Sage-Tips

What do you understand by thermal contact resistance?

Thermal contact resistance (TCR) is a phenomenon in which heat flow is impeded at the contact interface of two materials. W. A. Little, “The transport of heat between dissimilar solids at low temperatures,” Can.

What is thermal contact resistance in heat transfer?

When two solid bodies come in contact, such as A and B in Figure 1, heat flows from the hotter body to the colder body. Thermal contact resistance is defined as the ratio between this temperature drop and the average heat flow across the interface.

What is the main cause of thermal contact resistance?

The limited number and size of the contact spots results in an actual contact area which is significantly smaller than the apparent contact area. This limited contact area causes a thermal resistance, the contact resistance or thermal contact resistance.

What is contact resistance What are factors affecting the contact resistance?

The apparent contact pressure and the mean junction temperature, combined with the thermophysical and mechanical properties of the contacting materials and the surface characteristics, are the primary factors in determining the magnitude of the contact resistance.

How does contact pressure affect thermal contact resistance?

Therefore, the thermal contact resistance decreases and the heat transfer rate increases under the higher contact pressure. (3)The heat transfer decreases and the thermal contact resistance increases under the melting process of PCM.

What are the methods to reduce the thermal contact resistance?

As a result, engineers must find ways to minimize the thermal resistance from the electronic device junction to ambient air. Therefore, one way to reduce Rja is to reduce Rcs, the contact resistance between the electronic device case and ambient-cooled, finned heat sinks or liquid-cooled cold plates.

Does contact resistance increase with temperature?

In the temperature range 100 to 300 K. The electrical resistances from both the 2-P and 4-P configurations increase linearly as temperature increases, and the two curves are almost in parallel, so the derived electrical contact resistance is nearly temperature-independent.

What is the difference between thermal contact and thermal equilibrium?

When two objects in contact with each other are at different temperatures, they are said to be in thermal equilibrium. When two objects in contact with each other are at the same temperature, they are said to be in thermal equilibrium.

What is the effect of thermal contact resistance on heat transfer rate?

Moreover, the real contact areas significantly increase with increasing the contact pressure. Therefore, the thermal contact resistance decreases and the heat transfer rate increases under the higher contact pressure.

Is Contact a conduction?

In contrast to induction, where the charged object is brought near but never contacted to the object being charged, conduction charging involves making the physical connection of the charged object to the neutral object. Because charging by conduction involves contact, it is often called charging by contact.

What do you mean by zeroth law of thermodynamics?

The zeroth law of thermodynamics states that if two bodies are each in thermal equilibrium with some third body, then they are also in equilibrium with each other.

How do you measure contact resistance?

The standard method for measuring contact resistance is the 6Volt 1Amp method, sometimes referred to as four wire measurement. It is a simple method that can be easily implemented with two power supplies, and a digital voltage meter (DVM). The following schematic is used to measure contact resistance in our lab:

How does contact pressure effect thermal contact resistance?

The pressure holding the two surfaces together also influences the contact resistance. Thermal contact resistance is observed to decrease with decreasing surface roughness and increasing interface pressure. This is attributed to the fact that the contact surface between the bodies grows as the contact pressure grows.

What is meant by thermal resistance?

Thermal resistance is a measure of a material’s ability to resist heat transfer. The more a material is able to block heat transfer through its surface, the greater its thermal resistance. This concept is often applied to the building industry as a measure of insulation effectiveness and energy efficiency.

What material has the highest thermal resistance?

The most extensively used high working temperature resistance materials are alloys of nickel, chromium and iron called Nichrome and alloys of aluminium, iron and chromium. The quality of these alloys, especially the working temperature strongly depends upon the chromium content.