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Experiment 3: " AIR-CONDITIONING"
Objective:
To study air conditioning in practice. Heating and cooling of a stream of air.
Apparatus:
Air-conditioning unit consists of two parts:
1. Air system : a) fan and speed control.
b) Electrical heater.
c) Boiler; to add moisture.
d) Air flow measurement.
2. Refrigerant system : a) compressor.
b) Condenser.
c) Refrigerant evaporator.
Procedure:
After operating the fan to have air stream;
Part 1 " Heating " :
Start the electrical heaters to heat the air stream, take the temperatures ( wet and dry ) for the three sections.
Part 2 " cooling and humidification " :
Both of these done together but cooling in section 3 and the humidification in section 2, in this we operate the devise under the air conditioning unit, take the temperature
Calculation and Data Analysis:
Theoretically:
Applying the steady flow equation at sections D and G , the energy balance will be
Qa - Wa = ma [(hg – hd) + (V²g - V²d )/2]
Where:
Qa = sum of the rate of heat transfer at the heating or cooling surface and the external heat transfer to or from the surrounding atmosphere.
Wa = rate of work done or by the system.
ma = mass flow rate of air flowing in the duct.
hd = enthalpy of air at section D.
hg = enthalpy of air at section G.
Vg = mean velocity of air at section D.
Vd = mean velocity of air at section G .
Since Wa = 0 and Vg = Vd the equation reduces to :
Qa = ma(hg- hd)
From the continuity equation :
ma = [Ad*Vd] / Vd
=Vod / Vd
Where:
Ad = cross sectional area of the duct =0.0645 m²
Vd = spesific volume of air (obtained from psychometric chart)
Vod = volume flow rate.

** Applying it on our data :