort can affect how visitors view the museum. If visitors are uneasy, they could think the museum is badly built or maintained, which could have an impact on how they perceive the ins�tu�on. If a visitor is comfortable, they are more inclined to stay in a museum for longer. This may result in a more engaging experience and a deeper understanding of the displays.

5 Cognizance

5.1 Climate

London's museums face challenges in preserving ar�facts due to the city's hot summers, which can damage temperature-sensi�ve materials. However, museums in London have different approaches to climate control and ven�la�on systems. Some museums have air condi�oning, but not on all levels and not at the low temperature levels found in many parts of the world. To save thousands of dollars a month, several museums have loosened their climate control requirements and re-calibrated their systems to permit a wider range of temperatures and humidity levels in some galleries. The London Transport Museum is commited to working towards being carbon neutral by 2030 to reduce its own impact on the planet. Hea�ng accounts for 70% of a museum's energy savings, and sustainable and energy-efficient building design can help reduce energy consump�on. The Guggenheim Bilbao and the Rijksmuseum, two of Europe's top museums, have loosened their climate control requirements and retuned their systems to permit a wider range of temperatures and humidity levels in select galleries, saving them thousands of

dollars each month. Overall, London's museums are taking steps to address climate change and reduce their impact on the environment, including implemen�ng innova�ve climate control and ven�la�on systems.

Figure 5 source Climate London (Greater London), averages - Weather and Climate (weather-and-climate.com)

London has a temperate oceanic climate that is influenced by the ocean, making it cool, humid, and rainy. The average temperature in London ranges from 2.7°C (37°F) in January to 18.5°C (65°F) in May. London receives an average of 600-700 millimetres (24-28 inches) of rainfall per year, which is rela�vely moderate compared to other parts of the UK. The driest month in London is March, with an average of 47 mm (1.9 inches) of rainfall, while the most precipita�on falls in November, with an average of 67 mm (2.6 inches). Other ci�es in the UK, such as Edinburgh and Glasgow, have cooler temperatures and higher levels of precipita�on than London. Overall, London's climate is mild compared to other ci�es in the UK, with moderate levels of rainfall and temperatures that are generally warmer than other parts of the country.

5.2 Museum ven�la�on Systems

There are certain museums that were built to be naturally ven�lated structures without mechanical hea�ng or cooling. This strategy has the poten�al to be sustainable and energy efficient. For museum visitors and artefacts, companies like Halton offer solu�ons for producing thermally comfortable and energy-efficient environments, including developing unique microclimates to conserve priceless na�onal treasures. The ability of a typical museum's HVAC system to disinfect the air within has been improved using strategies including documen�ng ven�la�on system design and opera�on compliance and adhering to exterior air ven�la�on regula�ons. Providing filtra�on, cooling, hea�ng, dehumidifica�on, and other characteris�cs, HVAC systems for artwork conserva�on should be well-adapted to museum standards. Halton offers methods for lowering the danger of viral transmission and fostering a sanitary environment for people's health and safety.

5.2.1 Mixed air distribu�on

An HVAC system that produces mixed air that is at the intended temperature of the space is known as a mixed air system. The chiller supplies the numerous air handler coils with cooling, circula�ng cold water. These coils effec�vely chill the air travelling over them, cooling the museum. The heat that the refrigerants generate while being u�lised in the coils is released through the cooling tower. Either steam or hot water is produced by the boiler. Both can be u�lised for dehumidifica�on or hea�ng reasons. The coil, filtra�on, and fan make up the air handlers. They are employed to distribute fresh, heated, or cooled air.

U�lizing a constant air volume system involves the con�nuous circula�on of air at its maximum volume. In many cases, architects or mechanical engineers opt for a variable air volume (VAV) system as an alterna�ve. The VAV system works by supplying cooled or heated air in accordance with the specific hea�ng or cooling requirements of a par�cular zone. Although this strategy reduces energy expenses, it introduces the possibility of compromising stable humidity levels. Moreover, these systems struggle to effec�vely filter the air or ensure adequate airflow, thus increasing the likelihood of stagnant air pockets. Restric�ng the introduc�on of outdoor air to the minimum amount mandated by local codes is recommended. Museums should refrain from u�lizing air economizers,

which introduce substan�al outdoor air to achieve "cost-free" cooling and hea�ng. Such systems significantly hinder the ability to uphold consistent rela�ve humidity levels Museum should adhere to the outside air makeup limits specified by local codes. It is advisable for museums to avoid employing air economizers, which introduce excessive outdoor air to achieve cost-effec�ve cooling and hea�ng. These systems considerably hinder the ability to maintain stable rela�ve humidi�es, making it a challenging endeavour.

opt for a design approach cantered around humidity control rather than temperature. It is more desirable for temperature to vary than rela�ve humidity (RH), and all control systems should be developed with this guideline in considera�on. U�lise electronic controls instead of highly insensi�ve pneuma�c controls within occupied areas, excluding the return ductwork. Employ reheat coils for dehumidifying cooling air and clean steam humidifica�on purposes. Reheat coils enable air to undergo super-cooling via the coils, elimina�ng excess moisture, and subsequently rehea�ng it to the required level. U�lizing desiccant drums for dehumidifica�on is not only expensive but also challenging to upkeep and might release fine par�cles into the air stream. Among various humidifica�on methods, clean steam dehumidifica�on stands out as the preferred choice.

Incorporate pre-filters and ul�mate high-efficiency filters, each set equipped with a manometer for monitoring. It is recommended to steer clear of electrosta�c air cleaners due to their emission of ozone into t Maintain con�nuous opera�on of the HVAC system to guarantee sufficient environmental control and mi�gate abrupt spikes and excessive fluctua�ons in temperature and rela�ve humidity. Incorpora�ng these fundamental design elements will contribute to ensuring that the museum's system can successfully atain and uphold a preserva�on-quality environment.

To construct the mixed air system, an air-mixing plenum or mixing box is used. Two air streams one for fresh air and the other for exhaust air are combined by the mixing box, in which the two air streams are also mixed by a damper. The ra�o of recirculated air to fresh air can be changed to accommodate the needs of the building's residents. The building management system or other control system regulates the air mixing in many mixed air systems through motorised dampers. In most mixed air systems, With the help of motorised dampers, a building management system or another type of control system can regulate the air mixing.

It would be inefficient to use just fresh air, rejec�ng bringing in clean, treated air to the surrounding atmosphere, as It's possible that the amount of fresh air needed for building inhabitants is less than that required for air condi�oning. To maintain the occupants' comfort level, mixing is employed to decrease the hea�ng/cooling load and raise the supply air temperature. In commercial buildings with significant ven�la�on needs, mixed air systems are frequently used. Addi�onally, they are employed to lessen the HVAC system's energy requirements and enhance indoor air quality.{8}

Figure 6 source: How an Air Side Economizer Works - MEP Academy

5.2.2 Components of mixed air ven�la�on System

A boiler, a chiller, a cooling tower, and one or more air handlers are typical components of a large HVAC system. The chiller supplies the numerous air handler coils with cooling, circula�ng cold water. These coils effec�vely chill the air travelling over them, cooling the museum.

I. Air mixing box or plenum

This is the system's primary component, and it is placed close to the HVAC supply outlet. A mixing damper separates the two air streams that are combined in the mixing box, one for exhaust air and one for fresh air

The ra�o of recirculated air to fresh air can be changed to accommodate the requirements of the building's residents.

II. Dampers

There are three kinds of dampers in the mixing box: one for exhaust air, one for fresh air, and one for mixing the two air streams. In most systems, the air mixing is controlled by motorised dampers, which is regulated by the control system or building management system.

III. Air handling unit

For supplying air to the building, we may thank the air handling unit. It may involve energy-intensive steps including humidifica�on, dehumidifica�on, hea�ng, and cooling.

IV. Filters

To eliminate airborne par�cles from the supplied air, filters are u�lised.

