Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

121) According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

Answer is:

directly proportional to the surface area and directly proportional to the difference of temperatures between the two bodies

Explanation:

The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called Newton's law of cooling.

122) The freezing point of carbon dioxide is equal to boiling point of R-12.

Answer is:

Incorrect

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

Answer is:

superheated vapour

124) The super-heating in a refrigeration cycle

Answer is:

decreases C.O.P.

125) Thermal conductivity of a material may be defined as the

quantity of heat flowing in one second through a slab of the material of area 1 cm² and thickness 1 cm when its faces differ in temperature by 1 Degree Centigrade

quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1 Degree Centigrade

heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

all of the above

Answer is:

all of the above

Explanation:

Thermal conductivity of a material may be defined as the
* quantity of heat flowing in one second through a slab of the material of area 1 cm² and thickness 1 cm when its faces differ in temperature by 1 Degree Centigrade
* quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1 Degree Centigrade
* heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces