The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner.
Same
Less
More
None of these
Correct Answer :
B. Less
Related Questions
The vapour compression refrigerator employs the following cycle
Rankine
Carnot
Reversed Rankine
Reversed Carnot
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 saturated liquid
After passing through the condenser
Before passing through the condenser
After passing through the expansion throttle valve
Before entering the expansion valve
The process, generally used in summer air conditioning to cool and dehumidify the air, is called
Humidification
Dehumidification
Heating and humidification
Cooling and dehumidification
The evaporator used in household refrigerators is
Frosting evaporator
Non-frosting evaporator
Defrosting evaporator
None of these
An Electrolux refrigerator is called a __________ absorption system.
Single fluid
Two fluids
Three fluids
None of these
R-12 is generally preferred over R-22 in deep freezers since
It has low operating pressures
It gives higher coefficient of performance
It is miscible with oil over large range of temperatures
All of the above
Refrigeration in aeroplanes usually employs the following refrigerant
CO2
Freon-11
Freon-22
Air
The sub-cooling in a refrigeration cycle
Does not alter C.O.P.
Increases C.O.P.
Decreases C.O.P.
None of these
Ammonia absorption refrigeration cycle requires
Very little work input
Maximum work input
Nearly same work input as for vapour compression cycle
Zero work input
Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system
Strong solution to weak solution
Weak solution to strong solution
Strong solution to ammonia vapour
Ammonia vapours to weak solution
On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process
Involves no change in volume
Takes place at constant temperature
Takes place at constant entropy
Takes place at constant pressure
The moisture in a refrigerant is removed by
Evaporator
Safety relief valve
Dehumidifier
Driers
During adiabatic saturation process on unsaturated air __________ remains constant.
Relative humidity
Dew point temperature
Dry bulb temperature
Wet bulb temperature
The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
More
Less
Equally
Unpredictable
The refrigerant used in small tonnage commercial machines (hermetically sealed units) is
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
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
The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
Mean radiant temperature
Effective temperature
Dew point temperature
None of these
At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
Decreases
Increases
Remain same
Depends on other factors
The freezing point of sulphur dioxide is
-56.6°C
-75.2°C
-77.7°C
-135.8°C
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)
Moisture should be removed from refrigerants to avoid
Freezing at the expansion valve
Restriction to refrigerant flow
Corrosion of steel plates
All of these
Which of the following refrigerants has lowest freezing point?
Freon-12
NH3
CO2
Freon-22
A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
1 kW
2 kW
3 kW
4 kW
A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
Lack of cooling water
Water temperature being high
Dirty condenser surface
All of these
The specific humidity during heating and humidification process.
Remains constant
Increases
Decreases
None of these
The COP of a domestic refrigerator
Is less than 1
Is more than 1
Is equal to 1
Depends upon the make
The Freon group of refrigerants are
Halocarbon refrigerants
Zoetrope refrigerants
Inorganic refrigerants
Hydrocarbon refrigerants
The material of pipe lines for a system using Freon as a refrigerant should be
Brass
Copper
Steel
Aluminium
For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
Small
High
Equal
Anything