(1) In an ammonia refrigeration system, the capacity is 210 kW at a temperature of-20°C. The vapor from the evaporator is pumped by one compressor to the condensing pressure of 1431 kPa. Later, the system was revised to a two-stage compression operating on the cycle shown below with intercooling but no removal of flash at 555 kPa. (a) in the original system. (b) compressors in the revised system. Calculate the power required by the single compressor Calculate the total power required by the two-

(1) In an ammonia refrigeration system, the capacity is 210 kW at a temperature of-20°C. The vapor from the evaporator is pumped by one compressor to the condensing pressure of 1431 kPa. Later, the system was revised to a two-stage compression operating on the cycle shown below with intercooling but no removal of flash at 555 kPa. (a) in the original system. (b) compressors in the revised system. Calculate the power required by the single compressor Calculate the total power required by the two-

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

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Saturated vapor R22 refrigerant leaves the evaporator and enters the compressor at 131.68kPa. The refrigerant leaves the condenser as a saturated liquid at 40oC and enters theexpansion valve at 36oC. Heat rejected from the condenser amount to 105 kW. The work tothe compressor is 65 kJ/kg, while the heat loss from the compressor is 5.5 kJ/kg. A 7.4 kJkgof heat loss in piping between the compressor and condenser, Draw the p-h diagram(labeling the pressures and temperatures in each condition). Determine (a) the temperatureof refrigerant entering the condenser and (b) calculate the refrigeration capacity in tons.
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
The figure below shows a two-stage vapor-compression refrigeration system with ammonia as the working fluid. The system uses a direct-contact heat exchanger to achieve intercooling. The evaporator has a refrigerating capacity of 40 tons and produces -30°F saturated vapor at its exit. In the first compressor stage, the refrigerant is compressed adiabatically to 140 lbf/in.², which is the pressure in the direct contact heat exchanger. Saturated vapor at 140 lbf/in.² enters the second compressor stage and is compressed adiabatically to 250 lbf/in.² Each compressor stage has an isentropic efficiency of 85%. There are no significant pressure drops as the refrigerant passes through the heat exchangers. Saturated liquid enters each expansion valve. Determine: Expansion valve 6- Condenser Direct contact heat exchanger Expansion valve (a) the ratio of mass flow rates, m3/my. (b) the power input to each compressor stage, in horsepower. (c) the coefficient of performance Comp Comp Evaporator
9. A vapour compression plant is powered by a 2kW motor and circulates R12 at 5kg/min. The R12 leaves the condenser at its saturation temperature with a specific enthalpy of 74.59kJ/kg and leaves the evaporated dry saturated with a specific enthalpy of 187.53kJ/kg. Calculate: (a). the dryness fraction at the evaporator inlet (b). refrigeration effect (c). coefficient of performance
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An r-134a refrigerator operates a simple vapor compression cycle (SVCC). The evaporatoroperates at -10 °C, while the condenser operates at 1 MPa. R-134a flows around the system at 10 g/s.a. Graph the cycle in a P-h diagram and calculate the temperature at the exit of the compressor, assuming it is 100% isentropicallyefficient.b. Calculate the power required by the compressor (in W) and the cooling effect of the refrigerator (in kW) c. Compute for the COP of the system. What is its percent difference from the reversible efficiency?
4. A refrigerating plant having R-12 as the working fluid, comprises three evaporators of 10 TR at -10°C, 20 TR at 5°C and 30 TR at 10°C. Each of the evaporators is having the individual expansion valve arrangement. The refrigerant from the higher stage expansion valve is bled and mixed with delivery from the lower stage compressor and sent to the higher stage compressor suction thus effecting intercooling of the delivery gas from the lower stage and bringing the suction of the higher stage compressor to dry and saturated conditions. There is only one condenser operating at 40°C and sub- cooling the liquid refrigerant to 30°C. The compression during each stage of compression may be assumed isentropic. The evaporator discharge is dry saturated in cach of the evaporators. Determine the power required by the entire system. 5. A refrigeration system using R-12 as refrigerant consists of three evaporators of capacities 20 TR at - 5°C, 30 TR at 0°C and 10 TR at 5°C. The vapours leaving the…
A refrigeration system with a capacity of 15 tons of refrigeration, operates at 150 kPa in the evaporator, while in the condenser it is 1000 kPa. If R-134a refrigerant is in a saturated state, calculate the theoretical power required to operate the compressor. Compressor Power
11. A vapour compression refrigeration plant uses ammonia. The compressor takes vapour from the evaporator at 207.7kPa and -8°C and delivers to the condenser at 1470kPa and 113°C. The temperature of the liquid leaving the condenser at a rate of 12kg/min is 38°C. Calculate: (a). the dryness of the refrigerant entering the evaporator (b). the cooling load (c). the power to the compressor (d). coefficient of performance (e). plant capacity