Chapter 7, Problem 7.32P

A 3,500-seat auditorium is to be air-conditioned using window units 10 kW nominal value. Assume that a person at rest will dissipate heat at a rate of approximately 360 kJ/h. There are 200 lamps in the auditorium, each rated at 250 W. The rate of heat transfer to the auditorium through the walls and windows is estimated to be equal to 150,000 kJ/h. If the auditorium air goes to maintain at a constant temperature of 200°C, determine the number of air conditioning units of required window. Answer: 45 units.

2. A rectangular swimming pool is 1.5 m deep, 15 m wide, and 25 m long. Assume the bottom and sides of the swimming pool are insulated so that the pool exchanges heat with its environment through the top surface only. The density of water is 1000 kg/m³, the specific heat is 4180 J/kg-°C, and the heat transfer coefficient is 10 W/m²-°C. 1.5 m Heat exchange through top surface only 25 m T(t) To 15 m Complete the following. (a) Determine the thermal time constant of the pool and express your answer in days. (b) The swimming pool is being held at T0 = 30 °C when the power fails and external heating stops. The air temperature around the pool (T) drops quickly and can be assumed to be 10 °C at time t = 0. Write a script file in MATLAB® that plots the pool temperature for a duration of four thermal time constants.

Consider a wall that consists of two layers, A and B, with the following values: kA = 0.8 W/m⋅ºC, LA = 8 cm, kB = 0.2 W/m⋅ºC, LB = 5 cm. If the temperature drop across the wall is 18ºC, the rate of heat transfer through the wall per unit area of the wall is   a. 89.6 W/m2 b. 72.0 W/m2 c. 153 W/m2 d. 51.4 W/m2  e. 180 W/m2