Heat Pipe Evaporation and Condensation — ANSYS Fluent CFD SimulationDescriptionThis project presents a transient simulation of the evaporation and condensation occurring inside a thermosyphon heat pipe using ANSYS Fluent, with phase-change mass transfer as the central theme. The defining feature of a heat pipe is that it moves heat by repeatedly changing the phase of a working fluid, and capturing that behavior requires a model able to compute the transfer of mass between liquid and vapor. Heat added at the evaporator produces vapor, while heat removed at the condenser promotes condensation, establishing a continuous phase-change cycle that transports thermal energy efficiently through the device. The simulation resolves the transient evolution of vapor generation, condensate return, and the resulting fluid circulation. As the opening project of the Mass Transfer: Beginner CFD Training Package, it introduces the canonical evaporation-and-condensation problem, combining both phase changes in a single device to establish the phase-change mass-transfer workflow.MethodologyThe three-dimensional geometry was created in ANSYS DesignModeler and meshed in ANSYS Meshing. The model comprises three sections: the evaporator at the bottom (heat input), the insulated adiabatic middle section, and the condenser at the top (cooling). The domain was discretized with an unstructured mesh of approximately 3,900,000 elements, giving sufficient resolution to represent the phase boundaries accurately while keeping the computational cost manageable. A three-phase Volume of Fluid (VOF) model was adopted to track the interaction among liquid water, water vapor, and air as a non-condensable phase, with VOF providing the sharp interface tracking needed to follow the moving liquid–vapor boundary. The heart of the methodology, however, is the evaporation–condensation mass-transfer mechanism in ANSYS Fluent, which drives phase change based on the local pressure and temperature fields — converting liquid to vapor where the fluid is heated and vapor back to liquid where it is cooled. Turbulence is represented with the standard k-ε model and standard wall functions. A heat-flux boundary condition supplies energy at the evaporator wall, the condenser wall is held at a fixed temperature to promote condensation, and the remaining walls are adiabatic, so that heat transfer occurs only between the active evaporator and condenser regions. The problem is solved transiently to capture the dynamic evolution of the liquid and vapor distributions.AnalysisAt a transient time of 1.655 s, the results illustrate the coupled evaporation and condensation inside the heat pipe. The liquid volume-fraction contour shows the working fluid concentrated in the lower evaporator region, where the fraction approaches unity, while the upper zones contain little liquid — evidence of vapor formation and its movement toward the condenser. The mass-transfer-rate contour confirms this directly: positive values in the evaporator mark active vapor generation as the liquid absorbs heat from the wall, while near the condenser the mass transfer decreases as vapor condenses on the cooled surfaces. The temperature contour displays a clear gradient along the pipe, with the evaporator near 323 K and the condenser near 283 K — the difference that sustains continuous phase change and circulation. The velocity-magnitude contour shows enhanced flow near the interface, with vapor driving upward motion through the core and condensate returning slowly downward along the walls. Together, these transient results reveal the well-developed two-way flow loop characteristic of effective thermosyphon operation. By the end of this project, you'll be able to set up a transient multiphase VOF simulation with an evaporation–condensation mass-transfer mechanism, apply heat-flux and fixed-temperature boundaries to drive the phase change, and interpret the liquid-fraction, mass-transfer-rate, temperature, and velocity fields that reveal how a heat pipe transports thermal energy.

