Q.2 (a) Cold air at 10°C dry-bulb (db) temperature and 5°C wet-bulb (wb)
temperature is mixed with warm, moist air at 25°C db and 20°C wb in
a mass ratio of 1:2 respectively. Using the given psychrometric chart
(in Appendix 2-1), determine the below mixed air conditions:
(i) dry-bulb and wet-bulb temperatures,
(ii) relative humidity,
(iii) humidity ratio, and
(iv) specific volume.
(5 marks)
(b) A chilled water cooling coil receives 2.5 m³/s of air at 25°C db, 20°C
wb. It is necessary for the air to leave the coil at 13°C db, 12°C wb.
The barometric pressure is 101.3 kPa. Using the given psychrometric
chart (in Appendix 2-2),
(i) determine the sensible heat factor (SHF), the apparatus dew
point temperature and the bypass factor; and
(7 marks)
(ii) compute the total sensible heat transfer rate and sensible heat
transfer rate, respectively.
(5 marks)
(c) With the aid of a diagram, identify the acoustic energy flow in a
ventilation system to the receiver (occupants of ventilated space) if
the primary source is the fan noise.
(8 marks)
