The Disruption of Core System Operating Conditions Caused by Condensation and Liquid Backflow in the Low-Temperature Section of the Exhaust Pipe

I. Vacuum-Pressure Balance (Most Direct and Severe)

Liquid flows back into the evaporator chamber and condenser, occupying the vapor space and blocking vapor flow channels. This causes a sudden increase in flow resistance, leading to pressure buildup within the chamber, a continuous drop in vacuum level, and severe fluctuations;

The liquid impact on the liquid surface instantly generates a large amount of water vapor and foam, causing a sudden surge in steam production. This results in a sudden change in the vacuum pump’s suction load, leading to persistent instability in the negative pressure;

The accumulated liquid forms a liquid seal, preventing non-condensable gases in the exhaust line from being properly vented. As non-condensable gases continue to accumulate, the vacuum level drops further, the boiling point of the material rises, and evaporation efficiency decreases.

II. Gas-Liquid Separation and Defoaming Balance

Recirculated condensate dilutes the feed solution, reducing salinity and eliminating the anti-foaming effect of salt precipitation. Residual surfactants and organic matter in the water generate excessive foaming; fine foam surges into the exhaust duct with the gas flow, creating a vicious cycle. Uncontrolled entrainment of mist and foam causes salt to continuously enter the vacuum system and piping.

III. Heat Transfer and Condensation Heat Balance

Low-temperature condensate is directly injected into the high-temperature evaporation chamber, causing the temperature of the medium inside the tank to drop sharply. This results in a precipitous decline in evaporation intensity and severe fluctuations in the heat exchange load on the heat pump or heating side.

The interaction between hot and cold media generates a large amount of instantaneous non-condensable vapor, causing an imbalance in the heat exchange load of the condenser. This reduces condensation efficiency, disrupts the system’s thermal cycle, and increases energy consumption per unit of produced water.

IV. Balance Between Feed Concentration and Boiling Point

Continuous dilution of the feed solution by incoming fresh water causes the overall salt concentration to steadily decrease. The original vacuum-temperature calibration relationship becomes invalid, leading to persistent fluctuations in automatic temperature control and level regulation;

Uneven mixing of hot and cold fluids in localized areas causes concentration stratification within the tank. The viscosity of the circulating fluid and the heat transfer boundary layer continuously change, resulting in significant fluctuations in evaporation rate.

V. Balance Between Corrosion and Media Composition (Long-Term Latent Damage)

Condensate water often contains dissolved volatile organic acids and chloride ions, making it weakly acidic; acidic condensate flows back into the gas-liquid interface, causing chloride ions and acid anions to accumulate at the wet-dry boundary. This accelerates pitting corrosion of stainless steel and crevice corrosion at weld seams, compromising the stability of the equipment’s base material.

VI. Vacuum Pump Operating Load Balance

Accumulated liquid is drawn into the vacuum pump with the gas flow, causing liquid hammer. The increased volume of medium within the pump chamber reduces pumping efficiency, causing fluctuations in motor current and frequent overloads, which exacerbate pump body wear and disrupt the stable operating conditions of the vacuum system.