vi) The vapour-compression heat pump system below uses a heat exchanger to superheat the vapour entering the compressor while sub-cooling the liquid exiting the condenser. The refrigerant used (R134a) is at -10.1°C in the evaporator and is sub-cooled by 11.3°C at the throttle valve entrance. If the condenser pressure is 800 kPa, the maximum temperature reached by the refrigerant throughout the cycle is closest to:

vi) The vapour-compression heat pump system below uses a heat exchanger to superheat the vapour entering the compressor while sub-cooling the liquid exiting the condenser. The refrigerant used (R134a) is at -10.1°C in the evaporator and is sub-cooled by 11.3°C at the throttle valve entrance. If the condenser pressure is 800 kPa, the maximum temperature reached by the refrigerant throughout the cycle is closest to:

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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A freon 12 waste water system operating at 5 °C suction temperature and a 40°C condensing temperature has an evaporator load 17.6 KW. If the condenser is selected for a 70°C water temperature rises, how many gpm must be circulated through the condenser? The following enthalpies have been found; condenser entrance =377 kJ/kg; exitA=238.5 kJ/kg; evaporator entrance =238.5 kJ/kg; exit = 253.6 kJ/kg.
Condenser a steam power plant that operates on a simple ideal ranking cycle and has a net power output of 22MW. Steam enters the turbine at 7Mpa and 450.05°C and is cooled in the condenser at a pressure of 10kpa by running cooling water from a lake through the tubes of the condenser at rate of 1750 kg/s. Determine the mess flow rates of steam through the steam turbine assuming that the cp of superheated steam is 2.9593kJ/kg.K.
A two-evaporatoor compression refrigeration system like that in the Figure below uses refrigerant-134a as the working fluid. The system operates evaporator 1 at 30 psia, evaporator 2 at 10 psia, and the condeser at 180 psia. The cooling load for evaporator 1 is 9000 Btu/h and that for evaporator 2 is 24,000 Btu/h. Determine the power required to operate the compressor and the COP of this system. The regrigerant is saturated liquid at the exit of the condenser and saturated vapor at the exit of each evaporator, and the compressor is isentropic.
Question 3 In a vapour-compression refrigeration system, refrigerant - 134a enters the compressor superheated at 200 kPa and - 5 °C. The refrigerant enters the condenser at 1.4 MPa and 75 °C, and exits at 1.4 MPa as a saturated liquid. There is no significant heat transfer between the compressor and its surroundings, and the refrigerant passes through the evaporator with a negligible change in pressure. If the refrigerating capacity is 105 kW, represent the cycle on a T-s diagram and determine: a) the mass flow rate of the refrigerant in kg/s, b) the power input to the compressor in kW, c) the coefficient of performance, and (2) d) the isentropic compressor efficiency
An ammonia refrigerating system has a load of 250 kW and operates at a condensing pressure of 1400 kPa and an evaporating temperature of -20°C. The refrigerant exits at the evaporator with a 5- degree superheat. The vapor enters the compressor suction at 10-degree superheat. The compressed vapor is discharged from the compressor at the condensing pressure and 150°C. The refrigerant exits the condenser as saturated liquid. a. State the enthalpies at each point: Point enthalpy kJ/kg h kJ/kg kJ/kg h2 kJ/kg h3 kJ/kg h4 Answer: kg/sec b. Calculate the mass flow of refrigerant Answer: kW C. Determine the size of the motor drive if the mechanical efficiency of the motor- compressor is 77%. Answer: kW Calculate the total heat rejected in the condenser. d. Determine the refrigerating efficiency of the system. Answer: е.
A vapor-compression system produces 20 tons of refrigeration using R12 as a refrigerant while operating between a condenser temperature of 41.6°c and an evaporator temperature of – 25°c. The superheat at the compression suction and the sub-cooling at the condenser outlet are 10°K. The pressure drop are 10kPa across the evaporator and the condenser. Determine the refrigerating effect in kJ per kilogram, the circulating rate of R12 in kilograms per second, the power required, the COP, the heat rejected in kW and the volume flow rate of refrigerant at compressor inlet conditions. 10° K subcooling 4 Tm= 41.6° C h= C s =C Tevap =-25° C 10° K superheat
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
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