A 75-kW refrigeration load is to be carried by an air refrigerating system with a discharge pressure of 1,370 kPa and a refrigerator pressure of 345 kPa. Compression and expansion processes are polytropic with n = 1.37. The pressure at the start of expansion is 1344 kPa and the temperature is 32OC. Air temperature leaving the refrigerator is 0OC and entering the compressor is 5OC. Clearance for both compressor and expander is 5%. Draw the (a) Schematic diagram, (b) the P-V diagram and (c) the T-S diagram. Determine (d) the piston displacement of the compressor, (e) the piston displacement of the expand

A 75-kW refrigeration load is to be carried by an air refrigerating system with a discharge pressure of 1,370 kPa and a refrigerator pressure of 345 kPa. Compression and expansion processes are polytropic with n = 1.37. The pressure at the start of expansion is 1344 kPa and the temperature is 32OC. Air temperature leaving the refrigerator is 0OC and entering the compressor is 5OC. Clearance for both compressor and expander is 5%. Draw the (a) Schematic diagram, (b) the P-V diagram and (c) the T-S diagram. Determine (d) the piston displacement of the compressor, (e) the piston displacement of the expand

Refrigeration and Air Conditioning Technology (MindTap Course List)

8th Edition

ISBN:9781305578296

Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Chapter28: Special Refrigeration Applications

Section: Chapter Questions

Problem 15RQ: Why is two-stage compression popular for extra-low-temperature refrigeration systems?

See similar textbooks

Similar questions

Condensers in these refrigerators are all_______cooled.
Why is two-stage compression popular for extra-low-temperature refrigeration systems?
Welded ______sealed compressors are normally used in household refrigerators.
A vapor compression refrigeration systemhas an enthalpy of saturated liquid at the hightemperature side is 341.769 kJ/kg while at lowtemperature side is 131.27 kJ/kg and a latentheat of vaporization of 1312.63 kJ/kg. If themass flow rate of refrigerant is 0.50 kg/s.compute the tons of refrigeration.
Q2: A simple R134a vapor compression system operates between 40°C condensing temperature and-10°C evaporating temperature. The system compressor has a piston displacement of 3 m'/min and volumetric efficiency of 75%. The temperature of vapor leaving the compressor is 60°C. The liquid refrigerant is subcooled by 10°C before entering to the expansion device. Calculate: a. Refrigerant mass flow rate. b. Refrigeration capacity. c. Indicated power. d. The COP.
The large insulated flash chamber of a vacuum refrigeration plant is kept at low temperatureby a steam jet which pumps vapor to a condenser . The condensate pump removes thecondensate formed and an air ejector discharges air from the condenser to an air vent .Warm water returns enters the flash chamber at 13 deg C ; chilled water leaves the flashchamber at 4 deg C . The vapor leaving the flash chamber has a dryness factor of 97% andthe condenser inside temperature is 32 deg C . For 100 tons of refrigeration , determine thequantity in cubic meter per minute of chilled water at 4 deg C that the system can provide .A) 0.45 B) 0.56 C) 9.33 D) 0.75
1. A refrigeration system operates on an ideal vapor compression using R-12 with an evaporator temperature of -30°C and condenser exit temperature of 49 30 °C and requires 74.6 kW motor to drive the compressor. What is the capacity of the refrigerator in tons of refrigeration? Enthalpy at condenser entrance = 382 kJ/kg, exit = 248.15 kJ/kg, at evaporator entrance 248.15 KJ/kg, exit = 338.14 kJ/kg.
2. A freezer of 20 TR capacity has evaporator and condenser temperatures of 30°C and 25°C respectively. The refrigerant R-12 is sub-cooled by 4°C before it enters the expansion valve and is superheated by 5°C before leaving the evaporator. The compression is isentropic and the valve throttling and clearance are to be neglected. If a six-cylinder, single acting compressor with stroke equal to bore running at 1000 r.p.m. is used, determine: A- C.O.P. of the refrigerating system, B- Mass of refrigerant to be circulated per min, C- Theoretical piston displacement per minute and D- Theoretical bore and stroke of the compressor.
A refrigeration system with a capacity of 10 tons of refrigeration, operates at 210 kPa evaporator, while being condensed is 1240 kpa. If the refrigerator R-717 is saturated, calculate the theoretical power required to operate the compressor. compressor power =
A refrigeration system with a capacity of 15 tons of refrigeration, operates at 150 kPa in the evaporator, while the condenser is 1520 kPa. If refrigerant R-717 is saturated, calculate the theoretical power required to operate the compressor. Compressor Power Answer = kW.
A refrigerant 12 refrigeration system requires a load of 54 kW at an evaporator pressure of 270 kPa and a condenser pressure of 1009 kPa. The refrigerant is subcooled 10 degrees before entering the expansion valve and vapor is superheated 14 degrees before entering the compressor A twin-cylinder compressor with stroke equal to 1.25 times the bore is to be used at a speed of 27 r/s The volumetric efficiency is 84 per cent. Determine (a) the quantity of cooling water in the condenser for an 11-degree increase in temperature, (b) the bore and stroke, and (c) the compressor power. Ans (a) 1.40 kg/s, (b) 8.58 x 10.73 cm, (e) 10.5 kW
A simple air cooled system is used for an aero plane to take a load of 10 tons.Atmospheric temperature and pressure is 25°C and 0.9 atm respectively. Dueto ramming the pressure of air is increased from 0.9 atm, to 1 atm. The pressureof air leaving the main compressor is 3.5 atm and its 50% heat is removed inthe air-cooled heat exchanger and then it is passed through a evaporator for future cooling. The temperature of air is reduced by 10°C in the evaporator.Lastly the air is passed through cooling turbine and is supplied to the coolingcabin where the pressure is 1.03 atm. Assuming isentropic efficiency of the compressor and turbine are 75% and 70%,find i) Power required to take the load in the cooling cabinii) COP of the system.The temperature of air leaving the cabin should not exceed 25°C