1. The Benefits of Heat Pipes in Hot & Humid Climates
Allan Westbury
Managing Director
S & P Coils Ltd. Leicester, UK

2. Presentation Contents
Heat Pipes: Heat Recovery & Dehumidification
Presentation Contents
Problems of Hot & Humid Climatic Conditions
What is a Heat Pipe?
Heat Pipes & how they can HELP
Conclusion
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3. Problems of Hot & Humid Climates
Main influences on comfort:
Dry bulb temperature
Air speed
Air humidity
Radiation
Ideal Comfort Conditions:
RH %
Temperature °C ( °F)

4. Proper humidity levels
ASHRAE Recommended
Safety margin
Health Problems
Mildew Growth
% Relative Humidity

5. Typical Ambient conditions
Heat Pipes: Heat Recovery & Dehumidification
Typical Ambient conditions
80% RH
30% RH
20% RH
90% RH
80% RH
30% RH
20% RH
90% RH
80% RH
30% RH
90% RH
These are typical ambient conditions in the Middle and
Far East.
20% RH
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6. Heat Pipes: Heat Recovery & Dehumidification
Comfort conditions
30% RH
80% RH
90% RH
20% RH
Comfort condition,
20 to 24°C,
40 to 70% RH
Air conditioning is required virtually all of the time
to achieve comfort conditions.
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7. Historical Air Conditioning
Examples of wind towers on some older buildings.

8. Modern Air Conditioning

9. Dubai Convention Centre

10. Pyramid Centre

11. Mercato Mall

12. Heat Pipes: Heat Recovery & Dehumidification
Doha – Sheraton Hotel
Modern structures are often built for personal convenience
rather than optimum climatic conditions e.g. a holiday
hotel by the beach resulting in very high humidity levels.
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13. Heat Pipes: Heat Recovery & Dehumidification
Decorative features
Inside the hotel we have a water feature increasing the
humidity.
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14. Heat Pipes: Heat Recovery & Dehumidification
Recent Practice
Air is cooled to supply conditions
Saturated
air, 18°C
Warm humid
air, 42°C
Until recently outside air was just cooled and passed into
the building in a fully saturated state. This was bad for health & felt ‘cold & clammy’.
Condensation
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15. Recent Practice Taking a point in this envelope, 42°C @ 35% RH,
and then cooling to 18°C the air becomes saturated and unsuitable for supply.

16. Recent Practice
If this saturated air with a high moisture content is supplied into the space we will have two major problems:

17. Problem 1
The building occupants will feel very uncomfortable and health problems may arise.
HOTEL
Dissatisfied, unhappy customers and even potential insurance claims.
Reduction in employee efficiency and, at worst, lost working days due to sickness.
OFFICE

18. Problem 2
The building fabric and fittings will deteriorate due to the high moisture levels creating excessive maintenance costs.
This can manifest itself in several ways
Discolouration of walls
Mould growth
Corrosion of metalworks
Detachment of tiles etc. from walls/ceilings

19. Dehumidifying with coils
Heat Pipes: Heat Recovery & Dehumidification
Dehumidifying with coils
Generally the air is overcooled
Comfortable air,
18- 22°C
Warm humid
air, 42°C
More recent practice is to over cool air removing excess
moisture and then re-heat to reduce the relative humidity
to comfortable levels.
Condensation
Reheat Coil
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20. Increase in running costs
Heat Pipes: Heat Recovery & Dehumidification
Increase in running costs
Overcooling the air and then re-heating gives rise
to additional cooling &
heating loads.
Additional Cooling load A
Heating load B
The downside is increased cost. C D
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21. The downside of reheat The cost of reheating the air is high.
It also means we have to include a whole package of extra equipment and controls.

