Battelle has developed a mesoscale combustor/evaporator that provides a lightweight and compact source of heating, cooling, or energy generation for both man-portable and stationary applications. The device uses microscale flow channels that increase the available surface area for heat transfer and reduce the fluid boundary layer. These characteristics in turn result in heat fluxes for hydrocarbon/air combustion in excess of 25 W/cm2 and thermal efficiencies of 80 to 90%. Furthermore, high heat transfer rates allow for short channels and reduced pressure drops.
Recent development efforts have focused on obtaining low emissions and improving the combustor/evaporator fabrication process. By using spatially varying stoichiometry inside the combustor, catalyst coated microchannels, and increased coolant temperature, the combustor’s CO and NOx emissions were reduced to below California standards for hot water heaters and boilers. The fabrication process photochemically machines thin metal laminates and then uses diffusion bonding to form a monolithic component. This approach is capable of high fin aspect ratios and can be scaled up for mass production.