heatpipesforhot n humid climates june04

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

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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)

heatpipesforhot n humid climates june04

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