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Define Critical Point?

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Quantum Physics


A Refrigerant-12 vapour compression cycle has a refrigeration load of 3 tonnes. The evaporator and condenser temperatures are – 20°C and 40°C respectively. Find (a) The refrigerant flow rate in kg/s (b) The volume flow rate handled by the compressor in m3/s (c) The work input to the compressor in kW (d) The heat rejected in the condenser in kW (e) The isentropic discharge temperature. If there is o 5 C of superheating of vapour before it enters the compressor, and o 5 C sub cooling of liquid before it flows through the expansion valve, determine the above quantities.

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Quantum Physics


A vapour compression refrigeration system uses R-12 and operates between pressure limits of 0.745 and 0.15 MPa. The vapour entering the compressor has a temperature of – 10°C and the liquid leaving the condenser is at 28°C. A refrigerating load of 2 kW is required. Determine the COP and the swept volume of the compressor if it has a volumetric efficiency of 76% and runs at 600 rpm.

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Quantum Physics


A R-12 vapour compression refrigeration system is operating at a condenser pressure of 9.6 bar and an evaporator pressure of 2.19 bar. Its refrigeration capacity is 15 tonnes. The values of enthalpy at the inlet and outlet of the evaporator are 64.6 and 195.7 kJ/kg. The specific volume at inlet to the reciprocating compressor is 0.082m3/kg. The index of compression for the compressor is 1.13 Determine: (a) The power input in kW required for the compressor (b) The COP. Take 1 tonnes of refrigeration as equivalent to heat removal at the rate of 3.517 kW.

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Quantum Physics


Large quantities of electrical power can be transmitted with relatively little loss when the transmission cable is cooled to a superconducting temperature. A regenerated gas refrigeration cycle operating with helium is used to maintain an electrical cable at 15 K. If the pressure ratio is 10 and heat is rejected directly to the atmosphere at 300 K, determine the COP and the performance ratio with respect to the Carnot cycle.

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Quantum Physics


A heat pump installation is proposed for a home heating unit with an output rated at 30 kW. The evaporator temperature is 10°C and the condenser pressure is 0.5 bar. Using an ideal vapour compression cycle, estimate the power required to drive the compressor if steam/water mixture is used as the working fluid, the COP and the mass flow rate of the fluid. Assume saturated vapour at compressor inlet and saturated liquid at condenser outlet.

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Quantum Physics


A 100 tonne low temperature R-12 system is to operate on a 2-stage vapour compression refrigeration cycle with a flash chamber, with the refrigerant evaporating at – 40°C, an intermediate pressure of 2.1912 bar, and condensation at 30°C. Saturated vapour enters both the compressors and saturated liquid enters each expansion valve. Consider both stages of compression to be isentropic. Determine: (a) The flow rate of refrigerant handled by each compressor (b) The total power required to drive the compressor (c) The piston displacement of each compressor, if the clearance is 2.5% for each machine (d) The COP of the system (e) What would have been the refrigerant flow rate, the total work of compression, the piston displacement in each compressor and the compressor and the COP, if the compression had occurred in a single stage? .

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Quantum Physics


What is Compression ratio, (rc)

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Quantum Physics