Experimental evaluation of the cascaded energy storage radiator for constructing indoor thermal environment in winter

Clean heating technologies have been developed in past decades and numerous strategies have been adopted in improving the heat transfer performance of energy storage radiators. Nevertheless, the integrated heat storage/ release effect by enhancing thermal conductivities of PCMs and the radiator has rarely been studied, and the energy utilization efficiency needed to be evaluated by considering the cascading and stratification effect. Based on these, three kinds of energy storage radiators were designed with different types and layouts of energy storage bricks, i.e. (I) magnesium-aluminum (Mg-Al) energy storage bricks without aluminum foil wrapping, (II) Mg-Al energy storage bricks wrapped by aluminum foil and (III) cascaded energy storage bricks with Mg-Al and paraffin wax-expanded graphite (PW-EG) energy storage bricks wrapped by aluminum foil. These radiators were experimentally evaluated from aspects of heat storage/release amount, heat transfer capacity and indoor thermal environment characteristics. After using aluminum foil to package energy storage bricks, the temperature rise/ drop and heat storage/release rate of energy storage bricks were 21.0/56.8 degrees C higher and up to 95.7/119.0 W faster respectively (Radiator II vs Radiator I). While after using cascaded energy storage bricks, the heat storage/ release efficiency was 11.9 %/14.6 % higher, the indoor vertical/horizontal temperature difference was 2.5/ 0.2 degrees C smaller, and the energy utilization efficiency by occupied space to total power consumption was 24.3 % higher (Radiator III vs Radiator II). Therefore, the aluminum foil packaging energy storage bricks were shown to improve the thermal conductivity, and the cascaded energy storage radiator owned higher thermal storage/ release capacity and energy utilization efficiency.