Investigation of mixing and heat transfer characteristics of long-hole SK direct contact heat exchanger

In this study, in order to improve the efficiency of direct contact heat exchanger (DCHE), SK static mixers with different perforation index (PI) were applied. Numerical simulation (volume of fluid model) were used to investigate the performance of the static mixer, which shape was designed as long-holes, under fixed aspect and helical ratios. The feasibility and accuracy of numerical simulation results were verified by self-established direct contact heat transfer (DCHT) experimental platform. Under six different PI values (0 %, 10 %, 18 %, 26 %, 32 %, and 38 %), the heat transfer performance of DCHE was evaluated by applying two heat transfer mediums (THERMINOL62 and R141b). The results indicated that the gaseous working medium outlet temperature, turbulence intensity, turbulence kinetic energy, and volumetric heat transfer coefficient (VHTC) of the system showed an increasing trend as PI increased from 0 % to 32 %, then a decreasing trend can be observed from 32 % to 38 %. The maximum turbulence intensity and turbulence kinetic energy of 17.56 % and 0.015 m²/s² can be found in PI = 32 %, as well as a maximum enhancement ratio of 49 % in VHTC compared to PI = 0 % can be achieved. In addition, only a small pressure drop increase is observed in PI = 32 % compared to PI = 0 %.