The outcome of an experimental study carried to maximize the thermal efficiency of a rectangular section solar air heater duct having V-baffle blocks with staggered racetrack-shaped openings are presented in this paper. The investigation encompasses the methodology to determine first the baffle blocks' optimum parameters yielding the thermohydraulic performance factor (η) value greater than unity and then finalizing the 'best optimum parameters' that maximize the duct's thermal (${\eta }_{\mathrm{t}\mathrm{h}}$) and effective (${\eta }_{\mathrm{e}\mathrm{f}\mathrm{f}}$) efficiencies. The thermal and fluid flow characteristics are studied under a constant heat flux at the duct's top wall for turbulent airflow condition. The effect of relative roughness height (e ⁄H) ranging from 0.4 to 0.7, relative pitch (p ⁄e) ranging from 2 to 10 and Reynolds number (Re) ranging from 5000 to 15000 are investigated on 45° V-baffle blocks with apex pointing both in downstream and upstream directions. The result shows that the air jets issuing through racetrack openings intensify the turbulence in the wake of baffle blocks leading to a substantial rise in Nusselt number (Nu) and friction factor (f) relative to smooth duct. The V-down baffle blocks obtain the maximum enhancement of Nusselt number and friction factor over the smooth duct with range 1.358 to 4.559 and 4.03 to 39.07, respectively. The V-down baffle blocks' parameters, e/H of 0.5, p/e of 4 and Re of 13021, provides a maximum value of thermohydraulic performance factor as 1.435. V-up baffle block with e/H of 0.7, p/e of 6 at Re of 12,322 reports the highest thermal and effective efficiencies values as 96.6% and 91.8%, respectively.

本文介绍了为最大限度地提高矩形截面太阳能空气加热器管道的热效率而进行的实验研究的结果，该管道具有 V 形挡板块和交错的跑道形开口。调查包括首先确定挡板块的最佳参数的方法，使热工水力性能系数 (η) 值大于 1，然后最终确定使管道热力最大化的“最佳最佳参数”（${\eta }_{\mathrm{吨}\mathrm{H}}$) 和有效 (${\eta }_{\mathrm{电子}\mathrm{F}\mathrm{F}}$) 效率。在湍流条件下，在管道顶壁处的恒定热通量下研究了热和流体流动特性。在 45° V 形挡板上研究了相对粗糙度高度 (e ⁄H) 范围从 0.4 到 0.7、相对节距 (p ⁄e) 范围从 2 到 10 和雷诺数 (Re) 范围从 5000 到 15000 的影响顶点指向下游和上游方向。结果表明，通过跑道开口喷出的空气射流在挡板块的尾流中加剧了湍流，导致相对于光滑管道的努塞尔数 (Nu) 和摩擦系数 (f) 大幅上升。V 向下挡板块在平滑管道上获得最大的努塞尔数和摩擦系数增强，范围分别为 1.358 至 4.559 和 4.03 至 39.07。V 型下挡板块' 参数，e/H 为 0.5，p/e 为 4，Re 为 13021，提供了热工水力性能因子的最大值为 1.435。e/H 为 0.7、p/e 为 6、Re 为 12,322 的 V 型挡板块报告的最高热效率和有效效率值分别为 96.6% 和 91.8%。