Condensation inside a Shell and Tube Condenser — ANSYS Fluent CFD SimulationDescriptionThis project simulates condensation inside a shell and tube condenser using ANSYS Fluent, modeling the phase change that occurs when water vapor releases its latent heat and converts to liquid upon reaching saturation temperature — here set at 46°C, with a mass-transfer time-frequency coefficient of 0.1. The condenser is a horizontal shell-and-tube heat exchanger, with hot saturated steam flowing through the shell at 10 m/s while cooling water flows through four rows of internal tubes at 5 kg/s and 20°C. As the shell-side steam contacts the outer surface of these cold tubes, it loses heat, drops below its saturation temperature, and condenses into liquid water. Within the Mass Transfer: Beginner CFD Training Package, this project isolates condensation in a real industrial device, building on the heat-pipe case toward a single-phase-change application.MethodologyGiven the exchanger's symmetric structure, only a semi-model is drawn, built in 3D in Design Modeler with two baffles inside the shell directing the hot flow, and meshed in ANSYS Meshing with an unstructured grid of 342,486 elements. Since both liquid water and water vapor are present and thoroughly intermixed rather than existing as distinctly separated regions, the Mixture multiphase model is used to represent the two phases together. Condensation itself is defined through an evaporation-condensation mass-transfer mechanism, which governs how vapor converts to liquid as it cools past the saturation point on contact with the cold tube surfaces.AnalysisThe results include 2D and 3D contours of pressure, velocity, temperature, water vapor volume fraction, liquid water volume fraction, and the mass-transfer rate between vapor and liquid. These fields show the hot steam cooling as it exchanges heat with the cold tube bank, dropping below the saturation temperature exactly where contact with the tubes is strongest. This temperature drop drives the phase change directly, and the resulting condensation and liquid-water production are visible in the volume-fraction and mass-transfer-rate contours, confirming the condenser is performing its intended heat-exchange and phase-change function. By the end of this project, you'll be able to set up a Mixture multiphase model with an evaporation-condensation mass-transfer mechanism, define saturation conditions and cooling boundaries in a shell-and-tube geometry, and interpret the volume-fraction, temperature, and mass-transfer-rate fields that characterize condensation in a condenser.

Boiling inside a Nanotube — ANSYS Fluent CFD SimulationDescriptionThis project simulates boiling flow inside a nanotube using ANSYS Fluent, modeling the liquid-to-vapor phase change as water flows through an extremely narrow channel. Water enters the tube already close to its saturation temperature, so the incoming flow is essentially primed for boiling as soon as it picks up additional heat from the wall. Boiling is the phase change that completes the core evaporation–condensation trio, and here it is studied at the nanoscale, where the tube's tiny dimensions place the process in a distinctive regime. Within the Mass Transfer: Beginner CFD Training Package, this project introduces boiling as a mass-transfer mechanism, building on the evaporation and condensation cases with the third fundamental phase change.MethodologyWater enters the tube at 373.15 K and 1×10⁻⁵ m/s, close to the assumed saturation temperature of 383.15 K. Given the tube's symmetric geometry, small diameter, and correspondingly high computational cost in full 3D, the model is built as a 2D geometry in Design Modeler, with a tube length of 0.00005 m and a radius of 0.00000015 m, reflecting the true nanotube scale, and meshed in ANSYS Meshing with a structured grid of 100,000 elements. The tube wall is set to a constant heat flux of 100,000,000 W/m², which heats the water above its saturation temperature as it travels through the pipe, driving it into a superheated state. Once the water reaches saturation temperature, it begins converting to vapor, so the simulation uses the Eulerian multiphase model, with liquid water as the primary phase and water vapor as the secondary phase; as the most detailed of Fluent's multiphase formulations, it solves separate momentum and energy equations for each phase. The boiling model option is activated within this Eulerian framework, and phase change is defined through a mass-transfer mechanism keyed to the 383.15 K saturation temperature.AnalysisThe solution yields 2D fields for pressure, vapor velocity, vapor temperature, vapor volume fraction, and the mass-transfer rate from liquid to vapor. These results trace the physical progression of boiling directly: the water temperature rises under the applied wall heat flux, and once it reaches the saturation point, vapor begins forming — visible in the volume-fraction and mass-transfer-rate fields as the boiling process takes hold along the tube length. By the end of this project, you'll be able to set up an Eulerian multiphase simulation with the boiling model activated, define a wall heat flux and saturation-temperature-based mass transfer, and interpret the vapor volume-fraction and mass-transfer-rate fields that reveal where and how rapidly boiling occurs.

