Question

A commercial refrigerator with refrigerant R-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 18 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 450 W from the surroundings. Determine (a) The quality of the refrigerant at the evaporator inlet (b) the refrigeration load, (c) The COP of the refrigerator, and (d) the Theoretical maximum refrigeration load for the same power input to the compressor.

Answer #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 18°C
at a rate of 0.32 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 460 W...

Consider a commercial refrigerator which operates on the
refrigeration cycle. R-
134a is used as the working
uid and the refrigerated space is kept at -25oC by rejecting
its
waste heat to cooling water that enters the condenser at room
temperature, that is 20oC, at a
rate of 0.1 kg/s and leaves at 40oC. The refrigerant enters the
condenser at 1.2 MPa and 70oC
and leaves at 40oC. The inlet state of the compressor is saturated
vapor at 100 kPa...

R-134a enters the compressor of a refrigerator as superheated
vapour at 0.14 MPa, -10 °C at a rate of 0.12 kg/s, and it leaves at
0.7 MPa and 50 °C.
The refrigerant is cooled in the condenser to 24 °C and 0.65 MPa,
and it is throttled to 0.15 MPa.
Disregard any heat transfer and pressure drops in the connecting
lines between the components.
Show the cycle on a T-s diagram with respect to saturation
lines, and determine
(a) the...

A condenser is essentially a type of heat exchanger that is used
to remove heat from a vapor and convert it to liquid. The picture
below shows a condenser that is used in a commercial refrigerator
with refrigerant-134a as the working fluid. Water enters the
condenser at 18ºC at a rate of 0.25 kg/s and leaves at 26ºC. The
refrigerant enters the condenser at 1.2 MPa and 50ºC and leaves at
the same pressure but at T=41.3ºC. a) Find the...

An air conditioner using refrigerant-134a as the working fluid
and operating on the ideal vapor-compression refrigeration cycle is
to maintain a space at 36°C while operating its condenser at 1600
kPa. Determine the COP of the system when a temperature difference
of 4°C is allowed for the transfer of heat in the evaporator. (Take
the required values from saturated refrigerant-134a tables.)

Regarding a Vapor-Compression cycle: A refrigerant (HCFC-22)
enters the compressor of a refrigerator as a superheated vapor at
.14MPa and -20 degrees Celsius at a rate of .05 kg/s and leaves at
.8 MPa and 50 degrees Celsius. The refrigerant is cooled in the
condenser to 26 degrees Celsius and .72MPa and is then throttled
down to .15 MPa. Determine the rate of heat removal from the
refrigerated space and the power input to the compressor and the
Coefficient of...

Water is used to cool R-134a in the condenser of a heat
exchanger. The refrigerant enters the counter-flow heat exchanger
at 800 kPa, 80 0C and a mass flow rate of 2 kg/s. The refrigerant
exits as a saturated liquid. Cooling water enters the condenser at
500 kPa and 18 0C and leaves the condenser at 30 0C. Determine the
necessary mass flow rate of water. Each fluid is assumed to flow at
constant pressure.

A cooling plant adopted a two-stage cascade refrigeration system
to meet the required cooling load. In both upper and lower cycles,
the refrigerant leaves condenser as saturated liquid and enters
compressor as saturated vapor. The isentropic efficiency of the
upper cycle compressor is 80 %, while the lower cycle compressor is
70% efficient. The pressure limits of the upper and lower cycles
are 1 MPa and 0.2 MPa with refrigerant-134a, respectively. Heat
rejection from the lower cycle to the upper...

Refrigerant 134a is the working fluid in an ideal
vapor-compression refrigeration cycle operating at steady state.
Refrigerant enters the compressor at 1 bar, -12°C, and the
condenser pressure is 9 bar. Liquid exits the condenser at 32°C.
The mass flow rate of refrigerant is 7 kg/min. Determine:
(a) the magnitude of the compressor power, in kW. (b) the
refrigeration capacity, in tons. (c) the coefficient of
performance.

Refrigerant 134a is the working fluid in a vapor-compression
heat pump system with a heating capacity of 60,000 Btu/h. The
condenser operates at 240 lbf/in.2, and the evaporator temperature
is 0°F. The refrigerant is a saturated vapor at the evaporator exit
and a liquid at 110°F at the condenser exit. Pressure drops in the
flows through the evaporator and condenser are negligible. The
compression process is adiabatic, and the temperature at the
compressor exit is 180°F. Determine (a) the mass...

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