Cooling Towers and Evaporative Condensers
ASHRAE Technical Committee 8.6

Scope of TC 8.6

Technical Committee TC 8.6 is concerned with open and closed circuit cooling towers, evaporative condensers, adiabatic condensers and fluid coolers, spray ponds, and other types of contact type liquid-to-air heat rejection equipment along with their application and impact on complete HVAC, Industrial, and Refrigeration systems, including the associated energy and water usage as well as water treatment requirements.

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This TC is responsible for the following chapters in the HVAC Systems & Equipment Volume

The condenser in a refrigeration system is a heat exchanger that rejects all the heat from the system. This heat consists of heat absorbed by the evaporator plus the heat from the energy input to the compressor. The compressor discharges hot, high-pressure refrigerant gas into the condenser, which rejects heat from the gas to some cooler medium. Thus, the cool refrigerant condenses back to the liquid state and drains from the condenser to continue in the refrigeration cycle. Condensers may be classified by their cooling medium as (l) water-cooled, (2) air-cooled, (3) evaporative (air- and water-cooled), and (4) refrigerant-cooled (cascade systems). The first three types are discussed in this chapter; see Chapter 48 in the 2010 ASHRAE Handbook—Refrigeration for a discussion of cascade-cooled condensers.

Cooling Towers
Most air-conditioning systems and industrial processes generate heat that must be removed and dissipated. Water is commonly used as a heat transfer medium to remove heat from refrigerant condensers or industrial process heat exchangers. In the past, this was accomplished by drawing a continuous stream of water from a utility water supply or a natural body of water, heating it as it passed through the process, and then discharging the water directly to a sewer or returning it to the body of water. Water purchased from utilities for this purpose has become prohibitively ex-pensive because of increased water supply and disposal costs. Similarly, cooling water drawn from natural sources is relatively unavailable because the ecological disturbance caused by the in-creased temperature of discharge water has become unacceptable. Air-cooled heat exchangers cool water by rejecting heat directly to the atmosphere, but the first cost and fan energy consumption of these devices are high and the plan area required is relatively large. They can economically cool water to within approximately 20°F (11 K) of the ambient dry-bulb temperature: too high for the cooling water requirements of most refrigeration systems and many industrial processes. Cooling towers overcome most of these problems and therefore are commonly used to dissipate heat from refrigeration, air-conditioning, and industrial process systems. The water consumption rate of a cooling tower system is only about 5% of that of a once-through system, making it the least expensive system to operate with purchased water supplies. Additionally, the amount of heated water discharged (blowdown) is very small, so the eco-logical effect is greatly reduced. Lastly, cooling towers can cool water to within 4 to 5°F (2 to 3 K) of the ambient wet-bulb temperature, which is always lower than the ambient dry-bulb, or approximately 35°F (19 K) lower than can air-cooled systems of reasonable size(in the 250 to 500 ton [880 to 1760 kW] range). This lower temperature improves the efficiency of the overall system, thereby reducing energy use significantly and increasing process output.

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Technical committees develop and sponsor technical sessions at the winter and annual conferences. Information about their future technical program is discussed at each TC meeting and at the TC’s Program Subcommittee meeting.

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A recent program sponsored by this TC:

Winter Meeting 2011 in Las Vegas
TC 8.6 and TC 3.6, along with SSPC191 co-sponsored Seminar 33
"Want Peak System Efficiency from your Water Cooled System? Quit Cooling Dirt!".


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ASHRAE writes standards for the purpose of establishing consensus for: 1) methods of test for use in commerce and 2) performance criteria for use as facilitators with which to guide the industry. ASHRAE publishes the following three types of voluntary consensus standards: Method of Measurement or Test (MOT), Standard Design and Standard Practice. ASHRAE does not write rating standards unless a suitable rating standard will not otherwise be available. ASHRAE is accredited by the American National Standards Institute (ANSI) and follows ANSI's requirements for due process and standards development. Standards may be purchased at the ASHRAE Bookstore.

This TC is cognizant for the following standard:

ANSI/ASHRAE Standard 64: Methods of Laboratory Testing Remote Mechanical-Draft Evaporative Refrigerant Condensers

TC 8.6 is also cognizant for standards published by the Cooling Technology Institute

CTI STD-201 (09), Standard for Certification of Water-Cooling Tower Thermal Performance
CTI Code ATC-105 (00), Acceptance Test Code for Water-Cooling Towers

Supplement to CTI Code ATC-105 (96), Acceptance Test Code for Closed Circuit Cooling Towers 

Working Group Link

TIP: If MTG involvement add here otherwise leave blank.

The following link can be used to access the TC8.6 working group:


ASHRAE Technical FAQs are provided as a service to ASHRAE members, users of ASHRAE publications, and the general public. While every effort has been made to ensure their accuracy and reliability, they are advisory and provided for informational purposes only, and in many cases represent only one person’s view. They are not intended and should not be relied on as an official statement of ASHRAE. Technical questions not addressed may be submitted to the ASHRAE Technical Services department at

TC 3.6 is cognizant for an FAQ which overlaps TC 8.6 interests:
How does ASHRAE recommend that cooling towers be cleaned to avoid Legionellosis?