颗粒饲料冷却过程计算机数值模拟-农业机械化工程专业论文.docxVIP

ABSTRACTThe ABSTRACT The cooling process of pellet feed is very complicated．To provide the important theoretical foundation for feed and its equipment production，the temperature and moisture content during the process decide the cooling time and play important role in calculating the ventilation parameter．Therefore，it is significative tO do the theoretical analysis ofheat and mass transfer processes． Finite element method is one of computer-aided engineering CAE and has its application prospect The essence principle is to divide the domain to a group of finite and linked units．It has been developed to one modem method of calculation with the development of electronic computer．And ANSYS is a large scale general finite element analysis software wi也abroad application． In this thesis，the mechanism of heat and mass transfer in the cooling and moisture absorting process of pellet feed is in-depth studied and discussed．Taking the pellet feed as object，simulating the temperature and moisture content，building mathematical model in the cylindrical coordinate system and solving model with ANSYS Can get temperature and moisture content at any time and any point in the cooling time．By testing，it is approximate between simulated results and tested results． By the numerical simulation validation of moisture distribution and thermal field， it is indicated that the model in the thesis is feasible．The temperature and moisture distribution call be calculated on the premise of material characteristic parameters． keywords：pellet feed finite element ANSYS simulating cooling 第一章前青第一章前言 第一章前青 第一章前言 l。1问题的提出 在颗粒饲料的生产过程中，由制粒机刚刚生产出来的颗粒饲料，其温度高达70 一85℃，湿基水分含量为13％一17％。温度高不利于包装，容易产生水蒸汽，发霉， 易断裂。而水分超过国家标准．饲料中的微生物容易生长，极易发霉，不利于储藏。 为了便于包装、运输和贮存，颗粒饲料成品的温度和含水率必须符合行业规定的标 准。冷却后的颗粒料温度可以略高于室温，湿基含水率在12％以下。因此需要在制 粒后对饲料颗粒进行冷却(一般为强制风冷)处理，达到降低颗粒的温度和含水率 的要求[1 51。 冷却器利用冷空气来作干燥介质除去来自蒸汽调质工序大部分的热量和水分， 以及来自动力机械能转换的附加热量。 当颗粒从制粒机模孔压出时，颗粒具有纤维状结构，使水分在毛细管作用下从 颗粒中心向外传递。通常冷却器设计成使周围空气与颗粒的外表面紧密接触，只要 大气不呈饱和状态，它就会从颗粒表面带走水分。水分在蒸发