Phase Change: Simulate Evaporating Materials | Diabatix

January 13, 2023
Sachin Menon

Phase change is the process by which a substance changes from one state of matter to another. The most common phase changes include the transition from solid to liquid (melting), liquid to solid (freezing), liquid to gas (evaporation), and gas to liquid (condensation). The laws of thermodynamics govern these changes, which are caused by changes in temperature and pressure.

With ColdStream, you can simulate and design with evaporating and condensing fluid materials. Evaporation, or the transition from liquid to gas, occurs when a liquid absorbs heat. This heat counteracts the forces that hold the fluid particles together, allowing them to transition into a gaseous state.

On the other hand, condensation is the reverse process of evaporation. When a material in a gaseous state is cooled, the particles lose energy and begin to move more slowly. This effect forms bonds between the particles and the eventual transition into a liquid state.

Phase change can also be a result of a change in pressure. Sometimes, a combination of pressure and temperature changes is necessary to bring about phase change in some materials.

Table - Two-phase properties of ammonia at 80°C

Phase-changing materials play an important role in thermal applications due to their capability to store and release large amounts of thermal energy. During the optimization process, we can represent the solution space using a graph, with the optimal solution being the peak of the graph. In some cases, the graph may have multiple peaks representing multiple optimal solutions. However, in the case of a phase change, the graph may change its shape dramatically with small changes in the problem's parameters. This means that the optimal solution may vary from one peak to another, even though the problem's parameters are similar.

Figure - Two-phase cooling

Modeling two-phase flows introduce a much higher complexity to the problem when compared with single-phase flows. ColdStream uses the homogeneous model (HEM) to capture the physics of two-phase flows in two-phase cooling applications.

For more technical information, download our white paper here. Our case study on the two-phase evaporator demonstrates ColdStream’s capability to design components for two-phase cooling with generative design. Understanding phase change in the coolant material is important before starting your simulation or design runs, as it can change the results significantly.

Feel free to contact our team to check how ColdStream can be tailored to your needs.

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