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4

In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about

A. 1

B. 1.25

C. 2.15

D. 5.12

Correct Answer :

B. 1.25


Related Questions

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4

A refrigerant with the highest critical pressure is

A. R-11

B. R-12

C. R-22

D. Ammonia

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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

In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is

A. Heated and dehumidified

B. Heated and humidified

C. Cooled and humidified

D. Cooled and dehumidified

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4

The wet bulb temperature during sensible cooling of air

A. Remains constant

B. Increases

C. Decreases

D. None of these

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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

The leakage in a refrigeration system using Freon is detected by

A. Halide torch

B. Sulphur sticks

C. Soap and water

D. All of these

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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 human body feels comfortable when the heat stored in the body is

A. Positive

B. Negative

C. Zero

D. None of these

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4

A thermostatic expansion valve in a refrigeration system

A. Ensures the evaporator completely filled with refrigerant of the load

B. Is suitable only for constant load systems

C. Maintains different temperatures in evaporator in proportion to load

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 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

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4

In a bootstrap air evaporative cooling system, the evaporator is provided

A. Between the combustion chamber and the first heat exchanger

B. Between the first heat exchanger and the secondary compressor

C. Between the secondary compressor and the second heat exchanger

D. Between the second heat exchanger and the cooling turbine

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4

The coefficient of performance is the ratio of the refrigerant effect to the

A. Heat of compression

B. Work done by compressor

C. Enthalpy increase in compressor

D. All of the above

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4

A good refrigerant should have

A. High latent heat of vaporisation and low freezing point

B. High operating pressures and low freezing point

C. High specific volume and high latent heat of vaporisation

D. Low C.O.P. and low freezing point

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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

In Electrolux refrigerator

A. Ammonia is absorbed in hydrogen

B. Ammonia is absorbed in water

C. Ammonia evaporates in hydrogen

D. Hydrogen evaporates in ammonia

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4

During adiabatic saturation process on unsaturated air __________ remains constant.

A. Relative humidity

B. Dew point temperature

C. Dry bulb temperature

D. Wet bulb temperature

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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

During sensible cooling,

A. Relative humidity remains constant

B. Wet bulb temperature increases

C. Specific humidity increases

D. Partial pressure of vapour remains constant

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4

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

A. Increase

B. Decrease

C. Remain unaffected

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

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4

A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called

A. Automatic expansion valve

B. High side float valve

C. Thermostatic expansion valve

D. Low side float valve

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4

An evaporator is also known as

A. Freezing coil

B. Cooling coil

C. Chilling coil

D. All of these

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4

Which of the following statement is correct?

A. The constant enthalpy lines are also constant wet bulb temperature lines.

B. The wet bulb and dry bulb temperature are equal at saturation condition.

C. The wet bulb temperature is a measure of enthalpy of moist air.

D. All of the above

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4

The vapour compression refrigerator employs the following cycle

A. Rankine

B. Carnot

C. Reversed Rankine

D. Reversed Carnot

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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 heat rejection factor (HRF) is given by

A. 1 + C.O.P

B. 1 - C.O.P.

C. 1 + (1/C.O.P)

D. 1 - (1/C.O.P)

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4

Which of the following cycles uses air as the refrigerant?

A. Ericson

B. Stirling

C. Carnot

D. Bell Coleman

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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

Vapour compression refrigeration is somewhat like

A. Carnot cycle

B. Rankines cycle

C. Reversed Carnot cycle

D. None of the above

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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