On the anti-freezing of flat-plate collectors in sdhws under climatic conditions of Yunnan, China

Solar domestic hot water systems (referred to as SDHWS in the paper) with flat-plate collectors have been widely installed in residential and office buildings for the water heating due to their reliable performance, low cost and minimal need for maintenance. However, the substantial fear of the damaging due to the freezing of collectors has apparently hampered their popularization in the areas with cold winters, even in the areas with mild winters. Just like a water pipe, one approach to the anti-freezing of collectors is to make the water inside the collectors flow. For a thermosyphonic SDHWS, this can be achieved by appropriate measures which make the systems produce thermosyphonic or reverse circulation. The object of this study is to investigate the temperature depression of collector absorbers at nights and the feasibility to employ reverse flow of thermosyphonic SDHWS for anti-freezing under climatic conditions of Yunnan, China.