Experimental study on enhancement and recovery of turbulent heat transfer relating to the functionality of surfactant solution induced by inserted mesh

Suppression of the wall-turbulence in the water channel flow, by adding a surfactant, simultaneously induces a heat transfer and a drag reduction. Those reductions are attributed to micellar network structures (MNS) which form in the surfactant solution under suitable conditions in terms of temperature, concentration, and shear rate. We inserted a wire mesh into the channel and experimentally investigated the heat transfer enhancement by the destruction of MNS and the subsequent recovering process. The local heat transfer coefficient downstream of the mesh complexly depended on the combination of surfactant concentration and distance of flow direction due to the self-repair ability of MNS. Furthermore, the wall-normal distribution of the Reynolds shear stress, which was dramatically suppressed in the normal drag-reducing flow, had a characteristic distribution dependent on the surfactant concentration and Reynolds number in the MNS recovery flow. We can explain the complex distribution of the local heat transfer coefficient and Reynolds shear stress, considering the MNS recovery place and process based on the shear rate.