Generic mathematical formulation of the total heat transfer coefficients between heated radiant floor surfaces and rooms

Abstract

In radiant floor heating systems, the total heat transfer coefficients (THTCs) of floor surfaces represent a key parameter for design and performance calculations. A small change in the THTC exerts a non-negligible effect, but the THTC values or formulas given in the literatures are different. Moreover, no study has explained this phenomenon thus far. Therefore, the selection of THTC values is relatively subjective in practical engineering. In the context of promoting energy savings and realizing carbon neutrality as soon as possible, further research must investigate THTCs. On the based of the principle of heat balance, a generic calculation model of the THTCs is proposed, and its accuracy is verified with experimental data. The influence of each parameter on THTCs is analyzed and unified as the influence of temperature difference. Then, the improved formula is obtained, and its adaptability and accuracy are verified with experimental data from two studies. Results show that indoor design temperature greatly affects THTCs. The reason behind the different THTC formulas given in existing studies is also discovered. Given the same indoor design temperature, the relationships between THTCs and temperature differences caused by different parameters follow the same trend line. Only the improved THTC formula shows a good agreement with the experimental data in the literature and is even better than the recommended formula. The overall standard deviations of the proposed formulation from the experimental data in the two references decrease by 85.6% and 78.2% relative to the THTC formulation based on the EN/ISO Standards.