Here are the **top 50** commonly asked questions in **Heat Transfer** interviews. Whether you’re just starting your preparation or need a quick refresher, these questions and answers will help you tackle your interview with confidence.

## Basic Heat Transfer Interview Questions with Answers

### 1. What is Heat Transfer?

The form of energy that can be transferred from one system to another as a result of temperature difference is known as heat transfer.

### 2. Heat transfer deals with which systems?

Heat transfer deals with the systems that lack thermal equilibrium and thus heat transfer is a non-equilibrium phenomenon.

### 3. What is the driving force in Heat Transfer?

Temperature difference per unit area is the driving force in heat transfer.

### 4. What is microscopic energy in Heat Transfer?

The form of energy related to molecular structure and the degree of molecular activity are referred as the microscopic energy in heat transfer.

### 5. What is internal energy in Heat Transfer?

The sum of all microscopic forms of energy is known as internal energy.

### 6. What is sensible heat in Heat transfer?

The portion of internal energy of the system associated with the molecules is known as sensible heat.

### 7. What is Latent Heat in Heat Transfer?

The internal energy associated with the phase of a system is known as Latent heat.

### 8. What is Enthalpy in Heat Transfer?

Enthalpy is the summation of internal energy and product of pressure-Volume.

### 9. What is the Heat Transfer Rate?

The amount of heat transferred per unit area is known as heat transfer rate.

### 10. What is the heat flux in Heat Transfer?

The rate of heat transfer per unit area normal to the direction of heat transfer is called heat flux.

### 11. What is the direction of Heat Transfer Flow?

General direction of heat flow in every system is higher temperature to lower temperature.

### 12. What is specific heat in Heat Transfer?

Specific heat is the energy required to raise the temperature of a unit mass of substance by one degree.

### 13. What is the temperature gradient in Heat Transfer?

Temperature gradient is defined as the slope of the temperature curve on T-x diagram. Mathematically, it can be written as dT/dX.

### 14. What is the Heat capacity in Heat Transfer?

Heat capacity is the product of density and specific heat. It is the energy stored per unit volume.

### 15. What is the transient Heat transfer?

The process which implies variation with time or temperature dependent is known as transient heat transfer.

### 16. What are boundary Conditions in Heat transfer?

The mathematical expressions of thermal conditions at the boundaries are called boundary Conditions in Heat transfer.

### 17. What is the focal point in Heat transfer?

The point at which rays or waves meet after reflection or refraction, or the point from which diverging rays appear to proceed is known as focal point.

### 18. What is the friction factor in Heat transfer?

Friction factor determines the losses occurring in a system due to the shear stress at the surface which is related to the slope of the velocity profile at the surface.

### 19. What is the Darcy friction factor in Heat Transfer?

Darcy friction factor is the theoretical equation that predicts the frictional losses in a pipe. It gives relation between diameter, length and velocity of liquid in pipe.

### 20. What are the forms of Fourier’s law of heat conduction in Heat Transfer?

There are two forms of Fourier’s law of heat conduction,

- Differential Form
- Integral Form

## Intermediate Heat Transfer Interview Questions with Answers

### 21. What is Conduction?

Conduction is the mode of heat transfer that occurs due to collision or diffusion of molecules during their random motion, generally occurring in solids.

### 22. How Conduction occurs in Solid?

Conduction occurs in solid due to the combination of vibration of molecules in lattice and the energy transport by free electrons.

### 23. On what Factors does Conduction Depend?

Conduction depends on thickness and material of the medium, and it also depends upon the temperature depends across the medium.

### 24. What is Heat Generation in Conduction?

The material through which heat is conducted may involve the conversion of electrical, mechanical, nuclear or chemical energy to heat energy, such conversion possesses are characterized as Heat generation process in Conduction.

### 25. What are the Sources of Heat Generation?

Main sources of Heat generation are nuclear reactions, exothermic chemical reactions, solar energy and gamma rays.

### 26. Which Type of Phenomenon is Heat Generation?

Heat generation is a volumetric phenomenon and its unit is W/m^{3}.

