A refrigeration cycle driven by an electric motor must maintain a computer laboratory at 188C when the outside temperature is 308C The thermal load consists of heat transfers entering through the walls and roof of the laboratory at a rate of 75,000 kJ/h and from the computers, lighting, and occupants at a rate of 15,000 kJ/h. Required:
a. Determine the minimum theoretical power required by the electric motor, in kW, and the corresponding coefficient of performance.
b. If the actual power required by the motor for this duty is 8.3 kW, determine the coefficient of performance.
c. If the given temperature and thermal load data are observed for a total of 100 hours and electricity costs 13 cents per kWh, determine the cost, in $, over that period for each of cases (a) and (b).