The research of thermal condition of electrodes of thermionic converter with indirect heating


Аuthors

Akatev I. D.1*, Yashin M. S.2, Onufriev V. V.1

1. Bauman Moscow State Technical University, Moscow, Russian Federation
2. LUCH JSC, Podolsk, Russian Federation

*e-mail: akatevid@student.bmstu.ru

Abstract

The article is devoted to the study of the thermal state of electrodes of a thermionic emission convert-er (TEС) with radiant heating by incandescent products of natural fuel combustion. The authors con-ducted a study of the thermal state of electrodes using the COMSOL Multiphysics finite element (FE) analysis software package, which allows solving multiphysical problems represented by a system of partial differential equations. A simplified three-dimensional geometry consisting of flat cylindrical electrodes, a metal-ceramic assembly, and an internal interelectrode gap filled with cesium is consi-dered. The modules «Heat Transfer in Solids and Fluids» and «Surface-to-Surface Radiation» were used under the specified boundary conditions corresponding to the operation of the TEC in idle mode – in the absence of electronic cooling of the emitter. The calculated method has obtained the tempera-ture field in the electrodes and insulator of the TEC, which allows us to judge the effect of the thermal conditions of the structural elements on their temperatures. It is established that one of the main fac-tors influencing the efficiency of a TEC with a plane-parallel geometry of electrodes is the thermal re-sistance of the structural elements. The heat fluxes in the geometry under consideration are estimated using the heat balance equations for the elements of the TEC structure. It is determined that the main part of the heat flow from the emitter to the collector in the geometry under study is transmitted through an insulator. It is necessary to increase the thermal resistance of the structural elements be-tween the electrodes to ensure the required temperatures of the TEC electrodes. However, additional research is required depending on the chosen method of increasing the thermal resistance of structural elements – the use of materials with very low thermal conductivity or the use of geometric profiling of structural elements. It is advisable to take into account additional heat flows in the proposed model for a multiparametric study and optimization of the thermal condition of the TEC structure for various modes of its operation. A parameterized model of the three-dimensional geometry of TEC with vari-ous designs of insulator structures and the materials used can be a development of the presented model.

Keywords:

thermionic emission converter, flat electrodes, thermal state, finite element model, heating, cooling

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