南京林业大学.doc

南京林业大学
本科毕业设计(论文)
中密度纤维板热压传热特性的研究
学院:
木材工业学院
专业:
热能与动力工程
学号:
080403229
学生姓名:
张雨龙
指导教师:
刘翔
职称:
实验师
二O一二年五月七日
摘要
研究狼尾草生物质材料人造板热压过程中传热机理以及施胶量、含水率、目标密度等重要工艺参数对传热传质过程的影响。对纤维板板坯进行热压,通过控制并采用先进的温度测定手段对热压过程中板坯中心层的温度进行了连续、自动测定。通过对板坯中心层温度变化曲线的分析,得到了纤维板板坯在热压过程中传热的基本规律。1)施胶量对快速升温段和基本恒温段的影响可以忽略不计;在慢速升温段,施胶量少的升温速率较快。2)纤维板在热压过程中,其芯层温度上升的曲线可以分为三段,即水分开始汽化前的快速升温段、水分汽化时的恒温段和水分汽化之后的慢速升温段。恒温段和慢速升温段所占的时间比例较大,对中心层达到某较高温度(超过其汽化温度)所需要的总时间起决定性的作用;快速升温段所占的时间比例较小,对总热压时间的影响较小。3)板坯的热压温度对快速升温段的升温速度的影响:热压温度的影响,升温速度随热压温度的提高而增大。4)慢速升温段的升温速度,受热压温度的影响也很明显,热压温度升高,升温速度明显增大。5)板坯内水分汽化所需要的时间:水分汽化时间随热压温度的降低而增加。6)板坯内水分的汽化温度:热压温度对汽化温度没有影响。
关键字:纤维板,热压传热,施胶量,含水率,目标密度
Abstract
Study of biomass materials from wood-based panel hot pressing process of heat transfer mechanism and sizing, moisture content, density of the target and other important parameters on heat and mass transfer process influence. On the mat by hot pressing, control and the use of advanced temperature measuring instrument in the hot-pressing process on the center layer temperature were continuous, automatic measurement. Through the slab center layer temperature change curve analysis, got the mat in hot pressing process of heat transfer in a basic law. 1) the sizing of rapid heating section and basic constant effects can be neglected; in slow heating section, sizing quantity of heating rate. 2) fiber plate in hot pressing process, its core temperature rising curve can be divided into three sections, namely water vaporization before the rapid warming period, vaporization of water when the constant and vaporization of water after the slow heating section. The constant and slow heating period of time that take a larger proportion of the center layer, to a higher temperature ( more than the temperature of vaporization ) total time required to play a decisive role; rapid warming period of time that take a smaller proportion of total press time, small effect. 3) slab hot pressing temperature on rapid heating section heating rate ef