Research progress in optimization of fins for outdoor heat exchangers of low-temperature air source heat pumps

Abstract:

Against the backdrop of sustained growth in China′s air conditioning industry and climate change, heat pump air conditioners have emerged as a key solution for achieving the "dual carbon" goals due to their high energy efficiency. However, fins are prone to condensation and frost formation under humid operating conditions, leading to reduced heat transfer efficiency and increased system energy consumption. To achieve multi-objective optimization of low-temperature air-source heat pump outdoor heat exchanger fins, this study reviews performance evaluation metrics and optimization methodologies for fins under both dry and wet conditions. Results indicate that air-source heat pump outdoor heat exchanger fin performance can be comprehensively assessed across three dimensions: material properties, heat transfer flow characteristics, and drainage performance. Optimization under dry conditions primarily focuses on enhancing heat transfer through structural improvements. Existing strategies for enhancing single-fin performance under wet conditions primarily concentrate on micrometer-scale surface topography design and wettability control. Techniques such as laser etching or chemical deposition create micrometer-scale groove networks to reduce pressure drop while maintaining heat transfer efficiency. Fin surface protrusions and pits developed based on vortex induction principles, with heights ranging from 0.6 to 1.61 mm, increase the Nusselt number by up to 19.03%. Future trends involve integrating surface structures for induced nucleation in wet conditions while leveraging biomimetic principles for rapid drainage. Additionally, designing hybrid surfaces combining hydrophilic and hydrophobic properties can delay frost formation and enhance fin drainage. This paper further identifies key research directions to improve heat exchanger efficiency, flow dynamics, and drainage performance, meeting modern industrial and civil demands for high-efficiency, energy-saving heat transfer equipment.