Pore structure and airflow resistance of bulk solids

散装固体是固体颗粒和充满空气的气孔的混合物。许多农产品和食品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。散装固体的气流阻力知识在这些产品的加工和存储系统的设计和操作中至关重要，以确保产品质量和最大限度地减少能源消耗。一个典型的例子是谷物的干燥，在干燥过程中，热空气被迫流过谷层，以降低谷物的水分，以保持品质和安全储存。干燥速度(影响粮食品质)和能耗与粮食的气流阻力密切相关。传统上，确定气流阻力的方法在农业应用中一直是经验性的。从理论上讲，散装固体的气流阻力由流动的性质和散装固体的孔结构决定。我的研究将集中于量化气孔结构及其对气流阻力的影响，最终为散装固体系统的设计和操作开发合理的方法。在这项拟议的研究中，我们将首先开发一个数值模型来预测散体固体中的孔结构。然后，将该孔结构模型与孔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，以量化谷物散装中的孔隙结构。将进行试点试验，以测量储藏箱中粮食的气流阻力。这项研究的结果不仅将有助于了解散装固体的行为和流动的基本知识，而且还将为农业和食品工业设计和运行散装固体系统，特别是谷物处理和储存系统提供合理的工具。加拿大每年的谷物价值约为60亿美元，其中很大一部分(70%)用于出口。高质量是保持加拿大粮食在全球市场竞争力的关键，而处理和储存是保持收获后粮食质量的关键。本研究开发的气流模型将辅助粮食行业设计和管理粮食仓储系统，以实现最好的产品质量和最少的能源消耗。

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.