### 27. Which factors affect the Boundary Conditions in Heat transfer?

Two bodies in contact must have the same temperature at the area of contact and an interface (which is a surface) cannot store any energy, these are the factors which affects the boundary conditions in heat transfer.

### 28. What is the Critical Radius of Insulation?

Critical radius of insulation is the counterintuitive concept which states that adding insulation more than critical radius will increase heat losses.

### 29. Why Heat Losses Increases after Increasing Radius above Critical Radius?

When insulation radius is more than critical radius, convection heat transfer resistance decreases due to more surface being exposed to air, because of this heat losses increases.

### 30. Which Parameters affect the Critical Radius of Insulation?

Critical radius of insulation get affected by the thermal conductivity of insulation and convective heat transfer coefficient of insulation.

### 31. How to Calculate the Critical Radius of Insulation for a Cylinder?

Critical radius of insulation for cylinder is the ratio of thermal conductivity of insulation to heat transfer coefficient of insulation.

### 32. How to Calculate the Critical radius of Insulation for a Sphere?

Critical radius of insulation for sphere is the ratio of twice of thermal conductivity to the heat transfer coefficient of insulation.

### 33. Give example where Radius more than Critical Radius is an Advantage.

Insulation more than critical radius is favorable in electric wire.

### 34. Why is Insulation more than Critical Radius Favorable in Electric Wire?

Insulation more than critical radius is favorable in electric wire because it gives a cooling effect. Addition of more insulation will help wire to dissipate heat to the surrounding.

### 35. What are the Performance Characteristics of Fin?

Performance characteristics of fins are temperature distribution, rate of heat transfer and fin efficiency.

### 36. What is meant by Fin Efficiency?

The ability of fins to increase the heat transfer rate in comparison to the normal heat transfer rate is known as fin efficiency.

### 37. Why are Fns with Triangular and Parabolic Profiles Preferred?

Fins with triangular and parabolic profiles contain less material and more efficient than rectangular profile fins, therefore triangular and parabolic profile fins are preferred,

### 38. Which Factors affect the Overall effectiveness fin?

The overall effectiveness of fin get affected by the fin density i.e number of fins per unit length and effectiveness of individual fin.

### 39. What is a Lumped Heat Capacity Model?

Lumped heat capacity model is the model designed to find out heat transfer of such bodies who don’t show any temperature gradient.

### 40. What type of Conductive and Convective Nature followed in a Lumped System?

In a lumped system conductive heat transfer coefficient i.e thermal conductivity is very large than the convective heat transfer coefficient.

### 41. Lumped System is dependent on which Parameters?

Lumped system depends upon the surface area of convection, volume, density and specific heat of the body.

### 42. What is Convection?

Convection is the mode of heat transfer in which heat transfer occurs in presence of medium and heat transfer is taken by the actual moment of heated fluid molecules.

### 43. What is Viscous Flow in Convection?

The flows in which the effect of viscosity is significant are known as viscous fluids.

### 44. What is Steady Flow in Convection?

The flow which implies no change with time is known as steady flow of convection.

### 45. What is Transient Flow in Convection?

The flow which implies changes with time is known as transient flow in convection.

### 46. What are the General Examples of Steady Flow?

Generally, equipment like compressor, heat exchanger, boiler, condensers are operated at same conditions for a long period of time, therefore they are considered as steady flow equipment.

### 47. What is Natural Convection?

Convection which doesn’t require any external force to carry out heat transfer is known as natural convection.

### 48. What is Laminar Flow of Fluid?

The flow which gives highly ordered motion and characterized by smooth streamlines is known as laminar flow of fluid.

### 49. What is the no-slip condition in Convection?

When the fluid won’t flow on a surface like nonporous surfaces and get stuck to it, velocity becomes zero, this phenomenon is known as no-slip condition in Convection.

### 50. What is the no-temperature-jump Condition?

When the heat transfer occurs between two surfaces, at some point temperature of both surfaces become equal and no further heat transfer will occur, this condition is known as no-temperature-jump condition.

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