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REFRIGERATION CYCLES 773

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11. The function of a ...... is to remove the vapour from the evaporator and to raise its temperature and
    pressure to a point such that it (vapour) can be condensed with normally available condensing media.


12. The function of a ...... is to provide a heat transfer surface through which a heat passes from the hot
    refrigerant vapour to the condensing medium.


13. The function of ...... is to meter the proper amount of refrigerant to the evaporator and to reduce the
    pressure of liquid entering the evaporator so that liquid will vaporise in the evaporator at the desired low
    temperature.


14. ...... provides a heat transfer surface through which heat can pass from the refrigerated space or product
    into the vaporising refrigerant.


15. If the vapour is not superheated after compression, the operation is called .....


16. If the vapour is superheated at the end of compression, the operation is called ......


17. When the suction pressure decreases the refrigerating effect and C.O.P. are ......


18. ...... results in increase of C.O.P. provided that no further energy has to be spent to obtain the extra cold
    coolant required.


19. ...... efficiency is defined as the ratio of actual volume of gas drawn into the compressor (at evaporator
    temperature and pressure) on each stroke to the piston displacement.

ANSWERS

1. Refrigeration 2.Refrigerant 3.C.O.P.


2. Relative C.O.P. 5.

T

TT

2

12 −

6.

T

TT

1

12 −

7. Less 8.Less 9.Refrigeration effect + work done


8. Vapour compression 11.Compressor 12.Condenser


9. Expansion valve 14.Evaporator 15.Wet compression


10. Dry compression 17.Reduced 18.Sub-cooling


11. Volumetric.

Theoretical Questions

1. Define the following :
   (i) Refrigeration (ii) Refrigerating system
   (iii) Refrigerated system.


2. Enumerate different ways of producing refrigeration.


3. Enumerate important refrigeration applications.


4. State elements of refrigeration systems.


5. Enumerate systems of refrigeration.


6. Define the following :
   (i) Actual C.O.P. (ii) Theoretical C.O.P.
   (iii) Relative C.O.P.


7. What is a standard rating of a refrigeration machine?


8. What is main characteristic feature of an air refrigeration system?


9. Differentiate clearly between open and closed air refrigeration systems.


10. Explain briefly an air refrigerator working on a reversed Carnot cycle. Derive expression for its C.O.P.


11. Derive an expression for C.O.P. for an air refrigeration system working on reversed Brayton cycle.


12. State merits and demerits of an air refrigeration system.


13. Describe a simple vapour compression cycle giving clearly its flow diagram.