Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)
0.622 Pv / (Pb - Pv)
μ/[1 - (1 - μ) (Ps/Pb)]
[Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
None of these
Correct Answer :
B. μ/[1 - (1 - μ) (Ps/Pb)]
Related Questions
The advantage of dry compression is that
It permits higher speeds to be used
It permits complete evaporation in the evaporator
It results in high volumetric and mechanical efficiency
All of the above
The freezing point of sulphur dioxide is
-56.6°C
-75.2°C
-77.7°C
-135.8°C
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
Which of the following refrigerant is highly toxic and flammable?
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
Same
More
Less
More/less depending on rating
The relative humidity lines on a psychrometric chart are
Vertical and uniformly spaced
Horizontal and uniformly spaced
Horizontal and non-uniformly spaced
Curved lines
The coefficient of performance of Electrolux refrigerator is the ratio of
Heat supplied by the gas burner to the heat absorbed by the evaporator
Heat absorbed by the evaporator to the heat supplied by the gas burner
Heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner
Heat absorbed by the evaporator minus the heat supplied by the gas burner to the heat absorbed by the evaporator
The leaks in a refrigeration system using Freon are detected by
Halide torch which on detection produces greenish flame lighting
Sulphur sticks which on detection gives white smoke
Using reagents
Smelling
Air refrigeration operates on
Carnot cycle
Reversed Carnot cycle
Rankines cycle
Brayton cycle
The general rule for rating refrigeration systems (excepting for CO₂ system) is to approximate following h.p. per ton of refrigeration
0.1 to 0.5 h.p. per ton of refrigeration
0.5 to 0.8 h.p. per ton of refrigeration
1 to 2 h.p. per ton of refrigeration
2 to 5 h.p. per ton of refrigeration
A vapour absorption refrigeration system
Gives noisy operation
Gives quiet operation
Requires little power consumption
Cools below 0°C
The vapour compression refrigerator employs the following cycle
Rankine
Carnot
Reversed Rankine
Reversed Carnot
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
The domestic refrigerator uses following type of compressor
Centrifugal
Axial
Miniature sealed unit
Piston type reciprocating
A human body feels comfortable when the heat produced by the metabolism of human body is equal to the
Heat dissipated to the surroundings
Heat stored in the human body
Sum of (A) and (B)
Difference of (A) and (B)
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
Bell Coleman cycle is a
Reversed Carnot cycle
Reversed Otto cycle
Reversed Joule cycle
Reversed Rankine cycle
For obtaining high COP, the pressure range of compressor should be
High
Low
Optimum
Any value
The superheated vapour region, in a pressure enthalpy chart, is represented by the space
To the left of saturated liquid line
To the right of saturated liquid line
Between the saturated liquid line and saturated vapour line
None of the above
Refrigeration in aeroplanes usually employs the following refrigerant
CO2
Freon-11
Freon-22
Air
Highest temperature encountered in refrigeration cycle should be
Near critical temperature of refrigerant
Above critical temperature
At critical Temperature
Much below critical temperature
Reducing suction pressure in refrigeration cycle
Lowers evaporation temperature
Increases power required per ton of refrigeration
Lowers compressor capacity because vapour is lighter
All of the above
The dehumidification process, on the psychrometric chart, is shown by
Horizontal line
Vertical line
Inclined line
Curved line
Nusselt number (NN) is given by
NN = hl/k
NN = μ cp/k
NN = ρ V l /μ
NN = V²/t.cp
In larger industrial and commercial reciprocating compression systems, refrigerant widely used is
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to
Bright green
Yellow
Red
Orange
In a vapour compression system, the condition of refrigerant is dry saturated vapour
Before entering the compressor
After leaving the compressor
Before entering the condenser
After leaving the condenser
The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents
Condensation of the refrigerant vapour
Evaporation of the refrigerant liquid
Compression of the refrigerant vapour
Metering of the refrigerant liquid
The boiling point of ammonia is
100°C
50°C
33.3°C
0°C
During adiabatic saturation process on unsaturated air __________ remains constant.
Relative humidity
Dew point temperature
Dry bulb temperature
Wet bulb temperature