The unit of thermal diffusivity is
m/hK
m/h
m²/h
m²/hK
Correct Answer :
C. m²/h
Related Questions
For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
Reciprocating
Rotating
Centrifugal
Screw
The operating temperature of a cold storage is 2°C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40°C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is
1.86 kW
3.72 kW
7.44 kW
18.6 kW
The thermostatic expansion valve is also called
Constant pressure valve
Constant temperature valve
Constant superheat valve
None of these
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
One ton refrigeration corresponds to
50 kcal/ min
50 kcal/ hr
80 kcal/ min
80 kcal/ hr
The material of pipe lines for a system using Freon as a refrigerant should be
Brass
Copper
Steel
Aluminium
Which of the following statement is wrong?
The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.
In vapour compression cycle, the useful part of the heat transfer is at the condenser.
In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.
The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.
The wet bulb temperature during sensible cooling of air
Remains constant
Increases
Decreases
None of these
During cooling and dehumidification, dry bulb temperature
Remains constant
Increases
Decreases
None of these
Vapour compression refrigeration is somewhat like
Carnot cycle
Rankines cycle
Reversed Carnot cycle
None of the above
In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is
Less than 2 kg
More than or equal to 3.65 kg
More than 10 kg
There is no such consideration
Rick up the incorrect statement
Lithium bromide used in vapour absorption cycle is non volatile
Lithium bromide plant can't operate below 0°C
A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
Aqua ammonia is used as refrigerant in the following type of refrigeration system
Compression
Direct
Indirect
Absorption
A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in ________ power per tonne of refrigeration.
Same
Lower
Higher
None of these
During heating and dehumidification process, dry bulb temperature
Remains constant
Increases
Decreases
None of these
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
Short horizontal lines on pressure-enthalpy chart show
Constant pressure lines
Constant temperature lines
Constant total heat lines
Constant entropy lines
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)]
A refrigerant with the highest critical pressure is
R-11
R-12
R-22
Ammonia
Freon group of refrigerants are
Inflammable
Toxic
Non-inflammable and toxic
Nontoxic and non-inflammable
In which of the following refrigeration system, waste heat can be effectively used?
Vapour compression cycle
Vapour absorption cycle
Air refrigeration cycle
None of these
Domestic refrigerator working on vapour compression cycle uses the following type of expansion device
Electrically operated throttling valve
Manually operated valve
Thermostatic valve
Capillary tube
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
The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called
Kinetic theory of gases
Newton's law of gases
Dalton's law of partial pressures
Avogadro's hypothesis
Chaperon equation is applicable for registration at
Saturation point of vapour
Saturation point of liquid
Sublimation temperature
Triple point
During humidification process, dry bulb temperature
Remains constant
Increases
Decreases
None of these
The vapour compression refrigerator employs the following cycle
Rankine
Carnot
Reversed Rankine
Reversed Carnot
Moisture in Freon refrigeration system causes
Ineffective refrigeration
High power consumption
Freezing automatic regulating valve
Corrosion of whole system
The difference between dry bulb temperature and dew point temperature, is called
Dry bulb depression
Wet bulb depression
Dew point depression
Degree of saturation
The lowest temperature during the cycle in a vapour compression system occurs after
Compression
Expansion
Condensation
Evaporation