008. Frequenty asked mechanical interview questions

1. Difference between 'Thermodynamics and Heat Transfer'

• Thermodynamics mainly deals with the transfer of energy in form of heat or work between systems and surroundings with other systems in form of either heat or work in equilibrium conditions.  When there is change in one state, which was in equilibrium state and starting to change in other equilibrium state, this information helps to determine heat or work interactions due to this process. While
• Heat transfer deals with non equilibrium heat exchange or transfer due to temperature gradient while in thermodynamics, during thermal equilibrium (No temperature gradient) no heat exchange is possible.  [Read more interview questions on Thermodynamics]. Heat never transfer when there is no temperature gradient. 

2. Difference between Pipe and tube

• There always a debate between differentiation of pipe and tube. Pipe is always designated by its Inside Diameter (ID) because main purpose of pipe is to carry fluid, while the 
• Tube is always designated by its Outside Diameter (OD). Pipe's thickness is sometimes called as schedule and tube's thickness is gauge.
• As per the tolerance basis, tubes requires higher tolerances as to that of pipe and tubes are more costlier in manufacturing compared to pipe production.

3. Difference between Flywheel and Governor

The function of flywheel is to store the energy/power produced during the power stroke of an engine and this stored energy is used during remaining stroke to make piston up and down during working of engine while governor tries control the speed of an engine due to variation in load. It does this work by reducing or increasing the amount of fuel passing to the engine.

4. Difference between tempering and annealing  

Annealing is a process in which workpiece is heated up to certain temperature to get desired changes in grain or micro-structure and then allowed to cool slowly in order to relieve the stresses during work treatment. While tempering is a process wherein hardness and elasticity or ductility can be regain by use of heating and cooling cycle till desired properties can be obtained.