Homework Answers
Isentropic Compression and Isentropic Expansion are the two processes of reversed Carnot cycle, that are easiest to implement in real life.
Adiabatic compression , unintended heat to/from surroundings, Fluid friction
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Calculate the COP for a refrigerator with a QHdot of 8 kW, Qldot of 7 kW...
Find (a) the compressor power, in kW, (b) the refrigeration capacity, in tons, and (c) the...
Find (a) the compressor power, in kW, (b) the refrigeration capacity, in tons, and (c) the coefficient of performance (COP) for a real vapor-compression refrigeration cycle using refrigerant 134a. The refrigerant enters the compressor at a rate of 0.15 kg/s as a saturated vapor at −40 °C and leaves the condenser as a saturated liquid at 16 °C. The isentropic efficiency of the compressor is 80%.
(12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression cycle....
(12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression cycle. The cycle operates between 200 kPa and 1.2 MPa. The refrigerant flows through the cycle at a rate of 0.019 kg/s. The (actual) refrigerator has a compressor with an isentropic efficiency of 85%. The refrigerant enters the compressor slightly superheated by 56 C hint add this to the saturation temperature). The refrigerant leaves the condenser slightly subcooled by 1.9°C. What is the rate of...
Tt (12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression...
Tt
(12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression cycle. The cycle operates between 200 kPa and 1.2 MPa. The refrigerant flows through the cycle at a rate of 0.015 kg/s. The actual) refrigerator has a compressor with an isentropic efficiency of 82%. The refrigerant enters the compressor slightly superheated by 6.2°C (hint: add this to the saturation temperature). The refrigerant leaves the condenser slightly subcooled by 1.8°C. What is the rate of...
NOTE: This is a multi-part question Once an answer is submitted you will be unable to return to t...
NOTE: This is a multi-part question Once an answer is submitted you will be unable to return to this part Consider a two-stage cascade refrigeration system operating between the pressure limits of 1.4 MPa and 140 kPa with refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle takes place in an adiabatic counterflow heat exchanger where the pressure in the upper and lower cycles are 0.7 and 08 MPa, respectively. In both cycles, the...
A two-stage compression refrigeration system with an adiabatic liquid-vapor separation unit uses refrigerant-134a as working fluid....
A two-stage compression refrigeration system with an adiabatic liquid-vapor separation unit uses refrigerant-134a as working fluid. The system operates the evaporator at 0.4 MPa, the condenser at 1.6 MPa, and the separator at 0.8 MPa. The compressors use 25 kW of power. Given that the refrigerant is saturated liquid at the inlet of each expansion valve and saturated vapor at the inlet of each compressor, and the compressors are isentropic: (0) show the process on a T-s diagram; ) calculate...
Problem (25 points) A typical R134a dry vapor compression refrigerator has a COP of about 1.3 when operating betwee...
Problem (25 points) A typical R134a dry vapor compression refrigerator has a COP of about 1.3 when operating between 15° C and 30° C. For a refrigerator rated at 0.1 tons of refrigeration. Determine the power required and the mass flow rate of R134a. Assume that the refrigerant is saturated liquid leaving the condenser.
Problem (25 points) A typical R134a dry vapor compression refrigerator has a COP of about 1.3 when operating between 15° C and 30° C. For a...
In a vapor-compression refrigeration cycle, ammonia exits the evaporator as saturated vapor at -22 °C. There...
In a vapor-compression refrigeration cycle, ammonia exits the
evaporator as saturated vapor at -22 °C. There are
irreversibilities in the compressor. The refrigerant enters the
condenser at 16 bar and 160 °C, and saturated liquid exits at 16
bar. 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.
Calculate the coefficient of performance, b, and the isentropic
compressor efficiency, defined as:
2s Condenser Expansion...
1) A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated...
1) A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -30°C by rejecting its waste heat to cooling water that enters the condenser at 16 °C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and -34°C and the compressor is estimated to gain a net heat of...
15% A refrigerator using refrigerant-134a as the working fluid operates on an actual vapor compression ugeration...
