Observing the effect of different air leakage modes on evaporation of water at sub-atmospheric pressure

The performance of vacuum-operated equipment depends on maintaining an adequate vacuum. Any air leakage disturbs the pressure balance, decreases superheat, reduces evaporation efficiency, and can ultimately affect the system's stability and overall performance. An experimental system is fabricated to study the effect of leakage on the dynamic characteristics of vacuum-induced flash evaporation, and experiments are conducted using different air leakage modes. Experimental results show that a larger air intake occurs in the case of continuous air leakage mode, followed by intermittent mode and normal flashing mode. Furthermore, this air intake reduces flashing efficiency through a temperature drop. It is reported that a temperature drop of 38.1 °C, 18.4 °C and 3.1 °C is obtained for the cases of normal flashing, intermittent leakage, and continuous air leakage case respectively. It is also noted that a higher initial temperature (T<inf>w,0</inf>) and a more extended air extraction period (t<inf>2</inf>) boost the flashing process. It is observed that the temperature drop is improved by 23% and 21 % with an increase in t<inf>2</inf> by 2 s and initial water temperature T<inf>w,0</inf> by 10 °C keeping conditions of initial pool height (H<inf>w,0</inf>=60 mm) and vacuum tank pressure (P<inf>v,0</inf>=8.4 kPa) are constant. Further analysis shows that the temperature drop is enhanced by 18.4% by increasing the value of the air intake valve (B1)level (?) from 25 % to 100 % at constant initial conditions of pool height, water temperature, and vacuum tank pressure. These results are crucial for optimizing evaporation efficiency (in the form of temperature drop) and managing air leakage in sub-atmospheric systems. © 2025 Elsevier Ltd