Conduction Examples

Heat transfer is a branch of thermal engineering that deals with the generation, application, interchange, and exchange of heat between bodies. Heat transfer can occur in a body by three different processes: conduction, convection, and radiation. The heat always flows from a hotter body to a cooler body during heat transfer. Hence, heat transfer occurs due to differences in temperatures.

This article will explain the heat transfer occurring due to conduction. Moreover, we will also explain the concept of thermal conductivity, which is directly linked to conduction. In addition to explaining the concept of thermal conductivity, we will also provide solutions to some of the conduction questions.

What is Conduction?

Conduction is a process of heat transfer that occurs between the two adjacent ends of the body due to the temperature difference. To get a detailed introduction to conduction, we must understand the underlying process occurring during conductance. Internal collisions occur between the adjacent atoms and molecules when a body is heated. Due to these collisions, the heat is transmitted from one molecule to another. Thus the transfer of heat takes place from one end to another.

Conductance is a phenomenon that occurs readily in solids and liquids in comparison to gases. This is mainly because the atoms in the solids and liquids are stacked nearby. Moreover, the temperature transfer from one end to the other depends on the temperature difference between the two ends. If the temperature difference is more, heat transfer will also be more. Thus heat transfer is directly related to the difference in temperature.

One example of conductance is heating a frying pan over the gas stove. When the gas stove is lit up, the fire heats the molecules present in the frying pan. The heating of the molecules in the frying pan causes the molecule to vibrate. The vibrations are then transferred to the adjacent molecules through collisions. Thus, the thermal energy is transferred to the pan comprehensively due to collision. 

Concept of Thermal Conductivity

Conduction can be defined mathematically as the rate of flow of heat in a material depending upon the temperature difference. To prove this definition, we will take a metallic bar that has length L and a cross-section area A. We will keep the ends of the bar at different temperatures.

To keep the ends at different temperatures, we can keep one end of the bar in contact with a heat source having a temperature of T1. In contrast, the temperature at other sources is kept at T2. Also, we will keep the sides of the bar insulated so that no heat transfer occurs between the surroundings.

In the case of the steady-state condition, the heat is supplied to the end where the source is placed. Hence as we move along the bar, the temperature will keep on decreasing uniformly with the distance between T1 and T2. Thus, the flow rate of heat (H) is directly proportional to the difference between the temperatures T1 – T2 and the area of the bar. Furthermore, the heat transfer will reduce with the increase in length. Therefore, length and heat transfer are inversely related to each other.

The formula for heat transfer is: – 

HAT1–T2L

H=KAT1–T2L

Here K is the proportionality constant which is known as the thermal conductivity of a substance. Thermal conductivity is defined as the ability of the material to conduct heat. The SI unit of thermal conductivity (K) is J SmK orWmK . Thus a material which has a higher value of thermal conductivity, will be able to conduct heat in a better way.

Real-life application of the concept of Thermal conductivity

Conduction plays a significant role in cooking. Because during cooking, the cook puts the utensil on the burner, and then heat is transferred to cook the food present in the utensil. Now, if the conductance process is increased during cooking, then the food will be cooked faster. Therefore some utensils have been coated with a copper coating at the bottom. Copper has a high value of thermal conductivity; thus, coating the bottom of the utensil with copper increases the heat distribution in the utensil. Thus copper at the bottom of the utensil facilitates the cooking process.

Problems on Conduction

Conduction is a process of heat transfer between the adjacent ends of a material. Below we will solve one numerical based on the concept of conductance and thermal conductivity.

Question- What is the temperature of a steel copper junction in the steady state condition? Given that 

Length of the steed rod = 15 cm 

Length of the copper rod = 10 cm

Temperature of source = 300 degree Celsius

Temperature of other end = 0 degree Celsius

Area of the steel rod = 2 x area of copper rod

Thermal conductivity of steel = 50.2 J/smK 

Thermal conductivity of Copper = 385 J/smK

Due to steady state condition, an insulating material is present around the rods. This insulating material reduces the loss of heat from the sides. Thus it is evident that the heat flows along the length of the rod. Hence,

K1A1300TL1=(K2A2T-0)L2

Here the subscripts 1 and 2 refer to the steel and copper rod. Now,

50.2×2300-T15=385T10

From here we will calculate the value of T 

T = 44.4 degree Celsius

Conclusion

The different methods of heat transfer play a significant role in transferring the heat from the Earth to the atmosphere. Conduction plays a vital role in different atmospheric activities such as sea breeze and rain cycle. Moreover, the concept of thermal conductivity is extensively used in thermal engineering. The thermal conductivity of a material plays a significant role in the material selection process for designing a component. Moreover, the expansion of a material due to heating depends on thermal conductivity. Thus it is pretty evident that the concepts of conduction and thermal conductivity are vital for the different real-life applications.