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4

For unsaturated air, the dew point temperature is __________ wet bulb temperature.

A. Equal to

B. Less than

C. More than

D. None of these

Correct Answer :

B. Less than


Related Questions

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4

The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process)

A. (hA - h2)/ (h1 - h2)

B. (h2 - hA)/ (h1 - h2)

C. (h1 - h2)/ (hA - h2)

D. (hA - h1)/ (h2 - h1)

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4

In a vapour compression cycle, the refrigerant immediately after expansion valve is

A. Liquid

B. Sub-cooled liquid

C. Saturated liquid

D. Wet vapour

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4

In a psychrometric chart, specific humidity (moisture content) lines are

A. Vertical and uniformly spaced

B. Horizontal and uniformly spaced

C. Horizontal and non-uniformly spaced

D. Curved lines

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4

Short horizontal lines on pressure-enthalpy chart show

A. Constant pressure lines

B. Constant temperature lines

C. Constant total heat lines

D. Constant entropy lines

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4

The freezing point of R-12 is

A. -86.6°C

B. -95.2°C

C. -107.7°C

D. -135.8°C

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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

A refrigerant compressor is used to

A. Raise the pressure of the refrigerant

B. Raise the temperature of the refrigerant

C. Circulate the refrigerant through the refrigerating system

D. All of the above

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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 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

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

Which of the following refrigerants has lowest freezing point?

A. Freon-12

B. NH3

C. CO2

D. Freon-22

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4

Highest pressure encountered in a refrigeration system should be

A. Critical pressure of refrigerant

B. Much below critical pressure

C. Much above critical pressure

D. Near critical pressure

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4

The COP of a vapour compression plant in comparison to vapour absorption plant is

A. More

B. Less

C. Same

D. More/less depending on size of plant

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4

The leaks in a refrigeration system using Freon are detected by

A. Halide torch which on detection produces greenish flame lighting

B. Sulphur sticks which on detection gives white smoke

C. Using reagents

D. Smelling

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4

Condensing temperature in a refrigerator is the temperature

A. Of cooling medium

B. Of freezing zone

C. Of evaporator

D. At which refrigerant gas becomes liquid

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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 emissivity of a polished silver body is __________ as compared to black body.

A. Same

B. Low

C. Very low

D. High

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4

The wet bulb temperature during sensible heating of air

A. Remains constant

B. Increases

C. Decreases

D. None of these

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4

In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is

A. High pressure saturated liquid

B. Wet vapour

C. Very wet vapour

D. Dry vapour

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4

Chaperon equation is applicable for registration at

A. Saturation point of vapour

B. Saturation point of liquid

C. Sublimation temperature

D. Triple point

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4

The power per tonne of refrigeration is

A. 3.5/C.O.P.

B. C.O.P/3.5

C. 3.5 × C.O.P.

D. None of these

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4

The advantage of dry compression is that

A. It permits higher speeds to be used

B. It permits complete evaporation in the evaporator

C. It results in high volumetric and mechanical efficiency

D. All of the above

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4

The bank of tubes at the back of domestic refrigerator is

A. Condenser tubes

B. Evaporator tubes

C. Refrigerant cooling tubes

D. Capillary tubes

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4

The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by

A. (C.O.P.)P = (C.O.P.)R + 2

B. (C.O.P.)P = (C.O.P.)R + 1

C. (C.O.P)P = (C.O.P)R - 1

D. (C.O.P)P = (C.O.P)R

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4

A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is

A. Ammonia

B. Carbon dioxide

C. Freon

D. Brine

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4

The temperature of ammonia after compression in a vapour compression system is

A. 20 to 50°C

B. 50 to 70°C

C. 70 to 110°C

D. None of these

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4

The cooling system used for supersonic aircrafts and rockets is

A. Simple air cooling system

B. Bootstrap air cooling system

C. Reduced ambient air cooling system

D. Regenerative air cooling system

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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

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

Air refrigeration cycle is used in

A. Commercial refrigerators

B. Domestic refrigerators

C. Air-conditioning

D. Gas liquefaction