Superadiabaticity in reaction waves as a mechanism for energy concentration

Spatially propagating reaction waves are central to a variety of energy applications, such as high temperature solid phase or combustion synthesis, and thermopower waves. In this paper, we identify and study a previously unreported property of such waves, specifically that they can generate temperatures far in excess of the adiabatic limit. We show that this superadiabaticity occurs when a reaction wave in either one dimension (1D) or two dimensions (2D) impinges upon an adiabatic boundary under specific reaction and heat transfer conditions. This property is studied analytically and computationally for a series of 1D and 2D example systems, producing an estimate of the upper bound for excess temperature rise as high as 1.8 times the adiabatic limit, translating to temperatures approaching 2000 K for some practical materials. We show that superadiabaticity may enable several new types of energy conversion mechanisms, including thermophotovoltaic wave harvesting, which we analyze for efficiency and power density.