Question

11) A classroom that normally contains 40 people is to be air-conditioned with window air- conditioning units of 5-kW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of 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 mainatained at a constant temperature of 21 C determine the number of window air-conditioning units required. Answer: 2 units

Answer 1

solution. The output figures of an AC show the amount of cooling or heating the AC can produce. Here , ac has 6kw cooling capacity. Now heat generated or being transferred into room. Converting kJ/h to KW as 1 kW = 3600 kJ /h 40 people with 360 kJ lh = 14400 kJ/h = 4 kW. 10 lighbulb with 100 Watt each = 1000 to = 1kW. The Walls and Windows transferring = 15 000 kJ/h. = 4.167 KW. so tatal heat entering into room or generated inside room = 4+1 4 4.167 = g. 167 KW- Thus for this heat, maintaining constant cooling we will need sweßlus in cooling than heating. Thus 2 unit of AC will provide 10 kW of coaling, so 2 units could be required.