Cascade cooling system

Cycle data

Known properties
  • Refrigerant-134a is used as working fluid in both cycles;
  • The lower cycle has a mass flow of 2.5 kg/s;
  • The pressure at the inlet of the lower compressor is 250 kPa, and 600 kPa at its outlet;
  • The pressure at the inlet of the upper compressor is 500 kPa, and 1500 kPa at its outlet;
  • The upper compressor has an isentropic efficiency of 80%, and the lower one of 90%.
Input code
using CycleSolver

@solve begin

    evaporator_condenser([stD, st2], [stA, st3])

    stA.p = 500
    stB.p = 1500
    newRefrigerationCycle[R134a]
        compressor(stA, stB, 80)
        condenser(stB, stC)
        expansion_valve(stC, stD)
        
    st1.p = 250
    st2.p = 600
    newRefrigerationCycle[R134a: 2.5]
        compressor(st1, st2, 90)
        expansion_valve(st3, st4)
        evaporator(st4, st1)
        
end

PrintResults()

Output:

1- REFRIGERATION CYCLE [R134a]

State
Name		 T [K] P [kPa] h [kJ/kg] s [kJ/kg.K] x ṁ [kg/s] Mass-flux
fraction
stD 288.885 500.0 131.695 0.4823 0.3137 3.653 1.0
stA 288.885 500.0 259.327 0.9241 1.0 3.653 1.0
stB 336.769 1500.0 287.628 0.941 3.653 1.0
stC 328.383 1500.0 131.695 0.4665 0.0 3.653 1.0

Cycle Properties:

Total Component Value
qin
Q̇in		 127.6324 kJ/kg
466.2367 kW		 evaporator_condenser:
[stD, st2] >> [stA, st3]		 127.6324 kJ/kg
466.2367 kW
qout
Q̇out		 155.9332 kJ/kg
569.6185 kW		 condenser:
stB >> stC		 155.9332 kJ/kg
569.6185 kW
win
Ẇin		 28.3008 kJ/kg
103.3818 kW		 compressor:
stA >> stB		 28.3008 kJ/kg
103.3818 kW
wout
Ẇout		 0.0 kJ/kg
0.0 kW

Coefficient of performance (COP) = 4.5099


2- REFRIGERATION CYCLE [R134a]

State
Name		 T [K] P [kPa] h [kJ/kg] s [kJ/kg.K] x ṁ [kg/s] Mass-flux
fraction
st2 300.331 600.0 268.033 0.9407 2.5 1.0
st3 294.722 600.0 81.5384 0.3081 0.0 2.5 1.0
st1 268.866 250.0 247.94 0.934 1.0 2.5 1.0
st4 268.866 250.0 81.5384 0.3151 0.1755 2.5 1.0

Cycle Properties:

Total Component Value
qin
Q̇in		 166.4013 kJ/kg
416.0033 kW		 evaporator:
st4 >> st1		 166.4013 kJ/kg
416.0033 kW
qout
Q̇out		 186.4947 kJ/kg
466.2367 kW		 evaporator_condenser:
[stD, st2] >> [stA, st3]		 186.4947 kJ/kg
466.2367 kW
win
Ẇin		 20.0934 kJ/kg
50.2334 kW		 compressor:
st1 >> st2		 20.0934 kJ/kg
50.2334 kW
wout
Ẇout		 0.0 kJ/kg
0.0 kW

Coefficient of performance (COP) = 8.2814


SYSTEM PROPERTIES

Total Component Value
qin
Q̇in		 166.4013 kJ/kg
416.0033 kW		 evaporator:
st4 >> st1		 166.4013 kJ/kg
416.0033 kW
qout
Q̇out		 155.9332 kJ/kg
569.6185 kW		 condenser:
stB >> stC		 155.9332 kJ/kg
569.6185 kW
win
Ẇin		 48.3941 kJ/kg
153.6152 kW		 compressor:
stA >> stB

compressor:
st1 >> st2		 28.3008 kJ/kg
103.3818 kW

20.0934 kJ/kg
50.2334 kW
wout
Ẇout		 0.0 kJ/kg
0.0 kW

Coefficient of performance (COP) = 2.7081