Chapter 9, Problem 9.10P

A refrigeration system with a capacity of 10 tons of refrigeration, operates at 210 kPa in the evaporator, while in the condenser it is 850 kPa. If R-134a refrigerant is in a saturated state, calculate the theoretical power required to operate the compressor. Compressor power = ... W.

2. A refrigeration system with a capacity of 15 tons of refrigeration, operates at 150 kPa in the evaporator, while the condenser is 1450 kPa. If refrigerant R-717 is saturated, calculate the theoretical power required to operate the compressor. Compressor Power = Answer   kW.

How to do a heat/energy balance on a anode fuel cell and a condenser given that the fuel cell is isothermal and the outlet of the condenser is 25 degrees?

4. If the isentropic efficiencies of the turbine and the pump are 80% and 100% respectively in problem 3, determine the following: a. Actual moisture fraction of the exhaust steam. b. Actual Efficiency of the plant.   (number 3 question: In a Steam Power Plant steam enters the turbine at 6 bar and 400oC and is expanded isentropic ally to the condenser pressure of 0.1 bar. Find the condition of the exhaust steam and determine the cycle efficiency.)

An ideal vapor compression cycle operates between the temperature limits of -5 °c and 30 °C and uses R134a as the refrigerant, which flows at a rate of 0.6 kg/s. The P-h- as well as T-s-diagrams that illustrate the refrigerating process is given in diagram, and respectively. Refigerant is compressed to the state in the compressor and heat is rejected in the condenser at constant for ideal Vapour compression cycle.

A refrigeration system with a capacity of 10 tons of refrigeration, operates at 210 kPa in the evaporator, while in the condenser it is 750 kPa. If R-134a refrigerant is in a saturated state, calculate the theoretical power required to operate the compressor. Compressor Power = Answer kW.

13. A food storage locker requires a refrigeration system of 2500 kJ/min capacity at an evaporator temperature of – 10°C and a condenser temperature of 30°C. The refrigerant used is Freon-12 and sub-cooled by 5°C before entering the expansion valve and vapour is superheated by 6°C before leaving the evaporator coil. The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder single- acting with stroke equal to 1.3 times the bore and operates at 975 r.p.m. Determine (using thermodynamic tables of properties for Freon-12): (i) Refrigerating effect per kg. (ii) Mass of refrigerant to be circulated per minute. (iii) Theoretical piston displacement per minute. (iv) Theoretical power required to run the compressor, in kW. (v) Heat removed through the condenser per minute. (vi) Theoretical bore and stroke of compressor. Properties of Freon-12 Saturation Absolute Enthalpy Entropy Specific volume of temp. pressure Liquid kJ/kg Vapour kJ/kg °C vapour…

5. A refrigeration system using R-12 as refrigerant consists of throe evaporators of capacities 20 TR at – 5°C, 30 TR at 0°C and 10 TR at 5°C. The vapours leaving the three evaporators are dry and saturated. The system is provided with individual compressors and multiple expansion valves. The condenser temperature is 40°C and the liquid refrigerant leaving the condenser is saturatoed. Assuming isentropic compression in each compressor, find (a) the mass of refrigerant flowing through cach evaporator, (b) the power required to drive the system, and (c) the C.O.P. of the system. [Ans. 27.4 kg/min, 42.25 kg/min: 34.12 kg/min; 38.4 kW; 5.56]

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