The ground surface energy balance in modelling horizontal ground heat exchangers

34th UIT Heat Transfer Conference 2016

Bortoloni, M.^1 ; Bottarelli, M.^1 ; Su, Y.^2

Dipartimento di Architettura, Università di Ferrara, via della Ghiara 36, Ferrara

44121, Italy^1

Department of Architecture and Built Environment, University of Nottingham, Nottingham

NG7 2RD, United Kingdom^2

关键词: Climatic conditions;    Comsol multiphysics;    Horizontal ground heat exchangers;    Numerical solution;    Soil temperature;    Surface heat fluxes;    Surface temperatures;    Unsteady heat transfer;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/796/1/012024/pdf
DOI  :  10.1088/1742-6596/796/1/012024

来源: IOP

【 摘 要 】

The performance of horizontal ground heat exchangers (HGHEs) is strongly dependent on climatic conditions, due to the low installation depth. In numerical modelling of HGHEs, the estimation of shallow soil temperature distribution is a key issue, therefore the boundary condition (BC) at the ground surface should be assigned carefully. With this in mind, a model of the energy balance at the ground surface (GSEB), based on weather variables, was developed. The model was tested as the 3rdkind BC at ground surface in modelling HGHEs by means of the FEM code Comsol Multiphysics, solving the unsteady heat transfer problem in a 2D domain. The GSEB model was calibrated and validated with the observed soil temperature at different depths. In addition, the effect on numerical solutions of different BCs, when assigned at the ground surface, was analysed. Three different simulations were carried out applying the GSEB model, the equivalent surface heat flux and temperature as boundary conditions of the 1st, 2ndand 3rdkind, respectively. The results of this study indicate that the use of the GSEB model is a preferable approach to the problem and that the use of the equivalent surface temperature can be considered as a reasonable simplification.