This is a training model built from heat and mass balances. Each tab follows the schematic layout of its unit and is calibrated to 20 t/day at 32 °C sea water and 80 °C jacket water. Flows, pressures and limits are calibrated values. They are not maker's data, because the C80, E1 C and ISF-80 technical data were not available. All tabs use the same start and stop sequence, based on general practice. Your own instruction manual and the ship's procedures take priority over anything here.

Design point of each tab

• JWP-26-C80: about 46 °C boiling, 90 % vacuum, 80 m³/h sea water, 45 m³/h jacket water, feed 3 : 1.
• AQUA Blue E1 C: about 54 °C boiling, 86 % vacuum, 26.6 m³/h sea water, 53.4 m³/h jacket water, feed 3.25 : 1.
• ISF-80 tube: about 47 °C boiling, 90 % vacuum, 60 m³/h sea water through condenser then ejector, slow response, feed 3.5 : 1.
• Il Seung's public listing shows ISF-80 as a plate unit and its tube series under other names. This tab follows the tube unit you specified.

What is calculated

• Sea water: pump curve against suction, strainer, condenser, feed branch, ejector nozzle and overboard resistance. SW suction pressure is before the pump and SW inlet pressure is at its discharge. The flow then passes the condenser, feed leaves the line, and the rest reaches the ejector.
• Feed and brine flow: SW inlet pressure, less the condenser drop, is the pressure at the feed take-off. From there to the chamber the whole pressure difference is used up by the feed valve, the spring loaded valve and the orifice, and that sets feed flow. Brine flow is feed less vapour by mass, converted with the density of the brine at its strength and temperature. Feed leaves the line before the ejector and brine joins it after, so overboard back pressure comes from nozzle water plus brine.
• Ejector: nozzle flow follows Cd A √(2 Δp / ρ), where Δp is its inlet pressure less the suction pressure it discharges into, so back pressure does not change it until the overboard valve is nearly shut. Performance follows the head ratio N = (outlet − suction) ÷ (inlet − outlet) from jet pump theory. Its lowest reachable pressure and brine capacity fall with the pressure at its own inlet, which is SW inlet pressure less the line and condenser drop, nozzle wear and back pressure.
• Chamber: vapour pressure comes from the evaporator and condenser heat balance. Air is a separate partial pressure.
• Jacket water: bypass and valve positions set the flow. Effectiveness-NTU sets the outlet temperature. Heat taken from the engine can pull its jacket temperature down at low load.
• Vacuum limit: a water-jet ejector cannot pull below the vapour pressure of its own water, so warm sea water gives less vacuum. Pull-down takes about 10 minutes on the JWP, less on the AQUA and more on the tube unit.
• Start of evaporation: boiling needs vacuum, wetted surfaces and liquid at saturation temperature for the chamber pressure, with the jacket water hot enough above that temperature. Until then all heat only warms the liquid.
• Feed and heat: brine strength comes from the mass balance. Heat transfer peaks near design feed, collapses with dry patches below it and declines slowly above it. Priming grows with heat flux, brine strength and high level, and past its liquid limit the mesh re-entrains droplets. The onset points and multipliers are fitted to show these published trends and are not measured values.
• Control panel: the JWP and AQUA door holds the parts of Alfa Laval arrangement drawing 985 21732 and the DS-21 front view, laid out wide here so it reads larger on screen. The real door is upright. Ejector pump ammeter and hour meter only, as drawn: the fresh water pump has neither. AQUA motor 6.6 kW, 11 A, start 76.8 A at 440 V 60 Hz, from the pump data sheet. The JWP takes the 11 kW row of that sheet and the DS-21 face, because no DS-20 drawing is public. Il Seung publishes no panel, so the ISF-80 door and motor are assumed, with a digital indicator of the Sasakura SK203 pattern. The salinometer shown at larger scale than the real door so it can be read.
• Data basis: the JWP uses the instruction manual and order sheet of a 20 m³/24h JWP-26-C80B: sea water, jacket water, heat, pressures, pump duties, demister area and the ø10 mm feed orifice. The AQUA uses the manual of a 20 m³/24h AQUA-80-HW, including its ø8.6 mm orifice and 3.25 feed ratio, because no E1 C manual is public. Il Seung publishes only capacity and salinity for the ISF-80, so its flows and orifice are estimates. Your own order sheet takes priority.
• Feed orifice: flow uses a discharge coefficient of 0.62 and 2 bar across the spring loaded valve. The manuals give the diameter and the valve opening pressure, and the coefficient is the standard sharp-edged value.
• Pressure sources: the AQUA-80-HW manual gives 0.12 bar sea water drop through the condenser, 0.1 bar maximum for valves in the line, 0.2 bar minimum pump suction, 3 to 4 bar at the ejector inlet gauge PI-ES-01, 4 bar maximum sea water inlet and 0.6 bar maximum ejector outlet. Its flow chart puts PI-ES-01 after the condenser, where feed and ejector water divide. The 0.1 bar is applied to all three units. Condenser to feed take-off and to the ejector is treated as one point, as drawn. The JWP drop comes from its order data and the ISF drop is an estimate. The ejector performance curves are fitted to these limits, not measured, because no maker publishes them.
• Your plant readings: a typed value replaces the calculated one while the unit runs. A typed vacuum or boiling temperature fixes chamber pressure and assumes the condenser passes all the vapour. The healthy unit is a fault-free copy at your sea water and jacket conditions. Cleanliness figures come from heat duty divided by mean temperature difference. Suggestions come from the JWP-26-C80B instruction manual fault table and general FWG practice, so treat them as a starting point and follow your own manual.
• Demister: vapour here is taken as pure steam at chamber pressure, because air is swept on to the condenser, so bleeding air in raises density and slows it. Droplet loading rises with the cube of vapour velocity. The mesh keeps catching over 99 % until about 80 % of its velocity limit, then floods and catch falls away. Caught droplets drain back to the brine, and the rest reach the condenser as ppm. The droplet count shown is exaggerated so it can be seen, but its rate and the pass-through share follow the calculation.
• Output: follows the temperature gap between jacket water and boiling, and boiling follows sea water temperature through the condenser. Warmer sea lowers output by about 2 % per °C. Colder sea raises it until the distillate valve, the condenser or the demister limits it, about 115 to 125 % of rating. It can never exceed the heat the engine rejects: at low load the jacket cools until the two balance.
• Salinity: ppm is brine strength multiplied by the droplets carried over. Carry-over follows vapour velocity against the Souders-Brown limit, so low pressure (thin vapour) raises ppm. Brine level, demister condition, foaming, ingress and condenser leaks are added. Ingress and leaks are diluted by output, so ppm rises when output falls.

Simplified on purpose

• Scale builds far faster than in service, so its effect shows within a session.
• Salinity limits at high boiling temperature are empirical. The main real risk above 55 to 60 °C is scale.
• Dumped distillate leaves the model. Real units may return it to the evaporator or drain it.