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Use a common feed, concentrate target and quality boundary before comparing equipment arrangements.
| Common-duty question | Forced-circulation review | Falling-film review |
|---|---|---|
| Product movement | Pumped recirculation through an external heater | Distribution and film wetting across the heating surface |
| Electrical demand | Loop flow × pressure rise, plus other auxiliaries | Feed/transfer or recirculation duties, plus other auxiliaries |
| Thermal history | Circulating inventory, repeated passes and hold-up | Film passage plus separators, preheat and any recirculation |
| Mechanical exposure | Repeated pump/pipe/heater shear | Distribution, pumping and actual pass arrangement |
| Deposits & cleaning | Mechanism, inspection, pump and full-loop CIP | Wetting, surface deposits, distribution access and CIP |
| Combined process | May serve as a product-specific finishing stage | May pre-concentrate a suitable feed before a finishing stage |
Use identical feed composition and temperature, feed mass flow, target solids, evaporation load, operating hours and product acceptance criteria. State whether the material properties have been measured. Changing those inputs invalidates a simple energy or capacity comparison.
Include circulation and transfer pumping, vacuum service, cooling and any recompressor. Ask for electrical demand at the actual viscosity and flow condition. A thermal saving alone does not establish a lower total operating cost.
A falling-film arrangement relies on adequate distribution and wetting. A forced-circulation loop adds circulating inventory and repeated passes. Compare the actual thermal history, shear, deposition pattern, cleaning frequency and access requirements instead of ranking the names.
A suitable feed may be pre-concentrated in one arrangement and finished in another. Define the hand-off concentration and temperature, then reconcile both stages on the same mass and energy basis. A hybrid train still needs an integrated control and cleaning review.
Keep the loop moving. The circulation pump sets the flow through the heater. That flow is distinct from the incoming feed and from the mass of water evaporated. Selection must follow the concentrated liquid throughout the planned operating range, including start-up and restart after cooling.
Review structure & specification →
Add heat under pressure. In the common non-boiling heater arrangement, pressure in the circuit limits boiling within the heater. Heat is added before the liquid enters the flash zone. Tube or plate geometry is selected from product behaviour and pressure-drop constraints, rather than the circulation label alone.
Review structure & specification →
Recover heat within a defined duty. Effect count describes the evaporation arrangement, while TVR and MVR describe vapour recompression. They can be evaluated together. The circulation pump remains an additional electrical load regardless of the heat-recovery choice.
Review structure & specification →