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4

An infinite parallel planes with emissivities e₁ and e₂, the interchange factor for radiation from surface 1 to surface 2 is given by

A. (e₁ + e₂)/ e₁ + e₂ - e₁e₂

B. 1/e₁ + 1/e₂

C. e₁ + e₂

D. e₁e₂

Correct Answer :

A. (e₁ + e₂)/ e₁ + e₂ - e₁e₂


Related Questions

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4

In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature

A. Which lies between the dry bulb and wet bulb temperatures of the incoming stream

B. Which lies between the wet bulb and dew point temperatures of the incoming stream

C. Which is lower than the dew point temperature of the incoming stream

D. Of adiabatic saturation of incoming stream

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4

The condition of refrigerant after passing through the condenser in a vapour compression system is

A. Saturated liquid

B. Wet vapour

C. Dry saturated vapour

D. Superheated vapour

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4

The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature.

A. Same as

B. Lower than

C. Higher than

D. None of these

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4

The bypass factor of a cooling coil decreases with

A. Decrease in fin spacing and increase in number of rows

B. Increase in fin spacing and increase in number of rows

C. Increase in fin spacing and decrease in number of rows

D. Decrease in fin spacing and decrease in number of rows

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4

Most of the domestic refrigerators work on the following refrigeration system

A. Vapour compression

B. Vapour absorption

C. Carnot cycle

D. Electrolux refrigerator

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4

Dry bulb temperature is the temperature of air recorded by a thermometer, when

A. It is not affected by the moisture present in the air

B. Its bulb is surrounded by a wet cloth exposed to the air

C. The moisture present in it begins to condense

D. None of the above

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4

For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is

A. Zero

B. 20

C. 50

D. 100

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4

The wet bulb depression indicates _________ humidity of the air.

A. Absolute

B. Relative

C. Specific

D. None of these

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4

The evaporator changes the low pressure liquid refrigerant from the expansion valve into

A. High pressure liquid refrigerant

B. Low pressure liquid and vapour refrigerant

C. Low pressure vapour refrigerant

D. None of these

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4

Which of the following refrigerant has the lowest boiling point?

A. Ammonia

B. Carbon dioxide

C. Sulphur dioxide

D. R-12

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4

The evolution of heat of solution takes place in ammonia absorption plant when

A. Ammonia vapour goes into solution

B. Ammonia vapour is driven out of solution

C. Lithium bromide mixes with ammonia

D. Weak solution mixes with strong solution

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4

In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be

A. 0.3

B. 0.6

C. 0.67

D. 1.5

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4

In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is

A. Less than 2 kg

B. More than or equal to 3.65 kg

C. More than 10 kg

D. There is no such consideration

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4

The centrifugal compressors are generally used for refrigerants that require

A. Small displacements and low condensing pressures

B. Large displacements and high condensing pressures

C. Small displacements and high condensing pressures

D. Large displacements and low condensing pressures

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4

Choose the wrong statement

A. Temperature of medium being cooled must be below that of the evaporator

B. Refrigerant leaves the condenser as liquid

C. All solar thermally operated absorption systems are capable only of intermittent operation

D. Frost on evaporator reduces heat transfer

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4

The thermostatic expansion valve is used in __________ type of evaporators.

A. Flooded

B. DX coil

C. Dry

D. None of these

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4

In a refrigeration cycle, the flow of refrigerant is controlled by

A. Compressor

B. Condenser

C. Evaporator

D. Expansion valve

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4

During sensible cooling of air ________ decreases.

A. Wet bulb temperature

B. Relative humidity

C. Dry bulb temperature

D. Specific humidity

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4

The COP of a domestic refrigerator

A. Is less than 1

B. Is more than 1

C. Is equal to 1

D. Depends upon the make

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4

Ammonia is

A. Non-toxic

B. Non-inflammable

C. Toxic and non-inflammable

D. Highly toxic and inflammable

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4

One tonne of refrigeration (1TR) means that the heat removing capacity is

A. 21 kJ/min

B. 210 kJ/min

C. 420 kJ/min

D. 620 kJ/min

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4

The domestic refrigerator uses following type of compressor

A. Centrifugal

B. Axial

C. Miniature sealed unit

D. Piston type reciprocating

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4

In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = Bypass factor)

A. B.P.F. - 1

B. 1 - B. P.F.

C. 1/ B.P.F.

D. 1 + B.P.F.

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4

The C.O.P. of a heat pump working on a reversed Carnot cycle is

A. T₁/(T₂ - T₁)

B. (T₂ - T₁)/T₁

C. (T₁ - T₂)/T₁

D. T₂/(T₂ - T₁)

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4

The lowest thermal diffusivity is of

A. Iron

B. Lead

C. Aluminium

D. Rubber

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4

Under cooling in a refrigeration cycle

A. Increases C.O.P

B. Decreases C.O.P

C. C.O.P remains unaltered

D. Other factors decide C.O.P

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4

For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of

A. Copper

B. Aluminium

C. Steel

D. Brass

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4

During dehumidification process, __________ remains constant.

A. Wet bulb temperature

B. Relative humidity

C. Dry bulb temperature

D. Specific humidity

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4

The thermostatic expansion valve is also called

A. Constant pressure valve

B. Constant temperature valve

C. Constant superheat valve

D. None of these

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4

The thermostatic expansion valve operates on the changes in the

A. Degree of superheat at exit from the evaporator

B. Temperature of the evaporator

C. Pressure in the evaporator

D. None of the above