直型通道印刷电路板式冷却器流动传热实验研究

Experimental Study on Flow and Heat Transfer of Straight-Channel Printed Circuit Heat Exchangers Used as Coolers

摘要: 针对超临界CO₂布雷顿循环系统中冷却器在拟临界工况下传热与流动特性复杂、预测精度不足的问题，本文基于直型通道印刷电路板式换热器缩比样机开展了系统的实验研究。在不同质量流量和入口温度条件下，获取了换热器在多工况下的传热与压降数据，系统分析了入口温度与质量流量对换热性能及流动阻力的耦合影响规律，并在此基础上建立了适用于直型通道结构的流动传热经验关联式。结果表明，热侧CO₂入口温度升高可通过增大传热温差并强化拟临界区热物性效应显著提升换热能力，而冷侧入口温度升高则导致传热驱动力减弱，从而抑制换热过程；相较而言，入口温度变化对压降的影响较为有限。质量流量是主导换热器性能变化的关键参数，其增加可通过提高雷诺数和强化湍流作用显著提升对流换热强度，但同时引起压降快速增加，体现出明显的热工水力耦合约束特征。进一步地，基于实验数据通过非线性回归建立了CO₂侧与水侧努塞尔数及摩擦因子关联式，其预测结果与实验数据吻合良好，CO₂侧与水侧的最大偏差分别控制在±20%和±10%、±10%和±5%以内，具有良好的工程适用性。本研究从实验层面揭示了直型通道印刷电路板式冷却器在拟临界区域的流动与传热耦合机制，所得关联式可为超临界CO₂布雷顿循环系统中冷却器的设计优化与性能预测提供可靠依据。

Abstract: To address the complexity of flow and heat transfer characteristics and the insufficient prediction accuracy of coolers operating under pseudo-critical conditions in supercritical CO₂ Brayton cycles, a systematic experimental investigation was conducted on a scaled-down straight-channel printed circuit heat exchanger (PCHE). Experiments were performed over a wide range of operating conditions, including different inlet temperatures and mass flow rates. The thermal-hydraulic performance, including heat transfer capacity and pressure drop, was obtained and analyzed. Particular attention was given to the coupled effects of inlet temperature and mass flow rate on heat transfer performance and flow resistance. Based on the experimental data, empirical correlations applicable to straight-channel configurations were developed. The results indicate that increasing the inlet temperature of the hot-side CO₂ significantly enhances heat transfer performance by enlarging the temperature difference and intensifying thermophysical property variations near the pseudo-critical region. In contrast, an increase in the cold-side inlet temperature weakens the driving temperature difference, thereby suppressing heat transfer. Compared with these effects, the influence of inlet temperature on pressure drop is relatively limited. The mass flow rate is identified as the dominant parameter governing the overall performance of the heat exchanger. Increasing the mass flow rate markedly enhances convective heat transfer by elevating the Reynolds number and strengthening turbulence, while simultaneously leading to a rapid increase in pressure drop, reflecting a pronounced thermo-hydraulic trade-off. Furthermore, empirical correlations for the Nusselt number and friction factor on both the CO₂ and water sides were developed using nonlinear regression. The correlations show good agreement with experimental data, with maximum deviations within ±20% and ±10% for CO₂, and ±10% and ±5% for water, respectively, demonstrating good engineering applicability. This study experimentally elucidates the coupled flow and heat transfer mechanisms of straight-channel PCHE coolers in the pseudo-critical region. The proposed correlations provide reliable guidance for the design optimization and performance prediction of coolers in supercritical CO₂ Brayton cycle systems.