# Heat transfer-SSC JE Mechanical Engineering Practice Questions

Heat transfer questions for practice for SSC JE Mechanical Engineering exam. The answers for the questions have been shared below, in case of any doubt or query, feel free to leave a comment in the comment box below.

Q1) The door of a running refrigerator inside a room was left open. Which of the following statement is correct?

1. the room will be cooled to the temperature inside the refrigerator
2. the room will be cooled slightly
3. the room will be gradually warmed up
4. the temperature of the air in the room will remain unaffected

Ans: c

Q2) When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by:

1. conduction
2. convection
4. conduction and convection

Ans: a

Q3) Which of the following is a case of steady state heat transfer?

1. IC engine
2. Air preheaters
3. Heating of building in winter
4. None of these

Ans: d

Q4) The time constant of a thermocouple is

1. the time taken to attain the final temperature to be measured
2. the time taken to attain 50% of the value of initial temperature difference
3. the time taken to attain 63.2% of the value of initial temperature difference
4. determined by the time taken to reach  from

ANs: c

Q5) Which is expected to have the highest thermal conductivity?

1. steam
2. solid ice
3. melting ice
4. water

Ans: b

Q6) The rate of energy emission from unit surface area through unit soild angle, along a normal to the surface is known as

1. emissivity
2. transmissivity
3. reflectivity

Ans: d

Q7) Provision of fins on a given heat transfer surface will be more if there are ____.

1. fewer number of thin fins
2. fewer number of thick fins
3. large number of thick fins
4. large number of thin fins

Ans: d

Q8) Which of the following would lead to a reduction in thermal resistance?

1. In conduction, reduction in the thickness of the material and an increase in the thermal conductivity.
2. In convection, stirring of the fluid and cleaning the heating surface.
3. In radiation, increasing the temperature and reducing the emissivity.
4. All options are correct.

Ans: d

Q9) Inspite of large heat transfer coefficients in boiling liquids, fins are used advantageously when the entire surface is exposed to _______.

1. nucleate boiling
2. film boiling
3. transition boiling
4. all modes of boiling

Ans: b

Q10) The parameter(s) responsible for loss of heat from a hot pipe surface in a room without fans would include ______.

1. temperature of the surface and air in the room.
2. emissivity of the surface.
3. length and diameter of the pipe
4. all options are correct

Ans: d

Q11) On a summer day, a scooter rider feels more comfortable while on the move than while at a stop light because ______.

1. an object in motion captures less solar radiation
2. air is transparent to radiation and hence it is cooler than the body
3. more heat is lost by convection and radiation while in motion
4. air has a low specific heat and hence it is cooler

Ans: c

Q12) In radiative heat transfer, a gray surface is one ___.

1. which appears gray to the eye
2. whose emissivity is independent of wavelength
3. which has reflectivity equal to zero
4. which appears equally bright from all directions

Ans: b

Q13) Film coefficient is the ratio of ______.

1. thickness of film of fluid to thermal conductivity
2. thickness of film of fluid to temperature drop through film of fluid
3. thermal conductivity to temperature drop through film of fluid
4. thermal conductivity to equivalent thickness of film of fluid

Ans: d

Q14) Filling or decking in a cooling tower increases the rate of heat transfer by providing _________.

1. increased flow of water
2. increased flow of air
3. increased flow of water and air
4. a large amount of wetted surface

Ans: d

Q15) The engine oil at  is cooled to  in a parallel flow heat exchanger by water entering at  and leaving at . The heat exchanger effectiveness will be ______.

1. 0.36
2. 0.46
3. 0.56
4. 0.66

Ans: c

Q16) With an increase in the thickness of insulation around a circular pipe, heat loss to surroundings due to ________.

1. convection increases, whereas due to conduction decreases
2. convection decreases, whereas due to conduction increases
3. both convection and conduction decreases
4. both convection and conduction increases

Ans: a

Q17) Two balls of same material and finish have their diameters in the ratio of 2:1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

1. 1:1
2. 2:1
3. 1:2
4. 4:1

Ans: d

Q18) Thermal conductivity of non-metallic amorphous solids with decrease in temperature ______.

1. increases
2. decreases
3. remains constant
4. may increase or decrease depending on temperature

Ans: b

Q19) In a shell and tube heat exchanger, baffles are provided on the shell side to ______.

1. prevent the stagnation of shell side fluid
2. improve heat transfer
3. provide support for tubes
4. all options are correct

Ans: d

Q20) Two insulating materials of thermal conductivity K and 2K are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is the same _______.

1. material with higher thermal conductivity should be used for the inner layer and one with the lower thermal conductivity for the outer
2. material with lower thermal conductivity should be used for the inner layer and one with the higher thermal conductivity for the outer
3. It is immaterial in which sequence the insulating materials are used
4. None of these.

Ans: b