When creati ng modern eff ecti ve complex technical systems that realize the processes of thermal impact on bulk agricultural materials with the required quality and at a high energy level, it is important to know the conditi ons of heat and moisture transfer. The target functi on of our research was scienti fi c substanti ati on of the main thermophysical parameters of the studied process of thermal eff ect on the drying product as a whole, as well as identi fi cati on of the eff ect of the created temperature regime of the drying unit on the temperature gradient when heati ng the treated seeds, and, ulti mately, on the effi ciency of the enti re process. In case of contact drying of small-seeded crops, both external heat and moisture exchange processes are carried out - from the surface of the treated seeds to the external environment, and internal - the migrati on of heat and moisture inside the seeds. The main quanti tati ve factor that most fully describes the mechanism of moisture transfer is the Bio criterion (Bim). This criterion establishes a relati on between such parameters of the contact drying process as the intensity of moisture exchange on the surface of the processed grain and its moisture conducti vity. The descripti on of the process is reduced to solving an internal problem for the moisture contained in the processed grain, when considering the latt er as a colloidal body, Bim = 0.16. In this case, the removal of moisture with its transformati on into steam directly depends on the energy consumpti on for the heat treatment process. The driving force of this process is the temperature gradient arising from thermal acti on. Studies have established that the kineti c coeffi cient, which most fully describes this phenomenon, is the thermal and moisture conducti vity coeffi cient or the thermal gradient coeffi cient δ. This parameter characterizes the moisture content change in the processed grain at a temperature gradient equal to one degree Celsius. In order to confi rm the above theoreti cal dependencies, experimental studies were carried out to identi fy the features of contact thermal eff ects on various small-seed crops. Based on the results of the studies, it was revealed that the following operati ng parameters have the greatest infl uence on temperature regime during grain drying in the developed contact type grain dryer: the temperature of the heati ng surface and the rotati on frequency of the transporti ng working body. In this study, the rotati on frequency of the transporti ng working body was changed from 30 min-1 to 110 min-1, and the temperature of the heati ng surface - in the range from 40 ºС to 100 ºС. It was revealed that the temperature gradient of grain heati ng in the developed installati on for grain drying at appropriate drying modes is 9 ... 12 ºС and does not signifi cantly depend on the type of processed seeds. When improving the operati ng parameters of the drying process of seeds of one crop, it is possible to operate the developed grain dryer without loss of quality during heat treatment of small seeds of other crops.
Heat and moisture transfer kinetics and temperature during drying of fabrics
