Room surface convective heat transfer with ceiling fans and its effect on radiant cooling systems

The integration of ceiling fans with radiant systems remains underexplored despite their potential to address cooling capacity limitations. This study adopts a two-step approach to quantify the impact of elevated air movement on thermally activated building systems (TABS). First, we used OpenFOAM to calculate convective heat transfer coefficients under varying airflows, air-to-surface temperature differences, and zone sizes. These coefficients also apply to ceiling fans in buildings without radiant systems. Second, we implemented these coefficients in EnergyPlus to evaluate key radiant design parameters. Scenario 1 results show median steady-state cooling heat transfer rates increase of up to 47% relative to the no-fan cases when operative temperature is held constant. Scenario 2 demonstrates a median cooling effect of up to 4.8 K under fixed capacity, reflecting both lower zone temperatures and direct air movement on occupants. Overall, TABS-fans systems offer a scalable strategy to enhance comfort, increase capacity, and reduce energy demand.HighlightsWe use CFD to develop simplified surface convective heat transfer models that account for air movement with ceiling fans on room surfaces.We use simplified surface convective models in EnergyPlus to evaluate radiant system performance with ceiling fans.Ceiling fans increase the zone’s steady-state cooling heat transfer rate by a median of 47% at the highest fan speeds.Ceiling fans have a median cooling effect of up to 4.8 K at the highest fan speeds.A radiant and ceiling fan couple system has the potential to decrease HVAC energy use while maintaining occupant thermal comfort.