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

Cascade cooling system

Output:

1- REFRIGERATION CYCLE [R134a]

Cycle Properties:

Coefficient of performance (COP) = 4.5099

2- REFRIGERATION CYCLE [R134a]

Cycle Properties:

Coefficient of performance (COP) = 8.2814

SYSTEM PROPERTIES

Coefficient of performance (COP) = 2.7081