A R-12 refrigerant reciprocating compressor operates between

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A R-12 refrigerant reciprocating compressor operates between the condensing temperature of 30º and evaporator temperature of –20ºC. The clearance volume ratio of the compressor is 0.03. Specific heat ratio of the vapour is 1.15 and the specific volume at the suction is 0.1089 m³/kg. Other properties at various states are given in the figure. To realize 2 tons of refrigeration, the actual volume displacement rate considering the effect of clearance is

1. 6.35 × 10^–3 m³/s
2. 63.5 × 10^–3 m³/s
3. 635 × 10^–3 m³/s
4. 4.88 × 10^–3 m³/s

Correct Option: A

Given: Clearance volume ratio, C = 0.03
Specific volume at suction, υ₁ = 0.1089 m³ /kg
Net refrigerating effect = 2 ton = 2 × 3.516 kJ = 7.032 kJ/s
Specific heat ratio, c = 1.15

∴ Net refrigerating effect = ṁ(h₁ – h₄)
or 7.032 = ṁ(176 – 65)
or ṁ = 0.063 kg/s
Volume = 0.063 × 0.1089 = 6.89 × 10³ m^–3 /s

Volumetric efficiency = 1 + C - C		p₂		^{1 / n}
		p₁

Volumetric efficiency = 1 + 0.03 - 0.03		7.45		^{1 / 1.15}
		1.50

= 0.909
∴ Volume displacement rate considering clearance effect = 6.89 × 10^–3 × 0.909 = 6.26 × 10^–3 m³ /s