Research On Heat Transfer Performance And Engineering Application Of Pulsating Heat Pipe In Solar Collector

As a new and efficient heat transfer element,the working principle of pulsating heat pipe is quite different from that of traditional heat pipe,which is an important developing direction of heat transfer enhancement.At present,many scholars have made lots of experiments to study the heat transfer mechanism of pulsating heat pipe,especially the factors determining the heat transfer enhancement.The pulsating heat pipe has a wide range of potential applications in the fields of electronic cooling,low temperature waste heat recovery and other fields for its excellent heat transfer characteristics.However,little work has been conducted on the combination of pulsating heat pipe and solar collector,for this reason,a new type of heat pipe solar collector is designed in this paper,and its heat transfer characteristics are researched.There are for two aspects of innovation.First of all,compared with the traditional solar collector,the water tank of this new solar collector is located at the bottom,and the vacuum glass tube is embedded in the water tank without water inside,which increases the overall stability of the solar heat collector,and avoids the problems of frost crack or leakage caused by bad weather in winter.In addition,based on the instantaneous efficiency equation of the traditional evacuated tubular heat collector,this paper explores the relationship between the normalized temperature difference and the instantaneous efficiency of this new solar collector.In this paper,the pulsating heat pipe is used as the heat transfer element,and part of the pulsating heat pipe is placed in the vacuum glass tube,and the other part is sealed in the water tank.During the experiment,the start-up,operation and heat transfer performance of pulsating heat pipe under different conditions was studied by adjusting the proportion between cold and hot sections.It turns out that the oscillation curve illustrates the shape of “V” in evaporation section and the shape of “?” in condensing section.The equivalent thermal conductivity of pulsating heat pipe rises first and then falls with the decrease of the ratio of cold and hot section,when the dip angle is 70°and the filling rate is 55%.The pulsating heat pipe has the lowest start-up temperature and the best heat transfer characteristic when the ratio is 47%.In this condition,the responding equivalent thermal conductivity is 2604.4W/(m·K),and the thermal resistance is 0.83K/W.It is noticeable that the biggest instantaneous efficiency of this new type of solar collector is 77.08% in experiments.According to the data of experiments,the functional relationship of the traditional collector is not appropriate to this new type of solar collector.