Fig. 1
From: Thermodynamic considerations in renal separation processes
The black-box models of the kidney used in this study, showing the overall black-box model (solid borderline), which is then divided into two mass-transfer processes (dashed borderlines): filtration in the glomeruli and reabsorption in the tubular system. The valve symbol (▻◅) indicates positions where there is a pressure drop due to friction in the kidney