Fig. 14From: Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangersAverage heat transfer rates per unit borehole depth of BHEs (\(\bar{q}\) = (ρrcrMΔ\(\bar{T}\))/H) in the fine sand layer over the whole operation period under different pumping–injection flow volume ∑G: a ∑G = 0 m3 d−1; b ∑G = 200 m3 d−1; c ∑G = 400 m3 d−1; d ∑G = 600 m3 d−1; e ∑G = 800 m3 d−1; f ∑G = 1200 m3 d−1Back to article page