Chapter 5, Problem 5.43P

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A heat engine must provide 1000 Watts of power. Assuming it has an efficiency of 0.32, how much heat must be supplied to the engine, in Watts?

Kelvin-Planck statement defines the Second law of thermodynamics as a. It is impossible to construct a machine that will operate in a cycle, extract heat from a reservoir, and do an equivalent amount of work on the surroundings. b. It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower-temperature body to a higher-temperature body. c. It is possible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower-temperature body to a higher-temperature body. d. It is possible to construct a machine that will operate in a cycle, extract heat from a reservoir, and do an equivalent amount of work on the surroundings.

A heat pump with a coefficient of performance of 3.5 provides energy at an average rate of 70,000 kJ/h to maintain a building at 20 deg C on a day when the outside temperature is -5 deg C. If electricity costs 8.5 cents per kWh, (a) determine the actual operating cost and the minimum theoretical operating cost, each in $/day. (b) compare the results of part (a) with the cost of electrical-resistance heating.

A heat pump maintains a dwelling at 68°F. When operating steadily, the power input to the heat pump is 5 hp, and the heat pump receives energy by heat transfer from 55°F well water at a rate of 500 Btu/min. (a) Determine the coefficient of performance. (b) Evaluating electricity at $0.18 per kWh, determine the cost of electricity in a month when the heat pump operates for 300 hours. Part A Determine the coefficient of performance. y = i

An air conditioner is a device used to cool the inside of a home. It is, in essence, a refrigerator in which mechanical work is done and heat removed from the (cooler) inside and rejected to the (warmer) outside. A home air conditioner operating on a reversible Carnot cycle between the inside, absolute temperature T2, and the outside, absolute tempera- ture T1 > T2, consumes P joules/sec from the power lines when operating continuously. (a) In one second, the air conditioner absorbs Q2 joules from the house and rejects Q1 joules outdoors. Develop a formula for the efficiency ratio Q2/P in terms of T1 and T2. (b) Heat leakage into the house follows Newton's law Q = A(T, – T2). Develop a formula for T, in terms of T1, P, and A for continuous operation of the air conditioner under constant outside temperature T and uniform (in space) inside temperature T2. (c) The air conditioner is controlled by the usual on-off thermostat and it is observed that when the thermostat set at 20°C and an…

A heat pump cycle is used to maintain the interior of a building at 25°C. At steady state, the heat pump receives energy by heat transfer from well water at 9°C and discharges energy by heat transfer to the building at a rate of 120,000 kJ/h. Over a period of 14 days, an electric meter records that 1500 kW · h of electricity is provided to the heat pump.Determine:(a) the amount of energy that the heat pump receives over the 14-day period from the well water by heat transfer, in kJ.(b) the heat pump’s coefficient of performance.(c) the coefficient of performance of a reversible heat pump cycle operating between hot and cold reservoirs at 25°C and 9°C.

The larger the specific volume, the greater the work produced (or consumed) by a steady-flow device.

Between a heat source at temperature T and a low-temperature heat well at 280 K power cycle is working. In steady state, the cycle produces 50 kW of work, while the heat well is 1000 kl/min. heats up. Determine the minimum theoretical value for T in K (Kelvin).