Analytical model for short-time responses of ground heat exchangers with U-shaped tubes: Model development and validation

Min Li and Alvin C.K. Lai

Applied Energy, 2013, vol. 104, issue C, 510-516

Abstract: Short-time responses of borehole ground heat exchangers (GHEs) are difficult to predict because they involve heat capacity effect and various arrangements of U-shaped tubes within boreholes. To meet this engineering challenge, this paper builds a composite-medium line-source model. The central idea of the new model is that the downward and upward channels of U-shaped tubes (not the borehole) are approximated as line sources or sinks of heat placed in a composite medium. This approach can account for not only the influence of the heat capacity of grouting material but also the difference between properties of soil and grout, whilst it is flexible enough to model various U-pipe configurations. The new composite-medium model is validated by using a reported laboratory experiment; it can yield predictions matching the experimental response profiles with acceptable accuracy for times as short as 5min. Several uncertainties which may contribute to discrepancies between the model prediction and the laboratory data are analyzed, including heat input rate, thermal conductivities and heat capacities of the composite medium. The potential errors caused by these uncertainties are comparable to the observed discrepancies.

Keywords: Borehole ground heat exchanger; Ground-coupled heat pump; Composite-medium line-source model; Short-time response; Pile ground heat exchanger (search for similar items in EconPapers)
Date: 2013
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (36)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:appene:v:104:y:2013:i:c:p:510-516

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DOI: 10.1016/j.apenergy.2012.10.057

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