The radiant ceiling system is considered to be a promising technology capable of meeting sustainable cooling requirements. Correct evaluation of the heat transfer process is important for its design and practical applications. This article reports a research on developing new simplified correlations for the total heat transfer coefficient and total heat flux density of the radiant ceiling panels. The correlations are proposed based on experimental results. The experiments are conducted in a climate chamber under different combinations of indoor operative temperature and supply water temperature. Unlike the existing correlations expressed in literatures, the new correlation for the total heat transfer coefficient takes into consideration both the operative temperature and the supply water temperature. Results show that the calculated total heat transfer coefficients by this correlation differ from the experimental results within ±7%. The new correlation is also extended to total heat flux density based on the inherent relationship between it and the total heat transfer coefficient. Results demonstrate that the predicted difference of the total heat flux density is also smaller than 7%. The results and the method reported in this study could be helpful in practical engineering applications.

The correct evaluation of the heat transfer process is important to the radiant cooling/heating system's design and operation. For different types of radiant systems, the cooled/heated surface and indoor environments are actually subject to the same heat transfer process. Thus some basic rules can be revealed to simplify the research or the design for the radiant systems. The purpose of this research is to establish a basic characteristic curve for cooling ceiling radiant panel system and provide a simple approach to determine its cooling capacity. Considering the limitations to conduct exhaustive experiments, this research applies an experiment-oriented simulation method to determine the cooling capacity of cooling ceiling radiant panel systems. A model for capillary tube mats is first developed and then validated by available experimental data. Based on the validated model, more conditions are simulated and more data are generated to investigate the relationship between the specific cooling capacity and temperature difference. The model treats the cooling capacity as a function of cooled ceiling surface's temperature and the air temperature at the third-boundary condition. Results show that the key variables, for example, the total heat flux density and the cooled ceiling surface's temperature, agree well with the experimental data, thus it is feasible for the model to be used in the simulation. The coefficients for the simplified cooling capacity model are obtained by fitting the data generated from the model. In addition, it is found that the total heat transfer coefficient can also be expressed similarly to the correlation reported in a literature for the natural convective coefficient, but with different coefficients so as to include the effects of radiation indirectly. The experimental and simulation results reported in this study can provide guidance for engineering applications.