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artin, Stephanie A. M

Hoff, Brad W.

Rittersdorf, Ian M.

Yakovlev, Vadim

English

Engineering Conferences International

COMPUTATIONAL STUDY OF TEMPERATURE IN A MILLIMETER WAVE HEAT EXCHANGER WITH AN AlN:Mo SUSCEPTOR ON AN ISOTHERMAL METAL PLATE   Vadim V. Yakovlev, Department of Mathematical Sciences, Worcester Polytechnic Institute, USA vadim@wpi.edu Stephanie A. Martin, Department of Mathematical Sciences, Worcester Polytechnic Institute, USA Brad W. Hoff, Air Force Research Laboratory, USA  Ian M. Rittersdorf, Naval Research Laboratory, USA     Recent developments suggest using electromagnetic (EM) heating technology in EM heat exchangers (HX) for solar energy collectors and ground-to-ground millimeter-wave (MMW) power beaming. These devices convert EM energy into usable thermal energy, relying on the balanced EM, heat transfer, and fluid flow phenomena. The interactions between the MMW field and an absorbing ceramic element of a HX need to be well understood to develop an efficient device in which the material is controllably heated and the heat is efficiently transferred to another medium (e.g., fluid).  In this work, we develop a computational model to simulate EM and thermal processes in a simplified model of a MMW HX (Fig. 1) and examine different ceramic materials to find the one that maximizes the device's efficiency. EM and EM-thermal coupled problems are solved by the finite-difference time-domain technique (implemented in QuickWave) for a block of AlN:Mo composite that is backed by a thin metal plate and irradiated by a MMW plane wave. Computation is based on experimental data on temperature-dependent dielectric constant, loss factor, specific heat, and thermal conductivity. We focus on an operational regime in which the metal plate is maintained at a constant temperature Tc to prevent the ceramic block from overheating.   We show that, at 95 GHz, 10x10x10 mm blocks with Mo contents from 0.25 to 4% can be heated up to 1,000oC highly uniformly for 60-95 s, depending on concentration of Mo. The composite with the highest level of total dissipated power is found to have Mo around 3% (by volume). When Tc is fixed at the level of 600-800oC, maximum temperature in the susceptor stabilizes within 15-20 s (Fig. 2). Tempe-rature gradient throughout the block does not exceed 70-95oC and thus remains below the threshold for a mechanical robustness (Fig. 3).   Figure 1. A MMW HX – the considered scenario. Input power density 100 W/mm2.    Figure 3. Time evolution of temperature pattern through the AlN:Mo block with Mo = 3 %; Tc = 700oC.  Figure 2. Time evolution of maximum temperature in the AlN:Mo block for different concentrations of the doping; Tc = 700oC.  Approved for public release; distribution is unlimited. Public Affairs release approval numbers AFRL-2022-1177.  

Computational study of temperature in a millimeter wave heat exchanger with an AlN:Mo Susceptor on an isothermal metal plate

https://dc.engconfintl.org/cgi/viewcontent.cgi?filename=0&article=1057&context=uhtc_v&type=additional

Computational study of temperature in a millimeter wave heat exchanger with an AlN:Mo Susceptor on an isothermal metal plate

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Engineering Conferences International