22. Heat Pipes: Heat Recovery & Dehumidification
The pay-off
Overcooling means an increased cooling load = increased running costs.
This in turn means a larger chiller unit = increased capital costs.
Re-heating will require energy.
= increased running costs.
Re-heating also adds equipment and complexity.= increased capital costs.
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23. Heat Pipes: Heat Recovery & Dehumidification
The Economic Solution
So, while the theory is very attractive, the economics present a large deterrent.
Ideally we would like to cool the air to a comfortable temperature and remove moisture, but without the need for expensive reheat.
It sounds impossible, but by using heat pipes it can be achieved.
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24. Heat Pipes: Heat Recovery & Dehumidification
The principle of heat pipe operation
Heat Pipes and dehumidification
Heat Pipes and heat recovery
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25. Heat Pipes: Heat Recovery & Dehumidification
What is a Heat Pipe ?
Heat Pipes: Heat Recovery & Dehumidification
A heat pipe is an extremely efficient conductor of heat.
By using the latent capacity of the fluid the heat pipe transfers heat at a very high rate.
The shape and size of the container is very flexible, the main requirements being that it is impervious and that heat is easily transferred into and out of the working fluid.
The working fluid to be used should be selected such that it will evaporate and condense within the working temperature range of the heat pipe. For HVAC systems, a commercial refrigerant is ideal, preferably a single component, for instance R22 or R134a, or an azeotropic blend. For high temperature heat pipes, metals can be used such as sodium.
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26. Basic principle of operation
Heat Pipes: Heat Recovery & Dehumidification
Basic principle of operation
A simple heat pipe comprises a hollow tube partly filled with a working fluid
Heat
out
Using the latent capacity of the fluid, we can transfer large amounts of heat very rapidly from a hot point to a cold point on the tube wall.
Within the heat pipe, the fluid will be part vapour, part liquid and at a uniform temperature.
If the temperature of the top of the container wall falls below that of the fluid, the fluid vapour will tend to condense at this point and the liquid will then fall to the bottom of the tube where it will evaporate again. This process will continue until the temperature of the container is the same as that of the fluid. In this way, heat will be transferred very rapidly to the cold end of the container.
The heat pipe can operate across a wide range of temperatures as the pressure within the container will vary with changes in the fluid temperature, so continuously modifying the boiling point of the fluid.
Heat in
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27. Summary of Characteristics
Heat Pipes: Heat Recovery & Dehumidification
Summary of Characteristics
Heat is transferred by latent means giving a heat transfer rate of around 1000 times that of a solid copper rod
Vaporisation and condensation take place at the same temperature allowing high heat transfer at low temperature differences
Heat pipes without wicks (Thermosyphons) rely on gravity to return the condensed liquid.
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28. Heat Pipe applications
Heat Pipes: Heat Recovery & Dehumidification
Heat Pipe applications
1.) Heat Pipes for enhanced dehumidification.
Heat pipes should be considered wherever there is a requirement for reheat after the cooling process or where energy usage is a consideration in the design.
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29. Heat Pipes: Heat Recovery & Dehumidification
Adding a Heat Pipe
The heat pipe improves the efficiency of the system.
18°C
42°C
36°C
By adding a Heat Pipe across the air stream we are able
to pre cool incoming air either taking it on, or close to, the
saturation line. When this cooler, more saturated air
hits the cooling coil moisture will be removed. The heat we have removed from the incoming air is then fed back into the outgoing air reheating it and reducing the relative humidity. The pre cool and re heat actions of the Heat Pipe involve no additional energy usage and reduce the load on the cooling coil as well as removing the need for re-heat.
12°C
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30. Heat Pipe in practice Plan view of cooling coil. Heat Pipe pre-cool
Heat Pipe re-heat
Airflow
Cooling
Coil
Airflow
42/28.5°C
36/27.1°C
12/11.8°C
18/14.1°C

31. Heat Pipes: Heat Recovery & Dehumidification
A typical fresh air handling unit will have Heat Pipes wrapped around the cooling coil as shown.
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32. 2-Row ‘Horseshoe’.
‘Horseshoe’ Heat Pipes are used either for original supply or for retrofit applications.
The unit will be installed around an existing cooling coil.

