Question

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 and the

compressor is estimated to release a net heat of 450 W to the
surroundings. Determine

(a) the quality of the refrigerant at the evaporator inlet,

(b) the rate of heat removal from the refrigerated space,

(c) the coecient of performance of the refrigerator and

(d) the theoretical maximum coecient of performance of the
refrigerator.

Answer #1

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...

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 single-stage refrigeration system operating between the pressure limits of 1.4 MPa and 160 kPa
with refrigerant R134a as the working fluid. The refrigerant is a saturated liquid at the condenser exit and a
saturated vapor at the compressor inlet. The isentropic efficiency for the compressor is 80 percent. If the
mass flow rate of the refrigerant through the cycle is 0.11 kg/s determine (a) the rate of heat removal from the
refrigerated space, and (b) the coefficient of...

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...

Consider a 280 kJ/min refrigeration system that operates on an
ideal vapor-compression refrigeration cycle with refrigerant-134a
as the working fluid. The refrigerant enters the compressor as
saturated vapor at 140 kPa and is compressed to 800 kPa. The
saturated refrigerant-134a—pressure table (in SI units) is given
below. Determine the quality of the refrigerant at the end of the
throttling process.

A vapor-compression refrigeration cycle operates at steady state
with Refrigerant 134a as the working fluid. Saturated vapor enters
the compressor at 2 bar, and saturated liquid exits the condenser
at 8 bar. The isentropic compressor efficiency is 80%. The mass
flow rate of refrigerant is 7 kg/min. Determine: (a) the compressor
power, in kW, (b) the refrigeration capacity, in tons, (1 ton =
3.5168 kW) and, (c) the coefficient of performance, (d) rate of
entropy production in kW/K, for the...

An ice-making machine operates on the ideal vapor-compression
cycle, using R-134a. The refrigerant enters the compressor as
saturated vapor at 140 kPa and leaves the condenser as saturated
liquid at 600 kPa. Water enters the ice machine at 13oC and leaves
as ice at -4oC, while removing heat at 393 kJ per kg of water.
Estimate the mass flow rate of the refrigerant and the power input
to the ice machine for an ice production rate of 7 kg/h.

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.)

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 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...

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