Thermal Vapor Recompression (TVR) Evaporator Calculator
Supersonic steam ejector thermo-compressor modeling, steam economy optimization, and calandria sizing.
1. Evaporation Rate & Boiling Body
2. Thermo-Compressor Pressures
3. Calandria Heat Transfer Specs
Engineering Output & Thermo-Compressor Sizing
Thermal Heat Duties & Steam Balances
TVR Falling Film Evaporator & Supersonic Ejector Simulator
Visualizing motive steam De Laval expansion, boil-off vapor suction entrainment, mixed discharge into calandria, and cyclone separator.
5 Fatal Traps & Industrial Engineering Pitfalls
1. Ejector Diffuser Shock Stall & "Break" Pressure Collapse
Steam ejectors operate on a delicate supersonic shock wave boundary within the mixing tube and diffuser. Every thermo-compressor has a strict "break pressure" (maximum allowable back-pressure). If the calandria becomes fouled with organic scale or non-condensable gas accumulates, the calandria pressure exceeds the break pressure by even 3 kPa. The supersonic shock front collapses instantaneously inside the diffuser. The ejector stalls completely; suction entrainment plunges to zero, causing boiler steam to violently backfire into the vapor separator body.
2. Liquid Droplet Carryover & De Laval Nozzle Erosion
The suction boil-off vapor drawn into the ejector must be 100% dry saturated vapor. If the vapor separator cyclone has inadequate height or if feed foaming occurs, entrained droplets of concentrated liquid (e.g. caustic, milk concentrate, or salt slurry) are drawn into the ejector. In the mixing throat where motive steam speeds exceed 1,100 m/s, droplets act like high-velocity sandblasting media, carving grooves in the 316L stainless nozzle in under 3 months and ruining suction vacuum.
3. Wet Motive Steam & Wire-Drawing Nozzle Destruction
Motive steam from industrial boilers frequently contains 2% to 4% entrained moisture. When 10 barg wet steam expands across the convergent-divergent De Laval nozzle, moisture droplets accelerate to supersonic velocities, causing rapid "wire drawing" cavitation and erosion of the nozzle throat diameter. An enlargement of the nozzle throat by just 0.8 mm increases live steam consumption by 15% while degrading the entrainment ratio, completely erasing the TVR efficiency advantage.
4. Boiling Point Elevation (BPE) Creep & Ejector Turndown Starvation
As product concentration increases in batch or multi-stage evaporation (e.g. tomato paste from 8 to 32 Brix or caustic soda to 50%), Boiling Point Elevation (BPE) rises significantly. This increases the required calandria steam saturation temperature, forcing the required compression ratio (Cr) to climb from 1.4 to over 2.1. Thermo-compressors are fixed-geometry supersonic devices; as Cr climbs past design limits, the entrainment ratio collapses exponentially, starving the calandria of mixed steam.
5. Non-Condensable Gas Blanketing of Calandria Tubes
Feed solutions carry dissolved oxygen, nitrogen, and CO2 that flash into the vapor space and are entrained by the TVR ejector into the calandria. Because steam condenses on the outer tube walls, non-condensable gases concentrate against the heat transfer surface, forming an insulating stagnant gas film. A mere 1% concentration of air in condensing steam slashes the overall heat transfer coefficient (U) by up to 55%, forcing calandria pressure to skyrocket and triggering ejector shock stall.
Thermo-Compressor Gas Dynamics & Heat Transfer Formulations
The supersonic expansion of motive steam through a converging-diverging De Laval nozzle is governed by isentropic compressible gas dynamics:
The Entrainment Ratio ($Ra = dot{m}_{suction} / dot{m}_{motive}$) is predicted via the HEI / ESDU empirical thermo-compressor correlation:
Where $Er = P_{motive} / P_{suction}$ is the Expansion Ratio, $Cr = P_{discharge} / P_{suction}$ is the Compression Ratio, and $eta_{ej} approx 0.80 - 0.88$.
The overall Steam Economy and calandria heat transfer area $A_{cal}$ are: