Ultrafiltration Flux & Transmembrane Pressure (TMP) Calculator
Calculate ultrafiltration Transmembrane Pressure (TMP), operating permeate flux (LMH & GFD), 20°C temperature-normalized permeability, and backwash triggers.
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Frequently Asked Questions
What is Transmembrane Pressure (TMP) in ultrafiltration systems?
Transmembrane Pressure (TMP) represents the net pressure driving water through the porous hollow fiber membrane wall from feed to filtrate side. For pressurized crossflow modules, TMP = (Pfeed + Pret) / 2 - Pperm. As particulate foulants accumulate on the membrane surface, TMP rises continuously at constant permeate flow.
Why must membrane flux (LMH) be normalized to 20°C?
Water viscosity varies by roughly 2.5% per degree Celsius. At 5°C winter temperatures, water viscosity is 1.52 cP, whereas at 25°C it drops to 0.89 cP. Normalizing flux to 20°C using J20 = J * (mu_T / mu_20) isolates physical membrane pore fouling from harmless seasonal temperature variations.
What is the typical operating flux range for hollow fiber UF modules?
For surface water and tertiary wastewater treatment, sustainable design flux is typically 45 to 85 LMH (26 to 50 GFD). For clean groundwater or seawater RO pretreatment, flux can reach 70 to 100 LMH. Exceeding critical flux triggers severe cake compaction and accelerated chemical cleaning requirements.