Transient Conduction or Non-Steady-State Conduction

Introduction to transient conduction

Synonymous to Non-Steady-State Conduction, transient conduction refers to a process where heat energy transfers to the medium that is never constant. The rate of heat flow keeps fluctuating. This can  be due to the origin of differentiating rates of heat transfer can either be constantly changing over the medium or due to the properties of the medium. 

Examples of transient heat conduction include any form of conduction that does not end with steady-state conduction. For example, a hot copper ball immersing into a heavy liquid at a low temperature. 

In the discussion below, we will tackle several transient conduction questions and all the core concepts.

Meaning of Transient Heat Conduction

Transient conduction is referred to as a stage when there is a change in the temperature of a body. As it can be implied from the term itself, transient means non-steady. Thus, transient conduction refers to a process during which the temperature changes with time at any given place within an object.

Non-Steady-State Conduction is another term that refers to the dependence of temperature on time within an object. These situations usually occur when there is a significant change in the temperature of an object. 

The system is never likely to reach a state of unchanging distribution in time in terms of temperature. This situation usually occurs when the internal heat is generated too rapidly to reach temperature equilibrium.

Applications of Transient Conduction

Some of the major applications of transient conduction include –

• Electric iron

An electric iron is composed of a heating coil responsible for converting electrical energy to heat energy. When the switch is on, the existing heat energy from the element is transferred to the adjacent bodies, and the heated metal base of the iron conducts heat to the object. 

Since the handle of an electric iron is made up of insulating material, there will not be any significant increase in temperature.

• Quenching of a coronary artery stent

This is another significant application of transient conduction. A stent is an important medical device that is used to open a blocked artery to enable the blood to keep flowing. 

Now, if we look at the manufacturing process, it involves holding the metal at high temperatures for an extended period and then cooling it down. This entire process uses the phenomenon of simulation.

Lumped System Analysis

As far as heat transfer analysis is concerned, sometimes bodies play the role of a lamp with uniform temperature in the interior part while the heat transfer takes place. The temperature of set bodies can be considered only as a function of time, because the heat transfer analysis utilises this idea. This function is known as lumped system analysis. 

The main benefit of this analysis is that it provides a great opportunity to simplify certain categories of heat transfer issues with greater accuracy. Apart from this, it also helps in understanding the amount of heat transfer as it reaches its upper and lower limits in the temperature. 

Criteria for Lumped System Analysis

The lumped system analysis succeeds in providing a framework to understand heat transfer analysis. The first criteria is defined as the characteristic length identified by the Biot number expressed as 

Bi = Convection at the surface of the body / Conduction within the body

When a hot fluid heats a solid body, the heat is first conducted to the body and then within the same object. Here, biot number refers to the ratio of internal resistance existing in the body to the heat conduction concerning its external resistance. Thus, it represents the small amount of resistance to heat conduction and temperature gradients existing within the body.

Remarks on heat transfer in the lumped system

For any given heat transfer process, a poorly constructed ground transportation system will lead to poor conduction in the body. Similarly, the lumped system analysis is not applicable when there is overcrowding on the surface. Heat transfer from a body to a comparatively cooler surrounding can be taken as an example here. It takes place as a result of the temperature difference, but this energy originally arises from the area near the surface. Thus, the temperature near the body of the surface drops. 

This situation usually creates a scenario where the temperature gradient existing between the outer and the inner areas of the body is created. The resulting temperature difference between the two regions enables heat transfer, which results in maximum temperature difference between the body’s area. 

Thus, the temperature difference depends heavily on the ability of the object to conduct heat to the outer surface in comparison to the ability of the surrounding area to push the heat away from the surface.

Conclusion 

In conclusion, transient conduction is an important concept in studying several practical examples in our day-to-day life, and how it relates to the basic concepts of chemistry. The lump system analysis also plays an important role in understanding the application of transient conduction and its wide applications using certain criteria. This system is further supported by several remarks on heat transfer to understand the intricate details involved. Understanding these core concepts also helps in relating the introduction to transient conduction, and how it relates to various fields.