# Modes of Heat Transfer-Conduction, Convection, and Radiation [PDF]

Contents

## What is Heat?

Heat is the form of energy which is associated with the motion of molecules or atoms. The heat transfer takes place from the high-temperature body to low-temperature body. The extreme or moderate or low heated object leaves the heat at the room temperature.

## Modes of Heat Treatment

There are 3 Modes of Heat transfer which are as follows:

1. Conduction
2. Convection

### Conduction

In Conduction, the heat or energy is transferred by direct contact. When we heat the Iron at one side the other side automatically gets heated because the molecules present in it travels to another side and heats that area too. So we can say Conduction is equal to Direct contact. It is defined as the transfer of heat by means of molecular agitation within a material without any motion of the material as a whole.

#### Fouriers law of conduction

The Fourier’s law is a fundamental equation for heat transfer. It states that “The rate of heat transfer through a material is directly proportional to the temperature gradient across the material.”

Mathematically,

Fourier’s Law

q = -kA(dT/dx)

where,

q – rate of heat transfer, K – thermal conductivity, A – cross sectional area.

The negative sign indicates that the heat flows from hot to cold area.

#### Factors affecting heat conduction

Following is the list of factors affecting heat conduction:

### Convection

In convection, the heat or energy is transferred by mass motion of fluid which might be air or water. When heated fluid moves away from the source of heat-carrying energy with it convection takes place.

Example of Convection

When the heat is provided to water at the bottom, the pot is heated. The water particles move faster and far from each other. The heated water becomes less dense and we know that the less-dense fluid will float on top of a more dense one. Now, the heated water rises in the pot. The surrounding cooler water flows into its place. This flow creates circular motion, known as convection currents.

#### Types of heat transfer by convection

Following are the two main types of convection:

Natural Convection : This happens when the fluid becomes less dense and expands due to heating. In a natural convection a circulation pattern is created naturally. Example – Circulation of air due to temperature difference.

Forced Convection : In a forced convection, the fluid is forced to move due to an external source. Example – using a fan to cool electronic systems when heated.

#### Factors affecting heat convection

Following is the list of factors affecting heat conduction:

• Fluid Velocity
• Fluid Properties
• Surface Geometry
• Temperature Difference
• Obstructions

The Radiation is defined as emitting heat in the form of an electromagnetic wave or rays or particles. This process does not require a medium to transfer the Thermal (Heat) energy.

Example:

In summer when you go in the field and stand there for some time you will feel hot because of the sun which emits the heat. Also a car heats up after driving in extremely sunny days. That is how the radiation process works.

#### Types of heat transfer by radiation

Following is the list of factors affecting heat conduction:

Thermal Radiation : This type of radiation is emitted by an object that has a temperature above absolute zero. These radiation travels through space and is absorbed by objects causing increase in temperature.

Electromagnetic Radiation : These radiations are emitted due to generation of microwaves or radiowaves. Even though the electromagnetic radiation is not related to temperature still it can transfer heat.

Following is the list of factors affecting heat radiation:

• Distance
• Temperature
• Surface Properties
• Incident angle
• Environment

## FAQ’s

### What is Heat Transfer?

Heat transfer is the process by which thermal energy is exchanged between two or more objects or systems. This can occur through three main mechanisms: conduction, convection, and radiation. Understanding heat transfer is important in many fields, including engineering, physics, and materials science, as it can affect the performance and efficiency of systems and devices.

### How to use heat transfer vinyl?

Heat transfer vinyl (HTV) is a popular material used to create custom designs on fabrics. It is a versatile material that can be applied to a variety of fabrics, including cotton, polyester, and blends. The process of using HTV involves cutting the vinyl into the desired shape, and then pressing it onto the fabric using a heat press. Before applying the vinyl, it is important to ensure that the fabric is clean and free of any debris that could interfere with the adhesion process. Once the vinyl is applied, it is important to follow the manufacturer’s instructions for washing and caring for the garment.

## Conclusion

In conclusion, heat transfer is a fundamental concept in the field of thermodynamics that describes the movement of heat from one object to another. By using the principles of heat transfer, engineers and scientists can design more efficient and effective systems that can save energy and reduce costs. As our world continues to face energy and environmental challenges, the study of heat transfer will become increasingly important in finding sustainable solutions for the future.