Infrared thermospectroscopic imaging of heat and mass transfers in laminar microfluidic reactive flows

Abstract

In this work, a novel image-based method is presented to characterize the heat and mass transfer rates in a Hele-Shaw microfluidic reactor. A Fourier transform infrared (FTIR) spectrometer is used in transmission mode in combination with an infrared (IR) camera to simultaneously measure the molar concentration and the thermal fields in the microfluidic chip within few seconds. A classical exothermic NaOH + HCl → NaCl + H2O chemical reaction is used to produce a multiphase flow and a heat source in the reactor. The molar concentration fields of all the species are measured using the IR spectrum in the mid-IR region, and the heat fields are obtained simultaneously from the proper emission. The quantitative aspect of the method is illustrated by comparing the molar concentration profiles to a reactor model, based on the advection-diffusion-reaction equations. The good agreement between the model and experimental data validates the method, and the expected strong diffusion-limited reaction regime in laminar microfluidic reactor is achieved. Thus, the results of this work provide a new and efficient thermospectroscopic imaging method to perform rapid, contactless and in operando heat and mass transfer characterizations in laminar microfluidic reactive flows.