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Energy Management and Audit Take home asignment

Energy Management and Audit
Take Home Assignment. Due date is Tuesday 19th April 2022 in class
Question 1
Explain why it is preferred to use electrical power through Heat Pump for heating purposes
instead of using through resistance heat.
Question 2
A heat pump provides 30,000 Btu/hr to maintain a dwelling at 22 oC on a day when the outside
temperature is 10 oC. The power input to the pump is 1 hp. If electricity costs K117.30 per kWhr, compare the actual operating cost per day with the minimum theoretical operating cost per
day. Assume it operates on reversed Carnot cycle.
Question 3
A heat pump is to be use to heat a house and maintain the temperature at 22 oC in winter. On a
day when the average outdoor temperature remains about 15 oC, the house is estimated to lose
heat at a rate of 12 000 kilocalorie/hr. If the heat pump consumes 6 kW of power while
operating, determine the following:
How long the heat pump ran on that day
The total heating costs assuming an average price of K117.30 per kW-hr for
The heating cost for the same if resistance heating used instead of heat pump
Assume it operates on reverse Carnot Cycle
Question 4
A heat pump is use for space heating, providing 100MJ/hr to the room. The system, operating as
reversed Rankine Cycle, operates between 15 oC and 50 oC. Refrigerant is R134a (its p-h chart is
attached). Determine the following
The mass flow rate of the refrigerant
Theoretical power required to run the compressor
p-h Chart for Refrigerant R134a
Question 5
a) List down and explain four benefits of insulating a pipe conveying steam.
b) A steam pipe of 10 cm inside diameter and 11 cm outside diameter is covered with an
insulating substance k = 0.01 W/mK. The steam temperature is 250 oC and ambient
temperature is 27 oC. If the convective heat transfer coefficient between insulating
surface and air is 10 W/m2K, find the critical radius of insulation. Calculate the heat loss
per meter of pipe and the outer surface temperature. Neglect the resistance of the pipe
material. If this steam pipe is not insulated, calculate heat saved by insulating it as
indicated in this problem.