From HVAC: The Handbook of Heating, Ventilation and Air Conditioning for Design and Implementation


Introduction. The conservation of mass and energy is used in the study of air conditioning processes. Analysis of air conditioning processes is required for maintaining proper temperature and humidity in living space such as residential, commercial, and industrial facilities. The basic processes are as follows:

  1. simple heating and cooling processes;

  2. cooling with dehumidification;

  3. heating with humidification;

  4. adiabatic mixing of two air streams; and

  5. evaporative cooling.

These air conditioning processes are represented in Fig. 3-1. Simple diagrams of the psychrometric chart are shown in Figs. 2-5 and 2-6.



Simple heating

O to C

Simple cooling

O to G


O to A


O to E

Evaporative cooling

O to H

Evaporative heating

O to D

Heating and humidification

O to B

Cooling and dehumidification

O to F

Figure 3-1: Fundamental airconditioning processes

Simple Heating and Cooling ( W = constant). In some heating applications, air is heated without moisture being added. An example of this process is a heat pump with heating coil and no humidifier system. In the case of a simple cooling process, in some chilled water cooling applications air can be cooled without condensation. Figs. 3-2 and 3-4 shows schematics of simple heating process and a simple cooling process, respectively. The simple psychrometric diagrams of these processes are shown Figs. 3-3 and 3-5 respectively.

Figure 3-2: Schematic of simple cooling process (sensible cooling)

Figure 3-3: Psychrometric diagram of simple cooling process

Figure 3-4: Schematic of simple heating process

Copyright Industrial Press Inc. 2007 under license agreement with Books24x7

Products & Services
Cooling Towers
Cooling towers are defined as any open water recirculation device that uses fans or natural draft to draw or force air to contact and cool water by evaporation.
Heating Furnaces
Heating furnaces convert gas, oil, electricity or other fuels into heat for distribution within a structure. They are the central heating devices within HVAC systems.
Refrigeration Compressors and Air Conditioning Compressors
Refrigeration compressors and air conditioning compressors provide air conditioning, heat pumping, and refrigeration for large-scale facilities and equipment. Refrigeration compressors are sometimes called refrigerant compressors.
Compressed Air and Vortex Cooling Tubes
Compressed air and vortex cooling tubes are used for spot heating or cooling applications.
Air Handlers
Air handlers are a system-like device used in ventilating systems. They typically consist of a blower, heat exchange medium for heat or air conditioning, and housing.

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