A refrigeration unit utilises ammonia as the refrigerant. The diagram for the circuit is shown in Figure Q3 below, with the following conditions: point (1) is a saturated liquid at -30 °C, points (3), (4) and (7) is a saturated liquid at 10 °C and point (5) is a saturated vapour at -30 °C. The isentropic efficiency of the compressor and pump is 80% and it is assumed there are negligible heat losses to the surroundings. The liquid ammonia has a specific volume of 0.0015 m³ kg-¹. (a) Discuss which factors must be considered when selecting an appropriate refrigerant? (b) Calculate the coefficient of performance (COP) of the cycle. (c) If the effect of refrigeration is 10 kW, determine the required mass flow rate. 6 Compressor Condenser y 5 7 1 4 3 Spray Flash chamber Pump Figure Q3. Refrigeration circuit diagram. 1 Evaporator 2

A refrigeration unit utilises ammonia as the refrigerant. The diagram for the circuit is shown in Figure Q3 below, with the following conditions: point (1) is a saturated liquid at -30 °C, points (3), (4) and (7) is a saturated liquid at 10 °C and point (5) is a saturated vapour at -30 °C. The isentropic efficiency of the compressor and pump is 80% and it is assumed there are negligible heat losses to the surroundings. The liquid ammonia has a specific volume of 0.0015 m³ kg-¹. (a) Discuss which factors must be considered when selecting an appropriate refrigerant? (b) Calculate the coefficient of performance (COP) of the cycle. (c) If the effect of refrigeration is 10 kW, determine the required mass flow rate. 6 Compressor Condenser y 5 7 1 4 3 Spray Flash chamber Pump Figure Q3. Refrigeration circuit diagram. 1 Evaporator 2

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 refrigeration system like the one shown in the figure, in cascade uses R-22 refrigerant in the low temperature part of the system (B) and 134a refrigerant in the high temperature circuit (A). The R-22 refrigerant circuit operates between 1.1 and 5 bar.The enthalpies of the saturated vapor that leaves the evaporator at -39 ºC, of the superheated vapor that leaves the isentropic compressor at 29 ºC, and of the liquid that enters the throttling device at 0 ºC are 267.37; 304.16 and 78.47 respectively.The ideal cycle of the refrigerant circuit 134a operates between -12 ° C and 9 bar. The cooling capacity of the low temperature evaporator is 5 Ton. The COP of the cascade system is 2.13. Determine:a) the mass flows, in Kg / hr, in the two circuits. b) the input power in both compressors, in Kw c) Also determine the COP of a cycle with a single circuit using refrigerant 134a between -40 ºC and 9 bar.
A refrigeration system like the one shown in the figure, in cascade uses R-22 refrigerant in the low temperature part of the system (B) and 134a refrigerant in the high temperature circuit (A). The R-22 refrigerant circuit operates between 1.1 and 5 bar.The enthalpies of the saturated vapor that leaves the evaporator at -39 ºC, of the superheated vapor that leaves the isentropic compressor at 29 ºC, and of the liquid that enters the throttling device at 0 ºC are 267.37; 304.16 and 78.47 respectively.The ideal cycle of the refrigerant circuit 134a operates between -12 ° C and 9 bar. The cooling capacity of the low temperature evaporator is 5 Ton. Determine:a) the mass flows, in Kg / hr, in the two circuits. b) the input power in both compressors, in Kw,c) the COP of the cascade system.
with schematic diagram A vacuum refrigeration system consists of a large insulated flash chamber kept at low pressure by a steam ejector which pumps vapor to a condenser. condensate is removed by a condensate to an air vent. warm return water enters the flash chamber at 13 c, chilled water comes out of the flash chamber at 5 c. vapor leaving the flash chamber has a quality of 0.97 and the temperature in the condenser is 32 c. for 350 kw of refrigeration. a) how much chilled water at 5 deg C does this system provide b) how much make up water is needed c) how much vapor must the system ejector remove from the flash chamber answers: a) 10.41 kg/s b) 0.1521 kg/s c) 21.7 kg/s
draw the schematic diagram only A vacuum refrigeration system consists of a large insulated flash chamber kept at a low pressure by a steam ejector which pumps vapour to a condenser. Condensate is removed by a condensate to an air vent. Warm retum water enters the flash chamber at 13°C, chilled water comes out of the flash chamber at 5 C. Vapour leaving the flash has a quality of 0.97 and the temperature in the condenser is 32°C. For 350 kW of refrigeration.
Number 2 A refrigeration system with a capacity of 10 tons of refrigeration, operates at 210 kPa in the evaporator, while in the condenser it is 1100 kPa. If refrigerant R-717 is saturated, calculate the theoretical power required to operate the compressor. Compressor Power = Answer in kW.
3- A refrigeration system using R-134a has three a evaporators of capacities of 5, 10 and 15 TR respectively. The temperature to be maintained in the evaporators is 5, 0 and -12 °C respectively. Each evaporator is fitted with an expansion valve. The condenser pressure is to be 9 bar. The exit condition from evaporator is dry saturated vapour and liquid is sub cooled by 5 °C in the condenser. Determine 1-the refrigeration effect 2- rate of flow of the refrigerant in kg/s and 3-the theoretical horse power required.
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A refrigeration system operated on an ideal vapor-compression using R-12 with a vaporizing temperature of -10 degrees Celsius and a condensing temperature of 30 degrees Celsius, it requires 15 hp to drive the motor of the compressor. Find the ff: Enthalpies at each point of the cycle in kJ/kg Refrigerating Capacity in TOR • Mass of the Refrigerant in kg/s Percent Quality in the mixture Heat Rejected in kW Coefficient of Performance • Schematic and P-h Diagram
Q3/ In refrigeration system uses R22, the evaporator temperature is -10°C and the condenser temperature is 50°C. The system is ideal. Determine using the tables: 1. Compressor work (w). 2. Rejected heat from the condenser. 3. Refrigeration effect (RE). 4. Coefficient of Performance (COP).
Note : Use the relevant chart for each problem 3. A vapour compression refrigerator uses R-12 as refrigerant and the liquid evaporates in the evaporator at - 15 °C. The temperature of this refrigerant at the delivery from the compressor is 15°C when the vapour is condensed at 10°C. Find the coefficient of performance if (i) there is no undercooling , and (ii) the liquid is cooled by 5°C before expansion by throttling. Take specific heat at constant pressure for the superheated vapour as 0.64 kJ/kg.K and for liquid as 0.94 kJ/kg.K. (Same as Example 12) Please solve the question on a piece of paper and using tables with illustrations
a cooling system with a capacity of 10 tons of refrigeration, operates at 210 kPa in the evaporator, while in the condenser is 1100 kPa. if refrigerant R-717 is saturated, calculate the theoretical power required to operate the compressor. compressor power = .... kW
3.5 An ammonia refrigeration system operates between saturated suction temperature of -20°C, and saturated discharge temperature of +40°C. Com- pare the COP of the cycle using wet compression with that of the cycle using dry compression. Assume that the vapour leaving the compressor is saturated in the case of wet compression, and the vapour entering the compressor is saturated in the case of dry compression. The refrigerant leaves the condenser as saturated liquid.