The Vapour Compression Refrigeration Cycle

THE VAPOUR COMPRESSION REFRIGERATION CYCLE
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Introduction/Background
The vapor compression cycle has found applications in numerous industrial, medical as well as
domestic applications all over the world. Air conditions medical preservations as well as food
preservations alongside transport are among the applications that to a very great extent depend
on the use of the refrigeration plant. It is of importance thus that engineering students have a
grasp and be informed of the numerous parameters that influence the performance of the vapor
refraction cycle for the purposes of the design or utilizations of such a plant (Babarinde et al.,
2015). The design of the Hilton Refrigeration Laboratory Unit has been done to enable learners
to gain a full investigation of the vapor compression performance under different conditions of
evaporator load as well as condense preserve. All the useful parameters are instrumented and the
unit is entirely safe for the system to be operated by the student.
The cycle performance can be evaluated through the calculation of various Coefficient of
Performances. Coefficient of Performance defines the ration of useful energy introduced or
reacted to the work input
COPTH = Q¿
W ¿
= h1−h4
h2 −h1
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...(1)
The equation
COPov= Pevap−measured
Pcomp−calcuated
... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ...(2)
Pcomp−calculated =T . ω= ( F . r ) . ( Ne . 2 π
60 ) .Cr ... ... ... ... ... ... ... ... ... ... ... ... ... ...(3)
Can be used in the estimation of the overall coefficient performance

where Pcomp is the power of the compressor estimated using the compressor speed, T is the
torque, F, force of spring balance, Ne the diameter of the pulley belt ratio, Cr=3.08, r=165 which
is the radius of the dynamometer
The equation
COP¿= Pevap −measured
Pcomp−calcuated−P f
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...(4 )
Is used in the expression of the indicator of coefficient performance in which Pf is the loss in
power as a result of friction forces and is calculated as:
Pf = ( Ff ) . r . N e . 2 π
60 . Cr ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .(5)
In which Ff is the friction force that is equivalent to 5N. Besides, the mechanical efficiency of
the compressor can be calculated as
ηmech= Pevap −measured
Pcomp−calcuated
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (6)
The isotonic efficiency that is the efficiency of an ideal Vapor Compression Cycle may be
expressed as
ηisentropic = h2 s−h1
h2−h1
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...(7)