Course Summery

Air conditioning can be defined as the treatment of indoor air in order to control certain conditions required for human comfort. The desirable conditions may be temperature, humidity, dust particle level, odor level, and air motion. It is known that the physical properties of air can be controlled by cooling, heating, humidification, and dehumidification. These processes may be employed to maintain specific conditions desirable for comfort. Thus, simultaneous control of temperature, humidity, air motion, and cleanliness is known as air conditioning. Human body releases about 100 W to 450 W/person depending on the activity of the person due to metabolism. The body temperature is maintained to be 97°C. But the body surface temperature changes according to the surrounding temperature and relative humidity. The body heat must be dissipated from body surface to the surrounding. If the surrounding temperature is less than the body temperature, the flow of heat from body becomes quite easy and normal flow. If the surrounding temperature is low as in winter, the rate of flow of heat from the body is rapid and the person will feel cold. If the surrounding temperature is too hot, there would be no flow of heat.

In such situation, sweat glands become activated. The moisture of body gets evaporated which brings the temperature normal. If the outside temperature is hot and humid, little evaporation of moisture will occur from the body skin and so the person will feel hot and uncomfortable. The movement of air by fan helps to keep body comfortable. When the room temperature becomes high due to heat gain, it causes human discomfort. When the room moisture becomes high, the increased humidity causes difficulties in disposing the body heat. For human comfort, the indoor temperature of 20°C and relative humidity 60% is quite good. Any air conditioning unit will be able to achieve the above requirement and maintain the conditions for comfort.

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