In a pressure enthalpy chart, the space to the left of the saturated liquid line represents
Wet vapour region
Superheated vapour region
Sub-cooled liquid region
None of these
Correct Answer :
C. Sub-cooled liquid region
Related Questions
The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
Sub-cooling or under-cooling
Super-cooling
Normal cooling
None of these
A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be
0.2
1.2
5
6
Which of the following statement is wrong?
The value of C.O.P. is always greater than one.
In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour.
The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region.
None of the above
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
Ammonia is
Non-toxic
Non-inflammable
Toxic and non-inflammable
Highly toxic and inflammable
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
During dehumidification process, __________ remains constant.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
One ton of the refrigeration is
The standard unit used in refrigeration problems
The cooling effect produced by melting 1 ton of ice
The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
The refrigeration effect to produce 1 ton of ice at NTP conditions
In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is
High pressure saturated liquid
Wet vapour
Very wet vapour
Dry vapour
The desirable property of a refrigerant is
Low boiling point
High critical temperature
High latent heat of vaporisation
All of these
Air refrigerator works on
Reversed Carnot cycle
Bell Coleman cycle
Both (A) and (B)
None of these
Allowable pressure on high pressure side or ammonia absorption system is of the order of
Atmospheric pressure
Slightly above atmospheric pressure
24 bars
56 bars
The relative humidity lines on a psychrometric chart are
Vertical and uniformly spaced
Horizontal and uniformly spaced
Horizontal and non-uniformly spaced
Curved lines
In vapour compression cycle the condition off refrigerant is dry saturated vapour
After passing through the condenser
Before passing through the condenser
After passing through the expansion or throttle valve
Before entering the compressor
During a refrigeration cycle, heat is rejected by the refrigerant in a
Compressor
Condenser
Evaporator
Expansion valve
Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since
These react with water vapour and cause acid rain
These react with plants and cause greenhouse effect
These react with oxygen and cause its depletion
These react with ozone layer
The wet bulb temperature during sensible cooling of air
Remains constant
Increases
Decreases
None of these
In case of sensible cooling of air, the coil efficiency is given by
B.P.F. - 1
1 - B.P.F.
1/ B.P.F.
1 + B.P.F.
During heating and dehumidification process, dry bulb temperature
Remains constant
Increases
Decreases
None of these
In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the
Expansion valve to the evaporator
Evaporator to the thermostat
Condenser to the expansion valve
Condenser to the evaporator
If a gas is to be liquefied, its temperature must be
Increased to a value above its critical temperature
Reduced to a value below its critical temperature
Equal to critical temperature
None of the above
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 coefficient of performance is the ratio of the refrigerant effect to the
Heat of compression
Work done by compressor
Enthalpy increase in compressor
All of the above
The C.O.P. of an absorption type refrigerator is given by (where T₁ = Temperature at which the working substance receives heat, T₂ = Temperature of cooling water, and T₃ = Evaporator temperature)
[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]
[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]
[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]
[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]
In Electrolux refrigerator
Ammonia is absorbed in hydrogen
Ammonia is absorbed in water
Ammonia evaporates in hydrogen
Hydrogen evaporates in ammonia
In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be
High, of the order of 25°
As low as possible (3 to 11°C)
Zero
Any value
The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called
Wet bulb temperature
Dry bulb temperature
Dew point temperature
None of these
During dehumidification process, the relative humidity
Remains constant
Increases
Decreases
None of these
Nusselt number (NN) is given by
NN = hl/k
NN = μ cp/k
NN = ρ V l /μ
NN = V²/t.cp
Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.
Equalise
Reduce
Increase
None of these