33. Heat Pipes: Heat Recovery & Dehumidification
2-Row ‘Combi Coil’.
Heat Pipes can be supplied separately or combined with AHU cooling coils as shown here.
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34. Heat Pipe Effect 1-2 Heat Pipe pre-cool 2-3 Cooling coil
3-4 Heat Pipe re-heat 2 1
Resultant energy
saving of up to 30%. 3 4

35. Heat Pipes: Heat Recovery & Dehumidification
In Practice
If the heatpipe is designed
for a maximum temperature.
What would the off condition
be at other conditions?
Additional Heating load
If the Heat Pipe is designed for the maximum weather condition it will not operate as effectively at lower temperatures. We solve this problem by designing for the most common condition rather than the maximum.
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36. Heat Pipes: Heat Recovery & Dehumidification
Economic Design
Base design on commonest conditions not maximum conditions.
This in turn means removing need for additional reheat.
For close control some additional cooling may be required.
By designing for the most common condition the most energy efficient solution can be found. While some additional cooling may be required this could be provided very simply by means of either a secondary air handling unit, fan coils or duct mounted coils.
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37. Heat Pipes: Heat Recovery & Dehumidification
Bin Data
By using Bin Data we can identify the commonest or average condition.
Bin data is the hourly dry bulb temperature for a region sorted into a number of ‘bins’. These bins simply show the number of hours in that area that a particular temperature is recorded.
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38. Heat Pipes: Heat Recovery & Dehumidification
Worked Example
Based on average ambient
condition, 32 58% RH.
Cooling load kW
Heating load - 7.2kW
Total load kW
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39. Heat Pipes: Heat Recovery & Dehumidification
Worked Example
Air volume : 4.0 m3/s
Air on: 40/27.8°C, 40%RH
Supply air to room:
20/14.8°C
Add in the Heat Pipe,
Heat Pipe Pre-cool - 7.2kW
Heat Pipe Re-heat - 7.2kW
New Clg load kW
New Htg load - 0kW
Saving 14.4kW
This heat pipe has been designed for the most common condition of 32 degrees.
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40. Heat Pipes: Heat Recovery & Dehumidification
Worked Example
At alternative conditions:
Heat Pipe pre-cool : 9.5 kW
Heat Pipe re-heat : 9.5 kW
If the final air condition is
required at 18 °C, then a
secondary cooling unit
can trim the temperature.
Cooling load kW
Heating load - 0kW
Saving 19kW
AdditionalCooling unit
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42. Heat Pipes: Heat Recovery & Dehumidification
Summary
Requires no energy to run, being “driven” by the cooling coil.
Nett energy savings of around 30% compared to standard cooling and reheat.
Lower cooling load = smaller chiller/ compressor.
Design for average conditions to eliminate reheat.
Easy installation.
Controlled by the cooling coil.
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43. Heat Pipe applications
Heat Pipes: Heat Recovery & Dehumidification
Heat Pipe applications
2.) Heat and “coolth” recovery.
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44. Heat and “coolth” recovery
Used to transfer heat between supply and exhaust air streams where :-
There is a large difference between supply and exhaust temperatures.
There are high air volumes involved.
Efficiencies of up to 65% can be achieved giving significant energy savings.

45. Basic design features
The Heat Pipe unit straddles the supply and exhaust ducts
A centre tube plate prevents cross contamination between airflows
No pump requirement to transfer the heat as with a run around coil system
Airstreams must be in counterflow

46. Heat Pipes: Heat Recovery & Dehumidification
Heat Pipe efficiency
As Heat Pipes are manufactured as coil heat exchangers their efficiency is affected in the same way as any other coil. The main factors being the air velocity and the number of rows of the coil heat exchanger. As a general rule, the lower the velocity the higher the efficiency.
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47. Orientation Available in both vertical & horizontal arrangements.
The warmer airstream must be at the bottom in the vertical mode.
Exhaust Air
Supply Air

48. Horizontal orientation

49. Heat Pipes: Heat Recovery & Dehumidification
Benefits
Requires no energy to run.
No maintenance.
No cross contamination.
Can be sized to suit the ductwork or AHU.
Easy condensation removal.
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50. Conclusion Heat Pipes are extremely efficient heat transfer devices
By installing across supply and exhaust ducts we can recover waste energy.
Typical efficiencies – 50% to 60 %
By wrapping The Heat Pipe around a cooling coil we bypass a certain amount of heat, saving on the cooling load and giving free reheat.
Nett energy savings - around 30 %

