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4

During sensible heating of air _________ decreases.

A. Wet bulb temperature

B. Relative humidity

C. Dry bulb temperature

D. Specific humidity

Correct Answer :

B. Relative humidity


Related Questions

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The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as

A. Mean radiant temperature

B. Effective temperature

C. Dew point temperature

D. None of these

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4

The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to

A. Bright green

B. Yellow

C. Red

D. Orange

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4

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

A. 1.86 kW

B. 3.72 kW

C. 7.44 kW

D. 18.6 kW

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4

The refrigerant used in small tonnage commercial machines (hermetically sealed units) is

A. Ammonia

B. Carbon dioxide

C. Sulphur dioxide

D. R-12

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4

Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system

A. Strong solution to weak solution

B. Weak solution to strong solution

C. Strong solution to ammonia vapour

D. Ammonia vapours to weak solution

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4

In vapour compression refrigeration system, refrigerant occurs as liquid between

A. Condenser and expansion valve

B. Compressor and evaporator

C. Expansion valve and evaporator

D. Compressor and condenser

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4

Which of the following statement is correct?

A. The human body can lose heat even if its temperature is less than the atmospheric temperature.

B. The increase in air movement increases the evaporation from the human body.

C. The warm air increases the rate of radiation of heat from the human body.

D. Both (A) and (B)

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4

In a vapour compression system, the condition of refrigerant is dry saturated vapour

A. Before entering the compressor

B. After leaving the compressor

C. Before entering the condenser

D. After leaving the condenser

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4

In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by

A. Liquid pump

B. Generator

C. Absorber and generator

D. Absorber, generator and liquid pump

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4

Critical temperature is the temperature above which

A. A gas will never liquefy

B. A gas will immediately liquefy

C. Water will evaporate

D. Water will never evaporate

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4

When the air is passed through an insulated chamber having sprays of water maintained at a temperature higher than the dew point temperature of entering air but lower than its dry bulb temperature, then the air is said to be

A. Cooled and humidified

B. Cooled and dehumidified

C. Heated and humidified

D. Heated and dehumidified

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4

The conditioned air supplied to the room must have the capacity to take up

A. Room sensible heat load only

B. Room latent heat load only

C. Both room sensible heat and latent heat loads

D. None of the above

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4

If a gas is to be liquefied, its temperature must be

A. Increased to a value above its critical temperature

B. Reduced to a value below its critical temperature

C. Equal to critical temperature

D. None of the above

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4

In a reversed Brayton cycle, the heat is absorbed by the air during

A. Isentropic compression process

B. Constant pressure cooling process

C. Isentropic expansion process

D. Constant pressure expansion process

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4

The central air conditioning system has ________ overall efficiency as compared to individual systems.

A. Same

B. Lower

C. Higher

D. None of these

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4

For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be

A. Small

B. High

C. Equal

D. Anything

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In a refrigerating machine, heat rejected is _________ heat absorbed.

A. Equal to

B. Less than

C. Greater than

D. None of these

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4

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

A. Same as

B. Lower than

C. Higher than

D. None of these

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4

Air refrigeration cycle is used in

A. Domestic refrigerators

B. Commercial refrigerators

C. Air conditioning

D. Gas liquefaction

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4

For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is ________ that for counter flow.

A. Equal to

B. Less than

C. Greater than

D. None of these

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4

R-12 is generally preferred over R-22 in deep freezers since

A. It has low operating pressures

B. It gives higher coefficient of performance

C. It is miscible with oil over large range of temperatures

D. All of the above

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4

Which of the following refrigerants has lowest freezing point?

A. Freon-12

B. NH3

C. CO2

D. Freon-22

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4

The material of pipe lines for a system using Freon as a refrigerant should be

A. Brass

B. Copper

C. Steel

D. Aluminium

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4

The refrigerant widely used in domestic refrigerators is

A. Ammonia

B. Carbon dioxide

C. Sulphur dioxide

D. R-12

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4

Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.

A. Equalise

B. Reduce

C. Increase

D. None of these

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4

At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant

A. Decreases

B. Increases

C. Remain same

D. Depends on other factors

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4

In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively

A. Water and water

B. Water and lithium bromide

C. Ammonia and lithium bromide

D. Ammonia and water

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4

The bypass factor, in case of sensible cooling of air, is given by (where td₁ = Dry bulb temperature of air entering the cooling coil, td₂ = Dry bulb temperature of air leaving the cooling coil, and td₃ = Dry bulb temperature of the cooling coil)

A. (td₁ -td₃)/( td₂ -td₃)

B. (td₂ -td₃)/( td₁ -td₃)

C. (td₃ -td₁)/( td₂ -td₃)

D. (td₃ -td₂)/( td₁ -td₃)

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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

The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will

A. Increase

B. Decrease

C. May increase or decrease depending on the type of refrigerant used

D. Remain unaffected