Advances in Heat Transfer for Solar Thermochemical Applications

Thursday, November 12, 11:00 a.m.
Warnock Engineering Bldg. (WEB) 2230

Wojciech Lipiński, Ph.D.
Associate Professor
Research School of Engineering
The Australian National University

Abstract: Heat transfer in chemically reacting media is a complex transient phenomenon typically encountered in combustion, fuels and materials processing, extractive metallurgy, and other high-temperature processes involving media of time-dependent composition and morphology. Of special interest are endothermic processes that make use of concentrated solar radiation as the source of process heat.

Solar thermochemical processes are suitable for production of fuels, in which solar energy is stored in form of chemical bonds, and chemical commodities for industrial, agricultural and other applications, as well as high-temperature thermal energy storage. High-temperature solar thermochemical systems are designed for maximum solar-to-chemical energy conversion efficiency and fast process rates.

The reactors typically feature solid–gas heterogeneous media at temperatures exceeding several hundred degrees Celsius, and in some applications reaching more than 2000ºC. In directly-irradiated reactors, radiation is predominantly absorbed by a solid that provides surface to a chemical reaction. In indirectly-irradiated reactors, radiation is absorbed by an inert solid and then transferred to a chemical reaction by conduction, convection, and/or radiation through an intermediate heat transfer medium.

Thermal transport processes have been extensively studied at discrete spatial levels varying from nano- to micro- to macro-scale. Accurate characterization and simulation techniques connecting highly disparate spatial and temporary scales of solar thermochemical systems require significant advancements to become computationally effective. Such techniques are desired for direct design and optimization of reactors featuring prescribed materials of unknown continuum characteristics.

Advancements in materials and computational sciences have also enabled a less explored approach of materials-by-design, in which materials of prescribed continuum characteristics indicated by predictive reactor-level models are inversely engineered by targeted identification of suitable composition and morphology. Both the direct and materials-by-design approaches are useful for understanding and optimizing the complex thermal transport processes and, consequently, for minimizing irreversibilities and achieving high solar energy conversion efficiency.

In this presentation, recent advances in heat transfer for solar thermochemical applications are reviewed. Examples of computational studies of heat and mass transfer in solar reactors, reactive media and media features such as individual reacting particles are discussed together with recent developments in direct numerical predictions of thermal transport and optical properties of heterogeneous materials, from nano- to micro- to macro-structures, and their experimental radiative characterisation.

Bio: Wojciech Lipiński received his MSc Eng degree from Warsaw University of Technology (2000), and doctorate (2004) and habilitation (2009) from ETH Zurich. Currently, he is an Associate Professor and the Leader of the Solar Thermal Group at the Australian National University, and a Privatdozent at ETH Zurich. He previously held Senior Research Associate and University Lecturer positions in the Department of Mechanical and Process Engineering at ETH Zurich, and an Assistant Professor position in the Department of Mechanical Engineering at the University of Minnesota. His research interests are in thermal science, thermochemistry, applied optics, and applications to energy, environmental, biomedical and space engineering. Lipiński has published over 100 articles in peer-reviewed journals and conference proceedings, and contributed to several books, edited books and e-books. He was awarded the 2006 Hilti Award for Innovative Research from ETH Zurich, the College of Science and Engineering 2010–2011 Outstanding Professor Award from the University of Minnesota, and the 2013 Elsevier/JQSRT Raymond Viskanta Award in Radiative Transfer. Since 2011, he has served as the Associate Editor in Bioconversion and Solar Chemistry for the ASME Journal of Solar Energy Engineering, and the Elected Member of the Scientific Council of the International Centre for Heat and Mass Transfer. Lipiński is a member of AAAS, ACS, AIChE, ASME, EPS, ISES, and a senior member of AIAA and OSA