| 摘要: | 為了解決兩相蒸發冷卻技術應用於高發熱量電子元件散熱時所面臨的流動不穩定問題，並替代常用且具有高全球暖化潛勢（GWP = 1030）的冷媒 HFC-245fa，本研究提出了以階梯型式流道設計來改善微流道蒸發器之性能，並選用FMD-50為替代工作流體，其GWP值為7。
相較於直線型流道，階梯型流道可有效降低冷板的壓降。其原因在於，當相同流量進入熱交換器時，流體於下游區域不再受限於狹窄的微流道空間，流道長度亦相對縮短，使流體不易受到幾何限制而產生過大的流動阻力，進而降低整體壓降。反觀直線型流道，由於流體受到流道幾何限制，導致其壓降相對較高。
在階梯流道中，固定流道寬度為0.15mm，流道數量為80，並透過將鰭片高度為了解決兩相蒸發冷卻技術應用於高發熱量電子元件散熱時所面臨的流動不穩定問題，並替代常用且具有高全球暖化潛勢（GWP = 1030）的冷媒 HFC-245fa，本研究提出了以階梯型式流道設計來改善微流道蒸發器之性能，並選用FMD-50為替代工作流體，其GWP值為7。
相較於直線型流道，階梯型流道可有效降低冷板的壓降。其原因在於，當相同流量進入熱交換器時，流體於下游區域不再受限於狹窄的微流道空間，流道長度亦相對縮短，使流體不易受到幾何限制而產生過大的流動阻力，進而降低整體壓降。反觀直線型流道，由於流體受到流道幾何限制，導致其壓降相對較高。
在階梯流道中，固定流道寬度為0.15mm，流道數量為80，並透過將鰭片高度由3mm降低至1mm，以探討其對流動與熱傳特性的影響。以階梯型式流道來改善直線流道，在HFC-245fa中，可以將低13% 至68% 之壓降，然而其熱傳係數亦同時降低約 17% 至 20% 。在FMD-50中，無論階梯流道或是直線流道，其熱傳性能彼此間差異不大，但在壓降方面，只有在低流量中，直線流道之壓降高於階梯流道10% 至 70%，但在中、高流量中，兩者間的壓降差異不大。
由3mm降低至1mm，以探討其對流動與熱傳特性的影響。以階梯型式流道來改善直線流道，在HFC-245fa中，可以將低13% 至68% 之壓降，然而其熱傳係數亦同時降低約 17% 至 20% 。在FMD-50中，無論階梯流道或是直線流道，其熱傳性能彼此間差異不大，但在壓降方面，只有在低流量中，直線流道之壓降高於階梯流道10% 至 70%，但在中、高流量中，兩者間的壓降差異不大。
;To address the flow instability encountered in two-phase evaporative cooling applied to the thermal management of high–heat-flux electronic components, and to replace the commonly used refrigerant HFC-245fa with a high global warming potential (GWP = 1030), this study proposes a stepped-channel design to enhance the performance of microchannel evaporators and adopts FMD-50 as an alternative working fluid, with a global warming potential (GWP) value of 7.
Compared with straight channels, the stepped-channel design effectively reduces the pressure drop of the cold plate. This improvement is attributed to the fact that, under the same inlet flow rate, the downstream region is no longer constrained by narrow microchannel geometry and the effective flow length is shortened. Consequently, the flow resistance induced by geometric confinement is alleviated, leading to a lower overall pressure drop. In contrast, straight channels impose continuous geometric constraints along the flow path, resulting in a relatively higher pressure drop.
In the stepped-channel configuration, the channel width is fixed at 0.15 mm with a total of 80 channels, and the fin height is reduced from 3 mm to 1 mm to investigate its effects on flow and heat transfer characteristics.When HFC-245fa is used as the working fluid, the stepped-channel design reduces the pressure drop by approximately 13% to 68% compared with the straight-channel design; however, the heat transfer coefficient is simultaneously reduced by about 17% to 20%. For FMD-50, the heat transfer performance of the stepped and straight channels shows no significant difference. In terms of pressure drop, the straight-channel design exhibits a 10% to 70% higher pressure drop than the stepped-channel design under low flow rate conditions, whereas at medium and high flow rates, the pressure drop difference between the two configurations becomes negligible. |
