Choose the correct statement
A refrigerant should have low latent heat
If operating temperature of system is low, then refrigerant with low boiling point should be used
Pre-cooling and sub-cooling bf refrigerant are same
Superheat and sensible heat of a refrigerant are same
Correct Answer :
B. If operating temperature of system is low, then refrigerant with low boiling point should be used
Related Questions
The desirable property of a refrigerant is
Low boiling point
High critical temperature
High latent heat of vaporisation
All of these
During heating and humidification, the final relative humidity of air
Can be lower or higher than that of the entering air
Is lower than that of the entering air
Is higher than that of the entering air
None of the above
In vapour compression cycle the condition of refrigerant is superheated vapour
After passing through the condenser
Before passing through the condenser
After passing through the expansion or throttle valve
Before entering the expansion valve
The coefficient of performance of Heat Pump is always __________ one.
Equal to
Less than
Greater than
None of these
The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)
(hA - h2)/ (h1 - h2)
(h2 - hA)/ (h1 - h2)
(h1 - h2)/ (hA - h2)
(hA - h1)/ (h2 - h1)
In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid
After passing through the condenser
Before passing through the condenser
After passing through the expansion or throttle valve
Before entering the expansion valve
The dehumidification process, on the psychrometric chart, is shown by
Horizontal line
Vertical line
Inclined line
Curved line
The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
High pressure saturated liquid
Wet vapour
Very wet vapour
Dry vapour
Vertical lines on pressure-enthalpy chart show constant
Pressure lines
Temperature lines
Total heat lines
Entropy lines
If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be
0.2
1.2
5
6
One of the purposes of sub cooling 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
A refrigerant compressor is used to
Raise the pressure of the refrigerant
Raise the temperature of the refrigerant
Circulate the refrigerant through the refrigerating system
All of the above
The horizontal and non-uniformly spaced lines on a psychrometric chart indicates
Dry bulb temperature
Wet bulb temperature
Dew point temperature
Specific humidity
The specific humidity during humidification process
Remains constant
Increases
Decreases
None of these
The refrigerant supplied to a compressor must be
Superheated vapour refrigerant
Dry saturated liquid refrigerant
A mixture of liquid and vapour refrigerant
None of these
In a saturated air-water vapour mixture, the
Dry bulb temperature is higher than wet bulb temperature
Dew point temperature is lower than wet bulb temperature
Dry bulb, wet bulb and dew point temperature are same
Dry bulb temperature is higher than dew point temperature
The evolution of heat of solution takes place in ammonia absorption plant when
Ammonia vapour goes into solution
Ammonia vapour is driven out of solution
Lithium bromide mixes with ammonia
Weak solution mixes with strong solution
Most of the domestic refrigerators work on the following refrigeration system
Vapour compression
Vapour absorption
Carnot cycle
Electrolux refrigerator
A thermostatic expansion valve in a refrigeration system
Ensures the evaporator completely filled with refrigerant of the load
Is suitable only for constant load systems
Maintains different temperatures in evaporator in proportion to load
None of the above
The difference between dry bulb temperature and wet bulb temperature, is called
Dry bulb depression
Wet bulb depression
Dew point depression
Degree of saturation
The lowest thermal diffusivity is of
Iron
Lead
Aluminium
Rubber
Choose the wrong statement
Temperature of medium being cooled must be below that of the evaporator
Refrigerant leaves the condenser as liquid
All solar thermally operated absorption systems are capable only of intermittent operation
Frost on evaporator reduces heat transfer
As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.
Same as
Lower than
Higher than
None of these
In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
1
1.25
2.15
5.12
Ammonia is
Non-toxic
Non-inflammable
Toxic and non-inflammable
Highly toxic and inflammable
Condensing temperature in a refrigerator is the temperature
Of cooling medium
Of freezing zone
Of evaporator
At which refrigerant gas becomes liquid
An Electrolux refrigerator is called a __________ absorption system.
Single fluid
Two fluids
Three fluids
None of these
Superheating in a refrigeration cycle
Increases C.O.P
Decreases C.O.P
C.O.P remains unaltered
Other factors decide C.O.P
The process of under-cooling is generally brought about by
Circulating more quantity of cooling water through the condenser
Using water colder than the main circulating water
Employing a heat exchanger
Any one of the above
The temperature of ammonia after compression in a vapour compression system is
20 to 50°C
50 to 70°C
70 to 110°C
None of these