Effects of rheological properties on heat transfer enhancements by elastic instability in von-Karman swirling flow

Elastic instability is proposed as a promising method to intensify heat transfer under very low Reynolds number conditions. However, the onset of elastic instability and its influence on heat transfer is highly dependent on the rheological properties of polymer solution, which has not been revealed. By varying polymer concentration, sucrose proportion and the degree of salinity, the heat transfer performance due to the variations of rheology is investigated in a swirling flow configuration between parallel plates. The results indicate that both the increase of polymer concentration and the reduction of the salinity can induce elastic instability easily, leading to a better heat transfer performance when the swirling velocity is fixed. However, the salinity effects become weakened as the swirling velocity continually increases and the maximum enhancement becomes independent on salinity. In particular, the heat transfer performance based on pure elastic instability shows larger enhancement than that of inertial-elastic instability at low Reynolds number.