Water Jet Considering Cavitation — ANSYS Fluent CFD SimulationDescriptionThis project presents a CFD simulation of cavitation inside a water jet — a device that produces a thin, ultra-high-speed water stream (often mixed with an abrasive) to cut or clean hard materials. As water accelerates through the jet, the pressure can fall to its vapor pressure, triggering cavitation: the local formation of vapor bubbles within the liquid. Capturing this phenomenon is essential, because cavitation drives erosion, noise, and performance loss in many fluid devices. In this project, you'll model the phase change between water and vapor and study how the vapor region forms and grows. Within the Mass Transfer: Beginner CFD Training Package, this project introduces cavitation as a pressure-driven phase change, extending the mass-transfer methods from temperature-driven boiling and condensation to a phenomenon governed by pressure.MethodologyThe 2D water jet geometry is designed in Design Modeler and meshed with a structured grid of roughly 57,018 elements for the internal nozzle flow. The VOF multiphase model is set up with water and vapor phases using sharp interface modeling and an implicit formulation, and the cavitation mass-transfer mechanism is activated between the two phases with a defined vapor pressure of 3540 Pa. The boundary conditions are a velocity inlet (10 m/s, pure water) and a pressure outlet. Coupled pressure–velocity coupling is chosen with PRESTO! pressure and Compressive volume-fraction discretization for the cavitating flow, and the k-ε RNG turbulence model with standard wall functions is applied.AnalysisPost-processing produces pressure, velocity, water volume fraction, and vapor volume fraction contours, used to locate where cavitation begins. The results show the pressure falling as the water accelerates through the jet, and where it reaches the vapor pressure, vapor forms — visible in the vapor volume-fraction field as the cavitation region taking shape. From these you can identify exactly where cavitation initiates and how the vapor region grows. Cavitation is a critical concern in pumps, propellers, valves, injectors, and hydraulic machinery, and the VOF + cavitation mass-transfer workflow built here transfers directly to predicting and mitigating cavitation damage across countless fluid systems. By the end of this project, you'll be able to set up a VOF multiphase simulation with the cavitation mass-transfer mechanism, define the vapor pressure that triggers phase change, configure the solver and discretization for cavitating flow, and interpret the pressure and vapor-fraction fields that reveal where cavitation occurs.

DescriptionThis project presents a numerical simulation of the ammonia flashing that occurs when liquid ammonia is injected through a small orifice nozzle. Flash boiling is a rapid evaporation process triggered by a sudden pressure drop, which leaves the liquid in an unstable state and drives a very fast phase change. Using the VOF multiphase model in ANSYS Fluent, the interaction between the liquid ammonia, its vapor, and the surrounding gas is resolved in time. The mass transfer between the liquid and vapor phases is the heart of the study: the simulation captures the jet breakup, the liquid-to-vapor phase transition, and the subsequent development of the two-phase ammonia flow within the domain.Geometry & MeshThe geometry was created in ANSYS SpaceClaim as a 2D symmetric domain. The lower horizontal line acts as a symmetry boundary, so only half of the physical domain is modeled to reduce computational cost. The geometry consists of an inlet nozzle section and a larger downstream chamber where the flashing and mixing take place, with the inlet and the two outlets clearly defined on the schematic to specify the boundary conditions. Meshing was performed in ANSYS Meshing, producing approximately 95,000 high-quality structured elements to ensure the numerical stability and accuracy of the simulation.MethodologyThe simulation employs a transient, incompressible, pressure-based solver to resolve the unsteady behavior of the flow field. The k-ω SST turbulence model is used to accurately capture boundary-layer separation and the unstable vortical structures in the ammonia jet. For the multiphase treatment, the VOF model tracks the interfaces between air, liquid ammonia, and ammonia vapor. Crucially, the Lee evaporation-condensation model is coupled with VOF to represent the mass transfer — the phase change from liquid ammonia to ammonia vapor — within the flashing region.ConclusionThe results show the injected liquid ammonia jet expanding into the larger chamber and rapidly converting into a two-phase mixture. The volume fraction contours clearly reveal the formation of a liquid film near the bottom wall, with the ammonia vapor fraction increasing downstream as the flashing and evaporation intensify. The velocity field shows a high-speed jet along the lower boundary and a large recirculation zone in the upper chamber, indicating strong mixing between the phases. The temperature contours confirm cooling in the liquid-rich region (around 270 K) and a warmer, vapor-dominated layer (approaching 300 K) — a direct consequence of the energy consumed during the phase change. Together, these results demonstrate how coupling the Lee model with VOF captures the mass transfer that governs ammonia flash boiling, providing a detailed picture of the evaporation-driven two-phase flow.

