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7/31/2019 HeatPipesForHot n Humid Climates June04
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The Benefits of Heat Pipes in
Hot & Humid Climates
Allan Westbury
Managing DirectorS & P Coils Ltd.Leicester, UK
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Presentation Contents
Problems of Hot & Humid Climatic
Conditions
What is a Heat Pipe?
Heat Pipes & how they can HELP Conclusion
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Problems of Hot & HumidClimates
Main influences on comfort: Dry bulb temperature
Air speed
Air humidity
Radiation
Ideal Comfort Conditions: RH 40 - 60 %
Temperature 20 - 23C (68 - 75F)
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Proper humidity levels
0 10 20 30 40 50 60 70 80 90 100
Health Problems Mildew Growth
Safety margin
ASHRAE Recommended
% Relative Humidity
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Typical Ambient conditions
35C @ 80% RH
45C @ 30% RH
35C @ 20% RH
20C @ 90% RH
45C @ 30% RH
35C @ 80% RH
20C @ 90% RH
35C @ 20% RH
35C @ 80% RH
45C @ 30% RH
35C @ 20% RH
20C @ 90% RH
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Comfort conditions
45C @ 30% RH
35C @ 80% RH
20C @ 90% RH
35C @ 20% RH
Comfort condition,20 to 24C,
40 to 70% RH
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Historical Air Conditioning
Examples of wind towerson some older buildings.
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Modern Air Conditioning
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Dubai Convention Centre
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Pyramid Centre
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Mercato Mall
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Doha Sheraton Hotel
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Decorative features
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Recent Practice
and then cooling to 18C
the air becomes saturatedand unsuitable for
supply.
Taking a point in this
envelope, 42C @ 35% RH,
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Recent Practice
If this saturated air with a highmoisture content is supplied intothe space we will have two major
problems:
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Problem 1
The building occupants will feel veryuncomfortable and health problems mayarise.
HOTEL
OFFICE
Dissatisfied, unhappycustomers and even potentialinsurance claims.
Reduction in employeeefficiency and, at worst, lostworking days due to sickness.
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Problem 2
The building fabric and fittings will deterioratedue to the high moisture levels creatingexcessive maintenance costs.
This can manifest itself in several ways
Discolouration of walls
Mould growth
Corrosion of metalworks
Detachment of tiles etc. from walls/ceilings
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Generally the air is overcooled
Warm humid
air, 42C
Condensation
Dehumidifying with coils
Comfortable air,
18- 22C
Reheat Coil
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Increase in running costs
Overcooling the air and
then re-heating gives rise
to additional cooling &
heating loads.
A
B
C D
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The downside of reheat
The cost of reheating the air ishigh.
It also means we have toinclude a whole package of
extra equipment and controls.
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The pay-off
Overcooling means an increased coolingload. = 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 andcomplexity.= increased capital costs.
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The Economic Solution
So, while the theory is very attractive, theeconomics present a large deterrent.
Ideally we would like to cool the air to a
comfortable temperature and removemoisture, but without the need for expensivereheat.
It sounds impossible, but by using heatpipes it can be achieved.
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Heat Pipes
The principle of heat pipe operation
Heat Pipes and dehumidification
Heat Pipes and heat recovery
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What is a Heat Pipe ?
A heat pipe is an extremely efficientconductor of heat.
By using the latent capacity of the fluid the
heat pipe transfers heat at a very high rate.
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Summary of Characteristics
Heat is transferred by latent means giving aheat transfer rate of around 1000 times thatof a solid copper rod
Vaporisation and condensation take place atthe same temperature allowing high heattransfer at low temperature differences
Heat pipes without wicks (Thermosyphons)rely on gravity to return the condensedliquid.
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Heat Pipe applications
1.) Heat Pipes for enhanced
dehumidification.
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Adding a Heat Pipe
The heat pipe improves the efficiency of thesystem.
42C 36C 12C
18C
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Heat Pipe in practice
Plan view of cooling coil.
Airflow
42/28.5C
Heat Pipe
pre-cool
36/27.1C
Cooling
Coil
12/11.8C
Heat Pipe
re-heat
18/14.1C
Airflow
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42 / 28.5
oC
36 / 27.1oC
12 / 11.8oC
18 / 14.1oC
Airflow
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2-Row Horseshoe.
Horseshoe Heat Pipes
are used either fororiginal supply or for
retrofit applications.
The unit will be
installed around anexisting cooling coil.
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2-Row Combi Coil.
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Heat Pipe Effect
1-2 Heat Pipe pre-cool
2-3 Cooling coil
3-4 Heat Pipe re-heat12
43
Resultant energy
saving of up
to 30%.
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If the heatpipe is designed
for a maximum temperature.
What would the off condition
be at other conditions?
In Practice
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Economic Design
Base design on commonestconditions notmaximum conditions.
This in turn means removing need foradditional reheat.
For close control some additional coolingmay be required.
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Bin Data
By using Bin Data we can identify thecommonest or average condition.
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Worked Example
Based on average ambient
condition, 32 C @ 58% RH.
