Thermal Rectification in Similar and Dissimilar Metal Contacts

An investigation was conducted to verify experimentally the existence of thermal rectification and to determine the effect of surface roughness and material type. Four pairs of test specimens were evaluated: one with a smooth Nickel 200 surface in contact with a rough Nickel 200 surface, one with a smooth Stainless Steel 304 surface in contact with a rough Stainless Steel 304 surface, one with a smooth Nickel 200 surface in contact with a rough Stainless Steel 304 surface, and finally, one with a smooth Stainless Steel 304 surface in contact with a rough Nickel 200 surface. The thermal contact conductance was measured for heat flow from both the smooth to rough and rough to smooth configurations for all four pairs. The results indicate that thermal rectification is a function of surface characteristics, material type, and heat flow direction. For similar materials in contact, some thermal rectification was observed with heat flow from the rough surface to the smooth surface resulting in a higher value of contact conductance. For dissimilar materials, the thermal contact conductance was highest when the heat flow was from the Stainless Steel 304 to Nickel 200. In these cases, the surface roughness was shown to be of secondary importance.