PROBLEM 2 : An ammonia simple saturation cycle operates evaporator and condenser temperatures of -20°C and 35°C, respectively. The system is to be used in producing 6000 kg of ice at -12°C from water at 29°C in 10 hours. Assuming losses to be 30 per cent of the heat to be absorbed from the water, determine (a) the mass flow rate, (b) the heat rejected at the condenser, and (c) the power required by the compressor.

PROBLEM 2 : An ammonia simple saturation cycle operates evaporator and condenser temperatures of -20°C and 35°C, respectively. The system is to be used in producing 6000 kg of ice at -12°C from water at 29°C in 10 hours. Assuming losses to be 30 per cent of the heat to be absorbed from the water, determine (a) the mass flow rate, (b) the heat rejected at the condenser, and (c) the power required by the compressor.

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.
3. An ammonia simple saturation cycle operates between evaporator and condenser temperatures of -20°C and 35°C, respectively. The system is to be used in producing 5000 kg of ice at – 12°C from water at 29°C in 20 hours. Assuming losses to be 20 per cent of the heat to be absorbed from the water. Determine (a) the mass flow rate of the refrigerant, (b) the heat rejected at the condenser, and (c) the power required by the compressor.
Part C A surface condenser is required to condense 30,000 kg of dry steam per hour at a pressure of 0.04 bar at 29°C. The cooling water enters at 15°C and leaves at 27°C. Assume the overall surface area (As) of the tube is 1200 m² If the velocity of water in the tubes should not exceed 2 m/s, the outside diameter of the tube is 0.025 m and the inside diameter is 0.022 m, determine (i) the heat transfer (ii) mass of cooling water circulated (iii) the number of tubes (iv) the length of each tube and (v) the overall heat transfer coefficient of the tubes. Take the density of water =1000 kg/m3 and specific heat of water =4.187 kJ/kg K.
A Freon 12 vapour compression system operating at a condenser temperature of 45Co and an evaporator temperature of 0Co develops 20 tons of refrigeration. Using the p-h diagram for Freon 12, determine; (15) a) The mass flow rate of the refrigerant circulated. b) The heat rejected in the condenser, and c) The Carnot COP and the actual COP of the cycle.
4. Ammonia enters the compressor of a refrigeration plant and is compressed from 190.2kPa, 98% dry to 972.2kPa with 50K of superheat. The refrigerant leaves the condenser as a liquid at 24°C and circulates with a mass flowrate of 5kg/min. Calculate: (a). compressor power (b). heat rejected in the condenser per minute (c). coefficient of performance (d). condition at entry to evaporator (e). plant capacity if enthalpy of fusion is 333kJ/kg Ans: 17.442kW, 6543kJ/min, 5.2522, 0.1536, 23.769tonne/day
The evaporator and condenser temperatures are -20°C and 35°C, respectively, in an ammonia simple saturation cycle. The method will be used to produce 12,500kg of ice at -15°C in 32 hours from water at 25°C. Assuming that 25 percent of the heat absorbed from the water is lost. Ice has a specific heat of 2.094Kj/kg-K, while fusion has a heat of 335kj/kg. Determine the: a) Total Heat b) Mass flow rate
1. A 10-kW cooling load is to be served by operating an ideal vapor-compression refrigeration cycle with its evaporator at 400 kPa and its condenser at 800 kPa. If the compressor's isentropic efficiency is 68%, calculate the refrigerant mass flow rate and the compressor power requirement when refrigerant-134a is used.
5. A vapour compression refrigeration plant using R12 has saturation temperatures in the evaporator and condenser of -20°C and 35°C respectively. The R12 leaving the condenser is undercooled by 5°C and leaving the evaporator it is superheated by 15°C. The R12 circulates at 10kg/m. Calculate: (a). the dryness fraction of the R12 at the evaporator inlet (b). the cooling load in kW (c). the rate of work done on the R12 in the compressor (d). the plant capacity
Q.13 A vapour compression refrigeration system using refrigerant F-12 is employed to produce 8640 kg of ice per day. The condensing and evaporating temperature of refrigcrant are 48°C and-20°C respectively. Saturated liquid leaves the condenser and saturated vapour leaves the evaporator. Compression is isentropic, water at 35°C is used to form the ice. The temperature of ice should be-8°C. Heat flow into the brine tank from surroundings may be taken as 10% of total heat absorbed from water to form ice. Determine the power required to drive the compressor. Take specific heat of ice 2.26 kJ/kg-K. Latent heat of ice = 335 kJ/kg. Specific heat of water = 4.2 kJ/kg-K. The following data may be used: %3D Temp. Pressure Enthalpy Entropy °C bar kJ/lg kJ/kg-K Liquid Vapour Liquid Vapour 48°C 11.64 82.83 205.83 0.2973 0.6802 -20 1.51 17.82 178.74 0.0731 0.7087 Specific heat of vapour 0.82 kJ/kg %3D
A compressor serves two evaporators, one providing 5 tons of cooling at -20 degree F and the other, 10 tons of cooling at 10F. The system is a vapor-compression refrigeration system using R-12 with the condenser pressure at 200 psia. Assume saturated conditions leaving the condenser and evaporators and isentropic compression. Determine (a) the refrigerant flow through each evaporator, (b) the R-12 state entering the compressor, and (c) the compressor power.
The catalog for a refrigerant 22, four cylinder, hermetic compressor operating at 29 r/s, a condensing temperature of 40, and an evaporating temperature of -4 shows a refrigerating capacity of 115 kW. At this operating point the motor (whose efficiency is 90%) draws 34.5 kW. The bore of the cylinders is 87 mm and the piston stroke is 70 mm. The performance data are based on 8 of subcooling of the liquid leaving the condenser. Compute (a) the actual volumetric efficiency and (b) the compression efficiency.
3.) An ammonia compressor operates at evaporator pressure of 316.02 kPa and a condenser pressure of 1557 kPa. A twin-cylinder compressor with bore to stroke ratio of 0.85 is to used at 1200 rpm. The actual volumetric efficiency is 92% and compression and mechanical efficiency is 78% and 80% respectively. For a cooling capacity of 25 TR, (a) the sketch the p-h diagram labeling the evaporating and condensing temperature and pressures (b) define the all properties of ammonia taken from saturation table. Determine (c) the quantity of cooling water in the condenser in kg/min if the increase in temperature is 8°C, (d) the bore and stroke expressed in cm and (e) the size of the driving motor in hp. Given: h2 = h at 1557 kPa and s2 = s1 1695 kJ/kg