Experimental and simulated study on thermal environment of large-scale indoor spaces using radiant panel heating-cooling system

In some buildings with high ceilings and large areas such as the stadiums, there has been an increase in the implementation of radiant panel heating-cooling system (RPHCS) to avoid strong air convection currents. Unlike traditional air conditioning throughout whole room, the spaces that require air conditioning are limited to localized areas, which makes it difficult to achieve high efficiency and energy saving. In previous studies, the heat transfer performance and energy efficiency of RPHCS have been analyzed and some optimizations on the system have been proposed. The thermal comfort evaluation in general indoor spaces such as offices has also been explored. For those large-scale indoor spaces equipped with RPHCS, environmental design to reduce energy consumption while maintaining spatial comfort is unformed, as particular simulation method has not yet been fully established.

This study aims to develop a numerical simulation method and to improve its calculation accuracy to evaluate the thermal environment quantitatively, supporting the environmental design in the aforementioned cases. We conducted an experimental investigation of the thermal environment in a research institute with large-scale indoor spaces equipped with RPHCS in both summer and winter. Based on the experimental conditions, the study performed numerical simulations of the indoor thermal environment using the BES (Building Energy Simulation) method and CFD (Computational Fluid Dynamics) method. We applied dimensionless numbers in the field of fluid mechanics to achieve the convective heat transfer coefficient of the non-standard radiant panels and used measurement data to estimate their hypothetical effective areas.

In the case of summer, the dehumidification process of the radiant panel was analyzed, and the ambient humidity and dehumidification capacity of RPHCS were evaluated based on the theory of thermodynamic energy ‘water potential’[1]. For winter conditions, the temperature gradient in vertical direction was calculated by ways of dividing spaces and considering imaginary walls and ceilings. In this way, the amount of advection between spaces becomes a quite important parameter, which is difficult to estimate though. Therefore, a static coupling calculation of CFD and BES[2] was employed, so that reliable advection conditions can be provided by CFD which can clarify the flow distribution.

The simulation results showed good consistency with the experimental data and the appropriateness of these methods have been confirmed. It may provide a reference approach when analyzing the thermal environment of large spaces using RPHCS and help to establish precise numerical simulation support for environmental design and system optimizations.