Particle–particle heat transfer coefficient in a binary packed bed of alumina and zirconia-ceria particles

Kurzfassung

Solar thermochemical processes for fuel production require the incorporation of heat recovery Systems for substantial efficiency gains. A heat recovery concept for processes using a particulate redox material proposed by the authors utilizes a second particulate material as a solid heat transfer medium. This work is about the experimental investigation of the heat transfer between these two particle species in a binary packed bed. Experiments were performed at temperatures up to 250 °C regarding the influencing factors of contact time, mass ratio, average temperature, temperature difference and particle diameters. Design of experiments helped as a method to plan and analyze these experiments. In addition, the temperature dependent specific heat capacity, the density and the size of the investigated particles were experimentally analyzed. In order to consider heat losses to the experimental setup, a correction measurement campaign was undertaken. The results are in the form of a polynomial which predicts the heat transfer coefficient depending on its influencing factors. This polynomial was obtained by a stepwise linear regression method. Values between 90 and 260 W/m2 K are predicted for the given temperature range. In an alternative approach we characterized the heat transfer in terms of the temperature difference of one particle species.