表面處理對除濕熱傳之增強與抑制

Abstract

結露是一種相變化的過程，通常被預期有較高的熱傳效率，因此會希望藉由結露的增強來達到高效率的熱傳；此外，結露的發生也會造成室內濕度下降，過於乾燥也會使得人體不適。由此可見得人們在不同場合之下，對於結露的增強與抑制有不同的需求。 本研究以Al-5083作為基板，以十種不同表面處理方式對其進行改質，其中包含二氧化矽水溶液塗佈、二氧化矽之噴砂粗化、高分子疏水材料鍍膜接合OEGMA、類鑽碳鍍膜、陽極處理、電漿處理、碳化矽之噴砂粗化、高分子疏水材料鍍膜、奈米碳管分散液塗佈與鐵氟龍塗佈。將改質表面以原始表面作為對照組進行平行同步之結露實驗來探討不同表面性質對結露熱傳之影響。結露表面藉由顯微鏡表面觀測、接觸角量測、原子力顯微鏡表面形貌測量與表面粗糙度計算、表面熱通量計算、成核溫度判斷與表面處理之耐久度比較來進行討論。 十種表面處理中以鐵氟龍塗佈可達最大的接觸角104.0o，二氧化矽水溶液塗佈可達最小的接觸角3.9o。實驗結果顯示接觸角越大較易形成滴式結露；接觸角越小則較易形成膜式結露。接觸角降低使得成核現象提前發生，而接觸角上升則使得成核現象延後發生。其中延後成核之效果以鐵氟龍塗佈之0.75 oC為最佳，提前成核之效果則以高分子疏水鍍膜接合OEGMA之0.45 oC最佳。 親水表面相較疏水表面更利於穩定成核，不但使得成核現象可提前發生，也使得親水表面之成核速率高於疏水表面，越快將更多之相潛熱變化傳遞至實驗表面，使得親水表面之熱通量於結露初期較疏水表面上升快速，熱通量曲線之轉折也更加明顯。

Dehumidification heat transfer is a phase-change process, which is expected to have a higher heat transfer efficiency. As a result, it’s expected to achieve high heat transfer efficiency through enhancing the dehumidification. In addition, the occurrence of dehumidification can cause indoor humidity drops, and also body discomfort due to the excessive dry air. This shows that people on different occasions have different needs of the enhancement and restraint of dehumidification. In this study, Al-5083 was used as original surface with ten surface treatment including coating with SiO2 solution, roughing with Silica sand, coating with polymer bonding with OEGMA, coating with DLC, Anodizing, plasma treatment, roughing with Carborundum, coating with polymer, coating with carbon nanotube dispersions and coating with TEFLONR. Parallel synchronization dehumidification experiments with a modified surface and an original surface as a control group were conducted to discuss the different surface properties of the affectivity of the dehumidification heat transfer. Dehumidification surface by observing with microscope, measuring contact angle, topography with AFM, calculating surface roughness and surface heat flux, detecting onset of dehumidification and comparing durability was discussed in this paper. The maximum contact angle, 104o was achieved by coating with TEFLONR, the minimum contact angle, 3.9o was achieved by coating with SiO2 solution between these ten surface treatments. The results showed that the formation of DWC is prefer greater contact angle, otherwise FWC will be formed. Reduce the contact angle made nucleation occurred early. Increase the contact angle made nucleation occurred later. Coating TEFLON showed the best delay effect, and the onset of nucleation delayed by 0.75oC. Coating polymer with bonding OEGMA showed the best advance effect, and the onset of nucleation advanced by 0.45oC. Compared to hydrophobic surfaces, hydrophilic surface is easier to nucleate. Not only made nucleation occurred early, but also raised nucleation rate. More latent heat transfer to the surface make the heat flux of hydrophilic surface rising rapidly in the beginning of dehumidification and the turning of the heat flux curve become more apparent.