TITLE.PM5

COMPETITIVE EXAMINATIONS QUESTIONS 919

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\M-therm\Comp1.pm5

14. T 1 = T 2 ; V 2 = V^1
    2

...(Given)

From p 1 V 1 = p 2 V 2 , p 1 V 1 = p 2 ×

V 1

2

⇒ p 2 = 2p 1

15. Since (∆s)system > (∆s)surrounding, where both (∆s)system > 0 and (∆s)surrounding > 0.


16. The compressors seal cannot fail due to moisture, all the other conditions do occur due to
    presence of moisture.


17. All common refrigerants like F 11 , F 12 , F 22 , NH 3 etc. have approximately the same C.O.P.
    ranging from 4.76 to 5.09 and H.P./ton varies from 0.99 to 1.01.
    The electric resistance of the refrigerants is an important factor when it is used in hermetically
    sealed unit where the motor is exposed to the refrigerant.


18. The reason why centrifugal compressors are used to large tonnage is that they can handle
    larger volumes of refrigerant, also the part load efficiency of this kind is higher.


19. C.O.P. =

T

TT

2

12

200

− 300 200

=

− = 2

Power consumed =

Rn(net refrigerating effect)

C. O. P.

W

=

2

2

k

= 1 kW.