Experimental analysis of emission efficiency of parallel and serial connected radiators in EN442 test chamber

Highlights: • 11-type and 22-type serial-connected radiators are the most performing. • Correlation curves between various thermal comfort variables are derived. • The ratio of surface to total thermal resistance of the radiator is computed. • The convection coefficient dependency on the room geometry is quantified. • Improved analytical adjustment method for surface temperature variations. - Abstract: In the wide context of energy performance, the design of standard radiators has shown a large improvement in the past decades. Nevertheless, it is still necessary to achieve better understanding of the radiators emission losses. We conduct measurements of temperature and heat output of different types of emitters in a test chamber of the standard EN 442-2, aiming to quantify the emission efficiency differences of the radiators studied. We find that in the absence of ventilation, the air stratification is relevant and can explain the heat output differences between repeated tests of the same radiator. Moreover, correlation curves are derived between relative heat output and radiative component, and between heat output and air and operative temperature difference. Our detailed analysis shows that thermal comfort is more easily achieved with 11-type radiators, due to the bigger panel surface area, and with 22-type serial-connected radiators, due to their higher front surface panel temperature. From the measured data we derive the ratio of surface to total thermal resistance of the radiator, and the convective heat transfer coefficient dependency on the room geometry. While the majority of our results apply strictly to the EN442 test chamber, these can be used for the application to an ordinary room.