Heat transfer enhancement of plate heat exchangers with symmetrically distributed capsules to generate counter-rotating vortices

Capsule-type plate heat exchanger takes advantages of low flow resistance and high overall performance. To obtain greater energy efficiency, a new type named symmetrical capsule plate heat exchanger (SCPHE) is constructed based on the idea of counter-rotating vortices. For SCPHEs, the adjacent capsules distribute symmetrically at the same-side of the plate, and the capsules keep an angle of 45° with the main flow direction. The heat transfer enhancement and the influences of capsule geometries were studied numerically. Counter-rotating vortices generating in the channels promote the swirl flow and disturb the boundary layer. Both fluid impinging and the vortices dominate the heat transfer enhancement, which become much stronger under smaller capsule, resulting in higher heat transfer coefficient. The correlations of Nu and f considering the effects of the capsule geometries are developed. SCPHEs show higher energy efficiency than capsule-type plate heat exchangers and chevron-type plate heat exchangers in the view of PEC and EEI.