51. Heat Pipes: Heat Recovery & Dehumidification
Completed projects
Contractor
Consultant
AHU Supplier
Qty.
Type of Project
Project
Garmco BAH
York
Aluminium Store
Al Hamad - Shj.
Artek
Clever 8
New
Pyramid shopping center
SAS Raddison - Muscat
Saiver 4
Retrofit
Raddison
Thermo - Dubai
Mario & Ass.
SKM 2
Crown Plaza
Al Hamed
GHQ
Carrier 3
MW-1699
Nael Est. - Al Ain
Syna dev.
Hiltonia Beach
Samar Tower- Shj.
Al Ansari Bldg.
Geco - Sharjah
Sharjah Municipality 6
Swimm. Pool
Sensaire - Dubai
Dubai Municipality
Children's City
Majid Al Futtaim
City Center
Verger Delport
W.S. Atkins
145
Industrial city - ADH
Viking
RPW
Al Nahdha Shopping
Sharjah Mega Mall
Al Futtaim
Arab Consultants 1
Sharjah Cricket Stadium
ETA
Spectrum - Delhi
Novair 5
Grand Hayat - Mumbai 37
Le-Meridian - Dubai
Gibca - Sharjah
Petra
Coral Beach Resort
SPC have supplied a number of projects throughout the Middle East over the last four years. Specific references are available on request.
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52. Completed projects (Cont..)
Contractor
Consultant
AHU Supplier
Qty.
Type of Project
Project
Transgulf
RPW
York 8
New
Spinneys - Jumeira
ETA
RMJM
Clever 33
World Convention centre
Geco - Sharjah
Cab - Sharjah
SKM 90
Indoor Sports Hall
B K Gulf
Interklima 6
Sensaire - Dubai
Arif & Bintouk
Carrier
Novotel & Ibis Hotel
Gibca - Sharjah 4
Coral Beach Resort 24
Royal Mirage hotel
Remco
Shadid Engg.
Euroclima
Dubai Women's association
Mekar 30
Exhibition Hall 1 & 2
Al Futtaim
DPA
Aftron 1
DPA club
Emaar bank
Gulf Star - ADH
Pvt. Deptt. 2
pvt. Villa at Jebel Dana
SKM - Sharjah
Ian Banhem
Kharbash Bldg.
Dhabi Contracting
Al Turath 14
Wedding hall
McQuay
Mott / EMS
West Side Marina
FNC
Arkiteknik
Dunham Bush 41
Neighborhood centre
Bu-Haleeba
Gemac
Retrofit
Ruler's villa
Junker
Artek
Dawoodi Bohra center

53. Dehumidification selection
Heat Pipes: Heat Recovery & Dehumidification
Dehumidification selection
The SPC Heat Pipe Dehumidification computer selection program (HPD) allows heat Pipes to be selected for a wide range of conditions. The program also allows a particular Heat Pipe to be rated against different climatic conditions and uses bin data to allow calculations of pay back for a particular climatic area.
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54. Heat Recovery Selection
Heat Pipes: Heat Recovery & Dehumidification
Heat Recovery Selection
The SPC Heat Recovery Selection Program (HPHR) allows Heat Pipes to be selected in a range of climatic conditions to give the required effects of heat recovery. Bin data is included within the program to allow pay back periods to be calculated in different climatic conditions.
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55. Heat Pipes: Heat Recovery & Dehumidification
Any Questions ?
For further information or to download latest copies of our selection software, visit our website:
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56. HEAT PIPES: The Benefits of Heat Pipes in Hot & Humid Climates
Heat Pipes: Heat Recovery & Dehumidification
HEAT PIPES: The Benefits of Heat Pipes in Hot & Humid Climates
Allan Westbury
Managing Director
S & P Coils Ltd. Leicester, UK
S & P Coil Products Ltd

57. Problems of Hot & Humid Climatic Conditions
Main influences on comfort:
Dry bulb temperature
Air speed
Air humidity
Radiation
Ideal Comfort Conditions:
RH %
Temperature °C ( °F)