冰泥於超疏水表面的熱傳與流動特性

Abstract

近年來，隨著全球暖化的問題日益加劇，能源消耗量持續上升，而空調系統在建築領域的耗電量占比相當高。發展兼具減碳效益與高效能的空調系統成為當今最重要的課題之一。因此，儲冰式空調逐漸受到關注，此系統可於用電離峰時段製冰並儲存冷能，於尖峰負載時段釋放冷氣，達到削峰填谷與提高能源使效率的效果。冰泥作為儲冰式空調系統的工作流體，不僅在製備過程中能有效減少對環境的損害，更因冰具備相當高的潛熱，使其擁有良好的熱傳性能。然而，目前針對冰泥於水平管道內的熱傳機制與流動特性的研究仍相對有限，且尚無文獻探討冰泥在超疏水表面的熱傳與流動行為。 本研究探討冰泥於層流的條件下，於純銅表面以及超疏水表面下的熱傳與流動特性。冰泥為由冰顆粒與載體溶液所組成的固液二相流體，藉由冰本身高潛熱的特性，展現出優異的儲能與熱傳能力，同時具備良好的流動性。IPF (Ice Packing Factor)為冰泥中固態冰所佔的體積比例，為影響冰泥熱傳與流動性質的重要參數。本研究首先進行單相水的實驗，結果與文獻中的經驗公式相符，驗證了系統的可靠性。接續以IPF分別為5%、10%、與15%的冰泥進行實驗，探討IPF、雷諾數與表面親疏水性對冰泥整體熱傳與流動性能的影響。 熱傳實驗結果顯示，IPF 5%冰泥的熱對流係數與單相水相近，隨著IPF提升至10%，熱傳性能明顯增強，相較於單相水，熱對流係數提升大約49.82%；然而進一步提升至IPF 15%時，熱傳性能趨於飽和，此現象與冰泥在管道中的流動型態變化有關。除此之外，在超疏水表面下，冰泥的熱對流係數相較於純銅表面提升約35%；此外，壓降實驗結果顯示，冰泥的壓降隨著IPF與雷諾數增加而上升，其變化趨勢與Darcy-Weisbach Law相符。與此同時，當冰泥流經超疏水表面時，其壓降相較於純銅表面降低約15%。研究結果顯示，超疏水表面有助於提升冰泥的熱傳與流動性能。綜合上述，本研究於層流操作條件下，比較冰泥於純銅表面與超疏水表面的熱傳與流動特性，探討不同表面性質對其性能的影響。實驗結果顯示，冰泥的熱傳性能與其流動型態密切相關，且超疏水表面不僅能有效提升冰泥的熱傳同時降低流動阻力。本研究填補了冰泥於超疏水管道中熱流行為的研究空缺，亦為未來儲冰式空調系統的設計提供了實驗基礎，未來若能將此技術應用於實際熱交換器，可望進一步提升系統整體熱交換效率，實現節能減碳的目標。

In recent years, the global warming and higher energy demand have made it clear that building air-conditioning consumes an outsized share of electricity. Accordingly, the development of cooling technologies that combine high energy efficiency with carbon-reduction potential has become a critical research priority. Ice Storage air-conditioning has emerged as a promising approach: ice can be produced during off-peak hours, stored as cold energy, and discharged during peak demand, thereby flattening the load curve and improving overall energy utilization. As the working fluid in such system, ice slurry has two key benefits: it can be produced in an eco-friendly way, and its high latent heat gives it excellent thermal performance. However, fundamental knowledge of the convective heat transfer mechanisms and flow behavior of ice slurry in horizontal channels remains sparse, and no studies have investigated its performance on superhydrophobic surface. This study therefore investigated the heat transfer and flow characteristics of ice slurry flow over both plain copper and superhydrophobic surface, with the aim to guide the design of ice slurry storage air conditioning systems. This study investigates the heat transfer and flow characteristics of ice slurry under laminar flow regime in channels with plain copper and superhydrophobic surface. Ice slurry, a solid-liquid two-phase flow comprising ice particles and a carrier fluid, exhibits exceptional energy storage and heat transfer capabilities due to the latent heat of ice. The ice packing factor (IPF), defined as the volume fraction of solid ice in the ice slurry, significantly influences heat transfer performance and flow behavior. The single-phase experiment results confirm the validity of the experimental system, as a convective heat transfer coefficient of single-phase water showed a good agreement with established empirical correlation. Subsequent experiments were performed with ice slurry at IPF 5%, 10% and 15% to evaluate the effect of IPF, Reynolds number and surface wettability on overall thermal-hydraulic performance. The result indicate that the convective heat transfer coefficient of the IPF 5% ice slurry is comparable to that of single-phase water. As the IPF increase to 10%, a significant enhancement in heat transfer performance is observed. However, further increasing the IPF to 15% leads to performance saturation. The variation in heat transfer performance across different IPF is closely related to changes in the flow pattern of ice slurry. Furthermore, the use of a superhydrophobic surface result in an approximately 35% increase in heat transfer coefficient compared to plain copper surface. Pressure drop measurements reveal that the ice slurry pressure loss increase with both IPF and Reynolds number, following the trend predicted by the Darcy-Weisbach Law. Concurrently, when ice slurry flowing over the superhydrophobic surface, the ice slurry experiences a reduction in pressure drop about 15% compared to the plain copper surface. These finding demonstrate that superhydrophobic surfaces can enhance both the heat transfer efficiency and flow performance of ice slurry systems. Under laminar flow conditions, this study compared the heat transfer and flow characteristics of ice slurry flow over plain copper surface and superhydrophobic surface, clarifying how surface properties affect performance. Experiments results demonstrate that superhydrophobic surface simultaneously enhance heat transfer and reduce flow resistance. These findings close a knowledge gap on ice slurry behavior in superhydrophobic tube and provide an experimental foundation for future ice storage air conditioning system design. Implementing such surface in practical heat exchanger could raise overall heat transfer efficiency and contribute to energy savings and carbon reduction.