Adiabatic Air Dehumidification in Laminar Flow Desiccant Matrices

Adiabatic step transient heat- and mass-transfer and pressure drop experimental data were obtained for a dehumidifier test matrix that contained microbead silica gel desiccant in a parallel-plate geometry. The data were analyzed and compared with the results of two other test dehumidifiers: a parallel-plate matrix using crushed silica gel, and a staggered, parallel strip matrix using microbeadsilica gel. The analysis showed that the overall heat- and mass-transfer Nusselt numbers of the staggered, parallel-strip matrix were about 70% to 80% larger than those of the parallel-plate matrices. It also showed that the solid-side resistance to moisture diffusion in the smaller microbead silica gel was about 45% less than that of crushed silica gel because the particle size was 60% smaller.The ratio of heat- or mass-transfer coefficient to pressure drop of the microbead-silica gel staggered, parallel-strip matrix was higher than the other two test dehumidifiers. Based on these findings, a dehumidifier using microbead silica gel in a staggered, parallel-strip geometry can be made more compact than the other combinations.