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

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

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.46P

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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
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 103.5°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 3.45 hp. Step 1 B Inside, 70° F Determine the coefficient of performance for the air conditioner. = Evaporator i 30,000 Btu/h 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. Refrigerant loop Compressor Outside Q + Condenser
3. A reversible refrigeration cycle operates between cold and hot reservoirs at temperatures TC and TH, respectively. (a) If the coefficient of performance is 3.5 and TC = -40 deg F, determine TH, in deg F. (b) If TC = -30 deg C and TH = 30 deg C, determine the coefficient of performance. (C) If QC = 500 Btu, QH = 800 Btu, and TC = 20 deg F, determine TH, in deg F. (d) If TC = 30 deg Fand TH = 100 deg F, determine the coefficient of performance. (e) If the coefficient of performance is 8.9 and TC = -5 deg C, find TH, in deg C.
The heat pump cycle shown in the figure below operates at steady state and provides energy by heat transfer at a rate of 15 kW to maintain a dwelling at 22°C when the outside temperature is Toutside 5°C. The manufacturer claims that the power input required for this operating condition is W cycle = 4 kW. 0 = i Is this cycle possible? Yes No QH = 15 kW bok and Modia Tinside = 22°C kW/K = Heat pump cycle Applying energy and entropy rate balances determine the rate of entropy production, in kW/K. Toutside W cycle
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…
The thermal efficiency of a reversible power cycle operating between hot and cold reservoirs is 40%. 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.
Suppose a heat engine is made out of an ideal diatomic gas taken around a cycle represented by the following PV diagram: B P2 A P1 D V1 V2 Volume (a)Briefly explain why this cycle cannot be used in reverse for refrigeration. (b)Calculate the efficiency of an "ideal" engine operating between the same temperature extremes Pressure
4. Two and one-half pounds of air actuate a cycle composed of the following processes: polytropic compression 1-2, with n = volume 3-1. The known data are: D1 = 20 psia, ti = 100°F, Qr = -1682 Btu. Determine (a) T2 nd Ts, (b) the work of the cycle using the pV plane, in Btu; (c) Qu (d) the thermal 1.5; constant pressure 2-3; constant efficiency, and (e) pn. Ans. (a) 1120°R, 4485°R; (b) 384.4 Btu; (c) 2067 Btu; (d) 18.60%: (e) 106.8 psia
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 8 bar. The isothermal expansion occurs at 275 K. Determine: TH p-v diagram for a Carnot gas refrigeration or heat pump cycle. (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.
Q.2 A Carnot engine operates with ideal gas, using the Carnot cycle shown in the following Figure. Using the first law of thermodynamics and assume no change of internal energy, determine the thermal efficiency, the specific heat impute (q), and the work output (w) for each cycle of operation. (K=1.4 & R=0.287 KJ/Kg. K) T = 220 C 77 kPa T = 20 C 12 m'/kg
A Carnot vapor refrigeration cycle operates between thermal reservoirs at 40 ⁰F and 100 ⁰F. Determine the coefficient of performance.
Referring to the reversible heat pump cycle shown in the figure, p₁ = 14.7 lb/in², p = 41.5 lb/in², v₁ = 12.6 ft³/lb, v4 = 6.0 ft³/lb, and the gas is air obeying the ideal gas model. Step 1 Determine TH, in °R, and the coefficient of performance. Determine TH, in °R. TH= i P4 ºR P1 V4 VI 3 Tμ V