A review of the impinging stream dryer

Abstract

ABSTRACT The demoisturizing or drying process is an essential technique to prolong the life of agricultural product. Typically the impinging steam dryer (ISD), one of hot-air drying process, is suitable to dry particulate materials that contain very high moisture. This dryer allows high speed steam carrying the grains to impinge against each other at the middle point of two opposite steams. The particles can be theoretically accelerated to a velocity near the speed of gas. The impingement between solid-in-gas steams causes an impingement zone that has high turbulence with high concentration of particles so this two-phase turbulence area provides excellent heat and mass transfer. The literatures related to this research show that various parameters including distance between the tube and the drying chamber, inlet air temperature, loading ratio, material moving time through the system have affected the performance of an impinging stream dryer. The performance of an impinging stream dryer can also be evaluated in terms of the volumetric water evaporation rate, volumetric heat transfer coefficient and specific energy consumption. However, researches of impinging stream dryer are considered as a new technology in Thailand. Hence, it is necessary to study on the effects of various parameters on the performance of an impinging stream dryer in order to be really applied to the Thai industries.   Keyword: impinging stream dryer; volumetric water evaporation rate; volumetric heat transfer coefficient