The Benefits of Heat Pipes in Hot

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• The Benefits of Heat Pipes in Hot Humid
  Climates

Allan Westbury Managing Director S 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 Humid Climates

• 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
Relative Humidity
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Typical Ambient conditions
35C _at_ 80 RH 45C _at_ 30 RH 35C _at_ 20 RH 20C _at_
90 RH
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Comfort conditions
Comfort condition, 20 to 24C, 40 to 70 RH
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Historical Air Conditioning

• Examples of wind towers on 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

• Air is cooled to supply conditions

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Recent Practice
Taking a point in this envelope, 42C _at_ 35 RH,
and then cooling to 18C the air becomes
saturated and unsuitable for supply.
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Recent Practice

• If this saturated air with a high moisture
  content is supplied into the space we will have
  two major problems

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Problem 1

• The building occupants will feel very
  uncomfortable and health problems may arise.

Dissatisfied, unhappy customers and even
potential insurance claims.
Reduction in employee efficiency and, at worst,
lost working days due to sickness.
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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

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Dehumidifying with coils

• Generally the air is overcooled

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 is high.
• It also means we have to include a whole package
  of extra equipment and controls.

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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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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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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 efficient conductor
  of heat.
• By using the latent capacity of the fluid the
  heat pipe transfers heat at a very high rate.

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Basic principle of operation
A simple heat pipe comprises a hollow tube partly
filled with a working fluid
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.
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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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Heat Pipe applications

• 1.) Heat Pipes for enhanced dehumidification.

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Adding a Heat Pipe

• The heat pipe improves the efficiency of the
  system.

12C
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Heat Pipe in practice

• Plan view of cooling coil.

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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.

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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-heat
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2
Resultant energy
saving of up to 30.
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3
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In Practice
If the heatpipe is designed for a maximum
temperature. What would the off condition be at
other conditions?
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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.

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Bin Data

• By using Bin Data we can identify the commonest
  or average condition.

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Worked Example
Based on average ambient condition, 32 C _at_ 58
RH. Cooling load - 51.3kW Heating load -
7.2kW Total load - 58.5kW
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Worked Example
Air volume 4.0 m3/s Air on 40/27.8C,
40RH Supply air to room 20/14.8C
Add in the Heat Pipe, Heat Pipe Pre-cool -
7.2kW Heat Pipe Re-heat - 7.2kW New Clg load -
44.1kW New Htg load - 0kW Saving 14.4kW
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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 - 54.3kW Heating load - 0kW
Saving 19kW
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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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Heat Pipe applications

• 2.) Heat and coolth recovery.

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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.
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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

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Heat Pipe efficiency
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Orientation

• Available in both vertical horizontal
  arrangements.
• The warmer airstream must be at the 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 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

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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 - Dubai
Gibca - 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 villa
Junker Artek Junker 8 New Dawoodi Bohra center
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Dehumidification selection
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Heat Recovery Selection
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Any Questions ?

• For further information or to download latest
  copies of our selection software, visit our
  website
• www.spcoils.co.uk

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HEAT PIPESThe Benefits of Heat Pipes in Hot
Humid Climates

• Allan Westbury
• Managing Director
• S P Coils Ltd. Leicester, UK

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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)