(SEM V) THEORY EXAMINATION 2020-21 HEAT & MASS TRANSFER

SECTION A (Any 2 Questions Explained Briefly)
 

Explain the various modes of heat transfer.
Heat transfer takes place through three basic modes: conduction, convection, and radiation. Conduction occurs due to molecular interaction within a material without any bulk motion, convection involves heat transfer due to fluid motion along with conduction, and radiation is the transfer of heat through electromagnetic waves without requiring any medium. In practical systems, heat transfer often occurs through a combination of these modes.
 

Explain Newton’s law of cooling.
Newton’s law of cooling states that the rate of heat loss from a body is directly proportional to the temperature difference between the body surface and the surrounding fluid, provided this temperature difference is small. It is mainly applicable to convective heat transfer and is widely used to analyze cooling of solid bodies exposed to fluids.
 

SECTION B (Any 2 Questions Explained)
 

What is shape factor? Explain its importance.
Shape factor is a geometrical parameter used in steady-state heat conduction to account for the effect of shape and size of the body on heat flow. It simplifies heat transfer calculations in complex geometries by combining geometrical effects into a single factor. Shape factor is especially useful in conduction problems involving irregular shapes.
 

State Fick’s law of diffusion and its limitations.
Fick’s law of diffusion states that the rate of mass transfer is proportional to the concentration gradient and occurs in the direction of decreasing concentration. It is mainly applicable to steady-state diffusion. The law has limitations as it assumes constant diffusion coefficient and is not accurate for high concentration gradients or non-steady conditions.
 

SECTION C (Any 2 Questions Explained)
 

What is thermal diffusivity and what is its significance?
Thermal diffusivity is a property that indicates how quickly a material responds to changes in temperature. It is defined as the ratio of thermal conductivity to the product of density and specific heat. A high value of thermal diffusivity means the material heats up and cools down quickly, while a low value indicates slower temperature response.

Explain fin efficiency and fin effectiveness.
Fin efficiency is the ratio of actual heat transfer by a fin to the maximum possible heat transfer if the entire fin were at base temperature. Fin effectiveness is the ratio of heat transfer with a fin to that without a fin. Fins are considered useful when their effectiveness is greater than one, indicating enhanced heat transfer.
 

Most Questions in This PDF Are Related To
 

Most questions in the Heat & Mass Transfer (KME-501) paper are related to modes of heat transfer, conduction through composite walls, convection correlations, boundary layer concepts, fins and extended surfaces, radiation heat transfer, heat exchangers, mass diffusion, and dimensionless numbers such as Reynolds, Grashof, Nusselt, and Prandtl numbers. The paper mainly focuses on numerical problem-solving and fundamental heat and mass transfer concepts.