6 HX WARM Compressor medium Evaporator Condenser COLD mediumy Valve 8 3 A two-stage ideal cycle cascade refrigeration system with R-134a as the working fluid in both cycles. The left cycle operates between 0.4 MPa and 1.0 MPa, while the right cycle operates between 0.15 MPa and 0.4 MPa. Note that in an ideal cascade refrigeration, the compressor used are 100% efficient and the temperature in the evaporator in the left cycle is equal to the temperature in the condenser in the right cycle. Determine (a) the mass flow rate through the right cycle and (b) the COP of the whole system, considering the mass flow rate in the left cycle is 0.2 kg/s. As part of your solution, fill up the table below. Stream P (in bar) H (in kJ/kg) S (in kJ/kg-K) (you do not need to completely fill this table, only those needed in the calculations) 2 3 4 5 16 Condenser 7 18 Expansion Compressor Expansion Valve X Evaporator

6 HX WARM Compressor medium Evaporator Condenser COLD mediumy Valve 8 3 A two-stage ideal cycle cascade refrigeration system with R-134a as the working fluid in both cycles. The left cycle operates between 0.4 MPa and 1.0 MPa, while the right cycle operates between 0.15 MPa and 0.4 MPa. Note that in an ideal cascade refrigeration, the compressor used are 100% efficient and the temperature in the evaporator in the left cycle is equal to the temperature in the condenser in the right cycle. Determine (a) the mass flow rate through the right cycle and (b) the COP of the whole system, considering the mass flow rate in the left cycle is 0.2 kg/s. As part of your solution, fill up the table below. Stream P (in bar) H (in kJ/kg) S (in kJ/kg-K) (you do not need to completely fill this table, only those needed in the calculations) 2 3 4 5 16 Condenser 7 18 Expansion Compressor Expansion Valve X Evaporator

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

Chapter22: Condensers

Section: Chapter Questions

Problem 7RQ: When a standard-efficiency air-cooled condenser is used, the condensing refrigerant will normally be...

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Q1 Consider a two-stage compression refrigeration system operating between the pressure limits of 0.8and0.14 MPa(see Fig. Q 2). The working fluid isrefrigerant -134a. The refrigerant leaves thecondenser as a saturated liquid and is throttled to aflash chamberoperating at0.4 MPa. Part ofthe refrigerant evaporates during this flashing process, and this vapour is mixed with the refrigerantleaving the low-pressure compressor. The mixture is then compressed to the condenser pressure bythe high-pressure compressor. The liquid in the flash chamber is throttled to the evaporator pressure,and it cools the refrigerated space as it vaporizes in the evaporator. Assuming the refrigerant leavesthe evaporator as saturated vapor and both compressors are isentropic, determine(a) the fraction of the refrigerant that evaporates as it is throttled to the flash chamber,(b) the amount of heat removed from the refrigerated space and the compressor work per unit massof refrigerant flowing through the…
Q1.2 Consider a two-stage compression refrigeration system operating between the pressure limits of 0.8and0.14 MPa(see Fig. Q 2). The working fluid isrefrigerant -134a. The refrigerant leaves thecondenser as a saturated liquid and is throttled to aflash chamberoperating at0.4 MPa. Part ofthe refrigerant evaporates during this flashing process, and this vapour is mixed with the refrigerantleaving the low-pressure compressor. The mixture is then compressed to the condenser pressure bythe high-pressure compressor. The liquid in the flash chamber is throttled to the evaporator pressure,and it cools the refrigerated space as it vaporizes in the evaporator. Assuming the refrigerant leavesthe evaporator as saturated vapor and both compressors are isentropic, determine(a) the coefficient of performance (COP).Re-draw the schematic diagram and sketch the cycle accurately on a T-s diagram with the propertyvalues labelled at all state points.
Consider a two-stage cascade refrigeration system operating between -80 o C and 80 o C. Each stage operates on an ideal vapor-compression refrigeration cycle. Upper cycle use R-12 as working fluid, lower cycle use R-13. In the lower cycle refrigerant condenses at 0 o C, in the upper cycle refrigerant evaporates at -5 o C. If the mass flow rate in the lower cycle is 1 kg/s, determine the mass flow rate through the upper cycle. Group of answer choices 1.56 kg/s 2.46 kg/s 1.78 kg/s 2.30 kg/s
A refrigerator operates on an ideal vapour-compression refrigeration cycle and uses refrigerant R−134?? as the working fluid. The condenser operates at 1.6MPa and the evaporator at −6℃. If an adiabatic, reversible expansion device were available and used to expand the liquid leaving the condenser, how much would the COP improve by using this device instead of the throttle device?
In a Refrigerant 12 system which serves a 212 kw evaporator at - 30 0C. The system uses two stage compression with intercooling and removal of flash gas. The condenser temp is 400C . Given that, h2=356kJ/kg, h4=367kJ/kg Compute the following: a.) mass flow rate at low stage compressor (m1)ANSWER: 1.53661 kg/s b.) mass flow rate at high stage compressor (m3)ANSWER: 2.11791 kg/s c.) low stage compressor workANSWER: 27.43931 kw d.) high stage compressor workANSWER: 32.63926 kw e.) total compressor workANSWER: 60.078575 kw f.) COPANSWER: 3.52871 g.) heat rejected in the condenserANSWER: 272.07857 kw
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