Air-to-Refrigerant Heat Transfer Equipment
ASHRAE Technical Committee 8.4

Scope of TC 8.4

TC 8.4 is concerned with design, performance, and application of heat transfer equipment in which a refrigerant, including water or brine, is used to transfer heat with air. The processes of concern to the committee include both sensible heat transfer and combined sensible and latent heat transfer.


The ASHRAE Handbook is published in a series of four volumes, one of which is revised each year, ensuring that no volume is older than four years. The Handbooks can be purchased at the ASHRAE Bookstore by clicking on this link.

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

HVAC Systems & Equipment: Air-Cooling/Dehumidification Coils
Most equipment used today for cooling and dehumidifying an airstream under forced convection incorporates a coil section that contains one or more cooling coils assembled in a coil bank arrangement. Such coil sections are used extensively as components in room terminal units; larger factory-assembled, self-contained air conditioners; central station air handlers; and field built-up systems. Applications of each coil type are limited to the field within which the coil is rated. Other limitations are imposed by code requirements, proper choice of materials for the fluids used, the configuration of the air handler, and economic analysis of the possible alternatives for each installation.

HVAC Systems & Equipment: Air-Heating Coils
Air-heating coils are used to heat air under forced convection. The total coil surface may consist of a single coil section or several coil sections assembled into a bank. The coils described in this chapter apply primarily to comfort heating and air conditioning using steam, hot water, refrigerant vapor heat reclaim(including heat pumps), and electricity. The choice between the various methods of heating depends greatly on the cost of the various available energy sources. For instance, in areas where electric power is cheaply available and heating requirements are limited, heat pumps are a very viable option. With available power and higher heat requirements, electric heat is used. If electric power is considerably expensive, steam or hot water generated using gas-fired sources is used in larger buildings and district cooling. In smaller buildings, heat is supplied using gas furnaces, which are covered in Chapters 33 and 34. Water and steam heating are also widely used where process waste heat is available.

HVAC Systems & Equipment: Condensers
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.

The ASHRAE HVAC SYSTEMS & EQUIPMENT HANDBOOK may be purchased from the on-line bookstore by clicking on the highlighted text.

This TC is responsible for the following chapter in the Refrigeration Volume

Refrigeration: Forced-Circulation Air Coolers
Forced-circulation unit coolers and product coolers are designed to operate continuously in refrigerated enclosures; a cooling coil and motor-driven fan are their basic components, and provide cooling or freezing temperatures and proper airflow to the room. Coil defrost equipment is added for low-temperature operations when coil frosting might impede performance. Any unit (e.g., blower coil, unit cooler, product cooler, cold diffuser unit, air-conditioning air handler) is considered a forced-air cooler when operated under refrigeration conditions.

The ASHRAE HVAC REFRIGERATION HANDBOOK may be purchased from the on-line bookstore by clicking on the highlighted text.

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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

ASHRAE publishes papers and transactions from presentations at its conference events. In addition, ASHRAE records most of the seminar sessions from its conferences on DVD. These DVDs are ideal for use at chapter meetings, in university courses, or company lunch and learns. Products available from the most recent conference may be found here.


Technical Committees are responsible for identifying research topics, proposing research projects, selecting bidders, and monitoring research projects funded by ASHRAE. Information about their specific research program is discussed at each TC meeting and at the TC’s Research Subcommittee meeting.

This TC has the following active research projects:

The objective of this research is to develop airside heat transfer and pressure drop correlations for high performance compact heat exchangers under low air velocity conditions.

This work will provide essential design data for state-of-art micro channel heat exchangers by showing how much oil is held up, causing the heat transfer performance degradation and additional pressure drops at various operating conditions. This work provides key information that may challenge compressor manufacturers and installers to more carefully measure how much oil to add to systems.  

The objective of this research is to develop a new corrosion test, or justify the use of an existing standardized accelerated test, for both all-aluminum tube and fin and brazed micro-channel heat exchangers.  Therefore, it is expected that the final outcome of this work will be a standardized test that ASHRAE members can use to better predict HVAC&R component and system performance for a given family of alloy systems based upon the atmospheric conditions and mode of operation of an HVAC/HEX.


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 standards:

ANSI/ASHRAE Standard 20: Methods of Testing for Rating Remote Mechanical-Draft Air-Cooled Refrigerant Condensers

ANSI/ASHRAE Standard 25: Methods of Testing Forced Convection and Natural Convection Air Coolers for Refrigeration

ASHRAE Standard 33: Methods of Testing Forced Circulation Air Cooling and Air Heating Coils

Other Activities

TIP: If MTG involvement add here otherwise leave blank.

This TC is a member of the following MTG:

Lower Global Warming Potential Alternative Refrigerants
This MTG is established to coordinate TC/TG/TRG technical activities to help transition the HVAC&R industry to sustainable lower Global Warming Potential (GWP) alternative refrigerants. The MTG will further request participation from US EPA and AHRI. The MTG responsibilities include suggestions for research, development and presentation of technical programs of all types on alternative lower GWP refrigerants, suggestions for Life Cycle Climate Performance (LCCP) systems evaluation for different applications, development of lower GWP solutions for different applications, and a special publication detailing aspects of LCCP applied to the HVAC&R fields. 


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