Question

A classroom that normally contains 40 people is to be airconditioned with window air-conditioning units of 5-kW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of about 360 kJ/h. There are 10 lightbulbs in the room, each with a rating of 100 W. The rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kJ/h. If the room air is to be maintained at a constant temperature of 21°C, determine the number of window air-conditioning units required.

Answer 1

Answer:

About  2 units.

Explanation:

We assume that there is no heat dissipating instrument in the room

Total cooling load of the room is defined from the given below equation

$Q_{cooling}$=$Q_{light}$+$Q_{people}$+$Q_{heat gain}$

where

$Q_{light}$= 10*100 W =1 KW

$Q_{people}$ = 40*360 KJ/h= 4 KW

$Q_{heat gain}$=15000KJ/h= 4.17 KW

$Q_{cooling}$= 1+4+4.17=9.17 KW

the number of air conditioner unit is =$\frac{9.17}{5}$=1.83

 which is approximately 2 units