Cooling load - 51.3kW
Heating load - 7.2kWTotal load - 58.5kW
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Air volume : 4.0 m3/s
Air on: 40/27.8C, 40%RH
Supply air to room:
20/14.8C
Worked Example
Add in the Heat Pipe,
Heat Pipe Pre-cool - 7.2kW
Heat Pipe Re-heat - 7.2kW
New Clg load - 44.1kWNew Htg load - 0kW
Saving 14.4kW
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Cooling load - 54.3kWHeating load - 0kW
Worked Example
At alternative conditions:Heat Pipe pre-cool : 9.5 kWHeat Pipe re-heat : 9.5 kW
Saving 19kW
If the final air condition is
required at 18 C, then a
secondary cooling unit
can trim the temperature.
Secondary Cooling Schematic
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Fan Coil Unit
Air Handling Unit
Duct Mounted Coil
38 / 27.5oC
(45% RH)
19.5 / 14.5oC
(60%RH)
18 / 14oC
(65% RH)
Primary Cooling Secondary Cooling
Secondary Cooling Schematic
18 / 14oC
(65% RH)
18 / 14oC
(65% RH)
FAHU
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Summary
Requires no energy to run, being driven bythe cooling coil.
Nett energy savings of around 30% comparedto 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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Heat Pipe applications
2.) Heat and coolth recovery.
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Heat and coolth recovery
There is a large difference between supplyand exhaust temperatures.
There are high air volumes involved.
Used to transfer heat between supplyand exhaust air streams where :-
Efficiencies of up to 65% can be achieved
giving significant energy savings.
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Basic design features
The Heat Pipe unit straddles the supply andexhaust 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
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Orientation
Available in bothvertical & horizontalarrangements.
The warmerairstream must be atthe bottom in the
vertical mode.
Exhaust Air
Supply Air
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Horizontal orientation
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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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Conclusion
Heat Pipes are extremely efficient heattransfer devices
By installing across supply and exhaust ductswe can recover waste energy.
Typical efficiencies 50% to 60 %
By wrapping The Heat Pipe around a coolingcoil we bypass a certain amount of heat,
saving on the cooling load and giving freereheat.
Nett energy savings - around 30 %
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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 Retrofit Crown Plaza
Al Hamed GHQ Carrier 3 Retrofit MW-1699
Nael Est. - Al Ain Syna dev. Clever 4 New Hiltonia Beach
Al Hamad - Shj. Clever 2 New Samar Tower- Shj.
Al Hamad - Shj. Clever 2 New Al Ansari Bldg.
Geco - Sharjah Sharjah Municipality SKM 6 New Swimm. Pool
Sensaire - Dubai Dubai Municipality Clever 3 New Children's City
Majid Al Futtaim Saiver 2 Retrofit City Center
Verger Delport W.S. Atkins York 145 New Industrial city - ADH
Viking RPW Viking 2 New Al Nahdha Shopping
Viking RPW Viking 2 New Sharjah Mega Mall
Al Futtaim Arab Consultants SKM 1 New Sharjah Cricket Stadium
ETA Spectrum - Delhi Novair 5 New Grand Hayat - Mumbai
Carrier Carrier 37 Retrofit Le-Meridian - DubaiGibca - Sharjah Petra 1 Retrofit Coral Beach Resort
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Completed projects (Cont..)
Contractor Consultant AHU Supplier Qty.Type of
Project Project
Transgulf RPW York 8 New Spinneys - Jumeira
ETA RMJM Clever 33 New World Convention centre
Geco - Sharjah Cab - Sharjah SKM 90 New Indoor Sports Hall
B K Gulf RMJM Interklima 6 New World Convention centre
Sensaire - Dubai Arif & Bintouk Carrier 8 New Novotel & Ibis Hotel
Gibca - Sharjah Clever 4 New Coral Beach Resort
Transgulf RPW York 24 New Royal Mirage hotel
Remco Shadid Engg. Euroclima 6 New Dubai Women's association
Mekar RMJM Mekar 30 New Exhibition Hall 1 & 2
Al Futtaim DPA Aftron 1 New DPA club
Carrier Shadid Engg. Carrier 1 New Emaar bank
Gulf Star - ADH Pvt. Deptt. SKM 2 New pvt. Villa at Jebel Dana
SKM - Sharjah Ian Banhem SKM 8 New Kharbash Bldg.
Dhabi Contracting Al Turath Clever 14 New Wedding hall
McQuay Mott / EMS McQuay 6 New West Side Marina
FNC Arkiteknik Dunham Bush 41 New Neighborhood centre
Bu-Haleeba Gemac Mekar 2 Retrofit Ruler's villaJunker Artek Junker 8 New Dawoodi Bohra center
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Dehumidification selection
S
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Heat Recovery Selection
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Any Questions ?
For further information or to download latestcopies of our selection software, visit our
website:
www.spcoils.co.uk
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HEAT PIPES:
The Benefits of Heat Pipes in Hot & Humid Climates
Allan Westbury
Managing Director
S & P Coils Ltd. Leicester, UK
Problems of Hot & Humid Climatic Conditions
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Problems of Hot & Humid Climatic Conditions
Main influences on comfort: Dry bulb temperature
Air speed
Air humidity Radiation
Ideal Comfort Conditions: RH 40 - 60 %
Temperature 20 - 23C (68 - 75F)