V. Humidifiers and dehumidifiers

These elements are used to regulate the amounts of humidity in occupied areas.

VI. Building management system or control system

To ensure indoor air and quality thermal comfort, this component controls the supply air temperature and airflow rate.

Mixed air ven�la�on systems are indispensable within the context of museums, serving as a cri�cal tool for me�culous environmental control to safeguard invaluable ar�facts and artworks. These systems adeptly blend fresh outdoor air with recirculated indoor air, affording precise regula�on of both temperature and humidity, aligning with the exac�ng demands of museum preserva�on standards. The inclusion of high-efficiency filtra�on mechanisms guarantees that incoming air remains devoid of pollutants and par�culate mater, thereby for�fying the preserva�on of the exhibits' integrity. Furthermore, the inherent flexibility of mixed air systems empowers diverse galleries and exhibit spaces to uphold bespoke environmental condi�ons tailored to the dis�nct preserva�on prerequisites of varying collec�ons. The integra�on of sophis�cated monitoring and control systems empowers museums to perpetually evaluate and fine-tune indoor air quality parameters, assiduously ensuring that temperature, humidity, and air quality consistently adhere to predetermined benchmarks. In this way, mixed air ven�la�on systems assume a pivotal role in nurturing the preserva�on of priceless cultural treasures while concurrently eleva�ng visitor comfort, thus underpinning the overarching success of museums.

5.2.3

Displacement Ven�la�on

Displacement ven�la�on is an air distribu�on method that delivers cool air into a space at a typically low velocity and o�en at a lower level. The supplied air tends to accumulate near the lower region because of buoyant forces, enabling it to ascend within the thermal plumes generated by heat sources This approach to air distribu�on effec�vely delivers occupants fresh air, eliminates numerous impuri�es associated with heat sources, all while cul�va�ng a comfortable ambiance. Compared to mixed-air systems, displacement ven�la�on is intrinsically more energy-efficient.

In contrast to overhead mixing systems, displacement ven�la�on has been employed extensively in Europe over the past three decades as an energy-efficient method of improving indoor air quality. For the system designers and operators of displacement ven�la�on systems in buildings, research has been done to create new and improved guidelines, tools, and resources. The research has inves�gated integrated design solu�ons in which other advanced low-energy strategies, such as radiant systems, are combined with displacement ven�la�on. Displacement ven�la�on has been applied in various commercial and industrial se�ngs, including offices, industrial buildings, and large spaces.

Figure 7 Source: Displacement Ven�la�on Design (turnerbuildingscience.com)

When loads are concentrated to one side of a space that was intended to have a uniform load distribu�on, the system can make up for it buoyant forces act as the driving factor for the supply system, guiding the supply air towards the loads. At the high return, all the heated and dirty air is removed. When properly constructed, the breathing zone has cleaner air than in a typical dilu�on system, increasing ven�la�on effec�veness. Supply air temperatures for displacement systems are o�en greater than for overhead mixing systems, which might result in free cooling from more frequent economizer use. The greater supply temperature of DV systems can boost chiller efficiency in overhead systems that have a higher return temperature. When compared to a mixing system, it is also possible to lessen the volume of air outside that must be condi�oned. This is par�cularly important in humid climates where dehumidifying outdoor air is expensive. Diffusers with heat-cool transi�on or incorporated heat should be used in climates where there are considerable hea�ng loads An alterna�ve would be to u�lise a secondary hea�ng system like radiant panels. The DV system may be used in milder areas at slightly higher temperatures. Experience has shown that adequate performance can be atained with hea�ng air at a temperature of up to 5 °F [3 °C]. DV type of air distribu�on o�en uses less energy than MV since it has a higher ven�la�on efficiency than mixing and requires less fan power. Through ceiling diffusers, a tradi�onal mixed-air distribu�on system distributes supply air. Low-level diffusers in displacement air-distribu�on systems receive cool air at a slow velocity.

5.2.4 Advantages of displacement ven�la�on over other HVAC Systems

1. Beter Indoor Quality

By expelling contaminated air from the space, displacement ven�la�on offers enhanced indoor air quality. To accomplish this, low-velocity air is supplied at the floor, where it gradually rises to the ceiling while transpor�ng impuri�es.

2. Energy Efficiency

lowering airflow speeds to maintain or improve quality, displacement ven�la�on conserves energy. Addi�onally, the diffuser pressure losses are reduced, which enhances the acous�cs.

Improved ven�la�on efficiency

Compared to conven�onal overhead mixing-type systems, displacement ven�la�on is more effec�ve in providing condi�oned air to an area.

3. Quieter opera�on

Compared to tradi�onal overhead systems, displacement ven�la�on systems are quieter. This is because of the absence of noisy mechanical components.

4. Suitability for high-ven�la�on spaces

Places that need strong ven�la�on, such classrooms, conference rooms, and offices, should use displacement ven�la�on.

Due to the following factors, displacement ven�la�on is more energy-efficient than conven�onal HVAC systems.

5. Lower airflow rates

Compared to conven�onal mixing ven�la�on systems, displacement ven�la�on employs lower airflow rates. As a result, less condi�oned air needs to be delivered and distributed throughout the area, which saves energy.

6. Reduced fan energy

Instead of using mechanical fans or minimising their opera�on, displacement ven�la�on relies on buoyancy and natural convec�on forces to move the air. Because of this, there is a decrease in fan energy use.

7. No re-circula�on of pollutants

By exhaus�ng contaminated air from the space, displacement ven�la�on stops pollutants from being recirculated. This removes the requirement for elaborate filtra�on and purifica�on systems, which can cause conven�onal HVAC systems to use more energy.

8. Improved thermal comfort.

By dispersing low-velocity, 65°F air at a low temperature, displacement ven�la�on improves thermal comfort. This prevents the need for excessive cooling or hea�ng, which saves energy.

9. Efficient use of condi�oned air

Where it is most needed, the inhabited area receives direct delivery of condi�oned air thanks to displacement ven�la�on. This focused distribu�on lowers the amount of condi�oned air that is lost or wasted in the area, which results in energy savings.

10. Increased Free Cooling hours.

Free cooling and increased economizer use are made possible by warmer supply air. Displacement ven�la�on improves hours spent using the economy mode which can be u�lised to reduce the amount of energy consumed for air condi�oning in regions of the country where the ambient humidity permits.

11. Stra�fica�on

The area is heated differently ver�cally throughout displacement ven�la�on. This shows that even if the supply air is hot than the mixing systems, the return air is hoter than the predetermined temperature for the occupied space. According to ASHRAE 55 2017, standing occupants can have a temperature differen�al of 7.2°F and 5.4°F from the ankle region to the head region, respec�vely. By lowering the amount of airflow necessary, stra�fica�on should be maximised to maximise energy savings while also taking sufficient comfort into account. With taller rooms, this advantage can be very significant.

12. Reduced outdoor air requirement.

The air quality improves from a completely mixed system when fresh air is supplied at a low level and allowed to move around the area due to buoyancy. ASHRAE acknowledges this development and permits a decrease in the amount of outside air needed to condi�on a space. To evaluate this improvement, zone air distribu�on effec�veness is used. According to ASHRAE 62.1 (2013), Ez is a measurement of how effec�vely the zone air distribu�on uses its supply air to keep the breathing zone's air quality below acceptable limits. {9}

From ASHRAE 62.1 2013:

Breathing Zone Outside Airflow Outside airflow is necessary in the respiratory zone of the occupied space: Vbz.

Air Supply Method

Ez (ASHRAE 62.1)

Mixed - Heating 0.8 - 1.0

Mixed - Cooling 1.0

Displacement 1.2

Summarised value from Table 6.2.2.2 of ASHRAE 62.1 2013

Equa�on VOZ = Vbz / EZ must be used to determine the zone outdoor airflow (VOZ), or the outdoor airflow rate that the supply air distribu�on system must provide to the ven�la�on zone.

