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.
Highlights
The micro-reactor, a new micro-chemical device, is fabricated by micro-machining technology, and it has been widely used in various fields, such as micro-chemical1 analysis, agriculture,2 energy applications,3 and so on
The objective function was established based on the principle of least squares, and the control equation and boundary conditions were of finite difference
The three-dimensional temperature field distribution of the fixed bed reactor was calculated from the surface temperature
Summary
The micro-reactor, a new micro-chemical device, is fabricated by micro-machining technology, and it has been widely used in various fields, such as micro-chemical analysis, agriculture, energy applications, and so on It has advantages such as short reaction time, accurate control of reaction temperature, high heat and mass transfer efficiency, and good safety performance.. Based on the infrared thermal image and probe method, the effective thermal conductivity and surface temperature distribution of the fixed bed under adiabatic conditions were measured to obtain the temperature field and the corresponding thermal properties under a certain working condition. Using the MATLAB platform, the measurement results are used in the mathematical model established by the finite element method combined with the least square principle, and the conjugate gradient algorithm program is used to reconstruct the three-dimensional temperature field of the micro-reactor. A micro-thermocouple was used to measure the internal temperature of the reactor, and the experimental data and simulation data were compared and analyzed
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