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The Turbulent Flow, Low Reynolds k-ε interface, the Moisture Transport in Air interface, and the Heat Transfer in Moist Air interface are coupled through the Nonisothermal Flow, Moisture Flow, and Heat and Moisture coupling nodes. Let’s consider evaporative cooling at the water surface of a glass of water placed in a turbulent airflow. Example: Modeling Evaporative Cooling with the Moisture Flow Interface For the Interior Fan condition, the mass flow rate is conserved in an averaged way and the vapor concentration is homogenized at the fan outlet, as shown in the figure below.Īverage mass flow rate conservation across a boundary with the Interior Fan condition. A continuity condition is also applied on vapor concentration at the boundaries where the Screen feature is applied. Mass Conservation Across Boundariesīy using the Moisture Flow interface, an appropriate mass conservation is granted in the fluid flow problem by the Screen and Interior Fan boundary conditions. Note that the Low-Reynolds and Automatic options for Wall Treatment are also available for some of the RANS models.įor more information, read this blog post on choosing a turbulence model. The Navier-Stokes equations, to compute the airflow velocity field \mathbf, which accounts for the flux to and from the wall, is automatically defined by the Moisture Flow interface, based on the relative humidity.Īpproximation of the flow field and the moisture flux close to walls when using wall functions in the turbulence model for fluid flow.In moist air, moisture is transported by diffusion and advection, where the advecting flow field in most cases is turbulent.Ĭomputing heat and moisture transport in moist air requires the resolution of three sets of equations: When considering porous media, the moisture transport process, which includes capillary flow, bulk flow, and binary diffusion of water vapor in air, depends on the nature of the material. Licensed under CC BY-SA 3.0, via Wikimedia Commons. Moist air is the environing medium for applications such as building envelopes (illustration, left) and solar food drying (right).