NPTEL – Chemical – Mass Transfer Operation 1
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Assignment and Short type questions
Module 6: Humidification and Air Conditioning
Assignment Problems:
Assignment Problem 6.1: Determine the following psychrometric properties of a
moist air sample having a dry-bulb temperature 270C and a humidity of 0.015
kg/kg dry air, using the psychrometric chart and/or the vapor pressure equation
for water: (a) Relative humidity (b) Dew point (c) Adiabatic saturation temperature
(d) Wet-bulb temperature (e) Enthalpy (f) Humid volume (g) Humid heat. Antoine
Equation: ln
V
A
P
(bar)=11.96481-3984.923/(T-39.724). Total pressure is 1 atm.
Ans: (a) 66.8%; (b) 20.30C; (c) 22.50C; (d) 22.50C; (e) 64.7, 65.6, 64 kJ/kg dry
air; (f) 0.87, 0.88, 0.873 m3/kg dry air; (g) 1.033 kJ/kg dry air. 0C
Assignment Problem 6.2: A sample of air has a dry-bulb temperature of 330C
and wet-bulb temperature of 230C. The total pressure is atmospheric. (a)
Determine the following psychrometric properties – humidity; enthalpy; dew point;
humid volume and humid heat. (b) If the sample air is heated to 500C, what will
be its wet-bulb temperature? (c) How much heat is rejected if 1 kg of air (dry
basis) is cooled down from 330C to 150C? (d) If the air sample is heated to 500C
and its pressure is doubled (2 atm.), what would be its relative humidity and dew
point? Antoine Equation: ln
V
A
P
(bar)=11.96481-3984.923/(T-39.724).
Ans : (a) Humidity, Y/=0.014 kg/kg dry air; Enthalpy, H/=69.03 KJ/kg dry air; Dew
point, Td=19.95 C; Humid volume, vH=0.0886 m3/kg dry air; Humid heat,
cH=1.031 KJ/(kg dry air). C; (b) Twb=27ºC; (c) H=28.558 KJ/kg dry air; (d)
R.H.=37.77% and Td=31ºC