DescriptionThis research presents a numerical investigation of the fluid dynamics and heat transfer in a two-phase immersion (submerged) cooling system. The subject of the study is a set of chips with interposer components mounted vertically on a printed circuit board (PCB), submerged in the dielectric coolant HydroFluoroEther (HFE)-7100. The main objective is to understand how the physical architecture and geometry of these components influence the flow paths of bubbles, the phenomenon of bubble coalescence, and the extent of vapor coverage on the chip surfaces.The geometry was created in SpaceClaim, ensuring an accurate representation of the PCB and its components. A structured mesh was generated in ANSYS Meshing, comprising more than 19,000 elements to enable reliable numerical simulation of this configuration.A transient solver was used, since the problem requires tracking changes in the volume fraction of the two phases over time. Gravity was included in the model, fixed at −9.81 m/s² in the Y direction.MethodologyThe PCB was modeled in ANSYS Fluent. The evaporation and condensation mass transfer mechanisms were captured using a multiphase VOF (Volume of Fluid) model, which resolves the interface between the liquid coolant and the vapor phase as boiling occurs. The dielectric coolant was assigned a saturation temperature of 339 K. The turbulent flow was solved using the standard k-epsilon model together with the energy equation, allowing the temperature distribution throughout the domain to be computed.ConclusionThe study examines the fluid dynamics and heat transfer in a two-phase immersion cooling system featuring vertically mounted chips and an interposer component. Using a computational model based on the finite volume method and the VOF approach, it investigates how the interposer component affects the deflection of bubble streamlines, the coalescence of bubbles on the heated chips, and the overall cooling rate.The results show that the interposer component can significantly influence chip heat transfer, with the evaporation–condensation mass transfer at the phase interface governing how heat is removed from the chip surfaces. The work highlights the importance of electronic system topology in the efficiency of two-phase cooling and offers valuable guidance for designing electronic systems that achieve effective thermal management.

DescriptionThis simulation models a dehumidifier using ANSYS Fluent. A dehumidifier is an air-conditioning device that reduces and maintains the humidity level of the air. It is used to improve people's health and thermal comfort, eliminate musty odors, and prevent mildew growth by removing water from humid air.This project investigates a humidification–dehumidification system based on a phase-change process. These systems consist of two sections: the evaporator and the condenser. First, the airflow inside the copper pipes is heated and compressed by the compressor and then directed to the condenser section. In this section, the temperature of the air inside the pipes is reduced by the blowing fan, and condensation occurs. The resulting liquid then moves to the evaporator section, where it absorbs heat, evaporates, and returns to the gas phase. This heat is drawn from the humid air blown over the pipes, and because the humid air gives up its heat, dry air is obtained.In this study, the humid air is treated as water vapor. Therefore, a multiphase model consisting of water and vapor must be defined. The mass transfer between vapor and water is then defined as an evaporation–condensation type, so that steam turns into liquid water when the temperature drops below the saturation temperature. The amount of water produced by the phase change between vapor and water indicates the degree of dehumidification. Since the two phases of water and vapor are entirely separate from each other, the Volume of Fluid (VOF) model is used. Accordingly, a chamber is designed with spiral tubes, so that the pipes carry a flow of cold water while the chamber contains water vapor. The vapor enters the chamber at a saturation temperature of 373.15 K and a velocity of 0.05 m/s and contacts the surface of a pipe carrying water at a temperature of 358.15 K and a velocity of 0.01 m/s.Geometry & MeshThe present geometry is designed as a 3D model using Design Modeler. The computational zone is the interior of a dehumidifier, which consists of a chamber with spiral tubes. Steam flows inside the chamber, and cold water flows inside the spiral pipes. The mesh of the present model is generated using ANSYS Meshing. The mesh is unstructured, and the number of cells produced is equal to 1,522,772.Set-up & SolutionSeveral assumptions are applied in this simulation. A pressure-based solver is used, and the simulation is steady. The effect of gravity is considered, with the gravitational acceleration defined as 9.81 