FluidFlow
GREEN SHIP CASE STUDY ©Flite Software 2016
FluidFlow Green Ship Case Study
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1
Introduction ................................................................................................................................................... 2
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System Description ........................................................................................................................................ 3
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Project Overview............................................................................................................................................ 5
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Case Study Analysis ........................................................................................................................................ 6
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Conclusion .................................................................................................................................................... 11
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References ................................................................................................................................................... 13
Appendices ........................................................................................................................................................... 15 Appendix 1: Consumption and CO2 Calculation.................................................................................................... 16 Appendix 2: Conditions at Sea – 100% (SMCR) Main Engine Load – Tropical Condition...................................... 17 Appendix 3: Conditions at Sea – 100% (SMCR) Main Engine Load – Tropical Condition...................................... 18 Appendix 4: Case 1-1 Seawater Cooling System. .................................................................................................. 19 Appendix 5: Case 1-2 Seawater Cooling System. .................................................................................................. 20 Appendix 6: Case 2 Seawater Cooling System. ..................................................................................................... 21 Appendix 7: Case 3 Seawater Cooling System. ..................................................................................................... 22 Appendix 8: Case 4-1 Seawater Cooling System. .................................................................................................. 23 Appendix 9: Case 4-2 Seawater Cooling System. .................................................................................................. 24 Appendix 10: Case 4-3 Seawater Cooling System. ................................................................................................ 25 Appendix 11: Case 4-4 Seawater Cooling System. ................................................................................................ 26 Appendix 12: Case 4-5 Seawater Cooling System. ................................................................................................ 27 Appendix 13: Case 4-6 Seawater Cooling System. ................................................................................................ 28
FluidFlow Green Ship Case Study
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1 Introduction This case study is based on a report prepared by Grontmij Carl Bro, APV & DESMI in 2008. The co-operation between DESMI, APV and Grontmij Carl Bro was established in 2007 due to the increased demands for reduction of the CO 2 emissions from ships to the environment. This collaboration was initiated in an attempt to optimize auxiliary service systems on board ships by combining the designer’s knowledge with practical experience. The optimization study was focused on reducing the power required for the circulation pumps and as such, reducing the CO2 emissions to the environment. The partners involved in the study focused on the seawater cooling system. The vessel selected for the study was a bulk carrier which is very similar to many other vessel types and in that way, the conclusion of the study outlined in this report can be easily adapted for other similar new and existing vessels.
Figure 1.1: Green Ship Bulk Carrier Vessel.
Testimonial: “MAN Diesel & Turbo’s activities in the power plant sector are based on a wellestablished range of diesel engines and a rapidly growing gas engine offering. The products range from small emergency power generators to turnkey power plants with outputs of up to 400 MW. We use the liquid, gas, and two-phase modules of FluidFlow and make extensive use of its simulation capabilities for engineering sub systems as fuel gas lines or cooling water pressure systems, including for the development of new systems. Before we bought we carried out extensive product research and chose FluidFlow because of its completeness and value for money. We have had to make occasional technical support calls and have been impressed by the responsiveness. We have found Flite Software NI Ltd to be extremely knowledgeable and helpful, really excellent.” Norman Kurth, System Engineering, MAN Diesel & Turbo, Germany.
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2 System Description Cooling systems are one of the largest energy consumers on board a vessel and optimizing the design of these systems can lead to significant energy savings. This document will describe a study which was completed using FluidFlow software to achieve higher cooling water system efficiency and lower CO2 emissions.
Figure 2.1: Bulk Carrier Seawater Cooling System.
The system as outlined in Figure 2.1 includes three circulating pumps (two rated at 50% of the specified flow and one rated at 50% as a standby pump). The two operational pumps draw seawater from a common manifold pipe system which is connected to a low sea chest and high sea chest. The seawater is discharged from the seawater pumps through the two parallel-connected coolers and overboard to the sea.
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The system with three 50% capacity pumps has been used in this study as this is the most common approach to design the system and because it ensures flexible and reliable operation of the system.
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3 Project Overview A model of the cooling water system for the 35,000 DWT bulk carrier was developed in FluidFlow. The software was used to complete a series of calculations for four different operating scenarios. The four conditions considered were as follows; Case No.
