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What is the correct answer?

4

The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents

A. Condensation of the refrigerant vapour

B. Evaporation of the refrigerant liquid

C. Compression of the refrigerant vapour

D. Metering of the refrigerant liquid

Correct Answer :

B. Evaporation of the refrigerant liquid


Related Questions

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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 lowest thermal diffusivity is of

A. Iron

B. Lead

C. Aluminium

D. Rubber

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4

A vapour absorption refrigeration system

A. Gives noisy operation

B. Gives quiet operation

C. Requires little power consumption

D. Cools below 0°C

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4

The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called

A. Wet bulb temperature

B. Dry bulb temperature

C. Dew point temperature

D. None of these

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4

In a lithium bromide absorption refrigeration system

A. Lithium bromide is used as a refrigerant and water as an absorbent

B. Water is used as a refrigerant and lithium bromide as an absorbent

C. Ammonia is used as a refrigerant and lithium bromide as an absorbent

D. None of the above

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4

Which of the following statement is wrong?

A. The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

B. In vapour compression cycle, the useful part of the heat transfer is at the condenser.

C. In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

D. The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.

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4

In vapour compression cycle the condition of refrigerant is superheated vapour

A. After passing through the condenser

B. Before passing through the condenser

C. After passing through the expansion or throttle valve

D. Before entering the expansion valve

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4

The moisture in a refrigerant is removed by

A. Evaporator

B. Safety relief valve

C. Dehumidifier

D. Driers

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4

The condition of refrigerant as it leaves the compressor in a vapour compression system is

A. Saturated liquid

B. Wet vapour

C. Dry saturated vapour

D. Superheated vapour

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4

In vapour compression cycle the condition off refrigerant is dry saturated vapour

A. After passing through the condenser

B. Before passing through the condenser

C. After passing through the expansion or throttle valve

D. Before entering the compressor

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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 relative humidity is defined as

A. The mass of water vapour present in 1 m3 of dry air

B. The mass of water vapour present in 1 kg of dry air

C. The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.

D. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure

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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 operating pressure for refrigerating units using R-12 as a refrigerant is

A. 2 bar

B. 8 bar

C. 15 bar

D. 30 bar

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4

The value of C.O.P in vapour compression cycle is usually

A. Always less than unity

B. Always more than unity

C. Equal to unity

D. Any one of the above

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4

During heating and humidification, the final relative humidity of air

A. Can be lower or higher than that of the entering air

B. Is lower than that of the entering air

C. Is higher than that of the entering air

D. None of the above

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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

The vertical and uniformly spaced lines on a psychrometric chart indicates

A. Dry bulb temperature

B. Wet bulb temperature

C. Dew point temperature

D. Specific humidity

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4

The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called

A. Humidity ratio

B. Relative humidity

C. Absolute humidity

D. Degree of saturation

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4

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.

A. Same

B. Lower

C. Higher

D. None of these

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4

Degree of saturation or percentage humidity is

A. The mass of water vapour present in 1 m³ of dry air

B. The mass of water vapour present in 1 kg of dry air

C. The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.

D. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure

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4

If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be

A. 0.2

B. 1.2

C. 5

D. 6

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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

Formation of frost on evaporator in refrigerator

A. Results in loss of heat due to poor heat transfer

B. Increases heat transfer rate

C. Is immaterial

D. Can be avoided by proper design

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4

The minimum temperature to which water can be cooled in a cooling tower is

A. Dew point temperature of air

B. Wet bulb temperature of air

C. Dry bulb temperature of air

D. Ambient air temperature

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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

Oil separator in a refrigeration cycle is installed

A. Before compressor

B. Between compressor and condenser

C. Between condenser and evaporator

D. Between condenser and expansion valve

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4

Freon group of refrigerants are

A. Inflammable

B. Toxic

C. Non-inflammable and toxic

D. Nontoxic and non-inflammable

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4

The bypass factor (B. P. F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil, and td₃ = Dry bulb temperature of heating coil)

A. (td₂ - td₃)/(td₃ - td₁)

B. (td₃ - td₂)/(td₃ - td₁)

C. (td₃ - td₁)/(td₂ - td₃)

D. (td₃ - td₁)/(td₃ - td₂)

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4

The desirable property of a refrigerant is

A. Low boiling point

B. High critical temperature

C. High latent heat of vaporisation

D. All of these