Enhancing heat and moisture transfer of porous fabrics using arrayed opposed jets: Experimental and numerical investigations

Abstract

Achieving rapid fabric drying and ensuring a uniform distribution of surface temperature and moisture is essential for the post-processing stage in printing and dyeing. Although jet technology is commonly used to enhance heat transfer processes, the mechanism of heat and moisture transfer using array opposed jet for fabric drying is still unclear. This paper proposes that using opposed jet to enhance the drying process for four different fabric structural types, the influence of jet Reynolds number and excess temperature on the change of fabric moisture content was analyzed using experimental methods, then by defining the fabric as a porous medium containing two-phase components, the flow characteristics and temperature field distribution of the opposed jet were obtained using numerical methods. The results indicated that the four different structural types of fabrics exhibited similar heat-moisture transfer characteristics under the air supply mode of the opposed jet. Furthermore, the critical evaporation temperature of fabrics with hygroscopic properties was higher than that of non-hygroscopic fabrics. When the Reynolds number increased from 649.4 to 2165.3 and the excess temperature increased from 40 ℃ to 70 ℃, the drying time was shortened by a maximum of 56.2 % and 25.5 %, respectively. Under the impact of the array opposed jet, the thermal boundary layer on the fabric surface was thinned, and the local Nusselt number presented different peaks along the length direction of the impinging surface. Within the range of operating conditions considered, at a jet wind speed of 4.5 m/s and an excess temperature of 70 ℃, the maximum surface drying rate of the fabric was achieved. The relative deviations of heat flux and mass flux on the impact surface are all within 10 %. This study provides a theoretical basis for the structural design and drying mechanism exploration of fabric drying equipment.