PSPCL JE EXAM IMPORTANT QUESTIONS SET 1

PSPCL JE EXAM IMPORTANT QUESTIONS

Q1 - An ideal air compressor cycle (with clearance) on p-v diagram can be represented by ________ processes.

Options:
1) one adiabatic, two isobaric, and one constant volume
2) two adiabatic and two isobaric
3) two adiabatic, one isobaric, and one constant volume
4) one adiabatic, one isobaric, and two constant volume

Correct Answer: two adiabatic and two isobaric

Q2 - In a shell and tube heat exchanger, baffles are provided on the shell side to ______.

Options:
1) Prevent the stagnation of shell side fluid
2) Improve heat transfer
3) Provide support for tubes
4) All options are correct

Correct Answer: All options are correct

Q3- The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number)n, where n is______.

Options:
1) - 1/3
2) - 2/3
3) 1
4) – 1

Correct Answer: - 1/3

Q4- In regarding nucleate boiling _______.

Options:
1) The temperature of the surface is greater than the saturation temperature of the liquid
2) Bubbles are created by expansion of entrapped gas or vapour at small cavities in the surface
3) The temperature is greater than that of film boiling
4) All options are correct

Correct Answer: The temperature is greater than that of film boiling

Q5 - Boundary layer is defined as ______.

Options:
1) A thin layer at the surface where gradients of both velocity and temperature are small
2) A thin layer at the surface where velocity and velocity gradients are large
3) A thick layer at the surface where velocity and temperature gradients are large
4) A thin layer at the surface where gradients of both velocity and temperature are large

Correct Answer: A thin layer at the surface where gradients of both velocity and temperature are large

Q6 - 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 _____.

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

Correct Answer: Material with lower thermal conductivity should be used for the inner layer and one with higher thermal conductivity for the outer

Q7 - Critical thickness of insulation for spheres is given by _____.

Options:
1) k/h
2) k/4h
3) h/2k
4) 2k/h

Correct Answer: 2k/h

Q8- Which surface will have the least emissivity ?

Options:
1) Smooth glass
2) Plaster
3) Aluminium foil
4) Concrete

Correct Answer: Aluminium foil

Q9- The process of heat transfer from one particle of the body to another without the actual motion of the particle, is known as ______ .

Options:
1) Conduction
2) Convection
3) Radiation
4) All options are correct

Correct Answer: Conduction

Q10 - The process of heat transfer from a hot body to a cold body in a straight line, without affecting the intervening medium, is known as ______.

Options:
1) Conduction
2) Convection
3) Radiation
4) All options are correct

Correct Answer: Radiation