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

Description

Flat plate solar collectors (FPSC), and the photovoltaic-thermal (PV/T) systems built around them, convert sunlight into useful heat — most commonly by warming water that flows through pipes bonded to a sun-facing absorber plate. Their performance depends on the collector design, the materials of each layer, and the installation conditions: geographic location and tilt angle directly determine how much solar energy the panel receives.

This project uses ANSYS Fluent to simulate an FPSC installed in Doha at a 45° tilt angle, solving the full conjugate heat transfer (CHT) problem to capture how solar radiation heats the water passing through the collector's pipes. Because the model resolves the solid layers, the pipe walls, and the water flow as one coupled thermal system — and includes the heat generated inside the PV layer itself — it represents a true PV/T simulation rather than a simple solar-heating case.

Methodology

The collector geometry is created in Design Modeler, and a tetrahedral mesh of approximately 5,590,000 elements is generated in ANSYS Meshing. A mesh of this size is required to resolve the thin solid layers, the pipe walls, and the water domain together within a single coupled model.

The simulation couples three sets of physics:

• The Navier–Stokes equations for the water flow inside the pipes

• The energy equation for heat transfer through both the fluid and the solid layers (conjugate heat transfer)

• The Discrete Ordinates (DO) radiation model for the incoming solar irradiation, set at 800 W/m²

Water enters the collector at 300 K with a mass flow rate of 0.02 kg/s and exits at atmospheric pressure. A key feature of the model is the treatment of the PV layer: instead of representing the panel as a simple absorbing surface, the volumetric heat flux inside the PV layer is calculated from the solar flux, the glass transmittance, the PV absorption coefficient, the panel efficiency, and the PV layer thickness, and is then applied as a volumetric heat source. This physically based heat generation term is what distinguishes the case as a genuine PV/T simulation.

Analysis

At the end of the solution process, temperature contours and volume-averaged results are extracted to evaluate the thermal performance of the collector. The results clearly show how solar radiation progressively raises the water temperature as it travels through the collector pipes: the average water temperature reaches about 306.5 K, while the average PV layer temperature reaches about 310.1 K — the panel running hotter than the water it heats, exactly as expected in a PV/T system.

By completing this project, you will be able to set up a coupled CHT simulation with radiation, apply the DO model for solar loading based on location and tilt, implement a volumetric heat source derived from physical panel parameters, and interpret the temperature distribution across a multi-layer solar collector.