臺灣博碩士論文加值系統

本研究利用透明板式熱交換器，使用空氣與水為工作流體，模擬冷媒在蒸發器入口的狀態，雷諾數範圍為50到250，用數位相機錄影的方式記錄不同擋板配置流動分布情況進行可視化觀察，實驗參數有不同擋板位置、不同擋板開口、熱交換器之入口處配置擋板和擋板與擋板間的間距大小。
實驗結果得知入口集管內部的板擋對流動分布有明顯的影響，擋集管上部的配置可以使入口集管內液氣均勻混合。而之後實驗配置皆以擋集管上部為配置，集管內部配置擋集管直徑的25%和50%兩者配置，對整體的流動分布差異不大，但集管內擋集管直徑的50%液氣混合較擋集管直徑的25%均勻。在入口設置擋板，受擋板的影響能迫使液氣混合後再流入入口集管可以有效改善流動分布，在入口配置擋集管直徑的25%和50%的擋板皆有好的流動分布。改變擋板與擋板間，兩擋板間距為五個平行流道，液氣混合的效果有好的流動分布，相對進出口的壓降也是最大的。

In this study, air-water two phase flow visualization experiment has been carried out using transparent acrylic plate heat exchanger to understand the flow distribution inside header and channels. The purpose is to simulate the refrigerant’s flow distribution inside evaporator using air-water as working fluid and improve the flow distribution by introducing the baffles. Experiments are carried out for Reynolds numbers ranging from 50 to 250 for two different baffle arrangement, namely, baffle on top and baffle on bottom of the header. Detailed studies on the effect of different baffle flow area ratio, header inlet flow area ratio, and baffle spacing are also carried out.
The result shows that the insertion of baffle into the inlet of header has significant affect on flow distribution inside the plate heat exchanger without any header inlet flow area restriction. The baffle arrangement on upper half of the header showed uniform air-water mix in comparison to baffle arranged on bottom half of the header. So out of three different baffle flow area ratios (25%, 50% and 75%)at baffle arranged on upper half of header configuration, 25% and 50% flow area ratio significantly improved air-water mix compare to 75%. Between 25% and 50% flow area ratio, there is no significant difference in air-water mix has been observed. By restricting the flow at the entrance of header using baffle, the result showed significant improvement of air-water mix. Under restricted inlet flow condition, the baffle spacing on 5 channels, a uniform air-water flow distribution is achieved. But the pressure drop significantly increased.

摘要 i
Abstract ii
目錄 iii
圖目錄 vii
表目錄 xii
符號說明 xiii
第一章 前言 1
1.1 研究背景與動機 1
1.2 研究目的 4
第二章 文獻回顧 5
2.1 兩相流體在多平行流道分布不均的影響 6
2.1.1 平行流道熱交換器 7
2.1.2 平行流道和集管的擺設方向 8
2.1.2.1 集管垂直擺設 9
2.1.2.2集管水平擺設 11
2.1.3 流體性質影響 11
2.2 改善集管內流動分布不均的方法 12
2.3總結 20
第三章 實驗方法 21
3.1 測試段 22
3.1.1 板片幾何 22
3.1.2 板式熱交換器 23
3.1.3 檔板 25
3.2 實驗系統 27
3.3 實驗參數 28
3.4 實驗量測設備 29
3.4.1 溫度量測 29
3.4.2 差壓量測 31
3.4.3 流量量測 32
3.4.4 影像拍攝設備 32
3.5實驗步驟 32
3.6數據換算 33
3.7 流道速度分析 34
第四章 實驗結果與討論 35
4.1 擋板排列型式對流動分布的影響 37
4.1.1 無擋板 37
4.1.2 擋集管上半部 40
4.1.3 擋集管下半部 44
4.1.4 交錯擋 47
4.1.5 不同擋板位置比較 50
4.2 不同擋板擋集管直徑的比例對流動分布的影響 52
4.2.1 擋板擋集管直徑的25% 52
4.2.2 擋板擋集管直徑的75% 56
4.2.3 不同擋板擋集管直徑的比較 59
4.3熱交換器入口對流動分布的影響 61
4.3.1 擋集管直徑25% 61
4.3.2擋集管直徑50% 64
4.3.3擋集管直徑75% 68
4.3.4 熱交換器入口擋集管直徑比例的比較 71
4.4 入口和集管內不同擋板擋集管直徑比例對流動分布的影響 73
4.4.1 入口擋集管直徑的25%與集管內擋直徑的25% 73
4.4.2入口擋集管直徑的25%與集管內擋直徑的50% 77
4.4.3入口擋集管直徑的50%與集管內擋直徑的25% 80
4.4.4入口擋集管直徑的50%與集管內擋直徑的50% 84
4.4.5熱交換器入口和不同擋板擋集管直徑比例的比較 87
4.5 改變擋板與擋板間距對流動分布的影響 88
4.5.1 擋板間距每十個流道 88
4.5.2擋板間距每十五個流道 92
4.5.3擋板間距每二十個流道 95
4.5.4擋板間距每二十五個流道 99
4.5.5擋板間距每三十個流道 102
4.5.6 擋板與擋板間距的比較 106
第五章 結論 107
參考文獻 109

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