Chapter 5, Problem 5.37P

A heat engine operating between two reservoirs receives energy Q₁=2100 KJ by heat transfer from a hot reservoir(source) at T₁= 2000 K and rejects energy Q₂=500 KJ by heat transfer to a cold reservoir (sink) at T₂= 400 K. Determine the reversible and irreversible efficiencies of heat engine. -Calculate reversible and irreversible efficiencies To be: Q₁ = 2000KJ Q₂ = 400KJ -Wrev -Calculate practical (real) work

A household refrigerator draws 113.9 W of electricity in order to keep its refrigerated compartment at a steady 4.7 ºC; the insulation of the compartment is such that heat passes from the room to the refrigerated compartment at 53.9 kJ per minute. Rejected heat is dumped to the room in which the refrigerator is placed. By comparison to the coefficient of performance for an ideal refrigerator, determine the maximum room temperature in which the refrigerator could operate. Give your answer in ºC to 1 decimal place.

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.

A refrigerator operates at steady-state with a COP of 4.5 and power input of 0.8kW. If energy is rejected from the refrigerator to the surroundings at 20°C because of heat transfer from metal coils, the rate of energy rejection is computed as kW and the lowest theoretical temperature inside the refrigerator would be °C.

(b) A heat engine with a thermal efficiency of 40 percent rejects 1000 kJ/kg of heat. Determine the amount of heat it receives.

An air conditioner operating at steady state maintains a dwelling at 20°C on a day when the outside temperature is 40°C. Energy is removed by heat transfer from the dwelling at a rate of 3200 J/s while the air conditioner’s power input is 0.8 kW. Determine the coefficient of performance of the air conditioner. Determine the power input required by a reversible refrigeration cycle providing the same cooling effect while operating between hot and cold reservoirs at 40°C and 20°C, respectively, in kW.

A heat engine, operating between reservoirs at temperatures of 372 deg C and 17 deg C, performs 3.2 kJ of net work, and rejects 13.1 kJ of heat. What is the actual thermal efficiency (%)?

The Kelvin-Planck and Clausius statements of thermodynamics are equivalent.  In order to prove the equivalence, a heat-engine-refrigerator combined system is used as shown below. The system satisfies the following conditions, where QH and QL are known values. 1) Heat recieved by the heat engine from the source:  QH,HE=QH 2) Heat QH is completely converted into net work output from the heat engine: QH=Wnet 3) Heat recieved by the regrigerator from the sink:  QL,R=QL What is the heat exported to the source by the refrigerator, QH,R?__________     A. QH   B. QH+QL   C. QH-QL   D. QL

The Kelvin-Planck and Clausius statements of thermodynamics are equivalent.  In order to prove the equivalence, a heat-engine-refrigerator combined system is used as shown below. The system satisfies the following conditions, where QH and QL are known values. 1) Heat recieved by the heat engine from the source:  QH,HE=QH 2) Heat QH is completely converted into net work output from the heat engine: QH=Wnet 3) Heat recieved by the regrigerator from the sink:  QL,R=QL What is the thermal efficiency of the heat engine?__________     A. Wnet/QH=QH/QH=100%   B. QL/QH   C. QH/QL   D. (QH-QL)/QH