Sample Calculation:

Mixing Displacement

VOZ, M = Vbz / EZ,M = Vbz / 1.0 = Vbz

VOZ,DV = Vbz / EZ,DV = Vbz / 1.2

= 0.83 Vbz = 17% Reduction in outdoor air requirement

In hot and humid climates, lowering the ven�la�on rate might result in significant energy savings.

A method known as ver�cal displacement ven�la�on, also known as thermal displacement ven�la�on, should be considered by designers. This technique gently li�s air pollutants upward and out from the area of inhala�on while successfully reducing fan energy. It does this by u�lising natural convec�on forces.

The breathing zone in a classroom study using DV has peak CO2 levels that are 17% to 27% lower than those in the control space with mixed air.

Figure 8 reference: Modelling Approaches for Displacement Ven�la�on in Offices (strath.ac.uk)

When displacement ven�la�on is used, the thermal plumes around heat sources speed up air flow across the area, which depends on buoyancy. In addi�on to any other heat source that needs cooling, these plumes draw supply air towards the building’s inhabitants, it’s machinery. And it’s façade. The ability to provide the plumes with fresh, the collec�on of fresh air from the supply at floor level allows for the crea�on of cool air. The gathering of new supply at floor level makes it possible to supply the plumes with cool, fresh air.

This might cause the shot supply air to rise to the ceiling, where it could be expelled or returned while poten�ally avoiding the occupied area. Displacement diffusers with built-in heat have a cooling and a hea�ng component. A heater that is to be cycled or modulated as needed is included in the upper sec�on’s enclosure.

The raised floor system of a space incorporates floor panels with perfora�ons. A ver�cal temperature gradient results from the displacement of the preexis�ng air by rising warm air that is supplied through �ny holes or slots in the panelling.{10}

A minimum 20% improvement in air quality is acknowledged by ASHRAE. Comparing spaces employing overhead mixing air systems to spaces using displacement revealed air quality improvements ranging from 25% to 90%. Cogni�ve scores dropped by 21% with a 400 ppm CO2 increase.

Displacement Ven�la�on delivers air into the inhabited area at a low face velocity (usually 40 fpm) and at a temperature that is roughly 10°F lower than the set point. Superior thermal comfort is produced by the combina�on of the low velocity airflow and the rising supply air temperature.

To create more ceiling space, it can be incorporated into structural and furniture components. Available in a variety of colours, sizes, and bespoke finishes, blending in perfectly with any se�ng. Inlet loca�ons, unique moun�ng choices, and integrated u�li�es for high usage places like gyms, schools, and commercial environments, heavy-duty construc�on is offered. To reduce health and maintenance concerns, the EPA advises using central AHUs rather than unit ven�lators. Chiller beam systems are frequently employed in displacement ven�la�on installa�ons even though they aren't really diffusers. By harnessing convec�on to cool the air around them, chilled beams induce natural air circula�on paterns. Air is released from low-velocity jet diffusers at a low speed and angle. Thermal stra�fica�on is aided by them because they produce a stream of air that s�cks to the ground and rises as it heats.

The key components of displacement ven�la�on include:

• Air supply diffusers

• These are close to floor level and provide the occupied area with low-velocity condi�oned outdoor air.

• Exhaust grilles

• These are situated at ceiling height and draw warm, stale air from the area that is occupied.

• Supply Fan

• This part ensures that the area has the appropriate ven�la�on.

• Cooling Coil

• This element lowers the temperature of the supplied air by approximately 10°F compared to the set point.

• Filters

• These are employed to eliminate airborne debris from the supply air.

• Control System

To ensure thermal comfort and indoor air quality, this component controls the supply air temperature and airflow rate.{11}

Types of diffusers in displacement ven�la�on:

• Linear Diffusers

Diffusers that are posi�oned along walls or in the floor are elongated and thin in shape. They offer a linear patern for distribu�ng air, facilita�ng the dispersion of clean air throughout the floor area, and enabling it to rise gradually.

• Floor Swirl Diffusers

These diffusers are made to release air in a swirling patern at a low velocity. Due to its buoyancy, the air rises along the walls and gradually replaces the warmer, more contaminated air in the room's upper levels.

• Perforated Floor panels

Perforated floor panels are integrated into the raised floor system of a space. Air is supplied through small holes or slots in the panels, and the rising warm air displaces the exis�ng air, crea�ng a ver�cal temperature

gradient. Perforated floor panels are integrated into the raised floor system of a space. Air is supplied through small holes or slots in the panels, and the rising warm air displaces the exis�ng air, crea�ng a ver�cal temperature gradient.

• Low velocity jets

Air is released from low-velocity jet diffusers at a low speed and angle. Thermal stra�fica�on is aided by them because they produce a stream of air that s�cks to the ground and rises as it heats.

• Chilled beam Systems

Chiller beam systems are frequently employed in displacement ven�la�on installa�ons even though they aren't really diffusers. By u�lising convec�on to cool the air around them, chilled beams induce natural air paterns of circula�on.

• Underfloor Air Distribu�on (UFAD) Systems

To circulate the supply air using floor diffusers, these systems require a plenum beneath the floor. Naturally, the pollutants in the space are drawn higher by the warm air.

• Swirl Diffusers

Air is released by swirl diffusers in a circular or swirling manner. This arrangement ensures effec�ve displacement ven�la�on by encouraging a gently upward airflow.

• Displacement Grilles

Air is released near the floor using displacement grilles. They provide low-velocity air distribu�on, facilita�ng the upward transfer of warmer air.{12}

Figure 9 reference: allisonclairechang.org

Technical aspects of Displacement ven�la�on

Underfloor displacement ven�la�on (DV) systems prove highly suitable for open-floor-plan layouts. The inherent adaptability and poten�al for future modifica�ons of such layouts align well with open-floor plans. It is advisable for the engineer to strategize the inclusion of several air-delivery systems (ranging, for instance, from 5,000 cfm to 8,000

cfm) distributed across the floor area, establishing mul�ple zones for control. This approach not only enhances precise temperature regula�on within the expansive area but also ensures adherence to ASHRAE Standard 90.1. This standard pertains to energy guidelines for buildings excluding low-rise residen�al structures, specifically addressing constraints on fan-power. Through the u�liza�on of similarly sized and modelled air handlers, the convenience of maintenance will be standardized, facilitated by interchangeable components such as belts, fans, and filters.

The floor's systems have been enhanced with redundancy, enabling alternate units to temporarily increase output to offset the impact of a deac�vated blower unit. Op�ng for ver�cal fan units instead of horizontal ones can economize on floor area. When dealing with enclosed floor plans, the need for dis�nct control of terminal zones and specialized monitoring and management of ven�la�on becomes more pronounced compared to open-floor setups, which results in increased expenses. In scenarios where the floor primarily consists of smaller offices or enclosed areas, a me�culous evalua�on should be undertaken regarding the suitability of a system with overhead mixing or a fully vented central supply unit

Return air can be managed through two op�ons: it can either be channelled through ducts towards the air-supply blowers distributed across the floor or point returns can be implemented at an elevated posi�on in proximity to each blower system. However, it's important to ensure that the distance between the return inlet and the exterior wall doesn't exceed 40 to 50 feet. This arrangement of point returns requires thorough examina�on to prevent the transmission of noise from the fan room to the occupied space. It's worth considering the incorpora�on of silencers to effec�vely reduce poten�al noise disturbances.

In both ceiling configura�ons, it's crucial to insulate the floor deck situated above a floor serviced by a DV system. Without proper insula�on, an uninsulated floor deck permits the transfer of heat from the warm stra�fied air to the ceiling. This phenomenon can result in undesired elevated temperatures in the upper floor in a conven�onal overhead mixing setup. Furthermore, it can lead to significant challenges if the space above it is uninsulated, controlling an underfloor DV system.

