ASHRAE Journal - July 2009 - 16

Using Direct Evaporative + Chilled Water Cooling By Rick Phillips, P Associate Member ASHRAE .E., U sing evaporative cooling is a great way to save energy. It can be used in drier climates to provide a significant amount of the overall cooling requirements for a building. When it is coupled with chilled-water cooling, all the cooling requirements for any type of building can be achieved along with the energy savings. This article examines how to maximize the energy savings in HVAC systems using direct evaporative cooling (DEC) combined with chilledwater coils. Arranging the components in different sequences in an air-handling unit (AHU) has a significant effect on overall energy savings. A number of advantages exist to combining a chilled-water cooling coil with DEC. The primary reason is that the DEC is unable to provide all the cooling needed in most climates. With the addition of a cooling coil (CC), the use of evaporative cooling can be extended to many more climates. 16 ASHRAE Journal If one is designing an HVAC system using DEC combined with indirect evaporative cooling alone to provide all the cooling needs of a building, typical values used for the design supply air temperature for the Denver area are 60°F to 63°F (15.6°C to 17.2°C). With the addition of a CC, the traditional value of ashrae.org 55°F (12.8°C) can be used. If the 60°F (15.6°C) supply air temperature was used, compared to a 55°F (12.8°C) value, the supply fan cfm must be increased by 33% to provide the same amount of cooling, when trying to maintain a room temperature of 75°F (23.9°C). This also results in a 33% increase in fan horsepower if two fans with the same efficiency are selected, as well as a larger air-handling unit and ducts. The use of a CC allows the air-handling unit to provide all the needed cooling on days when there is high humidity outdoors. On those days, the DEC is ineffective by itself so the CC can provide the cooling. By the same means, if the indoor humidity level is too high, the DEC can be shut down and allow the CC to provide the cooling until the humidity levels are reduced to an acceptable level. About the Author Rick Phillips, P is an engineering specialist at .E., The RMH Group in Denver. July 2009

ASHRAE Journal - July 2009

Table of Contents for the Digital Edition of ASHRAE Journal - July 2009

ASHRAE Journal - July 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
     Using Direct Evaporative and Chilled Water Cooling
     Solving Kitchen Ventilation Problems
     Case Against Balancing Valves
     Integrated Design and UFAD
     Anniversary Feature: System Design for Compressor Reliability
Building Sciences
     Sustainable Products Capabilities
Special Products Information Section
Emerging Technologies
Washington Report
Products
People
Special Products
Classified Advertising
Advertisers Index
ASHRAE Journal - July 2009 - ASHRAE Journal - July 2009
ASHRAE Journal - July 2009 - Cover2
ASHRAE Journal - July 2009 - 1
ASHRAE Journal - July 2009 - 2
ASHRAE Journal - July 2009 - Contents
ASHRAE Journal - July 2009 - 4
ASHRAE Journal - July 2009 - Commentary
ASHRAE Journal - July 2009 - Industry News
ASHRAE Journal - July 2009 - 7
ASHRAE Journal - July 2009 - Letters
ASHRAE Journal - July 2009 - 9
ASHRAE Journal - July 2009 - 10
ASHRAE Journal - July 2009 - 11
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ASHRAE Journal - July 2009 - 13
ASHRAE Journal - July 2009 - Meetings and Shows
ASHRAE Journal - July 2009 - 15
ASHRAE Journal - July 2009 -      Using Direct Evaporative and Chilled Water Cooling
ASHRAE Journal - July 2009 - 17
ASHRAE Journal - July 2009 - 18
ASHRAE Journal - July 2009 - 19
ASHRAE Journal - July 2009 -      Solving Kitchen Ventilation Problems
ASHRAE Journal - July 2009 - 21
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ASHRAE Journal - July 2009 - 24
ASHRAE Journal - July 2009 - 25
ASHRAE Journal - July 2009 -      Case Against Balancing Valves
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ASHRAE Journal - July 2009 - 28
ASHRAE Journal - July 2009 - 29
ASHRAE Journal - July 2009 -      Integrated Design and UFAD
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ASHRAE Journal - July 2009 - BRC1
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ASHRAE Journal - July 2009 -      Anniversary Feature: System Design for Compressor Reliability
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ASHRAE Journal - July 2009 - Building Sciences
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ASHRAE Journal - July 2009 - Special Products Information Section
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ASHRAE Journal - July 2009 - 102
ASHRAE Journal - July 2009 - 103
ASHRAE Journal - July 2009 - Emerging Technologies
ASHRAE Journal - July 2009 - 105
ASHRAE Journal - July 2009 - 106
ASHRAE Journal - July 2009 - 107
ASHRAE Journal - July 2009 - Washington Report
ASHRAE Journal - July 2009 - Products
ASHRAE Journal - July 2009 - People
ASHRAE Journal - July 2009 - 111
ASHRAE Journal - July 2009 - Special Products
ASHRAE Journal - July 2009 - 113
ASHRAE Journal - July 2009 - 114
ASHRAE Journal - July 2009 - 115
ASHRAE Journal - July 2009 - 116
ASHRAE Journal - July 2009 - Classified Advertising
ASHRAE Journal - July 2009 - 118
ASHRAE Journal - July 2009 - 119
ASHRAE Journal - July 2009 - Advertisers Index
ASHRAE Journal - July 2009 - Cover3
ASHRAE Journal - July 2009 - Cover4
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