Question

Page 2 of 8 May 2018 16-MEC-B2 Environmental Control in Buildings ROBLEM 1. (30 POIN In sumimer a room is to be maintained at 20°C, RIIS0%, when the outside air is at 260 percentage saturation 50%. The mass flow of dry air supplied to the room, is 2 kg/s at 15°C Fresh air is mixed with recirculated air in the ratio three parts recirculated air to one part fresh air.The air after mixing is passed over a cooling coil with an apparatus dew point of 4°C and a coil bypass factor of 0.1. On leaving the cooling coil the air passes over a heating coil and is the delivered to the room by the fan; the fan and the ducting cause a 2°C rise in temperature between the heating coil and the room. a. b. e. Draw a diagram of the system. Draw the operating cycle on the psychrometric chart provided. Identify each significant point, on the diagram and psychrometric chart, and note for each of these points its dry bulb and wet bulb temperature. d. Calculate the capacity of the cooling coil (kW), e. Calculate the heating coil load Since there is no need to control the humidity in the room it is decided to remove the heating coil and use an arrangement as in the figure below, to supply the same mass flow of air as the same supply temperature as before. The design conditions for the room are assumed to be.unchanged. The mixing ratio for the first mixing box is now one part fresh air to one part recirculated air. Assuming that the cooling coil has the same apparatus dew point and bypass factor, and that there is 2C rise in temperature from the fan and ducting as before, calculate the percentage saturation of the air supplied to the room. ROOM OUT FAN SH AIR MIXING BOX 2 COOLING COIL MIXING BOX 1

Please provide detailed solution with schematic diagram and psychometric chart. your highly response will be appreciated.

Answer 1

Please take a note that the outlet of heating coil is less than 2 centigrade of the supply condition.

Feel free to ask any doubts regarding this question .

Thanks

Enjoy refrigeration and air-conditioning!
fig schemonc cianam Ma 20 L 9-50% |Room o) 26 Fotshour Miyi Coil Coi Cham Frshair+ 2 dehunidititaion ADR ouside aiy i 0.0073 k ooSI alkd a

d.a 0.1 72-7A =11 x 26) + (2x 20 Dp T- TADP 42-i el _ 16-assilas w,2-wapp 咬-o.oo5 1 - as-y 2 19 29 66 ka sa d Cooing Coit load 8-8216 kw