Column enclosures must ini�ate from the floor slab and con�nue up to the ceiling panel, ensuring a sealed connec�on between the column casing and the floor panel. It's impera�ve for the enclosure to possess a completely air�ght seal both at its upper and lower ends. Achieving strong construc�on integrity in the context of a raised-floor system holds significant importance. If posi�ve seals are absent at the upper and lower parts of the column casing, the whole assembly might behave like an air duct, allowing pressurised supply air to escape into an underfloor plenum.

Throughout the construc�on process, sealing should be closely monitored, notably in the centre, the electrical and mechanical rooms, etc. Place diffusers away from objects that will prevent preven�ng the airflow from touching the heat sources, such as rack stores or other obstruc�ons. Instead of a turbulent diffuser that would fling the air excessively high and result in a mixing effect, use a displacement-type exit.

For big open spaces, manually operated floor-mounted outlets may be more affordable and give users more control over their level of comfort. To guarantee that the required minimum ven�la�on rates are provided, Floor outlets should only have the bare minimum of restric�ng devices. Place hea�ng terminals with fans and variable air volume controls around the room's perimeter on the raised floor in areas with easy access that aren't directly under where the furniture will go. Place the both the hea�ng and outer zones components far enough apart to prevent them from encroaching on the inner cooling zones. There should be no people inside the perimeter zone, which is normally 15 feet from the outer glass. For this system, to connect the floor outlets to the terminal unit, duc�ng is required.

A common configura�on comprises a finned-tube radiator integrated into the upper sec�on of a wall-mounted DV outlet. The air-handling blowers situated in the floor plenum spaces should be both space-efficient and easily reachable. Key elements within these systems encompass the primary cooling coil, MERV 8 filters (employed in conjunc�on with pre-filters), control dampers for outdoor and return air, and smoke detectors.

Because inhabitants generate a significant amount of moisture and ven�la�on of external air can contribute anywhere between 50% and 80% of the moisture load in a building, humidity control is a crucial design factor in DV. The ven�la�on air is built for the occupancy's breathing-zone space, which is a crucial component of DV. Because the

displacement delivery is buoyant close to or at the floor, pollutants are effec�vely moved up and away towards the occupants, via high-return grilles. .{13}

5.3 Comparison

According to the Engineering Guide for Displacement Ven�la�on, it is stated that:

The typical effec�veness of mixed ven�la�on systems is e=0.9. However, when combined with a dedicated outdoor air system and radiant hea�ng/cooling systems, displacement ven�la�on (DV) systems can achieve a ven�la�on effec�veness of at least e=1.2 and have the poten�al for significantly higher ven�la�on efficiency.

Design considera�ons for displacement ven�la�on and mixed air ven�la�on are different due to the different approaches to delivering condi�oned air

Displacement ven�la�on

Appropriate for rooms that need to have strong ven�la�on, such classrooms, conference rooms, and offices enhances indoor air quality by removing contaminated air from the space.

More energy-efficient than mixed-air systems

Quieter opera�on than conven�onal overhead systems

Where cooling loads are needed, more air is needed, and higher ceilings are needed for ceiling-based filtra�on systems.

These systems are novel; therefore, contractors typically don't have much familiarity with them.

Mixed Air ven�la�on

Appropriate for commercial structures with significant ven�la�on needs maintains equilibrium between the HVAC system's energy usage and the occupants' need for fresh air controls the air mixing using motorised dampers, which are under the supervision of the building management system or control system. uses energy-saving parts, such as variable speed drives and high-efficiency filters, to reduce energy use while s�ll sa�sfying the building's ven�la�on needs. To guarantee that the air distribu�on system can distribute the necessary amount of fresh air to each zone, it is necessary to divide the building into zones according to occupancy and usage. imposes a requirement that the air distribu�on system be built to lower noise levels in occupied spaces.

While mixed air ven�la�on strikes a balance between the occupant’s need for fresh air and the energy usage of the HVAC system, displacement ven�la�on offers greater indoor air quality and is more energy efficient. {15}

Figure 10 source: How Does Displacement Ven�la�on Work? (priceindustries.com)

6 Case Studies

Six of the top 20 visited museums in Europe were found in London, which is home to several cultural ins�tu�ons. The Natural History Museum in London received the most visitors during that year. Prior to the pandemic, the Tate Modern and Bri�sh Museum used to get more visitors, but in 2021 the Natural History Museum was London's most popular free atrac�on.

6.1 TATE MODERN

The Tate Modern, a dis�nguished ar�s�c ins�tu�on in the heart of London, serves as a compelling embodiment of the fusion between contemporary art and sustainable design principles. In an age where ecological stewardship takes centre stage, the Tate Modern has embarked on a remarkable odyssey toward enhancing energy efficiency and fostering sustainability. This esteemed gallery, ingeniously repurposed from a former industrial power sta�on, not only reshapes the landscape of ar�s�c expression but also sets a pioneering benchmark in the domain of environmentally conscious architecture and opera�onal prac�ces. This introduc�on provides insight into the Tate Modern's endeavours to promote energy-efficient solu�ons, highligh�ng its successful fusion of art apprecia�on with a steadfast commitment to a more environmentally friendly and sustainable future.

To ensure the comfort of millions of visitors while providing the ideal environmental circumstances for the valuable works of art at the Tate, it uses waste heat from electrical transformers, desiccant dehumidifica�on, and even underground water extracted from river gravel underneath the site. for the best low-energy design to be used. To cut energy usage as much as was realis�cally possible, the hea�ng and cooling plan was developed. In compliance with interna�onal standards for art loan, the environment must be maintained between 18°C and 25°C with a rela�ve humidity of 40% to 65%. The addi�on's galleries, for instance, are maintained at lower temperatures and humidity levels throughout the winter while s�ll mee�ng acceptable loan condi�ons. To achieve these goals, the galleries aim for a RH of 50% +/- 5% and an interior temperature of 19°C +/- °C.

The restric�ons are raised to 22°C +/- 2°C and 55% RH +/- 5% in the summer. ‘Limi�ng the rate of change is crucial; you should aim for a maximum 10% change in RH and a maximum 4°C change in temperature over the course of a 24-hour period. The three gallery floors of the expansion receive condi�oned air through high-level grilles and floor extrac�on from a displacement ven�la�on system.

Figure 11 Source: Energy consumption of UK arts industries 2021 | Statista

Comparable techniques were u�lized in the ini�al design of the Tate Modern. The primary difference lies in the extension, where air is channelled to the floor grilles, whereas in the power plant sec�on, condi�oned air is supplied to floor-mounted grilles through a pressurized raised-floor cavity. The decision to duct the air in the extension simplifies maintenance due to the tendency of gallery floor areas to accumulate dust. The air supply duc�ng serving the floor grilles is directed at an elevated posi�on within the gallery below, ascending through the floor slabs alongside the highlevel extract ductwork of that gallery. In the larger, lower-level galleries, both the supply and extract ductwork have been painted white and inten�onally le� uncovered.

Each gallery is equipped with its dedicated air handling unit (AHU). The engineer innova�vely harnessed groundwater stored in a five-meter-deep river gravel bed beneath the site to provide cooling for the AHUs a notably rare and energy-efficient solu�on. Two boreholes near to the Tate's western gate are used to draw at a beneficial temperature of 14–15°C, water can be extracted out of the gravel at an intensity of up to 30 litres per second. Since the gravel lies between 5 and 12 metres below the surface, pumping water out of them doesn't require a lot of energy. The water is kept apart from the sealed gallery systems un�l it reaches the surface by passing via a heat exchanger. A�er being cooled by a borehole, the water is then run via massive coils atached to the extension's mul�ple AHUs. Despite going through a heat exchanger, it effec�vely used to cool the AHUs directly.

Three water-cooled chillers are also included in the plan. To cool a few of the basement rooms and other ancillary spaces, these provide higher-grade chilled water. To gather borehole water, three boreholes are bored into the landscape to the north of the gallery., which removes heat rejected by the chillers and returns it to the gravel. It is an extremely effec�ve solu�on when compared to employing air-cooled chillers. The borehole water is addi�onally heated by a heat pump in the winter. Part of the building's heat requirement is met by the heat produced. The exis�ng gallery's boilers' surplus capacity is used to generate backup heat. All the cooling and a significant por�on of the hea�ng is provided by the boreholes. The building's systems were designed in a novel way to make the most of the waste heat generated by the extensive network of transformers that UK Power Networks uses to supply 11kVA of power to the City of London.

