STUDY: EXTREME AMBIENT CONDITIONS

INTRODUCTION We are regularly confronted with specifications that refer to extreme conditions that can never occur in reality, leading to expensive, unnecessarily large and uneconomic installations that require a lot of room, energy and weight.

To get at the truth, research has been done in areas around the Equator where the most severe conditions are found and reliable measurements were taken. We first looked at the years from 2005 to the present. After that, we verified this by comparing the figures for the period from 2004 and further back. We have tried to find as much information on this as possible and then narrow things down to the main issues.

We have been able to uncover this information via the Google search site on the internet. This led to a site such as www.wunderground.com. Here we found temperature and atmospheric humidity measurements taken in recent years. They can be accurately called up on an hourly basis.

TABLE OF CONTENTS INTRODUCTION ..................................................................................................................................... 2 TABLE OF CONTENTS .......................................................................................................................... 3 1. CLIMATE INFORMATION WORLDWIDE ........................................................................................... 4 FIRST CONLCUSION................................................................................................................................ 4 2. SUMMARY CLIMATE INFORMATION 2005 MEASURED IN ABU-DHABI ........................................ 5 SECOND CONLCUSION ............................................................................................................................

5

3. DAY OVERVIEW OF MEASUREMENTS MEASURED IN ABU DHABI ON A HOT DAY ................... 6 4. COMBINATION TEMPERATURE AND RELATIVE HUMDITY ........................................................... 8 AVERAGE HIGHEST ENTHALPY ....................................................................................................... 8 5. FINAL CONCLUSIONS ...................................................................................................................... 9

1. CLIMATE INFORMATION WORLDWIDE Higher values measured H-value (enthalpy) NB.

Country

City

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

Australia India Philippines Hawaii Arab Emirates Brazil Peru Curacao USA Singapore Saudi Arabia

Darwin Bombay Manila Hilo Abu Dhabi Fortaleza Chiclayo Curacao Los Angeles Singapore Jeddah

°C

RH%

H

Date

28 32 39 27,2 36 34 36 35 37,2 26 36

79 38 57 65 75 56 41 53 35 94 60

79.6 63.8 109.1 67.4 114.5 85.7 78.1 86.7 75.6 80.6 98.3

Nov-05 March-06 Nov-05 Nov-05 Aug-05 Jan-06 March-06 Jul-05 Jul-06 March-06 Jun-06

°C= Temperatures in degrees centigrade RH%= Relative Humidity in % H= Energy content in the air Kilojoules per kilogram. (enthalpy) FIRST CONLCUSION We produced a print-out of all days with a high enthalpy in Abu Dhabi in June-September.

The figures showed July and August stood out because of their high enthalpy. Severe conditions were observed several times. However, some of these represented only peaks.

This means that a high enthalpy may occur at the end of the day for one to two hours. The rest of the days have an enthalpy that is mostly lower. There are also times that the enthalpy is quite constant for successive days.

Temperatures are a lot higher in July and August than in the rest of the year. Especially early in the day but also at the end of the day, humidity increases. This higher humidity is accompanied by lower temperatures. The most severe conditions are shown in a table. This table shows the highest H values (enthalpy) in 2005 until today measured in ABU DHABI.

2. SUMMARY CLIMATE INFORMATION 2005 MEASURED IN ABU-DHABI Date

Time

Temp (°C)

RH (%)

H (KJ/Kg)

7-6-2005 22-6-2005 23-6-2005 9-7-2005 10-7-2005 12-7-2005 23-7-2005 25-7-2005 26-7-2005 1-8-2005 2-8-2005 3-8-2005 4-8-2005 5-8-2005 8-8-2005 17-8-2005 31-8-2005 4-9-2005 8-9-2005 18-9-2005 19-9-2005

20:00 17:00 15:00 15:00 15:00 19:00 23:00 14:00 0:00 18:00 20:00 23:00 21:00 22:00 18:00 21:00 19:00 23:00 21:00 23:00 19:00

32 36 39 37 36 37 34 39 34 36 34 33 33 33 36 34 34 31 33 31 34

84 67 57 60 67 63 75 60 79 71 79 84 79 84 75 75 71 84 75 75 71

101.9 105.8 109.1 102.9 105.8 106.4 103.9 112.9 107.8 110.2 107.8 107.1 102.5 107.1 114.5 103.9 100 96.8 98.9 96.8 100

°C= Temperatures in degrees centigrade RH%= Relative Humidity in % H= Energy content in the air Kilojoules per kilogram. (enthalpy)

SECOND CONLCUSION To be able to ascertain the correctness of the recent data, we have also looked at the figures for the period 1996-2004. Again, we looked for the most severe conditions in this period and put them into a table. Because our earlier study showed that the most severe conditions occur in July and August, we compared the data for these months in recent years and it became quickly clear that they barely differ.

This means that the period from 2005 is a reliable indicator and can be used as a starting point.

3. DAY OVERVIEW OF MEASUREMENTS MEASURED IN ABU DHABI ON A HOT DAY

The highest temperature and highest humidity are often used to calculate the enthalpy of a day. However, this is not the right procedure, both measurements have to be taken at the same time. The enthalpy is determined by the combination of the humidity and the temperature measured at the same time.

