The longitudinal flow heat exchanger possesses lots of merits but it exhibits poor heat transfer coefficient at low Re condition, which makes it difficult to be applied in the high viscosity fluid area. In this paper, a heat transfer augment solution for lubricating oil flowing on shell side of a novel longitudinal flow twisted trifoliate tube oil cooler was proposed. Experiments were conducted to comparatively investigate the thermal–hydraulic performance of a twisted trifoliate tube oil cooler and a conventional segmental baffle oil cooler. The tube side study demonstrates that the Nu and f of the twisted trifoliate tube are 17.5–75.8% and 16.9–62.9% larger than that of the smooth circular tube. The shell side study shows that at the same oil mass flow rate, the shell side heat transfer coefficient of the twisted trifoliate tube oil cooler is 66.3–148.9% higher than that of the conventional segmental baffle oil cooler with pressure drop increased by 31.6–65.2%. Furthermore, the shell side performance evaluation criterion h/ΔP of the twisted trifoliate tube oil cooler is 1.46 times larger than that of the conventional segmental baffle oil cooler on average. The possible mechanisms responsible for the heat transfer enhancement are analyzed. In addition, the predictive correlations of tube side and shell side of the twisted trifoliate tube bundles for Nu and f are deduced based on the experimental data. Results from current research could provide useful correlations and beneficial guidance for design and application of the longitudinal flow heat exchanger in low Re ranging of 40–250.

纵流式换热器有很多优点，但在低Re条件下传热系数差，难以应用于高粘度流体领域。在本文中，提出了一种新型纵向流动扭曲三叶管油冷却器壳侧润滑油的传热增强解决方案。进行了实验以比较研究扭曲的三叶管油冷却器和传统的节段式挡板油冷却器的热工水力性能。管侧研究表明Nu和f扭曲的三叶管比光滑圆管大17.5-75.8%和16.9-62.9%。壳程研究表明，在相同的油质量流量下，扭曲三叶管式油冷却器的壳侧传热系数比传统的节段式折流板油冷却器高66.3-148.9%，压降增加31.6-65.2 %。此外，扭曲三叶管油冷却器的壳程性能评价标准h / ΔP平均比传统的节段式折流板油冷却器大1.46倍。分析了导致传热增强的可能机制。此外，Nu扭曲的三叶管束管侧和壳侧的预测相关性和f是根据实验数据推导出来的。当前研究的结果可以为纵流式换热器在40-250 的低Re范围内的设计和应用提供有用的相关性和有益的指导。