A Single-slope Solar Still, often called a Solar distiller, is a simple but brilliant device that uses the sun’s energy to produce clean drinking water. It functions exactly like the natural water cycle. The sun heats a basin of salty or dirty water, causing it to evaporate and turn into clean water vapor, leaving impurities behind. This vapor rises, touches a cool, tilted glass cover, and condenses into pure water droplets. Because it is low-cost and uses free renewable energy, it is a vital technology for water purification.

The main goal of this project is to perform a Solar Still CFD validation. This means we are not just running a simulation; we are proving that our 2D Solar Still Simulation is accurate by comparing it with real scientific data. We have recreated the numerical study from the reference paper by Rahbar and Esfahani [1]. For more insights into sustainable technologies, please visit our Renewable energy tutorials.

• Reference [1]: Rahbar, Nader, and Javad Abolfazli Esfahani. “Productivity estimation of a single-slope solar still: Theoretical and numerical analysis.” Energy49 (2013): 289-297.

Figure 1: The 2D geometry and coordinate system for the Single-slope Solar Still CFD model [1].

Simulation Process: Modeling Evaporation in Fluent

Even though the geometry of the Single-slope distiller is a simple rectangle and triangle, the physics inside are complex. To model this evaporative still correctly, we first created a high-quality mesh for the 2D domain. The real challenge in this Solar Still ANSYS fluent setup was the solver settings. The air inside the still is a mixture of dry air and water vapor that changes density based on temperature. To simulate this, we activated the Species Transport model. This model is essential because it allows the Solar Still CFD solver to track the concentration of water vapor as it evaporates from the hot water surface, moves through the air, and condenses on the cool glass. Setting the correct density and mass diffusivity parameters was critical for a successful validation study solar still CFD.

Post-processing: Validating the Solar Distiller Against Data

A real analysis of the contours and data reveals exactly why our Solar Still CFD keywords model matched the reference paper so well. The velocity contour in Figure 2 shows the engine of the still: a slow, circular current of air and vapor. This is called natural convection. The hot, moist air near the water basin becomes lighter and rises. When it hits the cool, sloped glass, it cools down, becomes heavier, and sinks back down. This creates a continuous loop that drives the process. Our simulation captured this behavior perfectly, showing a maximum flow velocity of 0.294 m/s. This specific speed is crucial because it transports the vapor to the glass. Because we captured this physics correctly, the quantitative validation was excellent. We compared our Single-slope Solar Still keywords results directly with the paper’s data. The paper reported a productivity (water output) of 5.29e-5 kg/m²·s. Our Solar Still fluent simulation predicted a value of 5.04e-5 kg/m²·s. This is an incredibly close match, with a very small error of only 4.7%. We also checked the heat transfer efficiency using the Nusselt number (Nu). The paper gave a value of 15.5, and our calculation was 14.48, resulting in a low error of 6.5%. These low error percentages prove that our evaporative distiller keywords model is valid and reliable for predicting solar still performance.

Figure 2: Velocity field inside the Distiller Fluent simulation, showing the natural circulation loop.

Figure 3: Water vapor mass fraction, showing high concentration above the water basin.

Key Takeaways & FAQ

• Q: What is the main benefit of a Single-slope Solar Still?
  • A: A Single-slope Solar Still is simple to build and maintain. As shown in this Solar Still CFD validation, it effectively uses the sun’s heat to evaporate water and condense it on a tilted surface, producing clean water with zero fuel cost.
• Q: Why do we use the Species Transport model in Fluent?
  • A: In a Solar Still ANSYS fluent simulation, the air is not empty; it is a changing mix of air and water vapor. The Species Transport model is required to calculate how much vapor moves from the water to the glass, which determines the productivity.
• Q: What does the validation error tell us?
  • A: The validation error of 4.7% for productivity tells us that our CFD simulation is very accurate. It means the virtual model behaves almost exactly like the real physical device reported in the scientific paper.