In this paper, a semi-analytical model is presented to evaluate the dynamical performance of a buried coil in providing and storing thermal power for HVAC applications. The present model considers simply a cylindrical pipe, in which a fluid is flowing, immersed in an infinite conductive medium. The radial conduction in the solid is coupled to the convective exchange with the flowing liquid by the thermal energy balance in the pipe. To solve the problem, the pipe is divided in segments of arbitrary length, and the conduction equation in the surrounding soil and the pipe thermal balance are solved via finite differences. Axial conduction is neglected. The resulting system of equations is implemented in a Matlab code, which gives as output the power transported by the fluid and the temperature trend in the solid. The model is validated by means of a comparison with the results obtained by Comsol Multiphysics, showing a good agreement and confirming the validity of most of the initial assumptions. The proposed model is a useful tool for design and operation of GSHP and SESPHS, allowing solution of design problems like determination of the diameter, burying depth and spacing of the collectors, or optimization of the thermal cycles of operation in order to get better performance.
A Soil Dynamics Model Suitable for Optimization of Geothermal Heat Pumps and Heat Storage Systems
DI MARCO, PAOLO;PELACCHI, PAOLO
2007-01-01
Abstract
In this paper, a semi-analytical model is presented to evaluate the dynamical performance of a buried coil in providing and storing thermal power for HVAC applications. The present model considers simply a cylindrical pipe, in which a fluid is flowing, immersed in an infinite conductive medium. The radial conduction in the solid is coupled to the convective exchange with the flowing liquid by the thermal energy balance in the pipe. To solve the problem, the pipe is divided in segments of arbitrary length, and the conduction equation in the surrounding soil and the pipe thermal balance are solved via finite differences. Axial conduction is neglected. The resulting system of equations is implemented in a Matlab code, which gives as output the power transported by the fluid and the temperature trend in the solid. The model is validated by means of a comparison with the results obtained by Comsol Multiphysics, showing a good agreement and confirming the validity of most of the initial assumptions. The proposed model is a useful tool for design and operation of GSHP and SESPHS, allowing solution of design problems like determination of the diameter, burying depth and spacing of the collectors, or optimization of the thermal cycles of operation in order to get better performance.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.