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Formulas for the subcooling cycle
1. (egerating *+ect, (*:
ℜ=h1
−h4
'
2. ass -o$ rate per ton m/ :
m' =
211
h1−h
4' =
kg
min−km
Where/ = mass -o$ rate per ton #or the subcoole! cycle
". Volume -o$ rate at suction, V/ :
V 1' =m' ν1
Where:
ν1 = specic volume
&. Coefcient o# per#ormance, C0' :
COP=h1−h
4
h2−h1
. Compressor Wor%, Wc :
W c=m' (h2−h1)
. 3eat (e4ecte! in the con!enser, 5r :
Qr=m' (h2−h1)
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Refrigeration Cycle with superheating the suction vapour :
Formulas for the superheating Cycle
1. (e#rigerating e+ect, (*:
ℜ=h1 ' −h4
2. ass -o$ rate per Ton m/:
m' =
211
h1' −h4
= kg
min−km
Where:
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m/ = mass -o$ rate per ton #or the superheate! cycle $ith use#ul
cooling
". Volume -o$ rate at suction, v/ :
V 1'
=m' ν1 '
&. Coefcient o# per#ormance, C0' :
COP= h
1 ' −h4h2 ' −h1'
. Compressor $or!, $c:
W c=m ' (h2 ' −h1 ' )
. 3eat re4ecte! om the con!enser, 5r:
Qr=m' (h2 ' −h3)
6. i# the superheating occurs $ithout use#ul cooling
1. (e#rigerating e+ect, (*:
ℜ=h1−h4
2. ass -o$ rate per Ton m// :
m' ' =
211
h1−h
4' =
kg
min−km
". Volume -o$ rate at suction
V 1' ' =m ' ν1
&. Coefcient o# per#ormance
COP= h
1−h
4
h2 ' −h1'
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. Compressor $or%, Wc
W c=m' ' (h2 ' −h1 ' )
. 3eat re4ecte! in the con!enser, 5r
Qr=m' ' (h2 ' −ha)
Refrigeration cycle with subcooling and superheating
7ormulas #or re#rigeration cycle $ith subcooling an! superheating
1. (e#rigerating e+ect, (*:
ℜ=h1 ' −h4 '
2. ass -o$ rate per ton m// 8
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m' = 211
h1 ' −h4 '
= kg
min−km
". Volume -o$ rate at suction, v1/
V 1' =m ' ν1 '
&. Coefcient o# per#ormance, C0' :
COP=h1 ' −h4 ' h2' −h1 '
. Compressor $or%, $c:
W c=m ' (h2 ' −h1 ' )
. 3eat re4ecte! in the con!enser, 5r
Qr=m' (h2 ' −h3)
Heat exchanger
(e#rigeration system use a li)ui!9li)ui!9to9suction heat echanger to ensure
that no li)ui! enters the compressor an! to prevent bubbles o# vapour #rom
impe!ing the -o$ o# re#rigerant through the epansion valve
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1. 3eat balance o# the heat echanger
2. (e#rigerating e+ect, (*:
". Coefcient o# per#ormance, C0'
ulti pressure system
; multi9pressure system us a re#rigeration system that has t$o or more lo$ si!e
pressures. The lo$ si!e pressure is the pressure o# the re#rigerant bet$een the
epansion valve an! the inta%e o# the compressor.
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(emoval o# 7lash
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Two evaporators and one compressor
n many situations one compressor serves t$o evaporators having !i+erent
temperature re)uirements. ;n eample is an in!ustry $hich nee!s lo$9temperature
re#rigeration #or a process an! $hich must also provi!e air con!itioning #or someofces.
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1. ass -o$ rate, through high temperature evaporator, m& :
2. ass -o$ rate, through lo$ temperature evaporator, m> :
". Total mas -o$ rate, m1 :
&. 3eat balance at 4unction
m1h1=m
6h
6+m
8h8
. Compressor po$er
W =m1(h2−h1)
Two compressors and one evaporator
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T$o stage compression $ith intercooling an! removal o# -ash gas us o#ten the i!eal
$ay to serve one lo$ temperature evaporator. This system re)uires less po$er than
$ith a single compressor, an! o#ten the saving po$er $ill 4usti#y the cost o# the
etra e)uipment.
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1. nterme!iate pressure #or minimum $or% :
P2=√ P1 P4
2. ass -o$ rate through evaporator, m1 :
m1=refrigeratingload
h1−h
6
". ass balance in intercooler :
m2=m
7
m2=m
6
&. 3eat balance in intercooler
m2h
2+m
6h6=m
7h7+m
3h3
. ?o$ stage 'o$er :
W Low stage=m1(h2−h1)
. 3igh @ stage 'o$er
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ha−h3W high stage=m3 ¿
>. Total po$er:
T$o compressor an! t$o evaporators
The system $hich has t$o evaporators operating at !i+erent temperatures is
common in in!ustrial re#rigeration. ; #roAen #oo! plant may re)uire t$o evaporators
at !i+erent temperature, one at 9&BC to )uic% #reeAe the #oo! an! the other at 92C
to hol! the #oo! a#ter it is #roAen