Interview Questions.

Question 1. Define Heat Transfer?

Answer :Heat switch can be defined because the transmission of power from one region to every other because of temperature distinction.

Question 2. What Are The Modes Of Heat Transfer?

Answer :

Conduction
Convection
Radiation.
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Question 3. What Is Conduction?

Answer :Heat conduction is a mechanism of heat switch from a area of excessive temperature to a area of low temperature within a medium [solid, liquid or gases] or unique medium in direct physical contact.

Question 4. State Fourier’s Law Of Conduction?

Answer :The charge of warmth conduction is proportional to the area measured normal to the route of warmth go with the flow and to the temperature gradient in that route. Q α – A dT / dx Q = -kA dT /dx Where, A – Area in m2 dT / dx – Temperature gradient, K/m okay – Thermal conductivity, W/mK.

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Question five. Define Thermal Conductivity?

Answer :Thermal conductivity is defined because the potential of a substance to behavior heat.

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Question 6. What Are The Factors Affecting The Thermal Conductivity?

Answer :

Moisture
Density of cloth
Pressure
Temperature e. Structure of fabric.
Question 7. What Is Meant By Free Or Natural Convection?

Answer :

It is fluid movement is produced due to trade in density as a consequence of temperature gradients, the mode of heat transfer is said to be unfastened or natural convection.

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Question 8. Define Grashof Number [gr].?

Answer :

It is described because the ratio of made from inertia force and buoyancy pressure to the rectangular of viscous pressure.

Gr = Inertia pressure x Buoyancy force / [Viscous force]2

Question 9. Define Stanton Number [st].?

Answer :

It is the ratio of Nusselt quantity to the manufactured from Reynolds wide variety andPrandtl range.

      St = Nu / Re x Pr.

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Question 10. What Is Meant By Newtonian And Non-newtonian Fluids?

Answer :

The fluids which obey the Newton’s law of viscosity are referred to as Newtonian fluids and those which do not obey are called no-newtonian fluids.

Question eleven. What Is Meant By Laminar Flow ?

Answer :

Laminar glide: Laminar glide is once in a while referred to as stream line flow. In this sort of waft, the fluid moves in layers and every fluid particle follows a clean continuous route. The fluid particles in every layer continue to be in an orderly series with out mixing with each other.

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Question 12. What Are The Dimensionless Parameters Used In Forced Convection?

Answer :

Reynolds number [Re].
Nusselt quantity [Nu].
Prandtl quantity [Pr].
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Question thirteen. Define Reynolds Number [re]?

Answer :

It is defined because the ratio of inertia pressure to viscous force.

Re = Inertia pressure / Viscous pressure

Question 14. State Newton’s Law Of Convection?

Answer :

Heat transfer from the shifting fluid to solid surface is given through the equation.

Q = h A = [Tw – T∞]

This equation is called Newton’s regulation of cooling.
Where h = Local warmth switch coefficient in W/m2K.
A = Surface vicinity in m2
Tw = Surface [or] Wall temperature in K.
T∞ = Temperature of fluid in K.

Question 15. Mention Stefan Boltzmann Constant?

Answer :

σ = Stefan Boltzmann regular = 5.6697 x 10-eight W/ (m² K4).

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Question sixteen. What Is Meant By Absorptivity?

Answer :

Absorptivity is described as the ratio among radiation absorbed and incident radiation. Absorptivity, α = Radiation absorbed / Incident radiation.

Question 17. What Is Meant By Direct Heat Exchanger [or] Open Heat Exchanger?

Answer :

In direct touch heat exchanger, the heat change takes area via direct mixing of warm and cold fluids.

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Question 18. What Is Meant By Indirect Contact Heat Exchanger?

Answer :

In this type of heat exchangers, the switch of warmth among  fluids may be done by means of transmission via a wall which separates the two fluids.

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Question 19. What Is Meant By Parallel Flow Heat Exchanger?

Answer :

In this type of warmness exchanger, hot and bloodless fluids move within the same direction.

Question 20. What Is Meant By Lmtd?

Answer :

We understand that the temperature difference among the new and bloodless fluids within the warmth exchanger varies from point to point. In addition numerous modes of heat transfer are involved. Therefore based on idea of suitable suggest temperature distinction, additionally referred to as logarithmic imply temperature difference, the overall warmness transfer fee inside the heat exchanger is expressed as

Q = U A [?T]m

Where, U=Overall warmth transfer co-coefficient [W/m2K], A=Area, m2
[?T]m = Logarithmic suggest temperature difference.

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Question 21. What Is Meant By Effectiveness?

Answer :

The heat exchanger effectiveness is described because the ratio of actual warmness transfer to the most viable warmness switch.

Effectiveness ε = Actual warmness transfer / Maximum possible warmness transfer = Q / Qmax

Question 22. What Is The Difference Between Air Conditioning And Refrigeration?

Answer :

Refrigeration is the process of offering and preserving the temperature in area beneath atmospheric temperature. Air conditioning is the process of offering enough quantity of easy aircontaining a selected quantity of water vapour and preserving the predeterminedatmospheric situation with in a specific enclosure.

Question 23. What Are The Advantages And Disadvantages Of Air Refrigeration System?

Answer :

Advantages:

1. The refrigerant used specifically air is cheap and without problems available.
2. There isn't any threat of fire or toxic consequences due to leakages.
3. The weight to tonne of refrigeration ratio is less in comparison to different systems.
Disadvantages:

1. The amount of refrigerant used per tonne of refrigeration is high in comparison to other gadget.
2. The COP of the device may be very low. Therefore jogging cost is high.
Three. The chance of frosting on the expander valves is more as the air carries moisture content material.
Question 24. What Is Net Refrigeration Effect Of The Refrigeration?

Answer :

Refrigeration impact is the full heat removed from the refrigerant within the evaporator.

COP = Refrigeration impact / Work carried out.
Refrigeration impact = COP x Work executed.

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Question 25. What Is Meant By Transmissivity?

Answer :

Transmissivity is defined as the ratio of radiation transmitted to the incident radiation.

Transmissivity, τ = Radiation transmitted / Incident radiation.