The Tate Modern's former life as a power sta�on is reflected in the loca�on of the transformers in Bankside. They were ini�ally kept throughout the en�re Switch House but were eventually relocated to its eastern end to make room for the addi�on's development. Being moved allowed the engineers to u�lise the rejected heat from them in the new extension because they are water-cooled.

Controlling humidity is crucial in the galleries. Dehumidifica�on of fresh air normally involves over-cooling it un�l moisture condenses from it, followed by rehea�ng it to an appropriate supply temperature. This process requires a lot of energy. Since they are water-cooled, moving them gave the engineers the ability to use the heat that was rejected in the new expansion. To eliminate humidity from the fresh air supply, desiccant dehumidifica�on could be applied for the extension thanks to the substan�al amount of low-grade cooling and heat made possible by the boreholes and transformers. The Switch House extension's fresh air supply is dehumidified using a desiccant wheel with a 4 m diameter. The desiccant is then refilled once the condensa�on collected by the wheel is pushed from it u�lising the low-temperature heat in the reac�vated air stream. Each dedicated gallery AHU receives ducted dehumidified air, which is combined with the recirculated gallery air there.

A significant por�on of its energy is sourced from the heat generated by the EDF transformers situated in the neighbouring, opera�onal Blavat Nik Building. Through its high thermal mass, extensive u�liza�on of natural ven�la�on, and effec�ve u�liza�on of daylight, the new structure surpasses exis�ng building code requirements by reducing energy consump�on by 54% and carbon dioxide emissions by 44%.

6.2 DESIGN MUSEUM

The Design Museum in London stands as a beacon of innova�on and crea�vity, and it does not stop at aesthe�cs alone. In a world increasingly atuned to environmental concerns, the Design Museum has taken bold strides in the realm of energy efficiency and sustainability. This introduc�on invites you to explore the museum's remarkable journey towards crea�ng a space that seamlessly marries design brilliance with ecological responsibility. As we delve into the museum's ini�a�ves and prac�ces in energy efficiency, we uncover a testament to its commitment to a greener, more sustainable future, while also showcasing how it sets an inspiring example in the world of design and architecture.

The building u�li�es at the Design Museum's new London loca�on must be silent and out of sight due to the building's austere style. The west London structure s�ll has its recognisable saddle-shaped roof, but under its hyperbolic paraboloid cap of copper, John Pawson's architectural design has completely transformed the interior. The challenge for the project's ligh�ng and building services engineers was to develop a flexible services solu�on that would suit Pawson's contemporary interior while also providing a welcoming space for guests that complied with BREEAM Very Good standards. A displacement ven�la�on system provides the gallery rooms with hea�ng, cooling, and fresh air. To hide supply ducts that are ver�cal that fall from the ceiling gap above, a false wall was built instead. This wall's botom half serves as a supply air plenum, distribu�ng air uniformly along its length. Each of the three main exhibi�on areas receives a displacement ven�la�on system, the gallery is ven�lated and cooled. A displacement ven�la�on system provides gallery ven�la�on and cooling to each of the three primary display sec�ons. Extrac�on ductwork is covertly

Figure 12 Tate modern gallery with floor diffusers

Figure 13 Building facade

Figure 14 Gallery in museum with floor diffusers

Figure 15 museum roof interior

posi�oned above the ceilings of the rooms around the museum's uppermost floor permanent display gallery, which has no ceiling.

The displacement system func�ons well because it sa�sfies the objec�ves of a minimalist interior design approach while also providing a flexible area that can accommodate a range of fresh air and cooling needs. An exclusive AHU at the basement of the building serves each gallery. The museum's double-height basement serves as the usual route for supply and return air ducts, which are then elevated into the building at each end of the museum using ver�cal risers. In considera�on of the building's listed facades and roof, the primary ven�la�on intake and exhaust systems have been strategically located below ground level. A substan�al intake plenum is situated on the building's southern side, while a corresponding exhaust plenum is posi�oned on the opposite side. Each of the seven AHUs is individually connected to the plenums, as are the smoke-extract systems, which are in a shared basement plantroom.

Two heat exchangers that are connected to a district heat network provide heat to the AHUs. The building is therefore boiler-free. Due to the listed status of the building, the engineers were unable to place ven�la�on louvres in the façade or roof, so two 400kW air-cooled chillers are hidden in an 8-meter-deep hole in the outside landscaping, and they provide the chilled water supply for the AHUs. The armoured supply cables and pre-insulated flow and return piping connec�ng the chillers to the main basement are buried beneath the landscaping. The chillers are equipped with sound atenua�on due to their closeness to the neighbouring residen�al development. The acous�c atenuators' design was the only thing that needed to be changed to account for this. Due to the chillers' subterranean configura�on, when only ver�cal air movement was allowed on and off each chiller, a strict noise level of 49dBA at 1m was atained. The smaller galleries are posi�oned on the top floors, where the extract ducts are hidden above a hanging ceiling.{14}

7 Inves�ga�ons

Analysis for the thesis topic on Displacement Ven�la�on in Energy Efficiency of Museum Galleries uses Thermal Performance of Buildings (TPLP) and Computa�onal Fluid Dynamics (CFD).

7.1

CFD

The energy efficiency of various ven�la�on systems in museum galleries can be compared using CFD analysis. CFD analysis enables the simula�on and energy efficiency comparison of various ven�la�on systems. CFD analysis sheds light on each system's individual energy usage and efficiency by modelling and simula�ng its airflow paterns and thermal performance. The temperature distribu�on in the museum galleries is assessed using CFD analysis for various ven�la�on systems. It provides details on how each system influences the temperature distribu�on and energy usage by analysing variables including air temperature, velocity, and heat transfer. CFD analysis makes it possible to evaluate how well airflow works in various ven�la�on systems. It aids in loca�ng places where airflow might be ineffec�ve or stagnant, which may affect energy efficiency. CFD analysis compares the distribu�on and paterns of airflow to shed light on the effec�veness of each ven�la�on system. The examina�on of thermal comfort condi�ons for various ven�la�on systems is possible with CFD analysis. It aids in determining the degree of comfort

Figure 16 source: The new Design Museum – engineering by stealth – CIBSE Journal

offered by each system by considering elements like air temperature, humidity, and air movement. U�lising this data, it is possible to evaluate how well each ven�la�on system maintains thermal comfort while using less energy.

Airflow paterns in museum galleries with displacement ven�la�on can be thoroughly examined using CFD analysis. This research shows how effec�ve the ven�la�on system is and aids in pinpoin�ng areas that need improvement. Energy efficiency can be improved by adjus�ng the airflow paterns. Hotspots and cold spots in museum galleries with displacement ven�la�on can be found using CFD analysis. This research aids in the energy-efficient design of displacement ven�la�on systems by ensuring that the indoor clima�c condi�ons are consistent throughout the gallery. Thermal resistance and heat transfer coefficients are two factors that the CFD study considers when evalua�ng the ven�la�on system's thermal performance. This research offers important insights for raising energy efficiency and controlling indoor environment. A thorough method for comprehending and improving the efficiency of the ven�la�on system in museum galleries using displacement ven�la�on is provided by CFD analysis.

A thorough evalua�on of the airflow paterns in museum galleries is possible thanks to CFD analysis.

It is possible to spot places where the displacement ven�la�on system may not be efficiently supplying condi�oned air to the occupied zone by analysing the airflow distribu�on. U�lising this data will enable the ven�la�on system's design and layout to be op�mised, resul�ng in effec�ve air distribu�on and reduced energy use.

