A compressible direct numerical simulation (DNS) has been conducted to analyze the behavior of low-speed flows submitted to a strong temperature gradient in a fully developed and asymmetrically heated turbulent channel flow. The focus is to understand the relevance of the variable thermophysical properties and their impact on the heat transfer mechanisms. The simulations have been performed at mean friction Reynolds number Ret m = 400 submitted to a high-temperature ratio between the two walls (Thot/Tcold = 2). The results show an increased flow mixing and recirculation due to the temperature difference between the walls.