COMPETITIVE EXAMINATIONS QUESTIONS 913dharm
\M-therm\Comp1.pm5
- A cube at high temperature is immersed in a constant temperature bath. It loses heat from
its top, bottom and side surfaces with heat transfer coefficient of h 1 , h 2 and h 3 , respectively.
The average heat transfer coefficient for the cube is
(a) h 1 + h 2 + h 3 (b) (h 1 h 2 h 3 )1/3
(c)
111
hhh 123++ (d) None of the above.- Match items in List I with those in Lists II and III and select the correct answer using the
codes given the lists :
List I List II List III
A. Reversed Carnot engine 1. Condenser 6. Generator
B. Sub-cooling 2. Evaporator 7. Increase in refrigeration effect
C. Superheating 3. Vortex refrigerator 8. Highest COP
D. Constant enthalpy 4. Throttling 9. Adiabatic - Heat pump 10. Dry compression
Codes :
(a) ABCD
3, 10 1, 7 2, 9 4, 6
(b) ABCD
5, 8 1, 7 2, 10 4, 9
(c) ABCD
4, 10 3, 8 3, 10 1, 6
(d) ABCD
2, 7 5, 8 4, 6 1, 9 - Consider the following statements :
In ammonia refrigeration systems, oil separator is provided because- oil separation in evaporator would lead to reduction in heat transfer coefficient.
- oil accumulation in the evaporator causes choking of evaporator.
- oil is partially miscible in the refrigerant.
- oil causes choking of expansion device.
Of these statements :
(a) 1 and 2 are correct (b) 2 and 4 are correct
(c) 2, 3 and 4 are correct (d) 1, 3 and 4 are correct.
- Consider the following statements :
Moisture should be removed from refrigerants to avoid :- compressor seal failure 2. freezing at the expansion valve
- restriction to refrigerant flow 4. corrosion of steel parts.
On these statements :
(a) 1, 2, 3 and 4 are correct (b) 1 and 2 are correct
(c) 2, 3 and 4 are correct (d) 1, 3 and 4 are correct.
- Consider the following statements :
- Practically all common refrigerants have approximately the same COP and power
requirement. - Ammonia mixes freely with lubricating oil and this helps lubrication of compressors.
- Practically all common refrigerants have approximately the same COP and power