Vortex augmented heat and humidity energy extraction and the variation of vortex strength behind the string grid

•Established relation between vortex strength and heat transfer efficiency.•The ΩR criterion is used to visualize the vortex field..•The formula of specific pressure loss of parallel spacing is obtained. In the process of upgrading the working quality of the heat pump, the mine waste heat flow is used as fuel to preheat the liquid working medium, and the string grid is used to enhance the process. In order to explored the mechanism of heat and moisture exchange in the string grid enhanced mine exhaust airflow, based on theoretical analysis, LBM model simulation is established. Using the third generation vortex identification criterion, comparing the experimental results, a positive global vortex strength-heat transfer efficiency correlation was found.Under the taken conditions, the maximum heat transfer efficiency can reach 28 % with vortex strength 0.00936, and the minimum heat transfer efficiency reaches 13 % with vortex strength 0.00893. Further, found that the parallel spacing ratio plays a decisive role in the enhancement of vortex strength. As the parallel spacing ratio increases, the vortex strength values decrease. In comparison to the parallel spacing ratio, the series spacing ratio exerts a lesser influence on vortex strength. Furthermore, when the parallel spacing ratio is dominant, the parallel and series spacing ratios exhibit a weak coupling. The weak coupling is manifested as(1) The vortex strength corresponds to a large series spacing for small parallel spacing ratios, and the opposite effect of series spacing on vortex strength for large parallel spacing ratios; (2) There are fluctuations in the vortex strength, and the interval of the series spacing ratio corresponding to the fluctuations is proportional to the parallel spacing ratio.