91Ó°ÊÓ

A window-mounted room air conditioner removes energy by heat transfer from a room and rejects energy by heat transfer to the outside air. For steady-state operation, the air conditioner cycle requires a power input of \(0.434 \mathrm{~kW}\) and has a coefficient of performance of 6.22. Determine the rate that energy is removed from the room air, in \(\mathrm{kW}\). If electricity is valued at \(\$ 0.1 / \mathrm{kW}\) - h, determine the cost of operation for 24 hours of operation.

An air-conditioning unit with a coefficient of performance of \(2.93\) provides \(5000 \mathrm{Btu} / \mathrm{h}\) of cooling while operating during the cooling season 8 hours per day for 125 days. If you pay 10 cents per \(\mathrm{kW}\). \(\mathrm{h}\) for electricity, determine the cost, in dollars, for the cooling season.

A heat pump cycle operating at steady state receives energy by heat transfer from well water at \(10^{\circ} \mathrm{C}\) and discharges energy by heat transfer to a building at the rate of \(1.2 \times 10^{5} \mathrm{~kJ} / \mathrm{h}\). Over a period of 14 days, an electric meter records that \(1490 \mathrm{~kW}\) - \(\mathrm{h}\) of electricity is provided to the heat pump. These are the only energy transfers involved. Determine (a) the amount of energy that the heat pump receives over the 14-day period from the well water by heat transfer, in \(\mathrm{kJ}\), and (b) the heat pump's coefficient of performance.

A heat pump maintains a dwelling at \(68^{\circ} \mathrm{F}\). When operating steadily, the power input to the heat pump is \(5 \mathrm{hp}\), and the heat pump receives energy by heat transfer from \(55^{\circ} \mathrm{F}\) well water at a rate of \(500 \mathrm{Btu} / \mathrm{min}\). (a) Determine the coefficient of performance. (b) Evaluating electricity at \(\$ 0.10\) per \(\mathrm{kW} \cdot \mathrm{h}\), determine the cost of electricity in a month when the heat pump operates for 300 hours.

A heat pump cycle delivers energy by heat transfer to a dwelling at a rate of \(40,000 \mathrm{Btu} / \mathrm{h}\). The coefficient of performance of the cycle is \(2.8\). (a) Determine the power input to the cycle, in hp. (b) Evaluating electricity at \(\$ 0.085\) per \(\mathrm{kW} \cdot \mathrm{h}\), determine the cost of electricity during the heating season when the heat pump operates for 2000 hours.