管间距对真空管家用太阳能热水器热性能的影响

依据现行的家用太阳能热水系统技术条件(GB/T19141),不管采用平板集热器还是真空管集热器,日采光量为17MJ/m2所对应的日得热量Q17是评价家用太阳能热水系统性能的主要指标.本文通过理论和实验研究真空管集热器的管间距对系统热性能的影响,结果表明:管间距对真空管家用太阳能热水系统的Q17有很大的影响,管间距越小,Q17越大,意味着系统的性能越好.但实际情况却完全相反,管间距越小,管与管之间的遮光越厉害,系统实际的日得热量越小,性能越差.这意味着以Q17来评价真空管家用太阳能热水系统的性能不合理,建议在家用太阳能热水系统技术条件中对管间距做出具体的规定,以消除管间距对Q17的影响.

Effects of Tube Space on the Thermal Performance of Water-in-glass Evacuated Tube Solar Water Heaters

In the present specification of domestic solar water heating systems （GB/T19141）,regardless of the type of collectors used in the systemQ17,the daily heat gain corresponding to the daily radiation of 17MJ/m2 on the collector surface,is a key indication to rate the thermal performance of a domestic solar water heaters.In this work,an attempt was made to investigate effect of the distance between two adjacent tubes in solar tube collectors of a water-in-glass evacuated tube solar water heater （SWH） onQ17 by theoretical calculations and experimental measurements.Results obtained by simulations and experimental measurement showed that the tube space had a significant effect onQ17 of the SWH,the shorter the tube distance,the higher theQ17,thus better the SWH performs.However,the actual situation is the case,the shorter the tube distance,the lower the real daily solar heat gain of the system,thus worse it performs.This implied that Q17 as the indication of thermal performance of the SWH is not reasonable,and specifying the tube distance in solar tube collectors of the SWH in the technical specification of GB/T19141 is advisable so as to eliminate effect of the tube distance on Q17.