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Weather, pump and brine
Evaporation grows with wind and temperature and falls with humidity; the basin salinity settles where the salt entering with the fresh feed equals the salt leaving with the product.
Operation
Model checks
The science
What is modelled
A well-mixed collection basin of fixed volume, fed with fresh brine and drained as a concentrated product. The pump lifts brine over brush-packed walls; each pass loses a fraction of its water to the air, so the returning stream is saltier than it left.
Equations
- Water loss fraction per pass:
(1 - RH) x 0.077 x (0.65 + 0.105 wind) x (1 + 0.036 (T - 23)), capped. - Evaporation
E = pump x loss; product withdrawalfeed - Ewith feed 1.8 m3/h. - Salt balance
dM/dt = feed x S_source - product x c, so at steady statec = feed x S_source / product; the model caps dissolved salt at 27 percent and crystallises the rest.
Checks run in the page
- Water balance over 48 h.
- Salt balance including crystallised salt.
- Steady-state salinity against the analytic value.
- Zero evaporation when the pump is off.
Honest simplifications
The evaporation law is an empirical toy fit, not a psychrometric calculation: no wet-bulb temperature, no drift losses, constant density and no real tower geometry. Not a field or process-design model.
What to try
- Press Hot windy day: evaporation rises and the basin salinity climbs towards a higher plateau.
- Press Pump off: nothing evaporates and the salinity stays at the source value.
- Press Still humid day and compare the steady salinity.