The temperature distribu�on in the museum gallery is evaluated using CFD analysis. It pinpoints regions where there may be temperature stra�fica�on or hotspots, which may signify ineffec�ve airflow or insufficient cooling or hea�ng. To increase temperature uniformity and energy efficiency, these loca�ons can be iden�fied, and changes made to the ven�la�on system design, such as changing diffuser placement or supply air temperature.

The distribu�on of contaminants within the museum exhibit can also be assessed using CFD analysis. This is crucial for protec�ng historical artefacts and sustaining air quality. Poten�al loca�ons of stagnant air or insufficient pollutant removal can be found by examining the pollutant dispersion paterns. U�lising this knowledge will enable the ven�la�on system design to be op�mised, resul�ng in efficient pollu�on removal and maintenance of a healthy indoor atmosphere.

The posi�oning of the diffusers, supply air temperature, and supply air velocity are only a few of the characteris�cs in the displacement ven�la�on system that can be op�mised using CFD analysis. Poten�al areas for improvement can be found through simula�ons of various scenarios and analysis of the outcomes. To maximise energy efficiency and indoor climate control, changes can then be made to these factors.

The computa�onal domain with the dimension of 20m X 19.5 m X 6m.

The space has doors located on opposite sides measuring 2.1m X 1.5m.

For the mixing ven�la�on case, ceiling supply diffusers are placed at ceiling height, whereas the supply diffuser for the displacement ven�la�on example is installed at floor level.

7.2 Comparison between mixed ven�la�on and displacement ven�la�on using CFD results. According to the guidelines developed by Chen and Glicksman

1.Summer Design load

Considering the non-uniform room air temperature atributed to displacement ven�la�on, the computer simula�on assumes a ver�cal temperature gradient of 1.1 °F per foot (2 °C per meter).

Occupants – 8

Set point - 22°C

Floor Area – 386.4 m2

Volume – 1560 m3

occupants, desk lamps and equipment qos – 700 W

overhead ligh�ng ql – (25 W/m2 x 386.4) = 9660 W

heat conduc�on through the room envelope and transmited solar radia�on qen = 40 m2 x 15 W/m2 = 600 W

Total cooling load qT = 10,360 W

Total cooling load for this space is 10,360 W and approx. 27 W/m2 .

ASHRAE standard 62-2004 requires 0.3l/sm2 outdoor airflow rate per unit area and 3.8 L/s person; be delivered to the space for moderately ac�ve museum applica�ons.

For displacement ven�la�on, ven�la�on effec�veness or zone air distribu�on effec�veness is assumed to be 1.2

2.Determine the Cooling Load Ven�la�on Flow Rate

flow rate required for summer cooling:

Qov = air required to sa�sfy the sensible cooling load in a DV system

p = air density

c” = specific heat of the air at constant pressure

t,if = temperature difference from head to foot level

(Table 6.2, ASHRAE Standard 62-2004)

Air flow rate to meet the cooling load.

QDV = [ 0.295 x (700) + 0.132(9660) + 0.185(600) ]/(1.2)(1.007)(3)

QDV = 439.95 lis

3. Determine Flow Rate of Fresh Air, Qo,

According to ASHRAE Standard 62.1-2004, equa�ons 6-1 and 6-2 are used to calculate the outdoor air flow in the breathing zone and the zone, respec�vely.

where:

Q,,, = the amount of outdoor air that is necessary, as calculated by the room applica�on and ASHRAE Standard 62.12004.

Rp is the outdoor air flow rate per person as calculated from ASHRAE 62.1-2004 Table 6-1, in cfm/person. Usual person RA is the outdoor air flow rate per unit area needed, as calculated from ASHRAE 62.1 Table 6-1, in cfm/�2 [Usm2].

P, = the biggest group of individuals an�cipated to be present in the area during normal use

A, = zone floor area, �2 [m2]

E, = the zone's air distribu�on system's ven�la�on efficiency

Fresh airflow rate –

QOZ = [ (13.8)8 + (0.3) (386.4) ] / 1.2

QOZ = 127 lis

4.Determine Supply Air Flow Rate, Q,.

Choose the higher amount of the needed flow rates for summer cooling and required ven�la�on rates as the design flow rate of the supply air:

5.Determine Supply Air Temperature:

Supply air temperature = 18°C

6.Determine Exhaust Air Temperature

Return air temperature = 24°C

7.Rebalance Supply Air Volume (As required)

QDV = qT / PCP(te – tss) = 10960 / (1.2)(1.006)(224 - 18)

= 10.360/7.24 = 1513 8 l/s

8.Selec�on of Diffusers

7.3 Calcula�ons for airflow varia�ons and comparison

Displacement Ven�la�on

Case 1 A

In the domain of Computa�onal Fluid Dynamics (CFD), the precise defini�on of boundary and ini�al condi�ons plays a cri�cal role in capturing the intricate interac�ons of thermal and fluid phenomena within a given system. In our specific context, these condi�ons have been rigorously specified. The boundary condi�ons encompass a heat genera�on rate of 75W per occupant, symbolizing the thermal contribu�ons of individuals within the enclosed space. The inlet temperature, reflec�ng the ambient environmental condi�ons, is set at 18 degrees Celsius, while the outlet temperature is established at 24 degrees Celsius. The ini�al velocity within the domain is designated as 0 m/s, indica�ng a tranquil ini�al environment. Simultaneously, the volume flow rate is prescribed at 858 cubic meters per hour, characterizing the rate at which air enters and exits the system. Furthermore, the outlet pressure is maintained at a reference level of 0 Pa. To ini�ate the simula�on, the ini�al condi�ons encompass a human temperature of 27 degrees Celsius, represen�ng the star�ng thermal state of occupants, and a box temperature of 20 degrees Celsius, signifying the ini�al thermal state of the enclosure itself. These me�culously defined condi�ons form the cornerstone of our CFD analysis, affording us the precision and accuracy required to explore the complex thermal and fluid dynamics within this system.

Figure 17 Temperature distribution under displacement ventilation scenario with flow rate of 858 cubic meters per hour

Case 1 B

In this simula�on, which focuses on a mixed ven�la�on scenario, we have me�culously defined several cri�cal parameters. The boundary condi�ons include a heat genera�on rate of 75W per human occupant, accurately reflec�ng the thermal contribu�ons of individuals within the confined space. In the context of the mixed ven�la�on setup, the inlet temperature, posi�oned at the ceiling level, has been set to 18 degrees Celsius, mirroring both the environmental condi�ons and the precise air intake loca�on. Addi�onally, an ini�al velocity of 0.2 m/s has been specified to represent the ini�al air movement dynamics within the space. The volume flow rate, me�culously calculated at 957 cubic meters per hour, effec�vely characterizes the air exchange rate, encompassing both inlet and outlet flows. To ini�alize the simula�on, ini�al condi�ons have been set with a human temperature of 27 degrees Celsius, serving as an accurate representa�on of the occupants' ini�al thermal state, while the box temperature is established at 20 degrees Celsius, symbolizing the ini�al thermal condi�ons within the enclosure.

Figure 19 Temperature distribution under displacement ventilation scenario with velocity vectors

Figure 20 Temperature distribution under displacement ventilation scenario with human thermal emission

Figure 21 Temperature distribution under displacement ventilation elevation

Mixed Ven�la�on System

Figure 24 temperature in degrees

Figure 25velocity in m/s

A higher standard devia�on of average temperatures in the mixing-ven�la�on system compared to the displacement ven�la�on system indicates greater temperature variability and inconsistency within the space.

A greater standard devia�on in a mixing-ven�la�on system could result in uneven temperature distribu�on within the room, causing certain areas to feel warmer than others. This variability in temperatures might make it less comfortable and predictable for occupants, especially when contrasted with the more uniform temperature distribu�on achieved in the displacement ven�la�on system.

