Numerical study on heat transfer enhancement in capsule-type plate heat exchangers

The capsule-type plate heat exchanger is proposed to address high viscosity fluid which has concave and convex ellipsoidal embossing similar to half capsules. In this paper, single-phase flow and heat transfer in a capsule-type plate channel are investigated numerically. Owing to the periodicity of the structure of the capsule-type plate channel, the heat transfers between the hot and cold fluid in a unit cell with periodic boundary conditions are modeled. Shear Stress Transport k-ω model is employed for turbulent flow. Streamlines, velocity and local convective heat transfer coefficient are presented for discussions. The heat transfer enhancement is found to be primarily attributed to the vortices, one of which has the unique butterfly-shaped head. The correlations of friction factor and Nusselt number in turbulent flow regime with Reynolds number from 500 to 12,470 are obtained based on the simulation results. Compared with other plate heat exchangers (e.g., chevron-type), the capsule-type plate heat exchanger has big Nusselt number, small friction factor f and a good performance with respect to Nu/f^1/3.