Principle and verification of a similar experiment system for vertical ground heat exchangers

Based on a heat transfer model of vertical ground heat exchanger considering soil vertical stratification, similarly converts the heat transfer model by the thermal similarity principle, obtains the similarity ratios such as flow velocity, geometry and time. Based on a project and the similarity criteria, develops a vertical single U-shape pipe similarity model experiment system. Using the test data of experiment system in 24 hours running (equivalent to 64 days of prototype operation), verifies the calculated results of the three-dimensional numerical model (similar model and prototype model). The results show that the average relative error of the outlet temperature of the buried pipe is 1%, the average relative error of the temperature difference between the inlet and outlet is 8%, and the relative error of the soil temperature is 3%.The similar experiment system realizes the study of the long-term heat transfer characteristics of buried pipes under complex conditions with relative low costs and controlled short-term operating time.