Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

• Published in: Review of scientific instruments 2014-12, Vol.85 (12), p.124702-124702
• Main Authors: Surducan, E, Surducan, V, Limare, A, Neamtu, C, Di Giuseppe, E
• Format: Article
• Language: English
• Subjects: Adiabatic conditions; Aluminum; CCD cameras; Circuit protection; Command and control; CONVECTION; Convection heating; DESIGN; EARTH MANTLE; Electric power distribution; Experiments; Fluid filters; HEAT EXCHANGERS; Heat sinks; Image acquisition; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; INVERTERS; Launchers; LIQUID CRYSTALS; Load matching; MAGNETRONS; MICROWAVE HEATING; MICROWAVE RADIATION; Particle image velocimetry; Pulsed current; Sciences of the Universe; Scientific apparatus & instruments; SIMULATION; Stability analysis; Temperature distribution; Thermal evolution; Velocity distribution; Velocity measurement; Viscous fluids
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4902323

We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.