A heat pump operates on the ideal vapor-compression refrigeration cycle and uses refrigerant-22 as the working fluid. The operating conditions for this heat pump are evaporator saturation temperature of −5°C and the condenser saturation temperature of 45°C. Selected data for refrigerant-22 are provided in the following table.
For R-22 at P = 1728 kPa and s = 0.9344 kJ/kg·K, T = 68.15°C and h = 283.7 kJ/kg. Also, take cp,air = 1.005 kJ/kg·K.
(a) Sketch the hardware and the T-s diagram for this heat pump application. (b) Determine the COP for this unit. (c) The condenser of this unit is located inside the air handler of an office. If the air flowing through the air handler is limited to a 20°C temperature rise, determine the ratio of volume flow rate of air to mass flow rate of R-22 through the air handler, in (m3 air/min)/(kg R-22/s).
Want to see the full answer?
Check out a sample textbook solutionChapter 11 Solutions
Thermodynamics: An Engineering Approach
- Problem 1 (Using thermodynamic tables)A large refrigeration plant is to be maintained at -12 C. It requires refrigeration at a rate of 120 kW.The condenser of the plant is to be cooled by liquid water, which experiences a temperature rise of 10 C as it flows over the coils of the condenser. Assuming the plant operates on the ideal vapor-compression cycle using refrigerant- 134a between the pressure limits of 100 and 700 kPa, determine (a) the mass flow rate of the refrigerant, (b) the power input to the compressor, and (c) the mass flow rate of the cooling waterarrow_forwardConsider a refrigrator that operates on the vapor compression refrigeration cycle with R-134a as the working fluid. The refrigerant enters the compressor as saturated vapor at 70 kPa, and exits at 1200 kPa and 90°C, and leaves the condenser as saturated liquid at 1200 kPa. The coefficient of performance of this refrigrator isarrow_forwardConsider a two-stage cascade refrigeration system operating between the pressure limits of 0.8 and 0.14 MPa. Each stage operates on the ideal vapor-compression refrigeration cycle with refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle takes place in an adiabatic counter-flow heat exchanger where both streams enter at about 0.4 MPa. If the mass flow rate of the refrigerant through the upper cycle is 0.24 kg/s, determine (a) the mass flow rate of the refrigerant through the lower cycle, (b) the rate of heat removal from the refrigerated space and the power input to the compressor, (c) the coefficient of performance of this cascade refrigerator, and (d) the intermediate pressure of the cascade cycle. For full credit, accurately, neatly draw the cascade system on an electronic PDF p-h diagram. Please only solve part d. If possible, show the ph diagramarrow_forward
- A Carnot refrigeration cycle is executed in a closed system in the saturated liquid-vapor mixture region using 1 kg of refrigerant-134a as the working fluid. The maximum and the minimum temperatures in the cycle are 22C and -4C, respectively. If the refrigerant is saturated liquid at the end of the heat rejection process, and the net work input to the cycle is 16 kJ, determine: b) The pressure at the end of the heat rejection process. Should correct please. (Gpt/ai Answer not allowed)arrow_forwardConsider a refrigeration system using refrigerant-134a as the working fluid. If this refrigerator is to operate in an environment at 20°C, what is the minimum pressure to which the refrigerant should be compressed? Why?arrow_forwardA standard vapor compression system produces 70.4 kW of refrigeration using R-12as a refrigerant while operating between a condenser temperature of 42 °C and anevaporator temperature of –25 °C.2.1 Draw the p-h diagram of the cycle. 2.2 Determine:(a) the refrigerating effect in kJ/kg, (b) the circulating rate in kg/s, (c) the power supplied, (d) the COP, (e) the heat rejected in kW, and(f) the volume flow rate in m3/s.arrow_forward
- Consider a two-stage compression refrigeration system operating between the pressure limits of 0.8 and 0.14 MPa. The working fluid is refrigerant-134a. The refrigerant leaves the condenser as a saturated liquid and is throttled to a flash chamber operating at 0.4 MPa. Part of the refrigerant evaporates during this flashing process, and this vapor is mixed with the refrigerant leaving the low-pressure compressor. The mixture is then compressed to the condenser pressure by the high-pressure compressor. The liquid in the flash chamber is throttled to the evaporator pressure, and it cools the refrigerated space as it vaporizes in the evaporator. Assuming the refrigerant leaves the evaporator as saturated vapor and both compressors are isentropic, determine (a)the fraction of the refrigerant that evaporates as it is throttled to the flash chamber, (b)the amount of heat removed from the refrigerated space and the compressor work per unit mass of refrigerant flowing through the condenser,…arrow_forwardAn ideal vapor-compression refrigeration cycle that uses refrigerant-134a as its working fluid maintains a condenser at 800 kPa and the evaporator at 15 kPa. Given 300 kW of cooling load, determine the following: 1. Construct didactic sketches, showing the operating principles of a refrigeration system.2. When you select a refrigerant for a certain application, what qualities would you look for in the refrigerant?3. Estimate the reversible COP values, if the low and high medium temperature are as for the evaporator and condenser.arrow_forwardRefrigerant 134a is used as the working fluid in a refrigerator, and it operates in an ideal vapor compression refrigeration cycle, if the refrigerant enters the evaporator at -4 ° C and enters the condenser at 1200 kPa. If the mass flow of the refrigerant is 180 kg / h, determine a) the Ts and Ph diagrams of the cycle with all the information b) the rate of heat removal from the refrigerated space and the power input to the compressor, and c) the COP Of fridgearrow_forward
- Consider a steady-flow Carnot refrigeration cycle that uses refrigerant-134a as the working fluid. The maximum and minimum temperatures in the cycle are 30 and -20C, respectively. The quality of the refrigerant is 0.15 at the beginning of the heat absorption process and 0.80 at the end. Show the cycle on a T-s diagram relative to saturation lines, and determine (a) the coefficient of performance, (b) the condenser and evaporator pressures, and (c) the net work input.arrow_forwardConsider a heat pump that operates on the vapor compression refrigeration cycle with R-134a as the working fluid. The refrigerant enters the compressor as saturated vapor at 180 kPa, and exits at 900 kPa and 40°C, and leaves the condenser as saturated liquid at 900 kPa. The coefficient of performance of this heat pump is a. 5.51 b. 4.58 c. 3.61 d. 4.06 e. 2.87arrow_forwardThe COP of vapor-compression refrigeration cycles improves when the refrigerant is subcooled before it enters the throttling valve. Can the refrigerant be subcooled indefinitely to maximize this effect, or is there a lower limit? Explain.arrow_forward
- Refrigeration and Air Conditioning Technology (Mi...Mechanical EngineeringISBN:9781305578296Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill JohnsonPublisher:Cengage Learning