Chapter 5, Problem 5.11CU

At steady state, a refrigeration cycle removes 800 kJ/min of energy by heat transfer from acold space maintained at -15o C and discharges energy by heat transfer to its surroundings at20o C. If the coefficient of performance of the actual cycle is 80 percent of that of areversible refrigeration cycle (ideal) operating between thermal reservoirs at these twotemperatures (β = 0.80 βmax), determine:a) Coefficient of performance;b) Power input to the cycle, in kW;c) Heat rejected to the surroundings.Draw sketch and show all calculations.

Select the Kelvin-Plank statement of the second law of Thermodynamics___________   A. 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.     B. It is impossible for any device that operates on a cycle to receive heat form a single reservoir and produce a net amount of work.

A thermodynamic cycle receives 150 J of heat from a cold reservoir and rejects 165 J of heat to a hot reservoir. What is its coefficient of performance as a refrigeration cycle, (B) ?

Two reversible cycles operate between hot and cold reservoirs at temperatures TH and TC, respectively. (a)If one is a power cycle and the other is a refrigeration cycle, what is the relation between the coefficient of performance of the refrigeration cycle and the thermal efficiency of the power cycle? (b)If one is a refrigeration cycle and the other is a heat pump cycle, what is the relation between their coefficients of performance?

An ideal gas within a piston–cylinder assembly undergoes a Carnot refrigeration cycle, as shown in the figure below. The isothermal compression occurs at 325 K from 2 bar to 6 bar. The isothermal expansion occurs at 275 K. Determine: (a) the coefficient of performance, (b) the heat transfer to the gas during the isothermal expansion, in kJ per kmol of gas, (c) the magnitude of the net work input, in kJ per kmol of gas.

Differentiate Refrigerator from Heat pumps in terms of: (a) Transfer of Heat, (b) Location of the evaporator, (c) Location of the condenser, and (d) Working of evaporator and condenser.

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…

Question 9

The thermal efficiency of a reversible power cycle operating between hot and cold reservoirs is 50%. Evaluate the coefficient of performance of: (a) a reversible refrigeration cycle operating between the same two reservoirs. (b) a reversible heat pump cycle operating between the same two reservoirs. Part A Evaluate the coefficient of performance of a reversible refrigeration cycle operating between the same two reservoirs. B = i