Question 4 (a) An air conditioning system is required to deliver air to a room at a temperature and relative humidity of

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Question 4 A An Air Conditioning System Is Required To Deliver Air To A Room At A Temperature And Relative Humidity Of 1 (252.59 KiB) Viewed 10 times

Question 4 (a) An air conditioning system is required to deliver air to a room at a temperature and relative humidity of 20°C and 42%, respectively. Air leaving the room has a temperature of 22°C, and a specific humidity that has increased by 0.008 kg/kg. 65% by mass of the air is then rejected and replaced by outside air at 27°C, which has a relative humidity of 70%. The mixture then passes through a cooler, a heater, and a circulation fan. The fan has no significant influence on the system other than to circulate the air. The air pressure is atmospheric throughout, which can be assumed to be 1.013 bar. a (i) Sketch a simple block diagram of the system. (2) (ii) Calculate the enthalpy of the air at each point in the cycle. (12) (111) Hence calculate the heat removed in the cooler. (2) (b) A natural draught cooling tower is used to cool 5 kg/s of water from 40°C to 25°C. Air with a relative humidity of 45% enters the tower at 18°C, and leaves it saturated at 32°C. Atmospheric pressure can be assumed to be 1.013 bar. (1) Calculate the enthalpy of the air entering and leaving the tower. (6) (ii) Use an energy balance to estimate the air mass flow rate. You may neglect the loss of water in your calculation. (3)