Chapter 5, Problem 5.43CU

As shown in the figure, an air conditioner operating at steady state maintains a dwelling at 70°F on a day when the outside temperature is 90°F. The rate of heat transfer into the dwelling through the walls and roof is 30,000 Btu/h and the net power input to the air conditioner compressor is 3 hp.    Determine   a. the coefficient of performance for the air conditioner b. power input required in hp c.  coefficient of performance for a reversible air conditioner providing the same cooling effect while operating between the same cold and hot temperatures.

As shown in the figure, an air conditioner operating at steady state maintains a dwelling at 70°F on a day when the outside temperature is 102°F. The rate of heat transfer into the dwelling through the walls and roof is 30,000 Btu/h and the net power input to the air conditioner compressor is 3.4 hp. Inside, 70° F Evaporator ← 30.000 Bu Refrigerant loop W. Compressor Outside Condonsor Que Determine the coefficient of performance of the air conditioner. Determine the power input required, in hp, and the coefficient of performance for a reversible air conditioner providing the same cooling effect while operating between the same cold and hot temperatures.

C5 6.

The thermal efficiency of a reversible power cycle operating between hot and cold reservoirs is 60%. 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 Save for Later Part R Attempts: 0 of 4 used Submit Answer

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…

An ammonia vapor refrigeration cycle operates at an evaporator temperature of −16°C and   a condensing temperature of 32°C. For an ideal saturation cycle, a. Draw the schematic diagram and the corresponding P-h diagram of the system b. Complete the table below State points  t, °C  p, kPa h, kj/kg 1       2       3       4

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.

A reversible refrigeration cycle operates between cold and hot reservoirs at temperatures Tc and TH, respectively. (a) If the coefficient of performance is 10 and Tc- -40°F, determine TH, in °F. (b) If Tc- -30°C and TH -30°C, determine the coefficient of performance. (c) If Qc - 500 Btu, QH-600 Btu, and Tc -20°F, determine TH, in °F. (d) If Tc-30°F and TH-100°F, determine the coefficient of performance. (e) If the coefficient of performance is 8.9 and Te--5°C, find TH, in °C.

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