Abstract In this study, the effect of various gases filling the space between the cover and the absorber coil on the thermal performance of a cylindrical solar water heater (CSWH) is experimentally investigated. Since the Prandtl number for argon gas is less than that for the air, the thermal performance of the CSWH increases. The experiments are conducted for mass flow rates of 2.5, 3, 3.5 and 4 kg/h. The results show that an increase in the flow rate leads to a decrease in the temperature difference the of water between the inlet and outlet of the coil due to reduction of the residence time of the fluid. The energy efficiency of the collector reaches its maximum at the mass flow rate until 3.5 kg/h, and then reduces at higher values of mass flow rate because the water temperature difference decreases dramatically. Hence, the optimum mass flow rate for a cylindrical collector is reported as 3.5 kg/h. The maximum energy efficiencies for argon and air are 52.14% and 48.17%, respectively. Finally, the constructed cylindrical solar water heater is also economically compared to a flat plate collector (FPC) and an electric water heater with similar thermal efficiency.

中文翻译：

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圆柱形太阳能热水器罩壳与吸收盘管之间空气和氩气的对比研究：实验研究

摘要 在这项研究中，通过实验研究了填充盖和吸收器盘管之间空间的各种气体对圆柱形太阳能热水器（CSWH）热性能的影响。由于氩气的普朗特数小于空气的普朗特数，CSWH 的热性能增加。实验是针对 2.5、3、3.5 和 4 kg/h 的质量流量进行的。结果表明，由于流体的停留时间减少，流速的增加导致盘管入口和出口之间的水温差减小。集热器的能效在质量流量达到 3.5 kg/h 时达到最大值，然后在更高的质量流量值时降低，因为水温差急剧减小。因此，圆柱形收集器的最佳质量流量报告为 3.5 kg/h。氩气和空气的最大能效分别为 52.14% 和 48.17%。最后，与平板集热器（FPC）和具有相似热效率的电热水器相比，构建的圆柱形太阳能热水器也具有经济性。