Latest Refrigeration and Air Conditioning mcq with answers-03

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Latest Refrigeration and Air Conditioning Questions and Answers

137. Choose the correct statement
(a) A refrigerant should have low latent heat
(b) If operating temperature of system is low, then refrigerant with low boiling point should be used
(c) Precooling and subcooling bf refrigerant are same
(d) Superheat and sensible heat of a. refrigerant are same
(e) Refrigerant is inside the lubes in case of a direct-expansion chiller.
Ans: b

138. The advantage of dry compression is that
(a) it permits higher speeds to be used
(b) it permits complete evaporation in the evaporator
(c) it results in high volumetirc and mechanical efficiency
(d) all of the above
(e) none of the above.
Ans: d

139. Choose the wrong statement
(a) Temperature of medium being cooled must be below that of the evaporator
(b) Refrigerant leaves the condenser as liquid
(c) All solar thermally operated absorption systems are capable only of intermittent operation
(d) frost on evaporator reduces heat transfer
(e) refrigerant is circulated in a refrigeration system to transfer heat.
Ans: a

142. The coefficient of performance is the ratio of the refrigerant effect to the
(a) heat of compression
(b) work done by compressor
(c) enthalpy increase in compressor
(d) all of the above
(e) none of the above.
Ans: d

143. The C.O.P of a refrigeration cycle with increase in evaporator temperature, keeping condenser temperature constant, will
(a) increase
(b) decrease
(c) remain unaffected
(d) may increase or decrease depending on the type of refrigerant used
(e) unpredictable.
Ans: a

144. Vertical lines on pressure-enthalpy chart show constant
(a) pressure lines
(b) temperature lines
(c) total heat lines
(d) entropy lines
(e) volume lines.
Ans: c

145. Most of the domestic refrigerators work on the following refrigeration system
(a) vapour compression
(b) vapour absorption
(c) carnot cycle
(d) electrolux refrigerator
(e) dual cycle.
Ans: a

146. The general rule for rating refrigeration systems (excepting for C02 system) is to approximate following h.p. per ton of Refrigeration
(a) 0.1 to 0.5 h.p. per ton of refrigeration
(b) 0.5 to 0.8 h.p. per ton of refrigeration
(c) 1 to 2 h.p. per ton of refrigeration
(d) 2 to 5 h.p. per ton of refrigeration
(e) 5 to 10 h.p. per ton refrigeration.
Ans: c

147. Reducing suction pressure in refrigeration cycle
(a) lowers evaporation temperature
(b) increases power required per ton of refrigeration
(c) lowers compressor capacity because vapour is lighter
(d) reduces weight displaced by piston
(e) all of the above.
Ans: e

148. Cooling water is required for following equipment in ammonia absorption plant
(a) condenser
(b) evaporator
(c) absorber
(d) condenser and absorber
(e) condenser, absorber and separator (rectifier).
Ans: e

151. Which of the following refrigerants has lowest freezing point
(a) Freon-12
(b) NH3
(c) C02
(d) Freon-22
(e) S02.
Ans: d

152. The COP of a vapour compression plant in comparison to vapour absorption plant is
(a) more
(b) less
(c) same
(d) more/less depending on size of plant
(e) unpredictable.
Ans: a

153. The C.O.P. of a domestic refrigerator in comparison to domestic air conditioner will be
(a) same
(b) more
(c) less
(d) dependent on weather conditions
(e) unpredictable.
Ans: c

154. The evolution of heat of solution takes place in ammonia absorption plant when
(a) ammonia vapour goes into solution
(b) ammonia vapour is driven out of solution
(c) lithium bromide mixes with ammonia
(d) weak solution mixes with strong solution
(e) lithium bromide is driven out of solution.
Ans: a

155. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
(a) more
(b) less
(c) equally.
(d) unpredictable
(e) none of the above.
Ans: a

156. Cooling water is required for following equipment in ammonia absorption plant
(a) condenser
(b) evaporator
(c) condenser and absorber
(d) condenser, absorber and separator (rectifier).

157. Absorption system normally uses the following refrigerant
(a) Freon-11
(b) Freon-22
(c) C02
(d) ammonia.

158. Which of the following is not a desirable property of a refrigerant
(a) high triiscibility with oil
(b) low boiling point
(c) good electrical conductor
(d) large latent heat

160. Choose the correct statement
(a) A refrigerant should have low latent heat
(b) If operating temperature of system is low, then refrigerant with low boiling point should be used
(c) Precooling and subcooling bf refrigerant are same
(d) Superheat and sensible heat of a. refrigerant are same

161. Aqua ammonia is used as refrigerant in the following type of refrigeration system
(a) compression
(b) direct
(c) indirect
(d) absorption

162. If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
(a) same
(b) more
(c) less
(d) more/less depending on rating

164. In a refrigeration cycle, the flow of refrigerant is controlled by
(a) compressor
(b) condenser
(c) evaporator
(d) expansion valve

166. The leaks in a refrigeration system using Freon are detected by
(a) halide torch which on detection produces greenish flame lighting
(b) sulphur sticks which on detection gives white smoke
(c) using reagents
(d) smelling

167.Pick up the incorrect statement
(a) lithium bromide used in vapour absorption cycle is nonvolatile
(b) lithium bromide plant can’t operate below 0°C
(c) a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
(d) concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

168. The wet bulb depression is the difference of
(a) DBT, WBT
(b) DPT, DBT
(c) DPT, WBT
(d) WBT, enthalpy

169. The dew point depression is difference of
(a) DBT, WBT
(b) DPT, DBT
(c) DPT, WBT
(d) WBT, enthalpy

170.The wet bulb temperature lines are
(a) parallel, equispaced
(b) inclined, parallel and equispaced
(c) inclined, parallel and non-equispaced
(d) horizontal and parallel to each other