Description
Case 1:
Calculation of the existing existing pumps and coolers.
Case 2:
As Case 1 above with the exception of a new optimized centrifugal pump.
Case 3
Solution with on a new cooler based on 2 x 50% of the cooling load as opposed to 2 x 65% cooling capacity combined with a new optimized pump corresponding to the new coolers. Calculations with optimized coolers in respect of low pressure drop combined with a new optimized pump corresponding to the new coolers.
Case 4:
final
design
including
All calculations and evaluations have been completed using FluidFlow which is a powerful design and simulation tool for piping systems. This facilitated quick and effective evaluations regarding for example, pressure loss calculations, optimal pump selection and pump cavitation control. Specification of Operating Conditions All of the evaluated cases considered in this document have been based on the same set of operating conditions, i.e. seawater temperatures, pipe diameters, equipment positions etc. Filter:
Inline seawater filter fitted to pump suction side.
Pump Running Time:
365 days per annum.
Pipes:
Normal steel pipe. DIN sizes.
Calculation:
Operating conditions used in the FluidFlow calculation: Ambient seawater temperature: Fresh water temperature out: Inlet location: Outlet location: Location of pumps: Location of coolers: Vessel draft:
FluidFlow Green Ship Case Study
32oC. 36oC. 2.5m above 6.0m above 3.5m above 9.5m above 7.0m above
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4 Case Study Analysis Case Study 1: This case is based on the original design of the seawater cooling water system from a preliminary specification with no specific knowledge of flow resistance for coolers, filters and elevation location of each component. This system was not optimized in the detailed production design by the shipyard when the system-related equipment and hydrostatic pressure heights were known. Furthermore, the pump was bought as a standard stock pump. This practice of using a “first qualified guess� as the final specification for the purchase of pumps and equipment was not uncommon. The coolers were selected with a cooling water heat transfer capacity of 2 x 65% of the total heat transfer requirement (mainly by the engine and auxiliary engines). This capacity was estimated by the designer and multiplied by an estimated load factor. Equipment Specification: Pumps:
3 x 230 m3/h at 3.0 barg.
Coolers:
2 x 4251 kW heat exchangers (cooling capacity based on cooling consumer load balance, Tropical Conditions). Appendix 2 provides an overview of the conditions at sea. Seawater flow based on the preliminary chosen pump capacity. Flow resistance for cooler is stated as 0.87 bar at 230 m3/h.
Results: Two scenarios have been considered where the two centrifugal pumps are in operation. The first scenario is described in 4-1 and the second scenario is outlined in 4-2. 4-1
The operator tries to maintain each of the pumps at the flow rate of 230 m3/h. To achieve this operating condition, it is necessary to throttle the discharge valves or insert an orifice due to the fact that the system pressure is lower that the specified operation point at 3.0 barg. In this scenario the mechanical power associated with the duty point of each pump is 25.85 kW which corresponds to the results outlined below: Fuel consumption (ts/annum/pump): CO2 Emissions (ts/annum): Running Cost (USD/annum):
FluidFlow Green Ship Case Study
51.30 159.6 32,807
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4-2
The operator lets each of the pumps operate at the system pressure. The pump duty point is very close to “run out� of its capacity curve and delivers approximately 321 m3/h seawater at 2.4 bar. In this scenario, mechanical power associated with the duty point of each pump is 29.09 kW which corresponds to the results outlined below: Fuel consumption (ts/annum/pump): CO2 Emissions (ts/annum): Running Cost (USD/annum):
57.70 179.6 36,919
The results described above will be used for comparison purposes when considering the remaining design cases. Note, Appendix 1 provides an overview of the results for the different cases under consideration. Case Study 2: In this scenario, the same cooler as specified in Case 1 was utilized in order to evaluate the reduction of the power consumption when changing the pump head and optimizing the pump efficiency to the system. The new pumps have been chosen that operate at the specified pressure. This means that throttling valves or orifices are not required to maintain the pump at the specified operating point. Equipment Specification: Pumps:
3 x 230 m3/h at 1.2 barg.
