“…While λ f and d p are usually known in ideal packed beds, Nu must be estimated using an appropriate correlation which commonly depends on the particle Reynolds number, Re , and the Prandtl number, Pr (see supporting information Table S1 for examples). Generally, such a correlation is empirically derived from laboratory experiments (Achenbach, 1995; Collier et al, 2004; Naghash et al, 2016; Nie et al, 2011; Shent et al, 1981; Wakao & Kaguei, 1982; Zanoni et al, 2017) or, more recently, by particle resolved direct numerical modeling (Chen & Müller, 2019; Singhal et al, 2017b; Sun et al, 2015; Tavassoli et al, 2015; Zhu et al, 2019). As natural porous aquifers are typified by Re < 50 and a porosity (fluid volume fraction) n < 0.5, the correlations established by previous studies are covering much broader ranges.…”