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Power Engineering and Rerigeration 525 Refrigeration & Air conitoning, , , , 5.19.3 Difference between Industrial Air Conditioning, and Commercial Air Conditioning, , , , , , , , , , Industrial Air conditioning ‘Commercial Air conditioning, 1. Aim of industrial air conditioning is to improve | 1. It is intended to provide human comfort for short, product quality and efficiency. period to number of people., 2. Conditions are maintained to suit industrial process. | 2. Conditions are maintained for human comfort for, short period of time., , , , , , 3. Conditions maintained inside room varies from | 3. Conditions maintained inside do not vary. General, , process to process. condition of temperature 22.2 to 25°C and relative, humidity 30 to 60% with air purity are maintained., 4. Itis used for photographic industry, textile industry, | 4 It is used for commercial establishment like, departmental store, mall, , , , , , , , , , , , ey, ‘Atmospheric air always contains water vapour. The amount of water vapour present in air plays an important, , role in comfort air conditioning. The amount of water vapour present in air depends on partial pressure of water, , vapour and temperature and total pressure of mixture. Due to change in temperature and pressure, amount of water, , ‘vapour present in air changes continuously, The science which deals with the study of the behaviour of air and water vapour mixture is known as, , Psychrometry. The properties of air and water vapour mixture are known as Psychrometric properties or psychometric, , terms., , Psychrometric Terms :, , 1. Dryair:, , Dry air is the mixture of nitrogen and oxygen neglecting the water vapour and other gases. The volumetric, composition of dry air is 77% nitrogen and 23% oxygen. Dry air does not contain any moisture., , 2. Moist air:, , Moist air is a mixture of dry air and water vapour. The amount of water vapour present in the air depends on, absolute pressure and temperature of mixture and partial pressure of water vapour., , 3. Saturated ai, ‘The water vapour present in air is known as moisture and its quantity in air is an important factor in all air, conditioning systems. The mixture of air and water vapour at a given temperature is said to be saturated when it, contains maximum amount of water vapour that it can hold. If the temperature of mixture of air and water, ‘vapour is above saturation temperature of water vapour, the vapour is called super heated vapour., , + Forsaturated air, relative humidity = 100 %, + For saturated air, Degree of saturation = 1, , 4. Dry bulb temperature (tos) :, , Dry bulb temperature of air is the temperature recorded by ordinary thermometer and it is not affected by the, moisture present in ar. It is denoted by tos., , 5. Wet bulb temperature (tws) :, , Wet bulb temperature is the temperature recorded by thermometer when its bulb is covered with wet cloth, (known as wick) and is exposed to air is known as wet bulb temperature. Itis denoted by ty., , Wet bulb depression :, , The difference between dry bulb temperature and wet bulb temperature is known as wet bulb depression., , 6. Dew point temperature (tor) : (S-17, 18; W-16,17., If the mixture of air and water vapour is cooled at constant pressure then the ability of air to hold water vapour, reduces and saturated condition will be reached. Further lowering of temperature will result in condensation of, water vapour or formation of dew., , , , , , , , , , , , , , , , , , - + 166/193