Problem 45PE

A 4-ton air conditioner removes 5.06 × 107 J (48,000 British thermal units) from a cold environment in 1.00 h. (a) What energy input in joules is necessary to do this if the air conditioner has an energy efficiency rating ( EER ) of 12.0? (b) What is the cost of doing this if the work costs 10.0 cents per 3.60×106 J (one kilowatt-hour)? (c) Discuss whether this cost seems realistic. Note that the energy efficiency rating ( EER ) of an air conditioner or refrigerator is defined to be the number of British thermal units of heat transfer from a cold environment per hour divided by the watts of power input.

Solution 45PE

- The required energy 1.44x103 J
- The cost of doing work is 40o C
- From the above result one can conclude that the cost of doing work is reasonable. This is because, the result says that if the air conditioner runs for the entire day continuously, it would cost about $9.59.