Solar Heat Exchanger, ANSYS Fluent CFD Simulation Tutorial

Description

This simulation is about a solar heat exchanger via ANSYS Fluent software. We perform this CFD project and investigate it by CFD analysis.

This system consists of two parts: the water flow moves in the central part of the heat exchanger, and the airflow is in the gap located in the front plate of the heat exchanger.

The water flow enters the heat exchanger at a velocity of 4 m/s and a temperature of 30 ° C and leaves the heat exchanger at atmospheric pressure. The heat exchanger absorber wall is exposed to solar radiation and absorbs heat through radiant heat transfer.

This means the air gap temperature in front of the absorber plate rises as the sun heats up. This increase in air temperature causes heat to be transferred to the absorber plate, and subsequently, heat is transferred from the absorber plate to the water flow inside the heat exchanger.

Therefore, the water flow inside the system increases with the temperature received by the absorber plate. Also, to enhance heat transfer, several rows of inner walls are designed as a barrier inside the heat exchanger to prolong the water flow and increase the chance of contact with the absorber plate.

The geometry of the present model is drawn by Design Modeler software. The model is then meshed by ANSYS Meshing software. The model mesh is unstructured, and 304200 cells have been created.

Solar Heat Exchanger Method

The radiation model is used to define radiation heat transfer, and the defined Radiation model is discrete ordinates (DO). The discrete ordinates model is used for cases where the radiation heat transfer equations are solved for a finite number of discrete solid angles.

This model is the most comprehensive radiation model. It is used for scattering light, semi-transparent environments, glossy surfaces such as mirrors, and wavelength-dependent transitions.

Also, the solar ray tracing model has been used to apply solar load on the heat exchanger. The amount of direct solar radiation is defined as 1150 W.m-2, the amount of diffuse solar radiation is defined as 80 W/m2, and the direction of the sun’s rays is perpendicular to the absorber plane.

Solar Heat Exchanger Conclusion

After simulation, 2D and 3D contours related to pressure, velocity and temperature are obtained. The results show that the water flow temperature increases from the inlet section to the outlet section.

These temperature changes indicate that the radiation heat transfer and the effect of the solar ray tracing are completely applied to the heat exchanger absorber plate and, consequently, to the water flow.