The volumetric effect indicator – A new dimensionless characteristic number for the optimum design and operation of volumetric solar receivers

Abstract

This work introduces a new dimensionless number Z that should aid in the design phase of volumetric receivers. The number Z is able to indicate whether the volumetric effect is achievable for a specific combination of absorber geometry and thermal boundary conditions. It can be seen as an indicator of the slope of the solid-phase temperature profile in direction of gas flow. The volumetric effect is expected to occur at values of Z smaller than 1, when the convective plus radiative cooling (Pc) outweighs the absorbed solar power (Pa). An experimentally validated numerical model is used for a parametric simulation study, which sheds light on the absorber’s operating conditions (incident solar flux density and operating temperature) that favor the ideal temperature profile.