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A vapour compression system using R12 works between -1500 C and 3500 C as evaporator and condenser temperature respectively.

Using P-H chart determine i) COP ii) Mass flow of refrigerant per TR iii) Piston displacement per TR using volumetric efficiency = 80% iv) Heat rejected in the condenser per TR.

Marks: 5M, 6M

Year: Dec2014, Dec2015, Dec2013, May2014

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TE=TsatPe=15,TC=TsatPc=35

From P-H chart of R-12,

We know that at point 1,

h1=181kjkg;h2=210kJkg;h3=h4=68kJkg

COP=R.EWc=18168(210181=3.896

Also,

Qa=ṁr×(h1h4)

For 1 TR capacity,

1×3.5=ṁr(18168)

ṁr=0.0309kgsec=1.8584kg/min

Also

m ̇_r×v_1=piston \ displacement \ per \ TR ×η_vol

v_1=0.076 m^3⁄kg \ from \ p-h \ chart

Therefore,

piston displacement per TR=0.1765 m^3⁄min

Rate at which heat is rejected in condenser per TR

Q_r=m_R×(h_2-h_3 )

=0.0309×(210-181)

=0.899\frac{ kJ}{sec}

We know, ideal COP

=\frac{T_E}{T_C-T_E}

=\frac{258}{308-258}

=5.16

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