[AHW30-P04] Comparing constant dispersivity with scale-dependent one: for heated water injection case
キーワード：aquifer, thermal dispersivity, scale dependence, analytical model, finite-element model
Prior studies indicated that the thermal dispersivity generally nonlinearly increases with the distance from a heat flow source in a porous medium. Such dispersivity is termed as scale-dependent dispersivity (SD). However, the existing analytical models for injecting heated water into an aquifer, e.g., aquifer thermal energy storage system, usually assume the dispersivity as a constant to obtain analytical solutions. A question arises here: Is it possible to use a fixed value of constant dispersivity (CD) to represent SD one? To address the question, this study first develops a finite-element model adopting a SD formula to describe the dispersion process due to heated water injection in a confined aquifer. Then, an analytical model considering the CD is used to compare with the aforementioned SD model. The results from this study show that a CD can be found by using an average value of the thermal frontal position over the entire operating period to approximate SD one.