Insight into the evaporation characteristics of vacuum environment describing the different zones

Abstract

The integrity of the nuclear reactor coolant system and the pressure within the pipes are of utmost concern during the practical operation. Any leakage in the pipes due to fracture/thermal stratification can cause the leakage of high-pressure fluid into the low-pressure environment. This results in a high-pressure drop and phase change from liquid to vapour, which causes accidental mishaps. In depth knowledge of the physics that regulates phase change is needed to forecast the consequences of phase change and guarantee the safety of nuclear activities. The present work aims to augment the understanding of low pressure vaporization through experimental observations. A new experimental setup has been set up to study low pressure vaporization. Experiments are conducted with different initial temperatures ranging from 65 °C to 80 °C, initial water heights between 100 mm to 140 mm, and high vacuum tank pressure varying from 11.32 to 31.32 kPa. Based on the pressure difference, The process is characterized into two different zones and their respective stages. The concept of static superheat and instant superheat is described in the work. The results show that the temperature drop during the first zone is much less than the flashing zone. Flashing time can be increased by increasing the pool height and initial temperature. Instant superheat has a direct relationship to the initial temperature but has an inverse relation to the initial height of the pool. These outcomes will be advantageous in enhancing the design of nuclear coolant systems and addressing safety concerns.