Reconstruction of three-dimensional temperature fields in micro-fixed bed reactor based on infrared thermography and thermal probe method

Abstract

Aiming at determining the characteristics of small volume and complex heat and mass transfer of micro-reactors, an online measurement system was designed and built. The temperature of the reactor surface was measured by infrared thermography. For reconstruction of the three-dimensional temperature field of the micro-fixed bed reactor, mathematical and physical models were established by finite difference of governing equations and boundary conditions, and the objective function was established based on the principle of least squares. Then, using the conjugate gradient algorithm, the three-dimensional temperature field was rebuilt in the fixed bed reactor. It was verified that the micro-reactor filled with resin particles had a porosity of 0.432 under an initial temperature of 20 °C and adiabatic conditions; distilled water of a constant temperature of 50 °C was introduced into the reactor at a flow rate of 3.2 ml/min, and the internal temperature field was deduced from the surface temperature of the reactor. The experiment also used micro-thermocouples to measure the internal temperature at multiple points to compare with the inverse temperature field. The temperature change trend was consistent, and the maximum error was 4.85% in a no reaction condition and 7.1% in catalytic reactions, which verified the accuracy of the inverse method.