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INDIRECT EVAPORATIVE COOLINGA FRESH APPROACH TO ENERGY EFFICIENCY IN HVAC DESIGNS
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Contents
Why evaporative cooling?
What is evaporative cooling
The road ahead
Cooling solutions based on indirect evaporative cooling with case studies
Types of evaporative cooling
Why evaporative cooling?
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Energy Environment HVAC
There’s a definite connect between these three:
Energy
Percentage of energy consumed by HVAC in a building – approximately 60%
Load demand variation – surge in demand during peak summer
Environmental impact
• Direct impact – in terms of CFC, ODP
• Indirect impact – total energy, GWP of power generation, Carbon emissions etc.,
Space conditioning (heating, cooling, and ventilation) is the most significant energy use in buildings and hence represents
the best opportunity for saving energy and reducing carbon emissions.
“It is the right time to re define comfort levels, that can open up newer alternative means of cooling”
Why evaporative cooling?
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Fore-runner of modern concepts of comfort
Temperature
Relative
humidity Air motion % of fresh air
Thermal Comfort: is 24⁰C the only choice?
ASHRAE 55 Standard defines comfort as “that condition of mind which expresses satisfaction with the
thermal environment and is assessed by subjective evaluation.”
Allows temperature in range of 23.30C - 26.70C, with Rh ranging from 30 to 60%
“A few degree rise in conditioned space temperature will open up options for use of several energy
efficient technologies, most significant being evaporative cooling”
What is evaporative cooling?
PLACE IMAGE HERE
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• One of the oldest & simplest comfort
conditioning technology
• Invented by mother nature and
perfected by man
• Uses world’s most clean natural
refrigerant: “Water (R718)”
When the sun is hot……
Water + Moving air =
Types of evaporative cooling – Direct (DEC)
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44.8ºC DBT,
18.9ºC WBT
Primary air
(ambient)
C
E
L
L
U
L
O
S
E
21.5ºC DBT
18.9ºC WBT
Adiabatically
cooled air
Water evaporates directly into the air stream, thus reducing the air temperature while humidifying the air.
Types of evaporative cooling – Indirect (IEC)
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44.8ºC DBT,
18.9ºC WBT
Primary air
(ambient)
24.1ºC DBT
11.7ºC WBT
Sensibly
cooled air
DAMA
Secondary air
(ambient)
Indirect evaporative cooling is about cooling air by water evaporation, but not allowing water and air to mix.
Pure sensible cooling: no humidity added, moisture level in air (grains) remains
constant.
Lower both temperature and enthalpy (total heat) of air.
Exhaust
air
Comparison of Direct vs Indirect
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IEC
Direct Evaporative
cooling (DEC)
Indirect Evaporative
cooling (IEC)Air & water contact Direct contact No contact
Cooling Adiabatic process Adiabatic process Sensible cooling
Dry bulb temp Reduces Reduces
Wet bulb temp No change Reduces
Moisture (grains) Increases No change
Enthalpy No change Reduces
Types of evaporative cooling – Indirect Direct (IDEC)
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44.8ºC DBT,
18.9ºC WBT
Primary air
(ambient)
24.1ºC DBT
11.7ºC WBT
Sensibly
cooled air
DAMA
Secondary air
(ambient)
Exhaust
air
C
E
L
L
U
L
O
S
E
14.0ºC DBT
11.7ºC WBT
Cooler
supply air
Supply air is cooled in two stages:
• first with indirect evaporative cooling, and then
• further with direct evaporative cooling
Thus lowering the air temp well below the ambient wet bulb
IDEC – Psychrometric representation
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DBT 44.8⁰C WBT 18.9⁰C,
Specific Humidity 4.10 gm / kg
Outdoor
(Ambient)
DBT 21.5⁰C WBT 18.9⁰C,
Specific Humidity 13.70 gm / kg
DEC Outlet
DBT 14.0⁰C WBT 11.7⁰C,
Specific Humidity 8.60 gm / kgIDEC Outlet
IDEC
Up to 60% less moisture added
Up to 8°C more
cooling * Riyadh 0.4% ASHRAE conditions
Cooling Solutions based on Indirect Evaporative Cooling
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Evaporative Air Cooling
HMX-AmbiatorIndirect Direct Evaporative
Cooling
HMX-IECIndirect Evaporative
Cooling
Fresh Air Handling Unit (FAHU)
HMX-PCUPre-cooling of fresh air
using fresh air
Hybrid Air-Conditioning
HMX-FAACHybrid air-conditioning with recirculation of air
HMX-DMAHybrid air-conditioning for once through applications
IDEC: Applications for standalone cooling
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Indirect evaporative cooling, either in pure
‘indirect form (IEC)’, or coupled with direct
evaporative cooling (IDEC) can be used for
variety of applications savings huge amount
of energy.
