Experimental and numerical study of the airflow distribution in mixed-flow grain dryers

Abstract

The aim of this study was to investigate the airflow distribution in the mixed-flow dryer (MFD) and to study the effect of different bed materials and air duct arrangements. The results were used to validate the numerical model developed in a previous work based on the Computational Fluid Dynamics (CFD). A series of experiments have been conducted at a semi-technical MFD test dryer with horizontal and diagonal air duct arrangement.Wheat and rapeseed were used as bed materials. The experiments were performed under isothermal conditions. Two experimental methods were selected and adapted to the measuring problem -the measurement of the isobar distribution within the grain bed and the residence time analysis using the tracer gas pulse method.As could be shown, the isobar distributions measured for wheat and rapeseed agreed well with the model predictions. The numerical model could well calculate the influence of the bed material with its different particle characteristics (e.g. particle shape, particle size, bed porosity). The results obtained from the residence time analysis confirmed the known quartering of the air stream flowing from one inlet air duct to the four surrounding outlet Downloaded by [New York University] at 20:13 22 July 20152 air ducts for the horizontal air duct arrangement. Whereas, in the diagonal air duct arrangement, the air steam from one inlet air duct was nearly halved flowing to the two adjacent diagonal outlet air ducts. These results were confirmed by investigations of the air velocity distribution within the grain bulk. Further experiments are necessary to refine the model. For it, the residence time and isobar measurements will be extended to study the influence of different air properties under real drying conditions, the effect of structural elements and dryer designs.

A Survey on Heat Transfer in the Aerated Drying Process of Stored Grains

“…For this review, reference articles are mostly related to the heat transfer problem, but four of them ( [1], [3], [8] and [9]) are mentioned by the fact they are articles of research in similar areas that use the heat transfer in their models supporting and complementing the study on mass transfer or the velocity of airflow.…”

“…Air temperature significantly affects the mass transfer process, whereas air velocity poses almost no effect, and a low velocity lessens energy consumption. Rice Vertical Silo [5] Soya Beans Cross Flow Grain Dryers [6] Paddy Columnar Dryer [7] Brown Rice Shallow Depth Forced-Air [8] Generic Grains Mixed-Flow Dryer [9] Corn and Rice Mixed-Flow Dryer [10] Corn Not specified…”

Research on Quality of Maize Grain as a Result of the Application of an Innnovative System for Storing Grain Under Operating Conditions

“…The silos are then much more heavily loaded, which requires additional reinforcement of their structure. The asymmetrical loading of silo walls decreases their durability and increases costs related to their use (Scaar et al, 2015;Tonui et al, 2014;Weigler et al, 2012).…”

Wheat grain drying kinetics in a thin layer

“…Besides, interaction of streams of the heat carrier and grain caused by design features of this dryer [7,11] is important. Therefore, determination of patterns of grain drying process at variable parameters of process for justification of the rational modes of wheat grain thermal treatment in dryers was the purpose of the research.…”

“…It is possible to dry grain in the different ways [1,2,7,8,9,13,14]. The greatest practical use received a convective way with the rapid course of a thermal mass transfer in grain-dryers to the given humidity of grain.…”