Interview Q & A (Part-4)

1.What is fluid ? What is fluid mechanics ?

1.A fluid is a substance which always responses to shear stress and doesn’t have any definite shape. It may or may not have any definite volume.

2.How to determine the characteristics of fluid flow ?

2.By the values of Reynolds Number.

3.What are laminar and turbulent flows ?

3.When a fluid is flowing around an object or flowing through an object, the flow may be smooth or may be distorted. The smoother flow occurs due to low velocity and distorted flow occurs due to high velocity. This low velocity smoother flow is called laminar flow and distorted flow is called turbulent flow.

4.What is buoyancy force ?

4.Buoyancy is the upward force which is felt on an object simply immersed into a fluid.

5.Which dimensionless number is used to determine the speed of aircraft ?

5.Mach Number.

6.What are compressible and incompressible flows ?

6.  compressible flow – variable density fluid flow .

     Incompressible flow – fixed density fluid flow .

7.What is the difference between machine and engine?

7. Engine converts heat energy to Mechanical Energy but machine converts all forms of energy to mechanical energy except heat energy.

8.What is viscosity? What is newton’s law of viscosity?

8.Viscosity is the property of fluid which measures the resistance of the fluid to the gradual deformation due the shear stress.

Newtons Law of Viscosity states that : the shear stress on the fluid is proportional to the velocity gradient.

9.What are newtonian and non-newtonian fluids ? Give examples.

9.Newtonian fluids follow the newtons law of viscosity and non-newtonian fluids do not follow the law.
Newtonian fluid : Water, air etc. Non-Newtonian Fluid : blood, tar , paste etc.

10.What is Bernoulli’s equation? 

10. pressure head + velocity head + datum head = constant

P1/γ + (v2 )1/2g + z1 = P2/γ +( v2)2 /2g + z1 = constant

11.What is Refrigeration ? What is the unit of refrigeration ?

11.Refrigeration is the process where heat is transferred from low temperature to high temperature medium with the help of external work. It’s unit is ton of refrigeration.

12.What is COP ?

12.COP = Co-efficient of Performance . It is used to measure the performance of a refrigeration system. It is generally expressed by the ratio of evaporation work or refrigeration effect to the compressor work or net work .

13.What is BTU ?

13.BTU = British Thermal Unit ; 1 BTU is the amount of heat required to raise the temperature of one lb water by one degree Fahrenheit.

14.What is the most commonly used refrigerant ?

14.R134a

15.Which thermodynamic cycle is implied in refrigeration system ?

15.Reversed Carnot or Reversed Rankin Cycle.

16.What is the difference between a cooler and an air conditioner ?

16.For a cooler to become air conditioner it must meet the following requirements :
It must control the

1.temperature 

2.Humidity 

3 .motion of air 

4.purity of air.

17.What is a chiller ?

17. Chiller is a device / machine for cooling something.

18.What is Cam ?

18.Cam is a mechanical linkage which transforms rotary motion to linear motion and vice versa. Cams can be very versatile. The most common use of cam is seen in automobile camshaft.

19.What are the different types of gear boxes ?

19.There are 4 types of gear boxes used in the machines and mechanisms :-

• Sliding Mesh Gear Box
• Synchromesh Gear Box
• Constant Mesh Gear Box
• Planetary Gear Box

20.What is boiler draught ?

20.It is process of supplying continuous air to the boiler furnace for efficient burning of the fuel for producing steam. It is actually the pressure difference between the grate level hotflue gases and the exit point gases. Draught can be natural or forced.

so, guys this is the part-4 of the Interview Q & A