(697a) Numerical Computations on Heat Transfer Characteristics in a Cavity Swepted by Hydrate Slurry Transported with Visco-Elastic Fluid

A two dimensional numerical study has been performed to investigate on heat transfer characteristics of a hydrate slurry transported by a visco-elastic fluid flowing between parallel plates with a one-sided cavity. Hydrate slurry of trimethyloleethan has high density of heat and addition of a small amount of surfactants, oleybishydrxyethylmethlyammonium chloride, shows very effective drag reduction of hydrate slurry, which shows high drag under the condition without surfactants. However, surfactant addition also causes heat transfer reduction. In order to improve this heat transfer reduction, we suggested a heat transfer augmentation method using visco-elasticity of the fluid. A visco-elastic fluid shows Barus effect at a sudden expansion often observed between ribs mounted on the heat transfer surface in a heat exchanger. This technique can be applied to the hydrate slurry treated with surfactants. In this study, the cavity length, rib height was changed in three steps, while the solvent Reynolds number were kept constant at 100. Heat flux on the solid wall was set at 20,000W/m2. The concentration of hydrate particles at inlet was set at 5wt%. From the results, it is found that hydrate particles dispersed with Newtonian fluid (water) flows over the cavity without penetration. On the other hand, hydrate particles dispersed with visco-elastic fluid are observed effectively to penetrate into the cavity and sweep the bottom of cavity by Barus effect. This causes effective heat transfer from the bottom wall of the cavity. Heat transfer difference was observed that the cavity length was changed. Consequently, there exists the optimum geometry for the heat transfer enhancement in a cavity by using Barus effect.