Experimental and numerical study on thermal protective performance of weft-knitted spacer fabric system against hot pressurized steam

•The impacts of spacer fabric (SF) design on heat and mass transfer within novel spacer fabric systems (SFS) were systematically investigated.•The thermal protective performance (TPP) of SFS decreased as meshes increased on SF top layer but was minimally affected by heat setting.•Coarser spacer yarn (80 D) improved TPP, with feeding structure II (Fig. 2) showing a stronger positive effect.•A heat and mass transfer model considering steam pressure was established for in-depth simulations of the transfer process within SFS. Hot pressurized steam is a dangerous environment threatening the safety of workers. Developing steam protective clothing with excellent thermal protective performance (TPP) and clarifying its design mechanism are essential to protecting workers. This study totally developed eleven spacer fabric systems (SFSs) and investigated the effects of four design factors of spacer fabrics (SFs) on TPP, including heat setting, spacer yarn fineness, feeding structure, and top layer structure. Additionally, a heat and mass transfer model was established to analyze the steam protective mechanism of SFSs. The results demonstrated that SF heat setting had a negligible effect on TPP of SFSs. As the spacer yarn thickened to 80 D, the TPP of SFSs improved and the positive effect of feeding structure II on TPP increased. Conversely, dense mesh on the SF top layer had a negative effect on TPP. The model predicted that skin burn times of SFSs decreased with the increasing of pressure. When the pressure was 2.5 kPa, the relative errors between experimental and predicted skin burn times were the smallest (0∼12 %), which could more accurately simulate the steam protective mechanism of SFSs. These findings provide a theoretical basis for the development of high performance steam protective clothing.