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Technical Interview Questions - 7 contains following interview questions about Unit operation, Unit process, Pressure test, catalysts are used in Chlorination and Hydrogenation, Ton of refrigeration in Chiller, Ton of refrigeration cooling water.

71. Define : Unit operation, Unit process
72. What is difference between Bubble point & Boiling Point? What is difference between Dew point and freezing point?
73. What is Avogadro number? What is its importance?
74. What is Pressure test?
75. Which gas occupied maximum percentage in air?
76. Which catalysts are used in Chlorination and Hydrogenation?
77.Define - Specific Heat. Latent heat and sensible heat
78. What is Ton of refrigeration?
79. Pressure drop equation for horizontal pipe line in laminar flow condition?
80.Define Potential flow,Ideal fluid, definition

71. Define : Unit operation, Unit process

Unit Operation

When any physical change takes place it is Unit operation.
Change in Concentration from inlet to outlet

Example: Distillation, Filtration, Drying, Extraction, Gas absorption, Crystallization

Unit Process

When any physical change takes place it is Unit operation.
Example: - Oxidation, Reduction, Alkylation, Sulphonation, Chlorination, etc.

72. What is difference between Bubble point & Boiling Point? What is difference between Dew point and freezing point?

Bubble point : It is temperature at which first bubble of liquid is formed.

Boiling Point : It is a temperature of liquid at which vapour pressure of liquid is equal to atmospheric pressure [1 atm, 1.03323 Kg/cm²].

Explanation:

We have 2 chemicals mixture.

1. Less volatile chemical
2. High Volatile chemical
Volatility of fluid : Capability of liquid to convert into vaporize.
When initial phase of boiling starts less volatile chemical starts to vaporize.
At last high volatile chemical starts vaporizing.

Dew point : When any chemicals temperature is dropping, Whole vapour phase starts converting to liquid phase. At certain temperature there will no traces of chemical in vapour phase. This is dew point of Chemical.

Freezing point: When any liquid is converted into solid phase at 1 Atmospheric pressure. This temperature is Freezing point of fluid.

73. What is Avogadro number? What is its importance?

Numbers of molecules present in 1 mole.

Value : 6.023 * 10²³ / mole

74. What is Pressure test?

Pressure test is carried When any new Piping system or Pressure vessel is installed 

For Piping system it should be capable to hold double pressure then maximum operating pressure for certain time.

For vessels and reactors it should be handle up to 1.5 times of maximum pressure for certain temperature.

If piping system is designed to 10 kg/cm² then pressure test should be carried to 20 kg/cm² [Some times this is carried on 15 kg/cm² it not recommended]

Reactor and vessel designed to 10 kg/cm² then pressure test should be carried to 15 kg/cm²

75. Which gas occupied maximum percentage in air?

Nitrogen-  78%
Oxygen- 21% 
Other gases-1%

76. Which catalysts are used in Chlorination and Hydrogenation?

AlCl3, FeCl3 and ZnCl2 is used in Chlorination 
Pt, Fe and raney Ni is used in Hydrogenation

77.Define - Specific Heat. Latent heat and sensible heat

Specific Heat: The amount of heat required for rise one degree temperature per unit mass.

Latent Heat Is energy absorption or release by substance during phase change at same temperature.
Latent heat of Fusion: When energy exchange during Melting Solid of Freezing liquid.
Latent heat of Vaporization: When energy exchange during Vaporization of liquid
Latent heat of Condensation: When energy exchange during Condensate of vapour

Sensible Heat: is heat transfer of system till phase change.

Sensible heat and latent heat

78. What is Ton of refrigeration?

Ton of refrigeration (TR)

Cooling capacity of an air conditioner or refrigerator equal to 12,000 British thermal units (Btu) per hour 200 Btu per minute and denotes the amount of heat required to melt one ton of ice in 24 hours.

 1 TR = 12,000 Btu/hr

79. Pressure drop equation for horizontal pipe line in laminar flow condition?

 In fluid dynamics, the Hagen–Poiseuille equation is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. 

The assumptions of the equation are that the flow is laminar viscous and incompressible and the flow is through a constant circular cross-section that is substantially longer than its diameter.

The equation is also known as the Hagen–Poiseuille law, Poiseuille law and Poiseuille equation.

The governing equation is,

80.Define Potential flow,Ideal fluid, definition

Ideal fluid is incompressible and it is having zero viscosity. 
Flow of Ideal fluid is known as potential flow. 

Potential flow is highly developed flow.

Main characteristics of potential flow are
 No eddies, no circulations within the fluid flow. So potential flow is irrotational flow.
 No friction is developed in the fluid. Therefore there is no dissipation of mechanical energy into heat.

Therefore: Potential flow is incompressible, irrotational, highly developed and having zero viscosity.

Thanks for reading - Technical Interview Questions - 7
Naitik Patel
Industrial Guide

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