Heat transfer-conduction

Introduction

You may be surprised to learn that two bodies of different temperatures may exchange heat. We will look at the thermal characteristics of matter and explore several heat transfer methods on this topic. It will help us understand heat transfer conduction better.

What Exactly is the Matter?

Everyone understands that matter refers to everything that has mass and takes up space. Solid, liquid, gas, and plasma are the four states of matter.

What is the Definition of Heat?

The term “heat” refers to a type of energy. You can trace its origins back to the molecular level. When you supply energy to a substance’s molecules, they vibrate in their set positions, whether fixed or not. As they vibrate, their energy is transferred to the molecules around them, causing them to vibrate as well.

On a macro level, this kinetic energy accumulates as more and more energy is delivered to the substance’s molecules. As a result, when this energy reaches a certain threshold (e.g. Melting point, Boiling point), the molecules or atoms are freed from interatomic forces of attraction, and phase transition occurs.

You can also define a body’s heat energy as a form of energy it can move from one body to another. A body can also generate it at the expense of other forms of energy when there is a temperature differential. 

The Joule, abbreviated as ‘J,’ is the SI unit of heat energy. The CGS unit to measure heat is ‘Calorie’ (Cal.), where 1 Calorie equals 4.186 J. 

Let us discuss the heat transfer conduction to understand more about the properties.

Thermal Properties of Matter

Thermal qualities of matter are the properties of matter that involve heat transfer and measurement.

Heat Transfer

Heat transfer is the study of the strategies and methods used to transfer heat energy. This heat transfer can be between two bodies or between different parts of a body.

There must be a temperature difference between two bodies to permit heat transfer. These bodies must be at two varying temperatures, one greater than the other, to allow heat to move from one body to the other.

Conduction

Heat transfer conduction is the process of molecules vibrating at their mean locations, transferring heat within a body or from one body to another. The bodies involved in the heat transfer must be close to one another. 

When transporting heat from one point to another, there is no physical movement of matter.

Conduction occurs most commonly in solids. Here, intermolecular forces of attraction securely bond together molecules in the structure. Therefore, they oscillate about their mean locations when they acquire heat energy, passing it on to the surrounding molecules via vibrations.

Convection

Convection is a technique of heat transfer that happens mostly in liquids and gases. When a material is transferred from one region within the body to another, heat transfer occurs in this mechanism. 

The bubbles and currents we see forming in boiling water is an excellent illustration of the convection process. The hot water at the bottom gets lighter and rises, causing the colder, denser water at the top to descend and heat up.

Radiation

In addition to heat transfer conduction and convection, another method of heat transport is radiation. It works without using a medium and can even transfer heat in a vacuum. Here, the transfer of heat from one location to another happens using electromagnetic waves.  

Radiation is how the sun’s heat and light reach our planet in our solar system.

Newton’s Law of cooling

According to Newton’s law of cooling, the rate of change in a body’s temperature is always proportional to the temperature differential between the object and its surroundings. 

It simply indicates that a heated body will cool down faster if its temperature is substantially higher than the surrounding temperature. On the other hand, a body with a temperature closer to the ambient temperature will take a bit longer.

Conclusion

Heat transfer conduction is the transport of heat within a material by molecular excitation rather than bulk motion. 

During their random motion, the collisions and diffusion of molecules cause conduction heat transfer in gases and liquids. On the other hand, heat transmission in solids is due to a mix of molecular lattice vibrations and energy transit by free electrons.