Characteristics analysis of water film in transpiring wall reactor

Abstract

Transpiring wall reactor can significantly overcome reactor material corrosion and salt deposition problems by forming a protective water film on its inner porous wall. In this work, a simplified physical model of transpiring wall reactor was built to analyze the process of heat and mass transfer between the water film and bulk fluid. Furthermore, two quantitative correlations between the thickness of water film and main operating parameters were proposed for the first time using theoretical analysis and mathematical deduction method. For a given transpiring wall reactor, appropriately increasing the flow rate and inlet temperature of transpiration water is conducive to maintain the growth of the water film thickness. A positive linear relation exists between the mass flow rate of transpiration water and the thickness of water film under constant feedstock parameters conditions. These quantitative correlations together with some meaningful conclusions help to guide the optimization of operating parameters as well as the design of transpiring wall reactor.

Simulation of a Transpiring Wall Reactor for Supercritical Water Oxidation: Characteristics of Water Film

“…Two quantitative correlations involving water film thickness and main operating parameters are put forward through theoretical analysis and mathematical deduction on heat and mass transfer between water film and bulk fluid in our latest publication. 24 This work further expands our previous research by numerical simulation and experimental validation. Apart from water film temperature, water film coverage rate and substance concentration in water film are proposed as evaluation indexes of water film characteristics.…”

“…Herein, F tw,w and F bulk,w are able to be obtained by numerical simulation, and F tw,w can also be calculated by the formula reported in our previous work. 24 Water film coverage rate can characterize the continuity and uniformity of the water film formation and distribution. Obviously, the closer it is to 1.0 ω, the better the water film quality is.…”

Effects of structural parameters on water film properties of transpiring wall reactor

“…Notably, the whole reactor zone was in supercritical state at γ = 1, which is unconducive to forming an excellent water film to dissolve inorganic salts and corrosive substances. 27 It can be also found that transpiration water layer hardly affected reactor center temperature at γ > 3. Inevitably, much high porosity and many transpiration water pipelines significantly reduce system stability and safety.…”

“…Transpiring wall porosity (β) is one of the vital structural parameters affecting the flow resistance of transpiration water. 16,27 Internal resistance coefficient (η) and permeability (ζ) are two significant factors to characterize the flow resistance above, 28 and can be obtained via the Darcy's law 22 and basic formulas of fluid flow. Internal resistance coefficient and permeabilities at various porosities conditions can be seen in Table 2.…”

“…30 However, transpiration water layers significantly affected water film coverage rages below L = 0.015 m. Water film coverage rate was only approximately 85% at γ = 1, which is unconducive to dissolving inorganic salts and corrosive substances. 27…”