Convective Air Drying of Stationary and Moving Moist Porous Medium With Slot Jet Reattachment Nozzle: A Numerical Study

Abstract Drying is an omnipresent operation present in various industrial sectors such as food and agriculture, forestry products, chemicals, and pharmaceuticals. Convective hot air drying with conventional impinging jet nozzles is among the widely used techniques in drying of moist porous materials. However, this method is generally inefficient in drying of fragile materials as a low air flow rate is required to avoid potential damage to the product due to the exerted force by impinging jet. To improve the drying efficiency and enhance the product quality, slot jet reattachment (SJR) nozzle has been developed as an alternative technology to the common in-line jet nozzle, slot jet (SJ) nozzle, and perforated plate. SJR nozzle allows for the control of the exerted impingement force by simply changing its exit angle. This paper numerically investigates the convective air-drying characteristics of an SJR nozzle and compares it to those of a common SJ nozzle for a moist porous medium. The comparison is made under identical air mass flow rate criterion. The results are presented for stationary and moving reattachment surface under a laminar flow condition. The governing transport equations within a moist porous medium are coupled with the governing equations of the resultant air flow. The results indicate a much higher drying rates with SJR nozzle compared to SJ nozzle.