Pore structure and airflow resistance of bulk solids

散装固体是固体颗粒和充满空气的孔隙的混合物。许多农产品和食品都是以散装固体的形式加工和储存的，如谷物、蔬菜、坚果和水果。在设计和操作这些产品的加工和储存系统时，了解气流通过散装固体的阻力是至关重要的，以确保产品质量和最小的能源使用。一个典型的例子是谷物干燥，其中热空气被迫流过谷物床，以降低谷物水分，以保持质量和安全储存。谷物的气流阻力与干燥速度（影响谷物品质）和能量消耗密切相关。传统上，用于确定气流阻力的方法对于农业应用是经验性的。理论上，散状固体的气流阻力由流动的性质以及散状固体的孔结构决定。我的研究将集中在量化的孔隙结构及其对气流阻力的影响，最终开发出合理的方法，设计和散装固体系统的操作。在拟议的研究中，我们将首先开发一个数值模型来预测散装固体的孔隙结构。然后将该孔隙结构模型与孔隙尺度流体流动模型相结合，以预测通过散装固体的气流。将进行实验室实验以量化谷物块中的孔隙结构。将进行中试试验，以测量粮仓中粮食的气流阻力。这项研究的结果不仅有助于散装固体行为和流动的基础知识，而且还为农业和食品工业提供了一个合理的工具，以设计和操作散装固体系统，特别是谷物处理和储存系统。加拿大每年的粮食作物价值约为60亿美元，大部分（70%）用于出口。高质量是保持加拿大谷物在全球市场竞争力的关键，而处理和储存是保持收获后谷物质量的关键。本研究所发展之气流模型，将可协助粮食产业设计及管理粮食储存系统，以达到最佳之产品品质及最少之能源消耗。

Bulk solids are mixtures of solid particles and pores filled with air. Many agricultural and food products are processed and stored in the form of bulk solids, such as grain, vegetables, nuts, and fruits. The knowledge of resistance to airflow through bulk solids is critical in the design and operation of processing and storage systems for these products to ensure product quality and minimal use of energy. A typical example is the drying of grain in which hot air is forced to flow through a bed of grain to lower the grain moisture for quality preservation and safe storage. The drying rate (affecting the grain quality) and energy usage are closely related to the airflow resistance of grain. Traditionally, the methods for determining airflow resistance have been empirical for agricultural applications. Theoretically, the airflow resistance of bulk solids is dictated by the nature of flow as well as the pore structure of bulk solids. My research will focus on quantifying the pore structures and their effect on airflow resistance, ultimately developing rational methods for design and operation of bulk solids systems. In the proposed research, we will first develop a numerical model to predict the pore structures in bulk solids. This pore-structure model will then be integrated with a pore-scale fluid flow model to predict airflow through bulk solids. Laboratory experiments will be conducted to quantify the pore structures in grain bulks. Pilot tests will be conducted to measure airflow resistance of grain in storage bins. The results from this research will not only contribute to the fundamental knowledge of bulk solids behaviour and flow through them, but also provide a rational tool for the agriculture and food industry to design and operate bulk solids systems, particularly grain handling and storage systems. The value of Canada's annual grain crops is about $6 billion and a large portion (70%) is exported. High quality is the key in maintaining the competitiveness of Canadian grain in global markets, whereas handling and storage is critical in maintaining the grain quality after harvest. The airflow model developed in this research will assist the grain industry in designing and managing grain storage systems to achieve the best product quality and the least energy usage.