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Heat And Mass Transfer MCQ Questions & Answers | Mechanical Engineering

Learn Heat And Mass Transfer MCQ questions & answers are available for a Mechanical Engineering students to clear GATE exams, various technical interview, competitive examination, and another entrance exam. Heat And Mass Transfer MCQ question is the important chapter for a Mechanical Engineering and GATE students. Page-6 section-1

Each section contains 100 MCQs on Heat and Mass Transfer .
51
Film coefficient is defined as the ratio of
Discuss
Answer & Solution
Answer: Option A
Solution:
Film coefficient is defined as the ratio of Thermal conductivity to the equivalent thickness of the film of fluid The heat transferred by convection per unit area per degree temperature difference between the surface and the fluid.
52
The highest thermal diffusivity is of
Discuss
Answer & Solution
Answer: Option B
Solution:
Thermal diffusivity is the thermal conductivity of the material divided by the product of density and specific heat capacity, at constant pressure. The highest thermal diffusivity is of Lead
53
The rate of energy transferred by convection to that by conduction is called
Discuss
Answer & Solution
Answer: Option B
Solution:
Nusselt number is the ratio of convection heat transfer to conduction heat transfer. Nu >> 1 , More effective Convection Nu = 1, For fluid layer represent heat transfer by pure conduction across layer
54
Thermal conductivity of water _________ with rise in temperature.
Discuss
Answer & Solution
Answer: Option C
Solution:
Thermal conductivity is a measure of a material’s ability to conduct heat.

In the case of liquids like water, thermal conductivity depends on the molecular motion and interactions between the molecules.

As temperature rises, the molecules in water gain kinetic energy and move more rapidly.

This enhanced molecular activity leads to better energy transfer between molecules, resulting in an increase in thermal conductivity over most of the liquid temperature range.

For water, thermal conductivity generally increases with temperature up to the boiling point.

Therefore, the correct answer is: Increases (Option C).
55
Which of the following property of air does not increase with rise in temperature?
Discuss
Answer & Solution
Answer: Option C
Solution:
Density of air does not increase with rise in temperature
56
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
Discuss
Answer & Solution
Answer: Option D
No explanation is given for this question. Let's Discuss on Board
57
Thermal conductivity of glass wool varies from sample to sample because of variation in
Discuss
Answer & Solution
Answer: Option D
Solution:
Thermal conductivity of glass wool varies from sample to sample because of variation in Composition,Density and Porosity
58
Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by
Discuss
Answer & Solution
Answer: Option B
Solution:
Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by Radiation
59
According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to
Discuss
Answer & Solution
Answer: Option C
Solution:
Stefan-Boltzmann law is applicable for radiation it states that the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature. The law applies only to blackbodies, theoretical surfaces that absorb all incident heat radiation.
60
The critical radius is the insulation radius at which the resistance to heat flow is
Discuss
Answer & Solution
Answer: Option B
Solution:
It is the radius of insulation before heat transfer increases and after heat transfer decreases.
The critical radius is the insulation radius at which the resistance to heat flow is Minimum