Aclassroom 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.

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

=++

where

= 10*100 W =1 KW

= 40*360 KJ/h= 4 KW

=15000KJ/h= 4.17 KW

= 1+4+4.17=9.17 KW

the number of air conditioner unit is ==1.83

 which is approximately 2 units

tbh i dont know ether

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.