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Research Into Heat Exchange Between Wells Of The U-Tube Ground Heat Exchanger

Posted on:2011-01-24Degree:MasterType:Thesis
Country:ChinaCandidate:D ZhangFull Text:PDF
GTID:2132360305971189Subject:Heating, Gas Supply, Ventilation and Air Conditioning Engineering
Abstract/Summary:PDF Full Text Request
In the U-tube ground heat exchanger designing, the heat transfer capacity of the ground heat exchanger is crucial for the entire ground-source heat pump system. At present, little research about multiple well heat exchangers is done; and most studies are limited to single well heat exchanger. In practical engineering applications, the heat exchange of the entire ground source heat pump is usually calculated by multiplying the heat amount of each exchange well by the number of the well, which usually influences the well designing of the ground source heat pump system greatly, since its inaccuracy. So, it is quite necessary to do a detailed research on the heat exchange of the multiple well exchanger system.With the help of FLUENT software, the numerical simulation of the heat exchange between the multiple well heat system and the surrounding soil is conducted in this paper. Unlike the traditional heat transfer model, a tri-dimensional model is adopted in the numerical simulation of the entire well heat system. With the fluid temperature at the import and export of the pipe taken into consideration, the numerical simulation model of U-tube ground heat exchangers is arrived at and verified by theoretical analysis and experiments. With the establishing of the multiple well model based on the single well model, the heat exchange of each well in the multiple system and that of the single well in the single model is worked out. In addition, with the comparison of the heat transfer in the single well model and that in the multiple well model, the correction factor of heat transfer for each well is obtained, which will be used to calculate the overall heat transfer of the heat exchangers and provide an appropriate way to calculate the heat exchange of the multiple well system in the ground-source heat pump.In this thesis, a research on the relation between the correction factors of multiple well system, the temperature and velocity of the fluid at the import, initial soil temperature, soil thermal conductivity coefficient, and variants in well spacing are conducted, as well as correlation factor for the heat exchange of multiple well under intermittent operating conditions.Finally, a simplified calculation method for the heat exchange of the ground heat exchanger in the case of a seepage layer is proposed and verified by numerical calculation, with which a calculation method for the heat exchange in per unit depth of the ground pipe heat exchanger in case of groundwater seepage and stratification layered soil is obtained. Moreover, the unit depth heat exchange of multiple well system in a specific area is worked out by testing it with the heat transfer calculation method which will be obtained by the exchange correction factor resulting from the above mentioned numerical simulation. The heat transfer calculation method proposed in this study provides a theoretical basis for practical design and is of great significance both theoretically and empirically.
Keywords/Search Tags:U-tube ground heat exchanger, Multiple well, Heat exchange, Thermal interference, Numerical Simulation
PDF Full Text Request
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