A thermal diode serves as a basic building block to design advanced thermal management systems in energy-saving applications. However, the main challenges of existing thermal diodes are poor steadystate performance, slow transient response, and/or extremely difficult manufacturing. In this study, the thermal diode is examined by employing an argon gas-filled nanogap with heterogeneous surfaces in the Knudsen regime, using nonequilibrium molecular dynamics simulation. The asymmetric gas pressure and thermal accommodation coefficients changes are found due to asymmetric adsorptions onto the heterogeneous nanogap with respect to the different temperature gradient directions, and these in turn result in the thermal diode. The maximum degree of diode (or rectification) is R max $ 7, at the effective gas-solid interaction ratio between the two surfaces of e* ¼ 0.75. This work could pave the way to designing advanced thermal management systems such as thermal switches (transistors).
Controlling thermal energy transport (thermal diode) for the desired direction is crucial to improve the efficiency of thermal energy transport, conversion, and storage systems as electrical diodes significantly impact on modern electronic systems. The degree of thermal rectification is measured by the difference between the heat transfer rate in favorable and unfavorable directions to the heat transfer rate in the unfavorable direction. A gas-filled, nano-gap structure with two different surface coatings is considered to design the thermal rectifier. In such a structure where the characteristic length scale is similar to the order of the mean free path of the fluid particles (Knudsen flow regime), the effective thermal conductivity is dominantly controlled by the gas-surface interaction, i.e., thermal accommodation coefficient. For the thermal rectification, the adsorption-based, nonlinear thermal accommodation coefficient change is a key design parameter. Here, these are examined using the kinetic theory for various pressure and temperature ranges. Optimal material selections are also discussed.
Motivation• Optimal thermal management systems are crucial to many applications in manufacturing, electronics, automotive, aerospace, and energy systems. • Thermal energy flow often needs to be controlled in direction for the desired flow control.
Challenges• Thermal flow control systems are rare.• They have poor steady state performance, slow transient response, and difficult manufacturing process.
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