Coolers:
2 x 4251 kW heat exchangers (cooling capacity based on cooling consumer load balance, Tropical Conditions). Figure 4.1 provides an overview of the conditions at sea. Seawater flow based on the preliminary chosen pump capacity. Flow resistance for cooler is stated as 0.87 bar at 230 m 3/h.
Results: Based on these conditions, the mechanical power at the duty point for each pump was 9.89 kW corresponding to the following values: Fuel consumption (ts/annum/pump): CO2 Emissions (ts/annum): Running Cost (USD/annum):
19.6 61.0 12,545
The total saving compared to Case Study 1 was estimated to be 66%.
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Case Study 3: In Case 3, the total cooling capacity has been reduced from 2 x 65% to 2 x 50%. After reducing the total duty to 2 x 50%, each cooler still has a built in heat transfer coefficient margin of 15%. The 15% reduction of the heat transfer coefficient corresponds to a 15% reduction in K value. Using this approach, the cooler is allowed to operate at a lower flow/pressure drop condition as we have excluded the 15% safety margin. This has an effect on the fuel consumption and resultant CO2 emissions. Equipment Specification: Pumps:
3 x 205 m3/h at 0.9 barg.
Coolers:
2 x 3270 kW heat exchangers (cooling capacity based on cooling consumer load balance, Tropical Conditions). Appendix 3 provides an overview of the conditions at sea. Flow resistance for cooler is stated as 0.69 bar at 205 m3/h.
Results: Based on these conditions, the mechanical power at the duty point for each pump was calculated to be 6.8 kW which corresponds to the following values: Fuel consumption (ts/annum/pump): CO2 Emissions (ts/annum): Running Cost (USD/annum):
13.48 42.0 8,630
The total saving compared with: Case 1: Case 2:
77%. 31%.
Case Study 4: In Case 2 and 3, significant savings had been identified. In case 4, consideration was given to the optimization of the coolers with regard to pressure drop, the annual system operating costs, CO2 emissions and system capital cost. The purpose of Case Study 4 was to determine the optimum between initial installation costs and operational costs.
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Equipment Specification: The study required that the following six scenarios were considered. Scenario Scenario 4-1 Pumps: Coolers:
Scenario 4-2 Pumps: Coolers:
Scenario 4-3 Pumps: Coolers:
Scenario 4-4 Pumps: Coolers:
Scenario 4-5 Pumps: Coolers:
Scenario 4-6 Pumps: Coolers:
Description
Pump Mechanical Power
3 x 180 m3/h at 0.4 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.2 bar.
2.69 kW
3 x 180 m3/h at 0.5 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.3 bar.
3.46 kW
3 x 180 m3/h at 0.6 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.4 bar.
4.11 kW
3 x 180 m3/h at 0.7 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.5 bar.
4.66 kW
3 x 180 m3/h at 0.8 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.6 bar.
5.21 kW
3 x 180 m3/h at 0.9 barg. 2 x 3270 kW heat exchangers. Seawater flow of 180 m3/h. Pressure drop 0.7 bar.
5.84 kW
Results: It was clear from the results of the simulations that a cooler with a pressure drop of 0.2 bar (scenario 4-1) was the most optimized seawater cooling water system with regard to low yearly operating costs and a very low CO2 emission to the environment. The necessary power for scenario 4-1 corresponds to the following: Fuel consumption (ts/annum/pump): CO2 Emissions (ts/annum): Running Cost (USD/annum):
FluidFlow Green Ship Case Study
5.33 16.1 3,414
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The total savings for scenario 4-1 compared with: Case Study 1: Case Study 2: Case Study 3:
91%. 73%. 60%.
It is worth noting that the cooler with a lower pressure drop is a larger cooler and as such had a more expensive capital cost.
Figure 4.1: Case Study 4 – Accumulated Running Cost + Installation Cost
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5 Conclusion When designing cooling water system, the pressure drop of the cooler plant is essential. The cooler has a significant impact on the overall system pressure in that, it is the single component of a sea water system which causes the highest resistance. Consequently, it has a significant impact on the overall system pressure and in as a result, facilitates the installation of smaller pumps. This in turn contributes to a reduction in the fuel consumption and the resultant CO2 emissions. This is often a sensible solution as the overall costs (purchase + operating costs) are reduced as well as the environmental impact. Historical studies have shown that it is possible to save up to 90% of the energy required to run the pumps in this type of system by installing the correct combination of pumps and coolers. 90% of the pump energy equals approximately 10% of the total generated electrical power on board or more than 160 tons of CO2 per year per pump. The following summarizes the results for the various studies: Case Study 1-2:
Fuel Consumption/ CO2 emissions (ts/annum):
57.7/179.6.
