模擬粒子床在焙炒爐內溫度場的變化

Simulation of the granule bed on the temperature field within heating furnace

徐榮照(Jung-Chao Hsu)

指導教授 ： 顏政雄

淡江大學/工學院/機械與機電工程學系碩士班/碩士(2007年)

https://doi.org/10.6846/TKU.2007.00659

摘要

本論文主要是探討粒子床加熱過程中，使粒子床出口的溫度約在200oC左右，利用有限元素ANSYS軟體模擬在焙炒的過程中，爐壁、芝麻及空氣的溫度變化。研究分為兩個部分:
第一為實驗部分，芝麻熱傳導係數的量測，在溫度範圍20~60oC時，以相同質量的芝麻，分別從3%~20%含水率的芝麻進行測量，以了解芝麻在不同含水率時溫度與熱傳導係數k值的關係，並且得知含水率越高，其熱傳導係數也越高，但是含水率超過13%其k值所增加的幅度也不多，所以本研究取13%含水率的熱傳導係數k值，來做為分析的參數，其熱傳導係數為k = 0.1507 + 0.0012T，式子中的溫度T單位為o C。
第二為模擬分析部分，利用ANSYS軟體進行分析，先建構三個部分的模型，粒子床、空氣、爐壁，然後輸入個別性質參數，如：爐內外的對流係數、爐內空氣流速、爐內粒子床流速及角速度、爐壁分別之不同的三段熱通量等參數，進行模擬，找出焙炒爐最佳化參數。
當給予爐壁的總熱通量為10,500 W/m2，熱通量比為2:3:2時，分別為前段、中段、後段(預熱、加熱、冷卻)，在沒有轉動效應且空氣流速為6.97m/s及4.2m/s，可以得知空氣流動的效應，當流速較大時，熱量就會被帶走，平均溫度也會降低，避免溫度過高。
而在總熱通量為8,000W/m2時，選用熱通量比分別為1:2:1，1:3:2，2:2:2，2:3:1，2:3:2，當轉速分別為10rpm和15rpm時，而出口平均溫度接近200 o C，就轉速10rpm的爐子而言，熱通量比為1:2:1時，粒子床出口平均溫度為最佳，就轉速15rpm的爐子而言，熱通量比為2:2:2時，粒子床出口平均溫度為最佳。

關鍵字

熱傳導 ； 對流 ； 旋轉爐 ； 模擬 ； 滾動效應 ； 有限元素 ； 粒子床

並列摘要

This thesis mainly studies heating process of the granule bed and makes the outlet of the granule bed temperature approximately in 200oC. Using the element software of ANSYS simulates the temperature changes of the furnace, sesame and air during the baking process. The research includes two parts:
The first part is the experimental part which is about the measure of the thermal conductivity coefficient of the sesame. In order to find out the relations between the temperature and the thermal conductivity coefficient k value in different moisture degrees of the sesame, the research proceeds to measure separately moisture degrees of the sesame from 3% to 20%, in the temperature range 20oC~60oC, and the same qualitative sesame. According to this measurement, It shows that the more moisture degree, the more conductivity coefficient. But the moisture degree which exceeds 13%, the k value does not increase too much range. Therefore, this research selects the thermal conductivity coefficient k value of the moisture degree of 13% to be the analytic parameter. Its thermal conductivity coefficient is k =0.1507 + 0.0012T, the temperature T unit in the equation is oC.
The second part is simulation analysis which uses ANSYS software. At the beginning, the model which includes three parts: granule bed, air, and furnace are chosen for analysis. Input date are the specific parameters such as the convection coefficient of inside and outside furnace, the air flow of the furnace, the granule bed flow and angular speed of the furnace, and different three sections of heat flux for furnace, then begin to simulate and find out the optimization parameter of heating furnace.
While providing the total heat flux of furnace is 10,500 W/m2 and the heat flux ratio is 2:3:2 which respectively is front section, mid section, and back section (preheating, heating, and cooling). In no rotary effect and the air flow is 6.97m/s and 4.2m/s, due to the effect of air flow, when the air flow is higher, the heat will be taken away and the average temperature will be reduced in order to prevent temperature from being too high.
When the total heat flux is 8000W/m2, the heat flux ratio is respectively 1:2:1, 1:3:2, 2:2:2, 2:3:1, 2:3:2. In the condition of the outlet of the granule bed temperature approximately in 200oC, when the rotational speed of the furnace is 10rpm and heat flux ratio is 1:2:1, the average temperature of outlet of the granule bed is the most optimal result; when the rotational speed of the furnace is 15rpm and heat flux ratio is 2:2:2, the average temperature of outlet of the granule bed is the most optimal result.

並列關鍵字

granule bed ； rotary kiln ； heating furnace ； thermal conductivity ； ANSYS ； temperature field ； heat flux

參考文獻

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