论文总字数：18652字

摘 要

本文针对原有果蔬低温高压膨化干燥技术，通过研究其发展的现状以及对厂家的现场调研，总结出了生产中存在的一些普遍问题。并对原加工设备进行了理论上的改进和研究，通过数值分析对加工设备进行了设计计算。

针对低温高压膨化干燥技术，利用传热学理论和热力学定律，对加热加压阶段、膨化阶段、真空冷却阶段三个过程进行分析，初步计算出每个阶段蒸发出的的水分质量以及需要提供的热量。加热加压阶段所需的膨化压力需要达到1.4MPa，而当膨化罐内水蒸气的分压力达到饱和蒸汽压力的时候，水分将不再析出，此阶段出来的水分有0.3kg。膨化阶段出现闪蒸，闪蒸出来的水分大约为0.17kg，最后还要有2kg左右的水分需要在保温真空抽干过程中进行蒸发干燥。

在计算膨化罐内自然对流换热系数时提出了简化计算方法的模型，将膨化罐内壁看做恒壁温；将热管的壁面和所带翅片的壁面近似看做均匀壁温；计算膨化罐内壁面的格拉晓夫数时，将内壁面分成上下两个半圆，分别将上下两个半圆看做平板换热，上壁面是热面朝下的平板换热，下壁面是热面朝上的平板换热；计算热管及翅片壁面的格拉晓夫数时，由于热管所带的翅片形式为纵向翅片，所以可以将热管圆管及翅片展开部分看做水平板，上下两个面分别看做热面朝上和热面朝下形式的换热，分别计算其换热系数。

用Gambit软件对新设计的膨化罐截面进行建模，利用ANSYS有限元分析软件对所设计的新型膨化罐内部的温度场进行了模拟，得到截面的温度分布图。模拟了膨化罐内几种不同的热管排布方式，得出了几种不同的温度分布。

关键词：果蔬干燥；低温高压膨化；加热热管；Gambit；Fluent

Analysis and Simulation of heat and mass transfer process of heating and drying of fruits and vegetables

Abstract

In this paper, refer to the low temperature and high pressure expanding and drying technology for fruits and vegetables, Some general problems in production are summarized by studying the present situation of the development and the field investigation of the factory, the improvement and research of the original processing equipment are also carried out.

Aiming at low temperature and high pressure expanding drying technology, by using the theory of heat transfer and the law of thermodynamics, the heating and pressure stage, the expansion stage, the vacuum cooling stage of the three processes were analyzed. Preliminary calculation of the water quality of each stage of evaporation and the need to provide the heat. The required expansion pressure during the heating and pressing need to reach 1.4MPa. When the partial pressure of water vapor when the expanded tank reaches the saturation vapor pressure, the water will no longer and the phase out of the water is 0.3 kg. The water rapid evaporation during the expansion stage, the flash out of the water is about 0.17kg. In the end, there are about 2kg of the water needs to be done during the thermal insulation vacuum drying process.

Gambit software was used to model the expansion tank section of the new design.The temperature field of the new expansion tank was simulated by ANSYS finite element analysis software, and the temperature distribution of the cross section was obtained. Experimental simulation of the expanded tank in several different heat pipe arrangement and distribution of the different temperature is obtained, finally choose the temperature distribution of heat pipe the optimum arrangement of the uniform.

key words: Heating and drying of fruits and vegetables; Low temperature and high pressure expanding; heat pipe； Gambit； Fluent

目录

摘要……………………………………………………………………Ⅰ

Abstract…………………………………………………………………Ⅱ

第1章 绪论……………………………………………………………………1

1.1 背景意义……………………………………………………………………1

1.2 果蔬干燥现有技术…………………………………………………………1

1.3 国内外研究现状……………………………………………………………2

1.4 本章小结……………………………………………………………………4

第2章 果蔬加热干燥工艺分析及热力计算…………………………5

2.1 果蔬加热膨化技术介绍…………………………………………………5

2.2 果蔬加热干燥工艺过程分析及工艺参数的确定………………………7

2.3 果蔬不同干燥过程的传热传质分析……………………………………9

2.4 果蔬加热干燥过程模型的分析与简化…………………………………13

2.5 本章小结…………………………………………………………………16

第3章 果蔬干燥设备内部温度场的模拟…………………………18

3.1 模拟软件的简介…………………………………………………………18

3.2 模拟模型的建立…………………………………………………………18

3.3 模拟求解…………………………………………………………………21

3.4 温度场分布………………………………………………………………24

3.5 本章小结…………………………………………………………………25

第4章 总结与展望…………………………………………………26

4.1 总结………………………………………………………………………26

4.2 未来工作建议……………………………………………………………26

致谢……………………………………………………………………28

参考文献………………………………………………………………29

第一章 绪论

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