Figure 22 Temperature and velocity distribution in mixed ventilation scenario with flow rate of 858 cubic meters per hour

Figure 23 Temperature and velocity distribution in mixed ventilation scenario with velocity vectors

Figure 26 Temperature and velocity distribution in mixed ventilation elevation

In the scope of research, a me�culous compara�ve analysis of two dis�nct ven�la�on strategies, denoted as Case 1 A and Case 1 B, to scru�nize their respec�ve impacts on indoor environmental quality was conducted. Case 1 A was characterized by the implementa�on of a displacement ven�la�on system equipped with floor diffusers, while Case 1 B entailed the u�liza�on of a mixed ven�la�on strategy featuring ceiling inlets. A noteworthy aspect of our inves�ga�on was the maintenance of a constant airflow rate of 957 cubic meters per hour across both cases, thereby facilita�ng a direct performance assessment.

The outcomes of our study have brought to light compelling dispari�es in the thermal dynamics within the indoor environment under scru�ny. Case 1 demonstrated a commendably homogeneous temperature distribu�on, with temperatures spanning a range of 18 to 24 degrees Celsius. This outcome is indica�ve of an environment characterized by a consistent and harmonious thermal profile, thereby fostering occupant comfort and well-being. Remarkably, despite the iden�cal airflow rates maintained in both cases, the choice of ven�la�on strategy profoundly influenced the resultant indoor thermal environment.

Conversely, Case 2 exhibited a markedly dissimilar thermal profile, characterized by a pronounced prevalence of warm air and an uneven spa�al dispersion of temperature. This divergence underscores the inherent challenges associated with mixed ven�la�on strategies, as the uneven thermal distribu�on may precipitate discomfort and a sense of thermal dissa�sfac�on among occupants.

Scenario in which occupancy load is increased which resulted into increase in air flow rate:

Case 2

Occupants – 16

Set point - 22°C

Floor Area – 386.4 m2

Volume – 1560 m3

occupants, desk lamps and equipment qos – 1300 W

overhead ligh�ng ql – (25 W/m2 x 386.4) = 9660 W

heat conduc�on through the room envelope and transmited solar radia�on qen =

Total cooling load qT = 11560W

Air flow rate to meet the cooling load is 1769.62 Lis

Fresh airflow rate is 157.4 Lis

Supply air volume is 1596.6 Lis

W

In the domain of Computa�onal Fluid Dynamics (CFD), the precise defini�on of boundary and ini�al condi�ons plays a cri�cal role in capturing the intricate interac�ons of thermal and fluid phenomena within a given system. In our specific context, these condi�ons have been rigorously specified. The boundary condi�ons encompass a heat genera�on rate of 75W per occupant, symbolizing the thermal contribu�ons of individuals within the enclosed space. The inlet temperature, reflec�ng the ambient environmental condi�ons, is set at 18 degrees Celsius, while the outlet temperature is established at 24 degrees Celsius. The ini�al velocity within the domain is designated as 0 m/s, indica�ng a tranquil ini�al environment. Simultaneously, the volume flow rate is prescribed at 957 cubic meters per hour, characterizing the rate at which air enters and exits the system. Furthermore, the outlet pressure is maintained at a reference level of 0 Pa. To ini�ate the simula�on, the ini�al condi�ons encompass a human temperature of 27 degrees Celsius, represen�ng the star�ng thermal state of occupants, and a box temperature of 20 degrees Celsius, signifying the ini�al thermal state of the enclosure itself. These me�culously defined condi�ons form the cornerstone of our CFD analysis, affording us the precision and accuracy required to explore the complex thermal and fluid dynamics within this system.

Scenario in which occupancy load is decreased which resulted into decrease in air flow rate:

Case 3

The 75W heat genera�on rate per occupant included in the boundary condi�ons represents the thermal contribu�ons of people inside the enclosed space. The exit temperature is set at 24 degrees Celsius, while the entrance temperature is set at 18 degrees Celsius to represent the surrounding environmental condi�ons. The domain's ini�al velocity is given as 0 m/s, indica�ng a calm star�ng condi�on. In addi�on, the volume flow rate, which describes the rate at which air enters and departs the system, is set at 800 cubic metres per hour. Addi�onally, a reference level of 0 Pa is maintained for the outlet pressure. The beginning condi�ons include a human body temperature of 27 degrees Celsius.

Figure 27 Temperature distribution under displacement ventilation scenario with flow rate of 957 cubic meters per hour

Figure 28 Temperature distribution under displacement ventilation elevation

Figure 29 Temperature distribution under displacement ventilation elevation

Occupants – 4

Set point - 22°C

Floor Area – 386.4 m2

Volume – 1560 m3

occupants, desk lamps and equipment qos – 300 W

overhead ligh�ng ql – (25 W/m2 x 386.4) = 9660 W

heat conduc�on through the room envelope and transmited solar radia�on

Total cooling load qT = 10560W

Air flow rate to meet the cooling load is 3786 Lis

is 111 8 Lis

Figure 30 Temperature distribution under displacement ventilation elevation

Figure 31 Temperature distribution under displacement ventilation elevation

Figure 32 Temperature distribution under displacement ventilation scenario with flow rate of 957 cubic meters per hour

There is a greater need for fluid to move through a system when the load on it increases. If there’s a hea�ng system, for instance, an increase in load could be brought on by a drop in exterior temperature, necessita�ng the circula�on of extra hot water or air to maintain the required internal temperature. The system must distribute more fluid at a faster rate to sa�sfy this increasing demand. This frequently entails accelera�ng the fluid's velocity in the context of CFD. On the other hand, the system can adjust the flow rate to match the decreased requirement when the load lowers, indica�ng a decreased demand for fluid flow. For instance, as the temperature rises, the burden on a cooling system lowers. As a result, the flow rate of chilled air or water can be lowered while s�ll maintaining comfort and energy efficiency.

Warm air from humans and equipment rises naturally because of an increase in the thermal load in a space, such as when more people are present to balance the rising heat load, displacement ven�la�on can adjust by delivering slightly cooler air at the floor level. This cooler air replaces the warm air that is ascending, resul�ng in a cosy and thermally stra�fied atmosphere.

Both cases were subjected to iden�cal analy�cal inputs in terms of temperature and pressure, with the variable of interest being the number of occupants and its corresponding influence on diffuser layout planning. In Case 2, where the space accommodated 16 occupants, a ven�la�on flow rate of 957 cubic meters per hour was implemented. In contrast, Case 3 involved a scenario with only 4 occupants, and an airflow rate of 800 cubic meters per hour was employed.

The results unveiled a noteworthy patern in both cases, characterized by a well-defined and evenly distributed thermal comfort profile. In Case 2, despite the higher number of occupants, the ven�la�on system effec�vely maintained a comfortable indoor environment, indica�ng the poten�al for op�mizing system opera�on. This op�miza�on could involve reducing the airflow rate within the space while concurrently reevalua�ng the diffuser layout. Case 3, with its lower occupancy and correspondingly adjusted airflow rate, similarly exhibited a desirable thermal comfort distribu�on.

7.4 TPLP energy calcula�ons

Total Primary Energy Consump�on is the abbrevia�on for TPLP. The total quan�ty of energy used in a system or process is measured using this metric in energy calcula�ons. All energy inputs, such as fuel, electricity, and other energy sources, are considered by TPLP.

TPLP is used to evaluate the en�re energy consump�on of the ven�la�on system in the context of energy calcula�ons for displacement ven�la�on in the energy efficiency of museum galleries. The energy inputs necessary for the ven�la�on system's func�oning, such as fan power, hea�ng or cooling energy, and any auxiliary equipment, are normally considered when calcula�ng TPLP. The total primary energy consump�on is then calculated by adding these energy inputs together. Direct comparisons between various ven�la�on systems are possible thanks to TPLP. It is feasible to detect which system is more energy-efficient and prospec�ve areas for development by calcula�ng the TPLP for each system. The energy sources needed to run the ven�la�on system are considered by TPLP. This is significant since the efficiency and influence on the environment of various energy sources varies. TPLP offers a more accurate evalua�on of the overall energy performance because it factors in all energy sources.

