Proposal of a design method for radiant ceiling cooling system using CFD analysis

In recent years, the adoption of water-based radiant ceiling cooling systems has been increasing in Japan with the aim of realizing comfort and energy savings. Conventionally, when designing radiant cooling systems, the target operative temperature for the indoor thermal environment is set, but these are usually combined with convection air conditioning system, which do not always achieve the target value during summer cooling. In addition, several parameters must be assumed at the design stage, originally not only operative temperature, but also temperatures of uncooled surface and radiant panel surface, etc. Therefore, it may not be possible to achieve the expected indoor thermal environment under the design conditions, which may affect the estimation of the cooling capacity of radiant panels and the calculation of the number of panels required.  
This study proposes a new design method that incorporates CFD analysis based on the conventional design method suggested by ASHRAE. By incorporating CFD analysis, several parameters can be determined at the same time under the assumed environment. In addition, determination of the optimal cooling capacity of radiant panels can be used to realize the target operative temperature by feedback control utilizing the results of CFD analysis. Therefore, in this study, the proposed method was used to redesign a real office with a radiant ceiling cooling system, and the effectiveness of the proposed method was evaluated. The results showed that the cooling capacity of radiant panels can be updated and that the number of panels required can be reduced without compromising indoor thermal comfort.