一种具有模式搅拌的微波反应釜内多物理场特性分析

doi:10.16085/j.issn.1000-6613.2021-1123

摘要/Abstract

摘要：

生物柴油作为一种新能源已引起了广泛关注，微波加热因其高效性被广泛用于制备生物柴油。然而，微波的不均匀加热是目前亟须解决的主要问题，因此本文在微波夹层反应釜内引入一种模式搅拌器，通过COMSOL软件耦合麦克斯韦、传热方程，对微波加热过程进行多物理场仿真，并采用动网格技术处理模式搅拌，探讨不同模式搅拌器参数对微波加热特性的影响，发现：①与无模式搅拌的微波加热模型相比，模式搅拌时刻改变物料中的电场分布，从而改善加热效率和加热均匀性；②物料平均温度与温度变异系数（COV）随搅拌器高度和长度的增加，整体上呈下降趋势；③物料平均温度随搅拌转速的增加线性提高，COV随转速的增加整体上呈上升趋势；④通过响应面分析发现对平均温度和COV产生影响的因素为：搅拌器高度>搅拌转速>搅拌器长度，其中搅拌器高度与转速的交互作用对平均温度影响显著；最后综合考虑平均温度和COV，响应面优化后的最佳搅拌条件为：搅拌器高度λ_H=0.164、搅拌器长度λ_B=0.31、搅拌转速N=30r/min，此时COV=0.11×10^-2、平均温度为22.15℃。

关键词: 微波反应釜, 生物柴油, 模式搅拌器, 动网格, 加热均匀性, 多物理场仿真

Abstract:

As a new energy source, biodiesel has attracted widespread attention. Microwave heating is widely used to produce biodiesel due to its high efficiency. However, the non-uniform heating of microwave is the main problem that needs to be solved urgently. So, a mode stirrer was introduced into a microwave reactor with an interlayer, and the multi-physics field simulation of microwave heating process was carried out by coupling the Maxwell and heat transfer equations with COMSOL software. The arbitrary Lagrangian-Eulerian method was used to deal with the mode stirring, and the influence of different mode stirrer parameters on the microwave heating characteristics was discussed. The results showed that compared with the microwave heating model without mode stirring, the electric field distribution in the material was changed at all times by mode stirring, thus improving the heating efficiency and heating uniformity. With the increase of the height and length of the mode stirrer, the material average temperature and coefficient of variation (COV) showed a downward trend on the whole. The average temperature of material increased linearly with the increase of stirring speed, and COV showed an overall upward trend with the increase of stirring speed. Through response surface analysis, it was found that the primary and secondary order that affected the average temperature and COV was: stirrer height > stirrer speed > stirrer length, where the interaction between the stirrer height and the speed had a significant effect on the average temperature. Considering the average temperature and COV, the best stirring conditions obtained by response surface optimization were stirrer height λ_H of 0.164, stirrer length λ_B of 0.31, stirring speed N of 30r/min, COV of 0.11×10^-2, and average temperature of 22.15℃.

Key words: microwave reactor, biodiesel, mode stirrer, moving grid, heating uniformity, multi-physical field simulation

中图分类号:

TQ052.5

邹鹏程, 金光远, 李臻峰, 宋春芳, 韩太柏, 祝玉莲. 一种具有模式搅拌的微波反应釜内多物理场特性分析[J]. 化工进展, 2022, 41(5): 2301-2310.

ZOU Pengcheng, JIN Guangyuan, LI Zhenfeng, SONG Chunfang, HAN Taibai, ZHU Yulian. Analysis of multi-physical field characteristics in a microwave reactor with a mode stirrer[J]. Chemical Industry and Engineering Progress, 2022, 41(5): 2301-2310.