m/s².For the models, the realizable k-epsilon model is selected to account for turbulence, together with the standard wall function for near-wall treatment. The multiphase flow is captured using the VOF model with two Eulerian phases (water and vapor), sharp interface modeling, and an evaporation–condensation mass transfer mechanism. The energy equation is also enabled.The boundary conditions are defined as follows. The wet-air inlet is set as a velocity inlet with a velocity magnitude of 0.05 m·s⁻¹, a temperature of 373.15 K, a water volume fraction of 0, and a vapor volume fraction of 1. The cool-water inlet is likewise a velocity inlet, with a velocity magnitude of 0.01 m·s⁻¹, a temperature of 358.15 K, a water volume fraction of 1, and a vapor volume fraction of 0. The dry-air outlet is defined as a pressure outlet with a gauge pressure of 0 Pascal, and the cool-water outlet is also a pressure outlet with a gauge pressure of 0 Pascal. The inner wall is a stationary wall with a coupled thermal condition, while the outer wall is a stationary wall with a heat flux of 0 W·m⁻².Regarding the solution methods, the pressure–velocity coupling is handled with the Coupled scheme. The PRESTO! scheme is used for pressure, and the modified HRIC scheme is used for the volume fraction. First-order upwind discretization is applied to the momentum, turbulent kinetic energy, turbulent dissipation rate, and energy equations.Finally, the solution is initialized using the standard method. The gauge pressure is set to 0 Pascal and the velocity to 0 m·s⁻¹ throughout the domain. The chamber is patched with a vapor volume fraction of 1 and a temperature of 373.15 K, while the tube is patched with a vapor volume fraction of 0 and a temperature of 358.15 K.

Horizontal Fluidized Bed Simulation for Soil Drying in ANSYS FluentIntroductionSolid particles, when sufficiently small, can behave like a fluid under vertical flow conditions—a phenomenon known as fluidization. By applying an upward flow to a bed of fine particles, the drag force exerted by the fluid on the particles can balance the gravitational force acting on them, causing the particles to levitate and exhibit fluid-like behavior. This phenomenon is widely used in industrial applications, including increasing residence time for burning waste biofuels and supporting catalytic processes in petroleum production. This project simulates a horizontal fluidized bed designed to dry incoming soil containing moisture. Soil enters the bed at a mass flow rate of 1 kg/s with a water mole fraction of 0.1, while air flows in from the bottom at 1.7 m/s and 393 K, driving evaporation of the moisture contained within the soil as it passes through the fluidized bed.Geometry and MeshThe geometry is two-dimensional, with a fluidizer height of 0.5 m and a length of 2 m. It was designed in SpaceClaim and meshed using ANSYS Meshing with a structured mesh totaling 22,000 elements.MethodologyThe simulation was solved as unsteady, with gravity activated to capture its effect on the soil particles and the energy equation enabled to resolve thermal behavior. The Eulerian multiphase approach was used to model the two-phase system, with each phase containing two species defined through the species transport model. The primary phase is a gas composed of air and water vapor, while the secondary phase is granular, with a particle size of 0.0018 m, containing soil and liquid water as its constituent species. Mass transfer between liquid water and vapor was captured using the evaporation-condensation method with the Lee model. Viscous effects were modeled using the standard k-ε model with standard wall functions, chosen for its robustness and relatively low computational cost.Results and ConclusionContours of temperature and species mass concentration illustrate the progressive evaporation of soil moisture within the fluidized bed, showing a decrease in liquid water concentration accompanied by a corresponding increase in vapor concentration. The air temperature drops to the saturation temperature of water by the outlet, while the soil temperature remains essentially constant throughout the bed, indicating that the heat lost by the gas phase is consumed by the evaporation process rather than by heating the soil. The gas-phase pressure drop across the fluidized bed was calculated as 284.8 Pa. Key quantitative results are summarized below:LocationArea-weighted avg. vapor concentration [kg/m³]Mass-weighted avg. vapor concentration [kg/m³]Temperature [K]Inlet gas0.00170393Outlet gas0.01081.85×10⁻⁵372.4Inlet soil0.00587.92373Outlet soil0.016141.91373.37These results confirm that the horizontal fluidized bed effectively facilitates moisture removal from the soil through convective drying, with the coupled heat and mass transfer behavior consistent with the physical expectations of an evaporation-driven fluidization process.

