Question

A classroom that normally contains 40 people is to be air-conditioned with window air conditioning units of 5-kW cooling capacityeach. A person at rest may be assumed to dissipate heat at the rate of about 360 kJ/hr.There are 10 light bulbs 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/hr. Ifthe room air is to be maintained at a constant temperature, determine the number of window air conditioning units required.

Answer 1

The correct answer will be "2".

Step-by-step explanation:

Given:

Heat generated through wall,

= 15000 kJ/h

=
`(15000)/(3600)`

=
`4.17 \ KW`

Heat generated by bulbs,

=
`10(100) \ W`

=
`1000`

=
`1 \ KW`

Heat generated by people,

=
`40(360) \ KJ/h`

=
`(14400)/(3600)`

=
`4 \ KW`

Heat removed by 1 AC,

= 5 KW

Now,

The total increase in heat will be:

=
`4+1+4.17`

=
`9.17 \ KW`

hence,

The required number of AC will be:

⇒
`5n=9.17`

⇒
`n=(9.17)/(5)`

⇒
`=1.83`

0r,

⇒
`2`