Abstract The use of flat plate solar collectors (FPSCs) is the most common technology to employ solar energy. FPSCs enhance thermal efficiency and, as a result, can reduce both the size and the costs of a system. Surface modification techniques are extensively used to improve the thermal performance of systems. Among such techniques, helically corrugated tubes play an important role in industrial applications. Therefore, an experimental study was conducted in accordance with ASHRAE 93 (2010) to examine the effects of roughness height and pitch length of corrugated risers on the heat transfer in an FPSC in a turbulent flow. Nine corrugated risers with roughness height to diameter ratios ( e / D H ) of 0.05, 0.1, and 0.15, and pitch ratios ( P / D H ) of 0.3, 0.5, and 0.7 were manufactured and examined. The results demonstrated that the maximum efficiency of the FPSC with corrugated risers ( e / D H =0.15 and P / D H = 0.3) was about 61.59%. The friction factor increased by about 59.3–97.6%. The thermal performance factor had the maximum value of 2.3 at the Reynolds number of 5153. Based on the experimental results, the helically corrugated risers in the FPSC have a potential for being used in thermal applications.

中文翻译：

---

利用螺旋波纹立管的平板太阳能集热器热性能分析：实验研究

摘要 平板太阳能集热器（FPSCs）是利用太阳能最常见的技术。FPSC 提高了热效率，因此可以减小系统的尺寸和成本。表面改性技术被广泛用于改善系统的热性能。在这些技术中，螺旋波纹管在工业应用中发挥着重要作用。因此，根据 ASHRAE 93 (2010) 进行了一项实验研究，以检查波纹立管的粗糙度高度和节距长度对湍流中 FPSC 传热的影响。制造并检验了九个粗糙度高径比 (e / DH ) 为 0.05、0.1 和 0.15，节距比 ( P / DH ) 为 0.3、0.5 和 0.7 的波纹冒口。结果表明，具有波纹冒口的FPSC（e / DH = 0.15和P / DH = 0.3）的最大效率约为61.59％。摩擦系数增加了约 59.3-97.6%。在雷诺数为 5153 时，热性能系数的最大值为 2.3。根据实验结果，FPSC 中的螺旋波纹立管具有用于热应用的潜力。