1. An air-conditioned room is maintained at 25 C dry-bulb temperature, and 50% relative humidity. The...

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1. An air-conditioned room is maintained at 25 °C dry-bulb temperature, and 50% relative humidity. The outdoor air is at 30 °C dry-bulb temperature, and 65 % relative humidity. In the air conditioning system, 25 % of the return air is exhausted and an equal quantity of outdoor air is mixed with the remaining return air. The mixture passes over a cooling coil whose coil surface temperature (apparatus dew-point) is 8 °C, and the bypass factor is only 0.5. The air from the cooling coil is then supplied into the room. The supply mass flow rate of dry air to the room space is 1.0 kg/s; and the air pressure is constant at 101.3 kPa. Using the psychrometric chart, estimate (a) the dry-bulb temperature and the relative humidity of the air leaving the cooling coil; (8 marks) (5 marks) (5 marks) (2 marks) (b) the enthalpy-humidity ratio of the cooling process, (c) the refrigeration capacity of the cooling coil, and (d) the sensible heat ratio (SHR) of the air-conditioned space. The air conditioning cycle is to be plotted on the psychrometric chart and submitted together with the BLUE answer book. 1. An air-conditioned room is maintained at 25 °C dry-bulb temperature, and 50% relative humidity. The outdoor air is at 30 °C dry-bulb temperature, and 65 % relative humidity. In the air conditioning system, 25 % of the return air is exhausted and an equal quantity of outdoor air is mixed with the remaining return air. The mixture passes over a cooling coil whose coil surface temperature (apparatus dew-point) is 8 °C, and the bypass factor is only 0.5. The air from the cooling coil is then supplied into the room. The supply mass flow rate of dry air to the room space is 1.0 kg/s; and the air pressure is constant at 101.3 kPa. Using the psychrometric chart, estimate (a) the dry-bulb temperature and the relative humidity of the air leaving the cooling coil; (8 marks) (5 marks) (5 marks) (2 marks) (b) the enthalpy-humidity ratio of the cooling process, (c) the refrigeration capacity of the cooling coil, and (d) the sensible heat ratio (SHR) of the air-conditioned space. The air conditioning cycle is to be plotted on the psychrometric chart and submitted together with the BLUE answer book.

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