Experimental investigation of energy-optimum radiant-convective heat transfer split for hybrid heating systems

• Radiant floor heating and electric fan heating hybridized.
• Optimum radiant-convective split of hybrid heating system is between 0.65 and 0.75.
• Exergy based rationality of the system analysed.

In this study, indoor radiant-convective heat transfer split of hybrid heating systems has been experimentally investigated in order to quantify the advantages of hybrid heating systems for thermal comfort in terms of operative temperature for thermal comfort and energy consumption. Operative temperature is a key parameter which is a function of indoor surface temperatures, clothing, air movement and dry-bulb air temperature. Controlled experiments were carried out in a special test chamber which was constructed according to ANSI/ASHRAE Standard 138. In this test chamber all interior surface temperatures and the dry-bulb air temperature were independently controlled. Two different types of electric fan heaters, with equal heating capacities but different fan powers, were hybridized with hydronic floor heating. In the series of experiments; fan heaters and the floor heating system were operated with different heating capacities simultaneously and hereby radiant-convective split was varied where the corresponding energy consumptions were recorded. During the process of obtaining the optimum radiant-convective heat transfer split; human comfort and energy consumption parameters were analyzed in terms of the operative temperature and exergy. According to the results of the experimental data and operative temperature-based optimization, optimum interval of radiant-convective split has been found to be between 0.65 and 0.75.