Impact of dissolved salts on two-phase flow and boiling heat transfer in a natural circulation loop. (12th October 2019)

• Record Type: Journal Article
• Authors: Franken, Daniel; Ahmed, Zayed; Eckels, Seth; Eckels, Steven; Bindra, Hitesh
• Is Part Of: Chemical engineering science. Volume 206(2019)
• Page Start: 463
• Page End: 470
• Publication Date: 2019-10-12
• Subjects: Seawater -- Flow oscillations -- Natural circulation -- Two-phase flow; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2019.05.046
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: Two-phase flow and boiling experiments are conducted with artificial seawater as a heat transfer fluid or process coolant. Steady state natural circulation flow rates observed in the loop are same as for deionized water. Bubble coalescence is inhibited in the riser section with the presence of dissolved salts. Pressure drop is lower for seawater case which can be due to bubbly flow regime at all power levels. Abstract: Two-phase natural circulation and boiling experiments are conducted in this study with artificial seawater as a heat transfer fluid or process coolant. This experimental work is focused on understanding the role of dissolved salts in water on the steady state two-phase natural circulation flow rates. Mass flow rates were measured at different heat flux levels with artificial seawater, deionized water and tap water in the experimental loop. It was found that the average quasi-steady state mass flow rates were the same at any particular heat flux level regardless of the fluid being used. Artificial seawater coolant exhibited more stable natural circulation at higher heat flux as compared to the other two coolants. Mass flow measurements recorded at 2 s intervals show that magnitude of flow oscillations are much higher in case of tap water and deionized water. Also, high speed camera images revealed that the bubble departure diameters are smaller in seawater compared to tap or deionized water. This can be attributed to the increased local wettability due to the presence of dissolved salts in the fluid. Visual observations of the riser section showed that bubble coalescence and formation of slugs is inhibited in the seawater. These observations also explain the reduced pressure drop across test section when seawater was used as a coolant.