Frequency-domain RC-coupled dynamic heat transfer model for floor-radiated rooms

In rooms with large glazed areas, the influence of solar radiation on radiant floor air-conditioning systems in summer cannot be neglected. In this study, the projection equation method is first used to determine the distribution of solar radiation within the room. Subsequently, a frequency-domain RC coupled dynamic heat transfer model for rooms with radiant floors is established by incorporating the effects of solar radiation. The proposed model enables dynamic heat transfer analysis of radiant floor rooms under solar radiation conditions and facilitates the calculation of nodal heat fluxes and temperatures under varying operating conditions. A calculation program based on the proposed model is developed in MATLAB, and a south-facing room in Chongqing is selected as a case study. The results indicate that solar radiation significantly increases both floor surface temperature and indoor air temperature, thereby enhancing the floor cooling load. When only the external envelope load is considered, the the solar heat gain absorbed by the floor accounts for an average of 16.75% of the total floor cooling capacity, with a maximum contribution of 58%. In addition, solar radiation distributed on the interior and exterior walls further increases radiative heat exchange with the floor. Therefore, the effect of solar radiation should not be neglected in the thermal analysis and design of radiant floor systems.