Multiple Choice Questions (MCQ) on Refrigeration and Air conditioning – set 2

Multiple Choice Questions (MCQ) on Refrigeration and Air conditioning – set 2

 

A domestic refrigerator, set at 2°C, handles on an average a thermal load of 8000 kJ per day. The ambient temperature is 30°C and the COP of the refrigerator is 0.15 times that of a Carnot refrigerator. The daily electricity consumption in kWh is approximately

(a) 1.47

(b) 1.51

(c) 3.28

(d) 2.86

(Ans:b)

 

COP of a reversed Carnot cycle refrigerator working between higher temperature T2 and lower temperature T1

(a) will increase with increase in T1 keeping T2 fixed

(b) will decrease with increase in T1 keeping T2 fixed

(c) will first increase with increase in T1 and then decrease with increase in T1 keeping T2 fixed

(d) none of the above

(Ans:a)

 

A refrigerating machine working on reversed carnot cycle takes out 2kW of heat from the cold body while working between the temperature limits of 300K and 200K. The COP and power consumed by the cycle will be respectively.

(a) 1 and 1kW

(b) 1 and 2kW

(c) 2 and 1kW

(d) 2 and 2kW

(Ans:c)

 

A 1 ton capacity water cooler cools water steadily from 35°C to 20°C. The specific heat of water is 4.18 kj/kg-K. The water flow rate will be nearly.

(a) 13.33 liter/hr

(b) 33.3 liter/hr

(c) 200 liter/hr

(d) 250 liter/hr

(Ans:c)

 

Consider the following statements:

Dry compression in reciprocating compressor is preferred it

  1. prevents valve damage
  2. enables use of thermostatic expansion valve
  3. minimizes irreversibility in the compressor
  4. prevents washing out of the lubricating oil from cylinder walls

Which of these statements is correct?

(a) 1 and 2

(b) 2 and 3

(c) 1 and 4

(d) 3 and 4

(Ans:c)

 

Sub-cooling heat exchanger is used in a refrigeration cycle. The enthalpies at condenser outlet and evaporator outlet are 78kJ/kg and 182 kJ/kg respectively. The enthalpy at outlet of isentropic compressor is 230kJ/kg and enthalpy of sub cooled liquid is 68kJ/kg. The COP of the cycle is

(a) 3.25

(b) 2.16

(c) 3.0

(d) 3.5

(Ans:c)

 

Waste heat can be effectively used in which one of the following refrigeration systems?

(a) vapour compression refrigeration cycle

(b) air refrigeration cycle

(c) vapour absorption refrigeration cycle

(d) vortex refrigeration cycle

(Ans:c)

 

In vapour absorption refrigeration system, heat is rejected in

(a) condenser only

(b) generator only

(c) absorber only

(d) condenser and absorber

(Ans:d)

 

An Electrolux refrigerator uses

(a) one pump

(b) two pump

(c) no pump

(d) three pump

(Ans:c)

 

Which one of the following refrigerants has the highest critical temperature?

(a) H2O

(b) CO2

(c) R-12

(d) NH3

(Ans:a)

 

Dew point temperature is the temperature at which condensation begins when air is cooled at constant

(a) volume

(b) entropy

(c) pressure

(d) enthalpy

(Ans:c)

 

The main process which takes place in a dessert cooler is

(a) sensible cooling

(b) dehumidification

(c) adiabatic saturation

(d) cooling and dehumidification

(Ans:c)