图/表 23

图1 微波夹层反应釜

表1 微波反应釜结构参数

腔体高度H₀/mm	底部高度c₀/mm	反应釜直径T/mm	波导高度h₀/mm	夹层厚度 d/mm	物料高度 /mm
390	60	260	344	20	240

表2 植物油参数

密度 /kg·m^-3	动力黏度/Pa·s	相对磁导率	热导率 /W·m^-1·K^-1	恒压热容 /J·kg^-1·K^-1	比热率	相对介电常数	电导率 /S·m^-1
965	0.065	1	0.15	3000	1	2.73- 0.13j^［24］	0

图2 仿真计算流程

图3 网格剖面

图4 网格独立性分析

图5 两种仿真计算方法的S11

图6 有无模式搅拌下物料的电场、温度分布

图7 有无模式搅拌器下物料内电场模的平均值

图8 有无模式搅拌器下物料的平均温度和COV

图9 长时间仿真有无模式搅拌下物料的平均温度与COV

图10 不同高度模式搅拌器下物料的电场、温度图

图11 不同搅拌器高度下物料的平均温度和COV

图12 不同搅拌器高度下S11的变化

图13 不同搅拌器长度下物料的电场、温度分布

图14 不同长度模式搅拌器下物料的平均温度和COV

图15 不同模式搅拌器长度下的S11变化

图16 不同搅拌转速下物料的电场、温度图

图17 不同搅拌转速下物料的平均温度和COV

图18 模式搅拌器不同转速下旋转一圈的S11

表3 响应面分析的试验方案和结果

试验号	A （搅拌器长度λ_B）	B （搅拌器高度λ_H）	C （搅拌转速N）/r·min^-1	Y₁（COV）	Y₂ （平均温度）/℃
1	0.31	0.06	18	0.164 $×$ 10^-2	21.890
2	0.46	0.06	18	0.196 $×$ 10^-2	22.005
3	0.31	0.32	18	0.187 $×$ 10^-2	21.421
4	0.46	0.32	18	0.146 $×$ 10^-2	21.401
5	0.31	0.19	6	0.074 $×$ 10^-2	20.665
6	0.46	0.19	6	0.064 $×$ 10^-2	20.660
7	0.31	0.19	30	0.121 $×$ 10^-2	22.026
8	0.46	0.19	30	0.117 $×$ 10^-2	21.761
9	0.385	0.06	6	0.243 $×$ 10^-2	20.955
10	0.385	0.32	6	0.185 $×$ 10^-2	20.733
11	0.385	0.06	30	0.252 $×$ 10^-2	22.791
12	0.385	0.32	30	0.140 $×$ 10^-2	21.917
13	0.385	0.19	18	0.126 $×$ 10^-2	21.290
14	0.385	0.19	18	0.126 $×$ 10^-2	21.290
15	0.385	0.19	18	0.126 $×$ 10^-2	21.290
16	0.385	0.19	18	0.126 $×$ 10^-2	21.290
17	0.385	0.19	18	0.126 $×$ 10^-2	21.290

表3 响应面分析的试验方案和结果

试验号	A （搅拌器长度λ_B）	B （搅拌器高度λ_H）	C （搅拌转速N）/r·min^-1	Y₁（COV）	Y₂ （平均温度）/℃
1	0.31	0.06	18	0.164 $×$ 10^-2	21.890
2	0.46	0.06	18	0.196 $×$ 10^-2	22.005
3	0.31	0.32	18	0.187 $×$ 10^-2	21.421
4	0.46	0.32	18	0.146 $×$ 10^-2	21.401
5	0.31	0.19	6	0.074 $×$ 10^-2	20.665
6	0.46	0.19	6	0.064 $×$ 10^-2	20.660
7	0.31	0.19	30	0.121 $×$ 10^-2	22.026
8	0.46	0.19	30	0.117 $×$ 10^-2	21.761
9	0.385	0.06	6	0.243 $×$ 10^-2	20.955
10	0.385	0.32	6	0.185 $×$ 10^-2	20.733
11	0.385	0.06	30	0.252 $×$ 10^-2	22.791
12	0.385	0.32	30	0.140 $×$ 10^-2	21.917
13	0.385	0.19	18	0.126 $×$ 10^-2	21.290
14	0.385	0.19	18	0.126 $×$ 10^-2	21.290
15	0.385	0.19	18	0.126 $×$ 10^-2	21.290
16	0.385	0.19	18	0.126 $×$ 10^-2	21.290
17	0.385	0.19	18	0.126 $×$ 10^-2	21.290

图19 以COV为响应值的响应面

图20 以平均温度为响应值的响应面

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