151. The central air conditioning system has __________ overall efficiency as compared to individual systems.
same
lower
higher
✅ The correct answer is option C.
Heat Transfer, Refrigeration and Air Conditioning MCQs
152. A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature drop, this can be replaced by a layer of diatomite earth of conductivity 0.14 W/mK and thickness
0.5 m
0.1 m
0.2 m
0.5 m
✅ The correct answer is option B.
153. The amount of heat flow through a body by conduction is
directly proportional to the surface area of the body
directly proportional to the temperature difference on the two faces of the body
inversely proportional to the thickness of the body
all of the above
✅ The correct answer is option D.
154. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.
TRUE
FALSE
✅ The correct answer is option A.
155. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg)
25 kJ/kg
50 kJ/kg
l00 kJ/kg
125 kJ/kg
✅ The correct answer is option B.
156. The operating pressure for refrigerating units using R-12 as a refrigerant is
2 bar
8 bar
15 bar
30 bar
✅ The correct answer is option B.
157. Which of the following refrigerant has the highest freezing point.
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
✅ The correct answer is option B.
158. Which of the following would lead to a reduction in thermal resistance?
In conduction, reduction in the thickness of the material and an increase in thermal conductivity.
In convection, stirring of the fluid and cleaning the heating surface.
In radiation, increasing the temperature and reducing the emissivity.
all of the above
✅ The correct answer is option D.
159. During sensible cooling,
relative humidity remains constant
wet bulb temperature increases
specific humidity increases
partial pressure of va
✅ The correct answer is option D.
160. The cooling system used for supersonic aircrafts and rockets is
simple air cooling system
boot-strap air cooling system
reduced ambient air cooling system
regenerative air cooli
✅ The correct answer is option D.