INTERVIEW QUESTIONS OF THERMODYNAMICS !!!

1.Why Entropy decreases with increase in temperature?

 Ans: ds=dQ/T. Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.

2.What is the difference between heat transfer and thermodynamics?
Ans: Heat transfer deals with the energy analysis which in transition and and depends on the modes of heat transfer like conduction, convection and radiation or combination of any modes. Heat transfer deals in non equilibrium domain and conditions while thermodynamics deals with study of system at equilibrium and does not depend on how heat transfer is calculated.

3.When a real gas behaves like ideal gas?

Ans:A real gas behaves like an ideal gas in low pressure and high temperature conditions.

4.What is Hess Law?

Ans:According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

 5.What do you understand by latent heat? Give examples of latent      heat.

Ans:For pure substances, the heat effects accompanying changes in state at constant pressure (no temperature change being evident) are known as latent heats. Examples of latent heats are the heat of fusion, vaporization, sublimation and change in crystal form.

6.What is the difference between heat capacity and specific heat of the material?

Ans:The heat capacity of material is the amount of heat transformed to raise unit mass of a material 1° in temperature.

The specific heat of material is the ratio of the amount of heat transferred to raise unit mass of a material 1° in temperature to that required raise unit mass of water 1° of temperature at some specified temperature.

For most of the engineering purposes, heat capacities may be assumed numerically equal to specific heat values.

7.Why gas containers are mostly in a cylindrical shape?

Ans:The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.

8.Explain why re-heater is used in gas turbine?

Ans:

The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.