Solar Still Integration with Renewable Solar Ray Tracing, Phase Change Materials and Multiphase CFD Modeling

Description

Introduction

In this project, we simulate a solar still with a PCM. The PCM zone saves the sun energy at day and releases this energy at night. This computational fluid dynamics (CFD) project investigates a complex thermal and multiphase system subject to environmental heating and phase change phenomena. The study aims to simulate the transient thermal behavior, fluid dynamics, and phase transformations occurring within a multi-component domain, providing critical insights into the coupled interactions of heat transfer, natural convection, solar radiation, and evaporation. For the computational cost, we solved just about 12 seconds of this simulation.

Geometry and Mesh

The physical geometry of the system was modeled using ANSYS SpaceClaim, capturing the multi-layered domain configuration and internal sub-regions such as the phase change material and fluid zones. To resolve the complex gradients and spatial interactions across all domains, a high-quality unstructured tetrahedral mesh consisting of approximately 3.3 million elements was generated using ANSYS Meshing.

Setup

Numerical simulations were performed using ANSYS Fluent with a pressure-based transient solver formulation incorporating gravitational effects. A VOF multiphase model with four distinct Eulerian phases was established, featuring water as the primary phase alongside vapor, air, and a phase change material (PCM). A custom user-defined function (UDF) was implemented to govern the mass transfer mechanism for phase change from liquid water to vapor. The energy equation was enabled along with a laminar viscous model, and the Discrete Ordinates (DO) radiation model with active solar ray tracing was utilized to account for radiative thermal loads. Pressure-velocity coupling was solved using the coupled algorithm.

Results

The simulation results illustrate the detailed transient thermal and phase distribution characteristics of the system. Temperature contours highlight the heat propagation paths and spatial thermal gradients, while liquid fraction and volume fraction contours successfully capture the melting behavior of the paraffin wax PCM and the vaporization dynamics of the water-vapor interface over the simulated timeframe.