In the present study, heat transfer and thermal efficiency of double-pipe heat exchangers with novel Double-Perforated Inclined Elliptic (DPIE) turbulators were experimentally investigated. The range of Reynolds number was between 5000 and 18,000 under turbulent flow regime. The inclination angle of the elliptic inserts $\left(\alpha \right)$, and the perforation diameters (d) varied from 15° to 25°, and 0.5 mm < d < 1.5 mm, respectively. The perforated vortex generators can significantly increase the flow perturbations and disrupt the thermal boundary layer to enhance the heat transfer without noticeable impact on the friction loss. The experiments revealed that the average Nusselt number was increased by 217.4% by using DPIE turbulators compared to the tube without vortex generators. The recirculations through the perforations of the elliptic turbulators, increase the fluid mixing between the walls and the core area. The maximum thermal efficiency parameter of 1.849 was obtained for DPIE vortex generators with d/b = 0.25 and $\alpha ={25}^{\circ }$. The Friction factor increment of 14.0% was observed for the double perforated elliptic turbulators with d/b = 0.25 compared to the typical elliptic inserts without perforations. It was found that the heat transfer is increased around 39.4% by using DPIE inserts with d/b = 0.25 compared to the typical louvered strips without perforations. The main benefits of the proposed novel turbulators are their much higher thermal efficiency compared to the previous turbulators at wide range of Reynolds numbers, and their simple installation together with low manufacturing costs.

在本研究中，实验研究了具有新型双穿孔斜椭圆（DPIE）湍流器的双管换热器的传热和热效率。在湍流条件下，雷诺数的范围在5000和18,000之间。椭圆形刀片的​​倾斜角度$（\alpha ）$，穿孔直径（d）从15°到25° 不等，分别为0.5 mm <  d <1.5 mm。穿孔的涡流发生器可以显着增加流动扰动并破坏热边界层，以增强热传递，而不会对摩擦损失产生明显影响。实验表明，与不带涡流发生器的管相比，使用DPIE湍流器可使平均Nusselt数增加217.4％。通过椭圆形湍流器的穿孔进行再循环，增加了壁和核心区域之间的流体混合。对于d / b  = 0.25的DPIE涡流发生器，获得的最大热效率参数为1.849。$\alpha ={25}^{\circ }$。与没有穿孔的典型椭圆形刀片相比，d / b = 0.25的双穿孔椭圆形湍流器的摩擦系数增加了14.0％。已发现，与 不带孔的典型百叶窗板条相比，使用d / b = 0.25的DPIE插件，传热增加39.4％左右。所提出的新型湍流器的主要优点是，与以前的湍流器相比，在广泛的雷诺数范围内，它们的热效率要高得多，并且安装简便且制造成本低。