Abstract: How to approach the limit of heat and humidity energy extraction from exhaust air flow is a difficult problem for low-grade waste heat recovery technology in mines, and the key is to explore new ways to strengthen heat and moisture transfer between gas and liquid. For the spray mine exhaust air flow heat recovery device, a theoretical model of gas-liquid tandem heat and moisture transfer based on the number of mass transfer units (NTU_m)-Lewis number (Le) was established, and the spray coupled fiber grid gas-liquid heat and mass exchange experiment was carried out, and the dimensionless spacing ratio was introduced to quantify the influence of geometric size and water-gas ratio on gas-liquid heat and moisture transfer. Using the theory of igneous dissipation, the theoretical model was solved to explore the internal mechanism of heat and moisture transfer between gas and liquid strengthened by fiber grids. The results show that with the minimum entransy dissipation as the optimization goal of the transfer process, Le is positively correlated with the heat dissipation resistance of the ignition deposition, and Le tends to be close to 1, and the smaller the heat dissipation resistance of the entransy deposition, the more heat is extracted, and the heat and moisture transfer process is strengthened. Specifically, when the fiber grid spacing ratio is 8 and the water-gas ratio is 0.73, NTU_m increases more significantly with the water-gas ratio, the maximum reduction of wind temperature is 8.1 ℃, which is 2 ℃ higher than that of the cavity state, and the enthalpy drop value reaches 17.62 kJ/kg. Furthermore, the larger the spacing ratio, the faster the renewal frequency of the water film, the higher the number of gas-liquid contacts, the higher the cooling amplitude, the air-side heat transfer efficiency reaches 33%, the heating efficiency of the water side shows an upward trend, and the degree of heat and moisture exchange is more perfect. The smaller the spacing ratio, the higher the fiber filling rate, the increase of the liquid holding capacity of the fiber grid, and the significant improvement of the heating efficiency on the water side, however, the lower the heat transfer efficiency on the air side, the heat and moisture exchange is far from the limit. The conclusions obtained reveal the mechanism of fiber grid to enhance heat and humidity energy extraction, guide the optimization of geometric parameters of fiber grid, realize the efficient extraction of exhaust air flow waste heat resources within a specific water-gas ratio range, and promote the construction of green mines.