# Prof. K. M. Joshi

## Head, T&P Cell Asst. Professor (MED), S.S.A.S. Inst. of Tech., Surat.

### ALA - 1                     Last date of submission:4/7/15

Conduction Basics

1.     1. Explain the difference between Thermodynamics & Heat transfer.
2. Explain the following terms: 
a. Thermal resistance
b. Thermal diffusivity
c. Thermal conductivity

3.     3. Write a short not on mechanism of heat transfer by conduction. 

4.     4. Explain that the thermal conductivity of metal decreases with increase in temperature. 

5.
Derive general heat conduction equation in Cartesian co-ordinates.   Also deduce the equation for

(ii) No heat sources

(iii) No heat source and steady state condition

(iv) One dimensional heat conduction equation without heat generation under steady State.

Convection basics

1.  What is difference between the mechanism behind the forced convection and natural convection? Cite the suitable examples. Also discuss the advantage and disadvantages.  + 

2.   State the Newton’s law of cooling and factor affecting convective heat transfer coefficient.    OR

State the general equation for the rate of heat transfer by convection and hence define the coefficient of heat transfer. What are the various factors on which the value of this coefficient depends?   

3.  Define local heat transfer coefficient and average heat transfer coefficient and state the relation between them. 

Dimensional Analysis and dimensionless numbers

1. What is dimensional analysis state its signification with advantages and disadvantages.

2. For natural convection heat transfer, show that Nu = f (Gr, Pr). 

3. By dimensional analysis show that for forced convection heat transfer the Nusselt number can be expressed as a function of Prandtl number and Reynolds number. 

4. What is the importance of the Dimensional analysis applied to the Convection? Explain the following dimensionless numbers with their physical significance.

a) Reynolds Number b) Nusselt Number c) Prandtl number d) Grashof number e) Peclet Number f) Stanton number