Radiator Thermal Performance with Fans: Paper Validation

Radiator Thermal Performance with Fans, Paper Numerical Validation, ANSYS Fluent Tutorial

Description

This project examines heat transfer and airflow behavior around a radiator, based on the reference article "CFD Study on Thermal Performance of Radiators in a Power Transformer: Effect of Blowing Direction and Offset of Fans," with results compared and validated against the paper's published data using ANSYS Fluent.

The radiator features three fans driving horizontal airflow, along with several rows of fins and aluminum plates designed to enhance heat transfer. The 3D geometry was built in Design Modeler, consisting of three main components: the radiator body, the fans, and the surrounding air domain. The radiator itself is divided into four sections, each containing fourteen rows of plate fins along with hot water transfer pipes running along the top and bottom.

Three fans are positioned along the left side of the radiator body, generating horizontal airflow across its surface. The domain was meshed in ANSYS Meshing using an unstructured grid, with inflation boundary layer mesh applied along the radiator wall surfaces to properly resolve heat transfer between the fins and surrounding airflow, and face sizing applied to the fin surfaces for additional mesh refinement. The total element count reached 4,683,472.

Methodology

Hot water flows through the radiator's upper and lower pipes and its internal fins, with all pipe and fin wall surfaces assigned temperature values that vary with height along the radiator plates. This temperature profile was implemented through a temperature boundary condition driven by a UDF: hot water enters the radiator's upper section at 366.15 K and, as it flows downward through the pipes while exchanging heat with the surrounding airflow, cools to a minimum of 353.15 K by the lower section. Since this temperature variation follows primarily from the vertical flow direction, the UDF defines it as a simple linear profile: 346.15+5*y.

The three fans were modeled using the fan boundary condition, positioned along the plates on the radiator's side. Since incoming flow to these fans runs horizontally, rotational speed was defined about the x-axis. Since the fan boundary condition defaults to suction-mode flow but this model required blowing instead, the Reverse Fan Direction option was activated to correctly orient the airflow. Each fan's pressure jump was defined using a polynomial pressure-velocity function with coefficients of 80 and -10.

Conclusion

The net heat loss rate from the radiator plates to the surrounding airflow was calculated and compared against the reference paper's results, using Figure 5 of the article under the ONAF mode (forced convection heat transfer). Since the rate of heat loss from the radiator body to its surroundings can be equated to the temperature difference between inlet and outlet airflow, this comparison was performed using the Report tool's Total Heat Transfer Rate option under Flux Reports, yielding a value of 3738 (units consistent with the reference comparison) that aligned well with the paper's reported results.

Additional 2D and 3D contours of temperature, velocity, and pressure were also obtained, along with 3D pathlines and velocity vectors, providing a comprehensive view of the flow and thermal behavior throughout the radiator assembly.