1. Water vapour at 90kPa and 150°C enters a subsonic diffuser with a velocity of 150m/s and leaves the diffuser at 190kPa with a velocity of 55m/s and during the process 1.5 kJ/kg of heat is lost to surroundings. Determine (i) The final temperature
(ii) The mass flow rate.
(iii) The exit diameter, assuming the inlet diameter as 10cm and steady flow.
2. A 0.5-m3 rigid tank contains refrigerant-134a initially at 200 kPa and 40 percent quality. Heat is now transferred to the refrigerant until the pressure reaches 800 kPa.
Determine (a) the mass of the refrigerant in the tank and (b) the amount of heat transferred. Also, show the process on a P-v diagram with respect to saturation lines.
3. It is proposed to use water instead of refrigerant-134a as the working fluid in air- conditioning applications where the minimum temperature never falls below the
freezing point. Would you support this proposal? Explain.
4. A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at-30°C by rejecting its waste heat to cooling water that enters the condenser at 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and -34°C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine (a) the quality of the refrigerant at the evaporator inlet, (b) the refrigeration load, (c) the COP of the refrigerator, and (d) the theoretical maximum refrigeration load for the same power input to the compressor.
5. In absorption refrigeration cycles, why is the fluid in the absorber cooled and the fluid in the generator heated? How is the coefficient of performance of an absorption refrigeration system defined?
6. Can water be used as a refrigerant in air-conditioning applications? Explain.