A new method for calculation of short time-step g-functions of vertical ground heat exchangers

Abstract The composite medium infinite line source model (CMILS) was recently developed to describe the heat transfer of borehole ground heat exchanges. But this model is very complicated and time-consuming to calculate the solutions, which limit its practical applications. This paper presents a method to simplify the CMILS model and develops short time-step response g-functions using the simplified CMILS model. The advantage of the new short time-step response g-functions is that they are simple in calculation with comparable accuracy compared with CMILS model. Simulation studies show that g-functions calculated by simplified CMILS model match nicely with the experimental data. Detailed comparisons are also carried out between the simplified CMILS model and other numerical or analytical models through simulation.

[1]  J. Spitler,et al.  Reference data sets for vertical borehole ground heat exchanger models and thermal response test ana , 2011 .

[2]  Björn Palm,et al.  Numerical generation of the temperature response factors for a Borehole Heat Exchangers field , 2013 .

[3]  Michel Bernier,et al.  A contribution towards the determination of g-functions using the finite line source , 2013 .

[4]  S. Kavanaugh,et al.  Simulation and Experimental Verification of Vertical Ground-coupled Heat Pump Systems , 1985 .

[5]  Z. Fang,et al.  A finite line‐source model for boreholes in geothermal heat exchangers , 2002 .

[6]  Björn Palm,et al.  Numerically generated g-functions for ground coupled heat pump applications , 2012 .

[7]  Alvin C.K. Lai,et al.  Full-scale temperature response function (G-function) for heat transfer by borehole ground heat exchangers (GHEs) from sub-hour to decades , 2014 .

[8]  Eui-Jong Kim,et al.  Development of numerical models of vertical ground heat exchangers and experimental verification : domain decomposition and state model reduction approach , 2011 .

[9]  Fleur Loveridge,et al.  Temperature response functions (G-functions) for single pile heat exchangers , 2013 .

[10]  Alvin C.K. Lai,et al.  New temperature response functions (G functions) for pile and borehole ground heat exchangers based on composite-medium line-source theory , 2012 .

[11]  Z. Fang,et al.  Heat transfer analysis of boreholes in vertical ground heat exchangers , 2003 .

[12]  Per Fahlén,et al.  Analytical modelling of short-term response of ground heat exchangers in ground source heat pump systems , 2010 .

[13]  Y. Gu,et al.  Development of an equivalent diameter expression for vertical U-tubes used in ground-coupled heat pumps , 1998 .

[14]  Min Li,et al.  Short-time performance of composite-medium line-source model for predicting responses of ground heat exchangers with single U-shaped tube , 2014 .

[15]  Louis Lamarche.  Analytical g-function for inclined boreholes in ground-source heat pump systems , 2011 .

[16]  L. Lamarche,et al.  New solutions for the short-time analysis of geothermal vertical boreholes , 2007 .

[17]  Louis Lamarche,et al.  A new contribution to the finite line-source model for geothermal boreholes , 2007 .

[18]  Jeffrey D. Spitler,et al.  A short time step response factor model for vertical ground loop heat exchangers , 1999 .

[19]  Alvin C.K. Lai,et al.  Analytical model for short-time responses of ground heat exchangers with U-shaped tubes: Model development and validation , 2013 .

[20]  Per Fahlén,et al.  Vertical ground heat exchangers: A review of heat flow models , 2009 .

[21]  Johan Claesson,et al.  An Analytical Method to Calculate Borehole Fluid Temperatures for Time-scales from Minutes to Decades , 2011 .

[22]  Fleur Loveridge,et al.  G-Functions for multiple interacting pile heat exchangers , 2014 .

[23]  Michel Bernier,et al.  A semi-analytical method to generate g-functions for geothermal bore fields , 2014 .

[24]  J. Claesson,et al.  New Analytical and Numerical Solutions for the Short-term Analysis of Vertical Ground Heat Exchangers , 2011 .

[25]  O. J. Zobel,et al.  Heat conduction with engineering, geological, and other applications , 1955 .

[26]  A. Lai,et al.  Review of analytical models for heat transfer by vertical ground heat exchangers (GHEs): A perspective of time and space scales , 2015 .