Reliability Design Research On GSHP Buried Pipe Based On Thermal Resistance Random Analysis

Energy shortage is a strict problem that the world confronts in 21 st century, the exploitation of environment friendly new energy becomes the hot subject of society. As renewable energy, ground source heat pump technology has become the research hotspot and applied broadly in engineering. At present, the research of ground source heat pump mainly focus on the heat transfer model of heat exchanger, coupled mass and heat transfer, thermal property of backfilled material and system matching. About buried pipe heat exchanger design, there is no uniform calculation method in the world. What's more, all the methods calculate the pipe length are fixed value calculation and never consider the randomness of parameter. This paper put forward the reliability design of buried pipe that considered the randomness of rock and soil thermal resistance.At first this paper reviewed the principle, classify and research status of ground source heat pump. In chapter 2, the present calculation methods of buried pipe heat exchanger are summarized and their advantages and disadvantages are discussed. In chapter 3, the structure, composing, thermal and humidity environment of underground rock and soil are analyzed, by what soil thermal resistance is considered not a fixed value but a variable. Parameter estimation method is used to get the numerical characteristics of variable, and then reliability design formula of buried pipe based on semi-empirical formula and considering the randomness of soil thermal resistance is deduced.Buried pipe heat exchanger reliability design results are discussed and contrasted with general calculation result in chapter 4, combined with engineering case. The result indicates:borehole length increase with the system reliability and soil thermal resistance standard deviation increase, the two parameters have great influence on the calculation result of borehole length; the more soil thermal resistance mean value is, the more calculated borehole length is, soil thermal resistance mean value have great influence on borehole length; under certain reliability and confidence level, reliability design result of borehole length is smaller than general calculation result, which result in the saving of drilling and pipe cost; buried pipe reliability design method considered variability of soil thermal resistance and have scientific significance, provide a new thought for the optimization design of buried pipe heat exchanger.