MCQ
2141. Air refrigeration operates on—
Carnot cycle
Rankine cycle
Reversed Carnot cycle
Brayton cycle
2142. At lower temperatures and pressures, the latent heat of vapourisation of a refrigerant-
decreases
increases
remains same
depends on other factors
2143. The basis for measuring thermodynamic property of temperature is given by-
Zeroth law of thermodynamics
First law of thermodynamics
Second law of thermodynamics
Third law of thermodynamics
2144. One of the purposes of subcooling the liquid refrigerant is to-
reduce compressor overheating
reduce compressor discharge temperature
increase cooling effect
ensure that only liquid and not the vapour enters the expansion (throttling) valve
2145. Accumulators should have adequate volume to store refrigerant charge at least-
10%
50%
25%
75%
2146. Aqua ammonia is used as refrigerant in the following type of refrigeration system--
compression
indirect
absorption
direct
2147. Air refrigeration cycle is used in--
domestic refrigerators
commercial refrigerators
air-conditioning
gas liquefaction
2148. Addition of heat at constant pressure to a gas results in-
Raising its temperature
Raising its pressure
Raising its volume
Raising its temperature and doing external work
2149. The value of COP in vapour compression cycle is usually--
always less than unity
always more than unity.
equal to unity
any one of the above
2150. In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to--
collect liquid refrigerant and prevent it from going to compressor
detect liquid in vapour
superheat the vapour
collect vapours
2151. A diathermic wall is one which-
Prevents thermal interaction
Permits thermal interaction
Encourages thermal interaction
Discourages thermal interaction
2152. Unit of temperature in SI unit is—
Celsin
Kelvin
Furenheit
Centigrade
2153. The term N.T.P. stands for-
Nominal temperature and pressure
Natural temperature and pressure
Normal temperature and pressure
Normal thermodynamic practice
2154. Bull bearing is usually made from-
low carbon steel
high carbon steel
chrome steel
medium carbon steel
2155. An evaporator is also known as—
cooling coil
freezing coil
chilling cod
all of these
2156. An adiabatic wall is one which-
Prevents thermal interaction
Permits thermal interaction
Encourages thermal interaction
Discourages thermal interaction
2157. If heat be exchanged in a reversible manner, which of the following property of the working substance will change accordingly?
Temperature
Enthalpy
Internal energy
Entropy
2158. Total heat of a substance is also known as-
Internal energy
Entropy
Thermal capacity
Enthalpy
2159. The vapour pressure of refrigerant should be—
higher than atmospheric pressure
equal to atmospheric pressure
lower than atmospheric pressure
could be anything
2160. A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67kg/cm The refrigerant used is--
Ammonia
Carbon dioxide
Freon
Brine