Clean Water: Flat Plate Solar Collector, Conjugated Heat Transfer (CHT)

Flat Plate Solar Collector — Conjugate Heat Transfer (CHT) ANSYS Fluent CFD Simulation

Flat plate solar collectors (FPSC), and the photovoltaic-thermal (PV/T) systems built around them, convert sunlight into useful heat — typically by warming water that flows through pipes bonded to a sun-facing plate. How well they perform depends on the collector design, the materials in each layer, and where the collector sits and how it's tilted. This project uses ANSYS Fluent to model an FPSC installed in Doha at a 45° tilt, solving the full conjugate heat transfer (CHT) problem to see how solar radiation heats the water passing through the collector's pipes.

The geometry is built in Design Modeler and meshed in ANSYS Meshing with a tetrahedral grid of roughly 5.59 million elements — a large mesh needed to resolve the thin solid layers, the pipe walls, and the water together as a coupled system.

The simulation couples three physics together: the Navier–Stokes equations for the water flow, the energy equation for heat transfer through both fluid and solid, and the Discrete Ordinates (DO) radiation model for the incoming solar irradiation. Water enters at 300 K with a mass flow rate of 0.02 kg/s and exits at atmospheric pressure, while solar irradiation is set at 800 W/m². A key feature of the model is the heat generated inside the PV layer itself: rather than treating the panel as a simple absorber, the volumetric heat flux in the PV layer is computed from the solar flux, the glass transmittance, the PV absorption coefficient, the panel efficiency, and the PV layer thickness — then applied as a volumetric heat source. This is what makes the case a true PV/T simulation rather than a plain solar-heating one.

At the end of the solution, the results show clearly how solar radiation raises the water temperature as it travels through the collector. The average water temperature reaches about 306.5 K, and the average PV layer temperature about 310.1 K — the panel running hotter than the water it's heating, as expected. By the end of this project, you'll be able to set up a coupled CHT simulation with radiation, apply the DO model for solar loading, implement a volumetric heat source from physical panel parameters, and interpret the temperature distribution across a multi-layer solar collector.