Study of dimple restraining heat transfer deterioration of supercritical methane under high heat flux in mini channel

To attenuate the heat transfer deterioration of supercritical methane under high heat flux in mini channel, dimple structure is employed and studied numerically. Flow friction factor (f), heat transfer coefficient (HTC), Nusselt number (Nu) and performance evaluation criteria (PEC) are adopted to compare the heat transfer and flow characteristics between dimple and smooth channel. Besides, local velocity, turbulence kinetic energy (TKE), temperature and HTC are discussed. The results indicate that higher heat flux could deteriorate the heat transfer of supercritical methane resulted from the buoyancy and flow acceleration effect. While dimple enhances tremendously the heat transfer performance under high heat flux with enhanced factor up to 2.2, and there exists an optimal inlet temperature for the enhanced factor. On the other hand, the friction factor is worsened. However, PEC is positive up to 1.9 increased by the heat-mass ratio and mass flux. For enhanced mechanism, dimple induces vortex and raises the TKE, which strengthens the heat transfer between wall and bulk fluid.