We put a hot day in Abu Dhabi in a diagram and table:

Time 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00

Temp (°C) 31 31 29 28 29 28 28 29 32 36 39 42 44 44 43 41 40 38 36 35 34 33 33 32

RH (%) 70 66 74 70 62 66 62 48 36 28 21 14 11 12 14 23 27 35 53 55 67 75 75 79

H (KJ/Kg) 85.5 82.3 80.2 73.5 71.7 70.8 68.2 61.9 61.3 64.6 64.3 61.8 61.3 62.9 63.9 77.4 74.4 78.1 90.7 88.7 96.2 98.9 98.9 97.5

Control list 1996-2004 measured in Abu Dhabi: Date

Time

Temp (°C)

RH (%)

H (KJ/Kg)

18-7-2004 27-7-2004 8-8-2004 25-8-2004 13-7-2003 17-7-2003 19-8-2003 28-8-2003 11-7-2002 18-7-2002 6-8-2002 11-8-2002 24-7-2001 25-7-2001 21-8-2001 23-8-2001 29-7-2000 31-7-2000 10-8-2000 11-8-2000 11-7-1999 22-7-1999 12-8-1999 27-8-1999 19-7-1998 31-7-1998 21-8-1998 27-8-1998 28-7-1997 31-7-1997 12-8-1997 17-8-1997 14-7-1996 15-7-1996 13-8-1996 14-8-1996

20:00 22:00 22:00 22:00 20:00 18:00 22:00 23:00 20:00 20:00 21:00 1:00 21:00 3:00 20:00 20:00 23:00 22:00 20:00 19:00 20:00 20:00 9:00 1:00 20:00 21:00 23:00 22:00 15:00 19:00 23:00 19:00 19:00 2:00 19:00 22:00

35 35 34 34 35 38 33 33 34 34 34 33 35 34 34 34 33 33 35 36 34 35 34 34 36 35 33 34 39 35 33 34 36 33 35 32

71 71 79 71 75 60 84 84 75 79 84 79 75 79 75 79 79 75 76 67 75 71 75 79 71 71 79 75 57 71 84 79 75 89 75 84

105 105 107.8 100 109.1 107.8 107.1 107.1 103.9 107.7 112.6 102.5 109.1 107.7 103.9 107.7 102.5 98.9 110.1 105.8 103.9 105 103.9 107.8 110.2 105 102.5 103.9 109.1 105 107.1 107.8 114.5 111.7 109 101,9

°C= Temperatures in degrees centigrade RH%= Relative Humidity in % H= Energy content in the air Kilojoules per kilogram. (enthalpy)

4. COMBINATION TEMPERATURE AND RELATIVE HUMDITY What stands out in the diagram is that the temperature and humidity is inversely proportional to each other. To get a good picture of how this process takes place on a day, it is explained by way of the diagram and the table. When the temperature rises, it becomes quickly clear that the humidity drops. Once the temperature has reached its maximum, the humidity is at its lowest.

Theoretical this process runs in exactly the same way. We found this in documents of ASHRA air conditioning systems”. The diagram gives a rough picture of how the temperature (blue line) and the humidity (red line) are inversely proportional to each other. We came to the same conclusion in our own study, meaning our findings were correct.

AVERAGE HIGHEST ENTHALPY The average highest enthalpy we found in this study was about 108 KJ/Kg. To get an idea of how high this value really is and what it can be compared to, we produced a comparative table whereby the combination of temperature and humidity had a value of about 108 KJ/Kg. Therefore, the highest value we found in the hottest parts of the world can be referred back to the table below.

Enthalpy ± 108 KJ/Kg Temp. (°C)

Rel. Hum. (%)

32.1 33 34 35.1 36 37 38.1 39.1 40.1 41.2 42 43 44 45 46.2 47 48.3 49.3 50.3 51.4 52

98 92 86 80 75 70 65 61 57 53 50 47 44 41 38 36 33 31 29 27 26

5. FINAL CONCLUSIONS Both by own extensive study and the measurements that have been taken (by others) we can now say with near-certainty that outside conditions of more than 35° and 80% RH or 40°C-55% RH or 45°C- 40% RH do not exist and are impossible.

Only even a few moments every year these values occur, in what is possibly the hottest part of the world (near the sea). So, when clients claim that an AC installation has to meet much more severe conditions, then this is incorrect based on the values that have been measured. Of course you do have to take into account that the thermal load (transmission heat) for a ship will be considerably lower at under 35°C than at 45°C. The study applies solely to inflow condition in relation to a cooling block in the air-treament (LBH) cabinet.

During our study, we only looked at peak moments on a day. It is often the case that (just) before or after these peak moments, conditions are more favourable from a cooling technical point of view.

What also stands out is that the highest enthalpy and relative humidity are often measured early in the evening or sometimes at night. At those times, the influence of the sun is obviously minimal.

In other words, we feel we can safely assert that on a ship where the accommodation is at temperature and there is a brief peak in the load, the cooling installation will not encounter any immediate problems because this is just a brief random moment in time.

The ISO 7547 adheres to the values of 35° and 70% RH. It also says humidity must never be less than 40%.

In our study area however, these values are higher, so it is more realistic to assume the following maximum outside conditions for an installation with a worldwide destination: 35° and 80% RH 40° and 55% RH 45° and 40% RH