The thermal performance of the ven�la�on system is assessed using TPLP analysis, which also considers thermal resistance and heat transfer coefficients. With the use of this analysis, indoor climate management and energy efficiency can be improved. The thermal performance of the ven�la�on system can be improved by iden�fying poten�al areas for improvement using TPLP analysis. It offers insights into poten�al regions of the system that may be inefficient or insufficient by analysing elements like heat transmission and thermal resistance. The ven�la�on system's design and opera�on can be op�mised using this informa�on to result in greater energy efficiency.

The placement of the diffuser, supply air temperature, and supply air velocity may all be op�mised in the displacement ven�la�on system thanks to TPLP analysis. To op�mise energy efficiency and indoor climate management, these se�ngs can be changed a�er analysing the thermal performance of the system.

In compliance with Part L regula�ons for 2021, an academic study was undertaken to assess and compare the energy consump�on of a shoebox-type building under two dis�nct ven�la�on systems: displacement ven�la�on and mixed ven�la�on. To calculate the energy consumed by the building, comprehensive data were selected and applied to various components of each ven�la�on system, thereby genera�ng Energy Performance Cer�ficate (EPC) informa�on.

The specific characteris�cs of each system, including air exchange rates, airflow distribu�on paterns, and thermal comfort considera�ons, were considered in detail. Data pertaining to the building's envelope proper�es, such as insula�on levels, window-to-wall ra�os, and roof characteris�cs, were incorporated into the analysis. Addi�onally, HVAC equipment specifica�ons, including the efficiency of fans, filters, and hea�ng/cooling systems, were me�culously factored into the energy consump�on calcula�ons. Weather data for the geographical loca�on of the building was also integrated to account for seasonal varia�ons and external temperature fluctua�ons.

The input data were sourced from TBD (To Be Determined) inputs based on NCM (Na�onal Construc�on Manual) standards and London weather data for different day types. These inputs encompass a wide range of clima�c and environmental condi�ons to ensure a comprehensive assessment of the indoor thermal performance. The internal condi�ons within the library museum gallery displays were retrieved from an established internal condi�on database. Notably, the thermostat condi�ons were set to maintain a thermally comfortable environment throughout the year, with an upper temperature limit of 150 degrees Celsius and a lower limit of -50 degrees Celsius. Furthermore, humidity control was integrated, with an upper limit setback value of 100% and a lower limit value of 0%, emphasizing the importance of preserving the environmental integrity of the exhibits. The building envelope characteris�cs played a pivotal role in the thermal modelling process. The exterior wall was assigned a U-value of 0.12 W/sq m degree Celsius, reflec�ng its insula�ng proper�es and ability to mi�gate external temperature fluctua�ons. Conversely, the internal floor exhibited a U-value of 1.39 W/sq m degree Celsius, indica�ve of its lower insula�on capacity compared to the exterior wall. Addi�onally, the aluminium duct framing was assigned a U-value of 2.7 W/sq m degree Celsius, contribu�ng to the overall thermal performance of the ven�la�on system within the museum gallery space.

This comprehensive thermal modelling approach, incorpora�ng TBD inputs from NCM standards, London weather data, and specific building envelope characteris�cs, allows for a detailed analysis of the indoor thermal dynamics within the library, museum and gallery. It enables the assessment of how the building responds to varying external condi�ons and aids in op�mizing the environmental control systems to safeguard the valuable exhibits while maintaining energy efficiency.

In accordance with CIBSE Guide F, adhering to annual energy consump�on benchmarks within the gross internal area represents good prac�ce for sustainable building design. These benchmarks provide crucial insights into energy usage paterns, aiding in the pursuit of more efficient and environmentally responsible building opera�ons. For instance, in the category of electricity consump�on, a benchmark of 57 signifies an exemplary standard of energy efficiency. Similarly, a benchmark of 96 for fossil fuel usage demonstrates a commendable commitment to reducing carbon emissions. These benchmarks serve as aspira�onal targets for the design and opera�on of buildings, encouraging stakeholders to adopt cu�ng-edge technologies and prac�ces to achieve beter energy performance. While these values represent good prac�ce, it's important to note that even typical prac�ce benchmarks, such as 70 for electricity and 142 for fossil fuel, can s�ll guide improvements in energy efficiency when compared to conven�onal building standards.

8 Conclusions

With the use of computa�onal fluid dynamics (CFD) and Total Primary Energy Consump�on (TPLP) analysis, the energy efficiency of museum galleries was compared between mixed ven�la�on and displacement ven�la�on. It has been demonstrated that displacement ven�la�on can improve museum galleries' energy efficiency. Displacement ven�la�on can efficiently distribute air and preserve thermal comfort in the gallery areas, according to the CFD analysis. When compared to mixed ven�la�on systems, this may result in less energy being used.

The CFD research also showed that displacement ven�la�on could help keep the interior air quality in museum galleries at a high level. Through displacement ven�la�on, it is possible to produce temperature distribu�on and airflow paterns that preserve artwork and artefacts while minimising the accumula�on of pollutants. The en�re primary energy consump�on of both ven�la�on systems was thoroughly evaluated using the TPLP study. This research provided a comprehensive picture of the energy performance of each system by considering all energy inputs. According to the findings, displacement ven�la�on has the poten�al to use less primary energy overall than mixed ven�la�on.

Figure 33 Annual Energy consumption in displacement ventilation case

Figure 34 Annual Energy consumption in mixed ventilation case

The study acknowledged the well-known drawbacks of displacement ven�la�on, including the development of ver�cal temperature gradients and poten�al difficul�es controlling rela�ve humidity. When crea�ng and using displacement ven�la�on systems in museum galleries, these downsides should be properly considered.

The results can be used to improve to increase thermal comfort, indoor air quality, and energy efficiency of future museum gallery designs while s�ll protec�ng artwork and artefacts. Based on the results of this study, recommenda�ons for displacement ven�la�on design can be created, boos�ng energy efficiency while maintaining air quality in museum galleries.

The findings of the inves�ga�on underscore the pivotal role of ven�la�on strategy selec�on in the quest for op�mal indoor thermal comfort. There’s an opportunity for enhancing ven�la�on system efficiency in various se�ngs by carefully modula�ng airflow rates and strategically designing diffuser layouts. These considera�ons can lead to the preserva�on of thermal comfort standards while concurrently minimizing energy consump�on and opera�onal costs. Further research into the dynamic interplay between occupancy, airflow rates, and diffuser layouts can offer valuable insights for the effec�ve design and management of ven�la�on systems in indoor environments, ul�mately benefi�ng both occupant comfort and energy conserva�on objec�ves.

To further elucidate the underlying mechanisms responsible for these observed dis�nc�ons, a more comprehensive explora�on into the intricacies of fluid dynamics and heat transfer is warranted. This deeper understanding will subsequently inform and enhance the design and implementa�on of ven�la�on systems to beter cater to the diverse needs of occupants in various indoor environments.

9 Table Of Figures

Figure 1 source: (pdf) a computa�onal method for the design explora�on and op�miza�on of dayligh�ng performance of museum buildings (researchgate.net) ....................................................................................................

Figure 2 Source: Energy consump�on of UK arts industries 2021 | Sta�sta

Figure 3 source : Applied Sciences | Free Full-Text | The Interplay between Air

Figure

-Text

Figure 5 source Climate London (Greater London), averages - Weather and Climate (weather-and-climate.com)

Figure

Figure

Figure

Figure 9 reference: allisonclairechang.org

Figure

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I confirm that I understand what plagiarism is and have read and understood Section 10 of the Handbook of Academic Regulations. The work that I have submitted is entirely my own (unless authorised group work). Any work from other authors is duly referenced and acknowledged

STUDENTS

REGISTRATION

MARKER

JOINT ASSIGNMENTS

Tutor’s summary comments and feedback to student(s):

All marks are subject to confirmation by the relevant Subject Board