Thermal contact resistance or thermal interface resistance refers to the resistance encountered at the interface between two solid materials when attempting to transfer heat. This resistance can greatly impact heat transfer efficiency and is a crucial consideration in many industries, including electronics and thermal management.

One example of thermal contact resistance is cooling a computer's central processing unit (CPU). The CPU generates significant heat during its operation, and it is essential to dissipate this heat quickly to prevent damage to the device. The CPU is typically mounted on a heatsink, which is then connected to a cooling fan. The interface between the CPU and the heatsink is where thermal contact resistance occurs.

The thermal contact resistance is affected by various factors, including the surface roughness of the materials, the contact area, and the interface material's quality. The surface roughness of the materials plays a significant role in thermal contact resistance, as a rough surface can create air pockets that impede heat transfer. The area of contact also plays a role, as a larger area of contact allows for more efficient heat transfer.

Thermal interface materials such as thermal paste or thermal pads are often used to reduce thermal interface resistance. These materials are applied to the interface between the CPU and the heatsink to improve the interface's quality and fill gaps or air pockets. While the thermal paste is a liquid applied to the interface and spreads to fill gaps, thermal pads are pre-cut material placed between the CPU and the heatsink. These materials are designed to improve thermal conductivity, which reduces thermal contact resistance.

In conclusion, thermal contact resistance is critical in many industries, including electronics and thermal management. It refers to the resistance encountered at the interface between two solid materials when attempting to transfer heat. In the case of a computer's CPU, thermal contact resistance can greatly impact heat transfer efficiency and can damage the device. Thermal interface materials such as thermal paste and thermal pads are often used to reduce thermal contact resistance and improve the quality of the interface.

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Reference

[1] Chen, J. and Gao, X., 2019. Directional dependence of electrical and thermal properties in graphene-nanoplatelet-based composite materials. Results in Physics, 15, p.102608.