1. What is meant by lumped heat analysis?

In a Newtonian heating or cooling process the temperature throughout the solid is considered to be uniform at a given time.

Such an analysis is called “Lumped heat analysis”.

Here Bi always less than 1. (Bi < 1)

2. What is meant by semi- infinite solid?

In a semi-infinite solid, at any instant of time, there is always a point where the effect of heating or cooling at one of its boundaries is not felt at all.

At this point the temperature remains unchanged.

The biot number value is ∞

3. What is meant by infinite solid?

 A solid which extends itself infinitely in all directions of space is known as infinite solid.

 Here the biot number value is in between 0.1 and 100.

 i.e, 0.1 < Bi < 100

4. Define Biot number and mention its significance.

It is defined as the ratio of the internal conductive resistance to the surface convective resistance.

            Bi = hL_c / K

Significance:

It is used to find Lumped heat analysis, Semi infinite solids and infinite solids.

5. What are Heisler chart.

In Heisler chart, the solutions for the temperature distributions and heat flows in a plane walls, long cylinders and spheres with finite internal and surface resistance are presented.

It is the analytical solutions in the form of graphs.

6. What is meant by free or natural convection? Give examples.

If the fluid motion is produced due to change in density resulting from temperature gradients, the mode of heat transfer is said to be free or natural convection.

Ex: (i) Ice Melting

(Heat move to the ice from air-This causes the melting from a solid to liquid)

  (ii) Steaming cup of hot tea

(The steam is showing heat being transferred in the air)

7. What is forced convection? Give examples.

If the fluid motion is artificially created by means of an external force like a blower or fan, that type of heat transfer is known as forced convection.

Ex: Steam turbines, Air conditioning, Heat exchangers, Car radiator using fluid

8. What are the dimensionless parameters used in forced convection.

            (i) Reynolds number (Re)

            (ii) Nusselt number (Nu)

            (iii) Prandtl number (Pr)

9. What are the dimensionless parameters used in free convection.

   (i) Grashof number (Gr)

  (ii) Nusselt number (Nu)

  (iii) Prandtl number (Pr)

10. Indicate the concept or significance of boundary layer.

  (i) A thin region near the body called the boundary layer where the velocity and the temperature gradients are large.

  (ii) The region outside the boundary layer where the velocity and the temperature gradients are very nearly equal to their free stream values.