Numerical thermal investigation on pile ground heat exchangers with groundwater seepage

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Numerical thermal investigation on pile ground heat exchangers with groundwater seepage

 

Author: Wang, Deqi
Title: Numerical thermal investigation on pile ground heat exchangers with groundwater seepage
Degree: M.Eng.
Year: 2013
Subject: Ground source heat pump systems.
Seepage.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xi, 80 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2641119
URI: http://theses.lib.polyu.edu.hk/handle/200/7119
Abstract: With widespread application of ground-sourced heat pump systems, more and more individuals and organizations are committed to system development and analysis. However, little numerical simulations and experiments were conducted to research the impact of groundwater seepage on the thermal performance of the pile ground heat exchangers (PGHE) of a ground coupled heat pump system and it is hardly to find relative analytical-models which are taken seepage effect into consideration in modeling process. Therefore, in this study, a 3-D transient numerical model, which is verified by ring-coil heat source model, is established to investigate the thermal performance of the spiral-coil PGHE with groundwater seepage. Particularly, it is focus on the influences of hydraulic gradient and inner structure of soil on the heat exchange rate of the PGHE system by means of a numerical model in the porous medium. According to the simulation results, the seepage flow greatly enhances the heat transfer performance of the geothermal heat exchangers. The strengthening effect is proportional to the hydraulic gradient and is found more obvious on the spiral coil system than the U-tube system. Besides, with the porosity as reference parameter, the heat exchange rate will increase with the porosity increase and the soil structure also impacts the thermal influencing radius of PGHE system with larger influencing scope found at lower porosity.

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