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研究生:吳允中
研究生(外文):Yeun-Jong Wu
論文名稱:鰭管式熱交換器於結霜條件時之熱流特性研究
論文名稱(外文):Study of Thermofluid Characteristics of Finned-and-Tube Heat Exchangers Under Frosting Conditions
指導教授:顏維謀顏維謀引用關係李弘毅李弘毅引用關係
指導教授(外文):Wei-Mon YanHung-Yi Li
學位類別:碩士
校院名稱:華梵大學
系所名稱:機電工程研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2000
畢業學年度:88
語文別:中文
論文頁數:79
中文關鍵詞:鰭管式熱交換器結霜熱傳率總熱傳係數壓降
外文關鍵詞:finned tube heat exchangerfrostingheat transfer rateoverall heat transfer coefficientpressure drop
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本研究係以實驗方式,探討平板型鰭管式熱交換器於結霜條件下,熱交換器形狀與環境參數對其熱傳及壓降特性之影響。其中,形狀參數包括不同鰭片間距與多種排管數;環境參數則包含不同風量、相對濕度、空氣側入口溫度及冷媒側入口溫度。
研究結果顯示,當固定形狀參數時,在結霜初期,熱交換器之熱傳率隨風量、入口空氣溫度、濕度增加或冷媒溫度減少而增加;但熱傳率隨時間下降幅度,則是隨入口空氣濕度增加或風量、冷媒溫度減少而增加。熱傳率、總熱傳係數U及空氣壓降ΔP等熱交換器性能隨時間而變化的幅度是結霜成長的函數,因此影響總熱傳係數與壓降變化幅度的參數與影響熱傳率的參數相同。若入口空氣相對濕度φ維持定值,入口空氣溫度Ta,i於5℃時,相較於其他入口溫度,會使 、U和ΔP有最大變化量,亦即當入口空氣高於或低於此一溫度,於相同時間時,結霜量均比Ta,i=5℃時少。
在排管數(N)效應方面,熱傳率隨排管數增加而增加,總熱傳係數則反之。總熱傳係數隨時間而下降的幅度則隨排管數增加而減少;空氣壓降上升幅度亦隨N增加而減少,但在φ=60%或Tr,i=-10℃等不利結霜的環境參數條件下,壓降上升幅度則隨N增加而增加。
In this study, the heat transfer and pressure drop performance of flat plate finned tube heat exchangers operating under frosting conditions was investigated by experiments. The experiment was conducted to show the effects of various geometric and environmental parameters on the thermofluid performance of the heat exchangers. The geometric parameters include the fin pitch and the row number. Environmental parameters include inlet air temperature, relative humidity of inlet air, air flow rate and inlet refrigerant temperature.
The experimental results show that, under a fixed geometric parameter condition, the heat transfer rate of the heat exchangers at the initial stage of frosting increases with the increase in the air flow rate, inlet air temperature and humidity or decrease in the inlet refrigerant temperature. The drop rate of the heat transfer increases with inlet air temperature or the air flow rate. Because the variations of the heat transfer rate, overall heat transfer coefficient U and pressure drop ΔP are function of the frost growth. Therefore, the parameters which affect the U and ΔP are the same to those which affect the variations of the heat transfer rate. If the relative humidity of the air is fixed, the variations of , U and ΔP are more significant under Ta,i=5℃. When inlet air temperature is higher or lower than 5℃, the amount of frost accumulation will be leas than that of Ta,i=5℃.
For the effects of the row number (N), the heat transfer increases with the increase in the row number. But the overall heat transfer coefficient shows the inverse trend. The drop rate of overall heat transfer coefficient decreases with the increase in the row number. Additionally, the rise rate of pressure drop decreases with the increase of row number. But under f=60% or Tr,i=-10℃ condition, the rise rate of pressure drop increases with N.
誌謝 ……………………………………………………………………Ⅰ
摘要 ……………………………………………………………………Ⅱ
ABSTRACT ………………………………………………………………Ⅲ
目錄 ……………………………………………………………………Ⅳ
表錄 ……………………………………………………………………Ⅵ
圖錄 ……………………………………………………………………Ⅶ
符號說明 ………………………………………………………………Ⅹ
一、前言 ………………………………………………………………1
二、文獻回顧 …………………………………………………………3
2.1 各種幾何形狀的結霜研究 …………………………………4
2.2 熱交換器結霜研究 …………………………………………7
三、實驗數據分析 ……………………………………………………11
3.1 熱傳率之計算 ………………………………………………11
3.2 總熱傳係數U 之計算 ………………………………………12
四、實驗設備與方法 …………………………………………………14
4.1 實驗設備 ……………………………………………………14
4.1.1 環控室 ………………………………………………14
4.1.2 測試本體 ……………………………………………15
4.1.3 風洞測試系統 ………………………………………15
4.1.4 冷媒循環系統 ………………………………………16
4.1.5 數據擷取系統 ………………………………………16
4.1.6 量測儀器 ……………………………………………16
4.2 實驗規劃及步驟 ……………………………………………17
4.2.1 實驗操作步驟 ………………………………………18
4.2.2 數據分析方法 ………………………………………19
五、結果與討論 ………………………………………………………33
5.1 空氣流率的效應 ……………………………………………34
5.2 相對濕度的效應 ……………………………………………37
5.3 入口空氣溫度的效應 ………………………………………39
5.4 入口冷媒溫度的效應 ………………………………………41
5.5 鰭片間距的效應 ……………………………………………41
5.6 排管數的效應 ………………………………………………42
5.6.1 排管數於不同空氣流率下的影響 …………………43
5.6.2 排管數於不同相對濕度下的影響 …………………44
5.6.3 排管數於不同入口空氣溫度下的影響 ……………45
5.6.4 排管數於不同入口冷媒溫度下的影響 ……………46
5.7 固定風量與固定離心風扇轉速的熱交換器性能比較 ……47
六、結論與未來研究方向 ……………………………………………69
6.1 結論 …………………………………………………………69
6.2 未來研究方向 ………………………………………………70
參考文獻 ………………………………………………………………72
附錄A 重複性試驗 ……………………………………………………76
附錄B 不準度分析 ……………………………………………………77
簡歷 ……………………………………………………………………79
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