High-resolution spatial estimation of abrupt heat flux fluctuations from infrared temperature measurements

The study presents a three-dimensional methodology for the fine spatial estimation of the heat flux exchanged at the interface between two contacting materials, based on the Sequential Function Specification Method (SFSM) with spatial regularization. A dedicated infrared camera provides a high-resolution measurement field (640 × 512 pixels at 120 Hz), enabling fine spatio-temporal reconstruction of the contact heat flux with sub-millimeter resolution and capturing abrupt spatial variations. The methodology is first validated through a numerical study based on a 3D conduction model. A complementary experimental validation is then performed, in which a prescribed Gaussian laser heat flux applied to an iron plate is retrieved at a resolution of 0 . 46 mm using infrared thermography data. Finally, the validated approach is applied to the target case, reconstructing the unknown contact heat flux between a French crêpe batter and an iron plate serving as a heating support, at a resolution of 0 . 92 mm based on the thermography grid. The effects of spatial regularization, spatial discretization (estimation and computational meshes), measurement noise, and future time steps are analyzed to assess the estimation accuracy. • SFSM is used to estimate fine spatial distribution (<1 mm) of heat flux with IR camera. • At each time step, up to 6000 values of heat flux are estimated. • Sharp Gaussian heat flux is well captured numerically and experimentally. • Interfacial heat flux transmitted to a thin crêpe batter was reconstructed.