Case Study 3:
Fuel Consumption/ CO2 emissions (ts/annum):
13.48/42.
Case Study 4-1:
Fuel Consumption/ CO2 emissions (ts/annum):
5.33/16.6.
Figure 5.1: Accumulated CO2 emissions for two pumps operating.
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The overall costs (purchase + operating costs) indicate that the installation of coolers with a very low pressure drop is a good investment both for low overall costs and for the environment. The following graph details the accumulated cost based on three pumps and two coolers (only two pumps operating).
Figure 5.2: Accumulated Cost.
Points for Consideration: 1. An additional benefit of the low pressure design solution is that there will be reduced erosion on piping and fittings as well as less stress on components. This combined with the fact that a low pressure drop on the sea water cooler side corresponds with a reduced pressure drop on the fresh water side. This allows for smaller pumps to be selected for both systems which helps contribute to a shorter investment payback period for the plant. 2. It is important that the pumps selected are high efficiency pumps. 3. A helpful tip is to let the pump specification remain open until the pipe system has been designed in detail and all components are well defined including positioning, pipe lengths, quantity of bends etc. This ensures the pump can be optimised to match the system pressure profile. FluidFlow has the advantage of allowing you to set your design flow rate/pressure rise for your system and the software will determine the pump performance requirements automatically.
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6 References 1. Optimisation of pump and cooling water systems by: DESMI Tagholm 1 DK-9400 Norresundby Denmark Grontmij Carl Bro Granskoven 8 DK-2600 Glostrup Denmark APV Heat Transfer Platinvej 8 DK-6000 Kolding Denmark 2. Green Ship Magazine. 3. FluidFlow (Pipe Flow Software) – www.fluidflowinfo.com
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Contact us at: support@fluidflowinfo.com Flite Software NI Ltd Block E Balliniska Business Park Springtown Road Derry Northern Ireland BT48 0LY T: +44 2871 279 227 F: +44 2871 279 806 Toll Free: +1 888 711 3051 www.fluidflowinfo.com
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Appendices
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Appendix 1: Consumption and CO2 Calculation.
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Appendix 2: Conditions at Sea – 100% (SMCR) Main Engine Load – Tropical Condition.
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Appendix 3: Conditions at Sea – 100% (SMCR) Main Engine Load – Tropical Condition.
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Appendix 4: Case 1-1 Seawater Cooling System.
Average Duty Power:
25.85 kW.
Average Duty Efficiency: 74.3 %.
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Appendix 5: Case 1-2 Seawater Cooling System.
Average Duty Power:
29.09 kW.
Average Duty Efficiency: 76.0 %.
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Appendix 6: Case 2 Seawater Cooling System.
Average Duty Power:
9.87 kW.
Average Duty Efficiency: 78.88 %.
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Appendix 7: Case 3 Seawater Cooling System.
Average Duty Power:
6.8 kW.
Average Duty Efficiency: 79.5 %.
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Appendix 8: Case 4-1 Seawater Cooling System.
Average Duty Power:
2.69 kW.
Average Duty Efficiency: 77.8 %.
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Appendix 9: Case 4-2 Seawater Cooling System.
Average Duty Power:
3.46 kW.
Average Duty Efficiency: 76.9 %.
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Appendix 10: Case 4-3 Seawater Cooling System.
Average Duty Power:
4.11 kW.
Average Duty Efficiency: 77.0 %.
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Appendix 11: Case 4-4 Seawater Cooling System.
Average Duty Power:
4.66 kW.
Average Duty Efficiency: 78.9 %.
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Appendix 12: Case 4-5 Seawater Cooling System.
Average Duty Power:
5.21 kW.
Average Duty Efficiency: 79.9 %.
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Appendix 13: Case 4-6 Seawater Cooling System.
Average Duty Power:
5.84 kW.
Average Duty Efficiency: 80.7 %.
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