混合山型紋角度之板式熱交換器性能比較;Performance evaluation of mixed chevron angle plate heat exchanger

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题名:	混合山型紋角度之板式熱交換器性能比較;Performance evaluation of mixed chevron angle plate heat exchanger
作者:	郭芸廷;KUO, YUN-TING
贡献者:	機械工程學系
关键词:	混合山型紋角度熱交換器;R1234yf;R134a;流動沸騰;冷凝;mixed chevron plate heat exchanger;R1234yf;R134a;flow boiling;condensation
日期:	2021-10-20
上传时间:	2021-12-07 13:47:38 (UTC+8)
出版者:	國立中央大學
摘要:	山型紋板式熱交換器已廣泛應用在家用及工業用途，本研究使用的是30+65o混和山型紋板式熱交換器及其對照組65o板式熱交換器，以單相水為流體、溫度30oC、從Re=300到1000的j及f利用Webb的PEC評估法中的VG-1比較兩種測試段之間的整體性能優劣，發現65o板式需要的熱傳面積比約為混和角度板式的0.6倍，代表65o板式的性能高了混和角度板式約1.67倍，且這樣的差異幾乎不隨流量改變而改變。而在流動沸騰的實驗中，R134a的山型紋角度65o測試段和混和角度測試段的面積比值約為1到1.2倍、R1234yf的面積比則為1.2到1.3倍，代表在流動沸騰的兩相實驗中30+65o板式表現較佳，可能是因為不同流譜及流體流動方式下造成主要影響的冷媒性質不同，進而讓兩種測試段及兩種冷媒之間的熱傳性質及壓降比值不同，讓得出的熱傳面積比會有約10-20%的差異。在兩相冷媒兩相冷凝實驗時，R134a和R1234yf對應到的熱傳面積比則是0.7-1倍及0.6-0.9倍，兩種冷媒間的差異也約是10%，也可以用同樣的方式解釋，因為不同熱傳機制及流譜的影響，而使得30+65o板式的性能在冷凝實驗中略低於65o板式。總體而言， 30+65o板片在流動沸騰時具備優勢，在冷凝時性能勉強和65o板式的性能持平，但是在單相水的實驗中完全不具有優勢。而冷媒性質造成的差異，導致30+65o板片在冷凝實驗中使用R134a會有較佳的性能表現，在流動沸騰中反而使用R1234yf會讓混和角度的板式熱交換器有性能優勢。 ;Chevron plate heat exchangers have been widely used in domestic and industrial applications. In this study, PHEs with 65o and 30+65o chevron angle were used as test sections. The experiment condition was temperature at 30oC and Re number ranging from 300-1000 when using single phase water as working fluid. After conducting experiment, the j and f of different chevron angle PHE were then evaluated by using Webb′s VG-1 PEC method. The results indicated that PHE with 65o angle required only 0.6 times of heat transfer area comparing to mix angle PHE when performing same heat transfer capability. Yet in flow boiling experiment, the heat transfer area ratio of PHE with angle 65o and the mixed angle PHE was about 1 to 1.2 times using R134a, and the area ratio of R1234yf was 1.2 to 1.3 times, which implied that mixed angle PHE has better heat transfer performance. It could be caused by the difference between refrigerant thermal properties, and the differences of flow patterns, heat transfer mechanisms, and the flow conditions between 65o angle PHE and mixed angle PHE. The interaction between these parameters result in 10-20% higher heat transfer area ratio of R1234yf comparing to R134a. As for condensation experiment, the consequences were similar with those of flow boiling, but because of heat transfer mechanism difference, the heat transfer area ratio corresponding to R134a and R1234yf is 0.7-1 times and 0.6-0.9 times. The difference between the two refrigerants is about 10%. In general, mixed angle PHE had advantages in flow boiling, barely equal to that of the 65o angle PHE when condensing, but no advantage in single-phase water experiments. The refrigerant property differences caused R1234yf was preferred when flow boiling while R134a was preferred when condensation.
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