916 ENGINEERING THERMODYNAMICS
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- Consider the following statements :
A psychrometer measures- wet bulb temperature
- dew point temperature
- dry bulb temperature.
Of these statements :
(a) 1 alone is correct (b) 2 and 3 are correct
(c) 1 and 3 are correct (d) 1, 2 and 3 are correct.
- Hot coffee in a cup is allowed to cool. Its cooling rate is measured and found to be greater
than the value calculated by conduction, convection and radiation measurements. The dif-
ference is due to
(a) properties of coffee changing with temperature
(b) currents of air flow in the room (c) underestimation of the emissivity of coffee
(d) evaporation. - For an air-conditioning plant above 300 ton, which one of the following systems would
normally be preferred?
(a) Ammonia reciprocating compressor (b) Centrifugal chiller
(c) Absorption refrigeration system (d) Hermetic compressor. - Fresh air intake (air change per hour) recommended for ventilation purposes in the air-
conditioning system of an office building is
(a) 1/2 (b) 3/2
(c) 9/2 (d) 25/2. - Give that
Nu = Nusselt number, Re = Reynolds number,
Pr = Prandtl number, Sh = Sherwood number,
Sc = Schmidt number, and Gr = Grashoff number,
the functional relationship for free convective mass transfer is given as :
(a) Nu = f (Gr, Pr) (b) Sh = f (Sc, Gr)
(c) Nu = f (Re, Pr) (d) Sh = f (Re, Sc). - Air refrigeration cycle is used in
(a) commercial refrigerators (b) domestic refrigerators
(c) gas liquification (d) air-conditioning. - The flash chamber in single-stage simple vapour compression cycle
(a) increases the refrigerating effect (b) decrease the refrigerating effect
(c) increases the work of compression (d) has no effect on refrigerating effect. - Consider the following statements :
In a vapour compression system, a thermometer placed in the liquid line can indicate whether
the- refrigerant flow is too low 2. water circulation is adequate
- condenser is fouled 4. pump is functioning properly.
Of these statements :
(a) 1, 2 and 3 are correct (b) 1, 2 and 4 are correct
(c) 1, 3 and 4 are correct (d) 2, 3 and 4 are correct.