Coronavirus Spread Due to a Cough in Open Air — ANSYS Fluent CFD Simulation TrainingThis project simulates the spread of coronavirus particles resulting from a human cough in open-air conditions, using ANSYS Fluent. When an infected person coughs, virus-laden particles disperse through the air and can potentially reach and infect a nearby healthy individual. Understanding this process, and determining the minimum safe distance needed to limit transmission, has become one of the most actively studied topics in CFD research, commonly referred to as social or physical distancing.The model consists of a human figure placed within a cube-shaped domain representing the open-air environment, with the mouth defined as the source of virus-carrying droplets. The 3-D geometry was created using SolidWorks and Design Modeler, and meshed in ANSYS Meshing with an unstructured mesh, refined further near the mouth region. The total element count is 584,587.MethodologyA two-way coupled Discrete Phase Model (DPM) is used to capture the unsteady behavior of the dispersed droplets and their interaction with the surrounding continuous airflow. The model accounts for stochastic collision, coalescence, and breakup of droplets. Droplets are injected at a temperature of 310 K, a velocity of 31.85 m/s, and a flow rate of 0.018 kg/s, released over a time interval of 0 to 0.1 s.Since droplet sizes vary, the Rosin-Rammler logarithmic distribution is used to define the diameter range, including the minimum, maximum, and mean diameters, the spread parameter, and the number of diameter classes per injection. The Species Transport model is enabled alongside the droplet model to capture droplet evaporation, meaning the airflow field around the patient is solved together with species mixing.ResultsThe simulation tracks the virus-laden particles over time, producing an animation that shows their release and gradual dispersal. Snapshots of the particle distribution at different time steps are also extracted. The results illustrate how the virus spreads during a cough event in open air, covering the period from 0.1 s to 1.75 s.

Hydrate Formation in Elbow Pipe (Mixture Multiphase) — ANSYS Fluent CFD SimulationDescriptionThis project uses ANSYS Fluent to simulate hydrate formation inside a 90-degree elbow pipe, applying the mass-transfer module to model the evaporation-condensation phase change between water vapor and liquid water. Hydrates form as a combination of water, water vapor, and methane, with the hydrate phase modeled as the product of water vapor condensing into liquid water as it flows through the bend. Hydrate formation is a significant concern in gas-transport pipelines, where it can restrict or block flow, making this a practically important mass-transfer problem. As the capstone of the Mass Transfer: Beginner CFD Training Package, it applies phase-change mass transfer to a specialized industrial flow-assurance scenario, combining condensation with a multi-species mixture in a real pipe geometry.MethodologyThe 3D geometry is a 2 cm diameter elbow pipe, built in DesignModeler and meshed in ANSYS Meshing with a structured grid of 55,040 elements. A transient solver is used to capture the time-progressing nature of the condensation process. The multiphase mixture model defines the water–water vapor–methane system, with mass transfer specified as an evaporation-condensation process occurring at a saturation temperature defined as a polynomial function of pressure. The inlet stream enters at 2 m/s and 315 K, composed of 80% methane and 20% water vapor by volume. The RNG k-epsilon turbulence model and the energy equation are enabled to resolve the turbulent flow and temperature distribution within the domain.AnalysisThe results include 2D and 3D contours of pressure, methane velocity, temperature, and liquid water volume fraction at multiple simulation times between 0.06 s and 0.24 s. The liquid-water volume fraction increases as the simulation progresses, confirming ongoing condensation and hydrate formation. The velocity and pressure contours reveal a pronounced wake region downstream of the bend, along with secondary flows forming at the outlet due to the pipe's 90-degree geometry. By the end of this project, you'll be able to set up a transient mixture multiphase simulation with an evaporation-condensation mass-transfer mechanism, define a pressure-dependent saturation temperature for a multi-species system, and interpret the liquid-fraction, temperature, and flow fields that characterize hydrate formation in a pipe bend.