Commercial buildings – Malls, Shops/Show
Rooms, Prayer Halls, Hotels, Restaurants
Commercial kitchens and laundries
Large warehouses & factories
Automobile workshops
Indoor stadiums & sports arena
IDEC: Hourly analysis for supply air temp (8760 hours)
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IDEC
supply air
Temp
Riyadh Dammam Jeddah
Hours In % Hours In % Hours In %
≤ 14°C 8053 92% 3923 45% 689 8%
≤ 16°C 8522 97% 5199 60% 1160 13%
≤ 18 °C 8684 99% 6329 73% 1983 23%
≤ 20°C 8760 100% 7101 82% 3465 40%
≤ 22°C 0 Nil 7669 88% 5280 61%
≤ 24°C 0 Nil 8095 93% 6685 77%
Case study – 1
One of the leading engineering company in Dubai
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Location Jebel Ali, Dubai, UAE
Project Electrical control panel manufacturing/assembly and
switchgear workshop
Total area cooled 48,000 ft2
Supply air 135,000 CFM
Problem faced Discomfort due to heat inside the workshop
Solution previously used Dry ventilation with exhaust fans
Solution provided Indirect-Direct Evaporative Cooling
Reason for selectionEnergy efficient comfort cooling system for people comfort
and related productivity enhancement
Case study – 1
One of the leading engineering company in Dubai
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Case study – 2
Middle East's Leader in Retail & Hospitality
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Location Sudair Industrial City, Riyadh (KSA)
Project Warehouse cooling
Total area cooled 485,000 ft2
Supply air 540,000 CFM
Problem faced Greenfield project
Solution previously used Air-conditioning was considered and compared
Solution provided by HMX Indirect Direct Evaporative Cooling
Reasons for selection
100% fresh air
Comfort at par with air-conditioning at a fraction of
energy cost
Case study – 2
Middle East's Leader in Retail & Hospitality
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HMX PCU: Working principle
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DBT 24ºC
Returned air from
conditioned spaceSupply air
AIR HANDLING UNIT (AHU)
Fresh air quantity: 15%
Recirculated air quantity: 85%
DBT 14ºC
HMX-PCU
(DAMA)
Sensibly
pre-cooled air DBT 24.1ºC
Ambient air DBT 44.8ºC,
WBT 18.9ºC
To conditioned space.
Room conditions
DBT 24⁰C, RH 60%
Fresh air can add up to 40% of the total cooling load in centrally air-conditioned spaces.
Pre cooling of outdoor fresh air before it mixes with return air reduces cooling load and thus energy consumed,
significantly
HMX PCU: Psychrometric representation
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5.1 TR per
1,000 cfm
TR Load without HMX-PCU
Ambient: 44.8⁰C
Coil Outlet:14⁰C
1.6 TR per
1,000 cfm
TR Load with HMX-PCU
Ambient: 44.8⁰C
IEC outlet: 24.1⁰C
Coil Outlet: 14⁰C
Savings with HMX-PCU:
3.5 TR per 1,000 cfm (68%)
* Riyadh 0.4% ASHRAE conditions
Sensible cooling
with PCU-F
Cooling with
cooling coil
14⁰C 24.1⁰C 44.8⁰C
HMX PCU: Hourly analysis of savings
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Analysis of savings in chiller load: 24 x 365 days (8760 hours in a year)
Location Saving
Riyadh 6.0 TRH/CFM/Year
Kuwait 8.7 TRH/CFM/Year
Abu Dhabi 6.5 TRH/CFM/Year
Cairo 4.2 TRH/CFM/Year
Advantages of HMX-PCU over other FAHU options
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50% lower capital
investment
Zero
cross-contamination
30% smaller
footprint
50% lower energy
consumption
Better
life-cycle cost
Eliminates
return-air ducting
Minimal
maintenance
Case study – 3
High-rise residential tower in Sharjah
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Location Sharjah, UAE
ProjectFresh air pre-cooling for common areas such as
lobbies, corridors, lift areas, etc.
Number of floors 44
Fresh air intake 60,000 CFM
Customer requirementPre-cooling of fresh air to reduce cooling load
and avoid addition of new chiller
Other solution suggesteda.Addition of a chiller
b.Recovery of air through ERW
Solution provided by HMXIndirect Evaporative Cooling
Retrofit to existing AHU
Reasons for selection Ease of retrofit and low Capex and Opex
Savings with HMX PCU in TRH 132 TR/hour
Case study – 3
High-rise residential tower in Sharjah
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Case study - 4
LEED Platinum rated IT office building
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Location Jaipur, India
Project Fresh air pre-cooling for office building
Office area 400,000 ft2
Fresh air intake 40,000 cfm
Customer requirementPre-cooling of fresh air to reduce TR load on
chiller
Other solution suggested Heat Wheel
Solution provided Indirect Evaporative Cooling
Reasons for selection
Better ROI than ERW
Low maintenance
Ease of operation
Case study – 4
LEED Platinum rated IT office building
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Hybrid air-conditioning
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MODE OF
OPERATIONWORKING DETAILS
Ventilation Only fresh air
IDEC (Ambiator)Indirect direct
evaporative cooling
IEC Only DAMA
IEC + Coil
DAMA + Cooling coil
(once through
application)
Air-conditioningCooling coil with re-
circulated air
Case study – 5
LEED Gold rated office building
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Location Ahmedabad, India
Project Office building
Total area cooled 3,000 ft2 with an occupancy of 20 people
System details 20,000 cfm + 20 TR DX coil (IDEC + Cooling
Coil)
Customer requirement 26 ± 2°C inside throughout the year
Other solution suggested Air-conditioning system of 20 TR
Solution provided Hybrid air-conditioning (IDEC + Cooling Coil)
Reasons for selection 25% lower annual power consumption
Annual power consumption 60,000 kWh
Annual water consumption 384,000 litres
Case study – 5
LEED Gold rated office building
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The road ahead
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The need for thermal comfort is universal and can’t be ignored.
HVAC demand is ever increasing and so is the pressure on our fast depleting energy resources.
Evaporative cooling offers a great opportunity to cut down on energy consumptions in buildings,
particularly in middle east region.
What is needed, is a responsible approach by all stake holders:
• User
• Designer
• Supplier
• Policy maker
Let’s make a beginning and think where all we can use “Evaporative Cooling”
Contact us
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FOR QUERIES
Global
+91 – 20 – 3088 1100
+91 – 93710 51636
Visit us at www.ategroup.com/hmx
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