An equivalent thermal resistance model to calculate the heat transfer of radiant floor heating and cooling systems using shape factor

An equivalent thermal resistance model for the heat transfer calculation of radiant floor based on shape factor was developed in this study. The proposed model was verified by numerical simulation, and compared with the data from the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The heat transfers obtained by the numerical simulation disagreed significantly with the existing methods including the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The maximum error rates were 20.2%, 30.4%, and 22.8%, respectively, when the tube space ranges from 50 to 250 mm, the thickness of fill layer above pipe ranges from 25 to 65 mm, and the average hot water temperature ranges from 25 to 45℃. On the other hand, the maximum difference of the heat transfer predictions between the proposed model and the simulation software was less than 3%. When the tube space ranges from 50 to 200 mm, the thickness of fill layer above pipe ranges from 15 to 55 mm, and the average cold water temperature ranges from 10 to 20℃, the maximum error rates of the heat transfer predictions between the numerical simulation and the existing methods were 80.1%, 17.7%, and 16.8%. On the other hand, the heat transfer predicted by the proposed model showed less than 2% of difference from that of the numerical simulation.