15% A refrigerator using refrigerant-134a as the working fluid operates on an actual vapor compression ugeration cycle between 0.12 MPa and 1 MPa. The refrigerant leaves the compressor at 60°C and leaves condenser as a saturated liquid. If the mass flow rate is 1 kg/s, determine the COP of the system. 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...
In a vapor-compression refrigeration cycle, ammonia exits the evaporator as saturated vapor at -22°C. The refrigerant...
In a vapor-compression refrigeration cycle, ammonia exits the evaporator as saturated vapor at -22°C. The refrigerant enters the condenser at 16 bar and 160°C, and saturated liquid exits at 16 bar. 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 150 kW, determine: (a) the mass flow rate of the refrigerant, in kg/s. (b) the power input to the...
(12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression cycle. The cycle operates between 200 kPa and 1.2 MPa. The refrigerant flows through the cycle at a rate of 0.019 kg/s. The (actual) refrigerator has a compressor with an isentropic efficiency of 85%. The refrigerant enters the compressor slightly superheated by 56 C hint add this to the saturation temperature). The refrigerant leaves the condenser slightly subcooled by 1.9°C. What is the rate of...
Tt
(12 points) A refrigerator using refrigerant-134a as the working fluid operates on the vapor compression cycle. The cycle operates between 200 kPa and 1.2 MPa. The refrigerant flows through the cycle at a rate of 0.015 kg/s. The actual) refrigerator has a compressor with an isentropic efficiency of 82%. The refrigerant enters the compressor slightly superheated by 6.2°C (hint: add this to the saturation temperature). The refrigerant leaves the condenser slightly subcooled by 1.8°C. What is the rate of...
NOTE: This is a multi-part question Once an answer is submitted you will be unable to return to this part Consider a two-stage cascade refrigeration system operating between the pressure limits of 1.4 MPa and 140 kPa with refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle takes place in an adiabatic counterflow heat exchanger where the pressure in the upper and lower cycles are 0.7 and 08 MPa, respectively. In both cycles, the...
A two-stage compression refrigeration system with an adiabatic liquid-vapor separation unit uses refrigerant-134a as working fluid. The system operates the evaporator at 0.4 MPa, the condenser at 1.6 MPa, and the separator at 0.8 MPa. The compressors use 25 kW of power. Given that the refrigerant is saturated liquid at the inlet of each expansion valve and saturated vapor at the inlet of each compressor, and the compressors are isentropic: (0) show the process on a T-s diagram; ) calculate...
Problem (25 points) A typical R134a dry vapor compression refrigerator has a COP of about 1.3 when operating between 15° C and 30° C. For a refrigerator rated at 0.1 tons of refrigeration. Determine the power required and the mass flow rate of R134a. Assume that the refrigerant is saturated liquid leaving the condenser.
Problem (25 points) A typical R134a dry vapor compression refrigerator has a COP of about 1.3 when operating between 15° C and 30° C. For a...
In a vapor-compression refrigeration cycle, ammonia exits the
evaporator as saturated vapor at -22 °C. There are
irreversibilities in the compressor. The refrigerant enters the
condenser at 16 bar and 160 °C, and saturated liquid exits at 16
bar. 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.
Calculate the coefficient of performance, b, and the isentropic
compressor efficiency, defined as:
2s Condenser Expansion...
1) A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -30°C by rejecting its waste heat to cooling water that enters the condenser at 16 °C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and -34°C and the compressor is estimated to gain a net heat of...
15% A refrigerator using refrigerant-134a as the working fluid operates on an actual vapor compression ugeration cycle between 0.12 MPa and 1 MPa. The refrigerant leaves the compressor at 60°C and leaves condenser as a saturated liquid. If the mass flow rate is 1 kg/s, determine the COP of the system. 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...
In a vapor-compression refrigeration cycle, ammonia exits the evaporator as saturated vapor at -22°C. The refrigerant enters the condenser at 16 bar and 160°C, and saturated liquid exits at 16 bar. 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 150 kW, determine: (a) the mass flow rate of the refrigerant, in kg/s. (b) the power input to the...
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