被動式降壓閥之壓降與流量穩定性能數值與實驗分析

Abstract

液冷系統中常面臨流動不穩定與流量分配不均等問題，尤其在採用平行多通道結構時，此類現象更為明顯。既有研究多聚焦於微通道幾何優化設計或在流道內設置限流元件以抑制局部不穩定性，然而對於宏觀尺度下冷卻通道間流量不均之調控機制探討相對有限。有鑑於此，本研究旨在探討無需外部控制之彈簧驅動型被動式降壓閥（pressure-reducing valve, PRV）於自我調節流量與提升系統穩定性之應用潛力。 本研究首先建立動網格CFD模型，以模擬PRV在不同流量條件下的瞬時響應，並透過單通道實驗加以驗證。接著進行九組彈簧參數組合之參數分析，探討彈簧常數（ks）與預壓縮長度（l₀）對於壓力調節性能與穩定性的影響。第二階段透過調整球閥開度模擬平行通道阻力不對稱情況，測試PRV在分支流量平衡上的調控能力。 模擬與實驗結果顯示，在出口壓力與流量變化上具高度一致性，平均絕對百分比誤差（MAPE）皆低於10.2%。增加彈簧剛度可提高出口壓力設定值（Pₛₑₜ），但對於靈敏度與啟動壓降影響有限；反之，增加預壓縮長度則能降低啟動壓力門檻。在雙通道不對稱阻抗測試中，PRV無論配置於阻塞元件前後，皆展現出良好的流量調節效果，顯著改善通道間之流量分配不均問題。然而，本研究亦指出PRV於調節流量的同時會引入額外壓降，對於如流動沸騰等對壓力預度高度敏感之應用，應審慎考量其對系統整體能耗與幫浦負載之影響。

Flow instability and maldistribution are critical challenges in liquid-cooling systems, particularly in multiple parallel-channel configurations. While most prior studies have focused on microchannel geometry optimization or the use of flow restrictors to mitigate local instabilities, limited attention has been paid to macroscale flow non-uniformity among parallel cold plates. This study explores the use of spring loaded passive pressure-reducing valves (PRVs) as a self-regulating mechanism to improve flow stability and pressure control without external actuation. A dynamic mesh-based CFD model was developed to simulate the transient response of PRVs under varying flow rates and was validated using single-channel experiments. A parametric analysis involving nine design configurations was performed to investigate the influence of spring constant (ks) and pre-compression length (l₀) on pressure regulation performance and dynamic stability. In the second part, parallel-channel experiments were conducted by varying ball valve openings to simulate asymmetric hydraulic resistance. The PRV's effectiveness in balancing branch flow rates was then evaluated. The results showed strong agreement between numerical predictions and experimental measurements, with mean absolute percentage error (MAPE) below 10.2% for both outlet pressure and flow rate. Increasing the spring constant raised the outlet pressure setpoint (Pₛₑₜ) but had minimal effect on sensitivity or activation threshold, whereas extending the pre-compression length reduced onset pressure. In dual-channel tests, PRVs successfully maintained flow balance regardless of installation position—either upstream or downstream of the restriction. However, the use of PRVs introduces additional system pressure drop. Therefore, their application in pressure-sensitive systems, such as flow boiling, should be accompanied by careful pump capacity and energy efficiency assessment.