Numerical calculation of temperature distribution in power sypply unit of a radio frequency ion thruster
Thermal flows emitted by power sypply unit (PSU) components lead to their heating, which, in its turn, may lead to changes of their operating characteristics up to their failure. Thus, the temperatures of these components should be maintained within the ranges ensuring maintenance of their operating characteristics. For this purpose a preliminary simulation of thermal processes in the PSU housing was performed. The article presents a model for temperature distribution calculation in separate components of a radio frequency ion thruster’s structure. These calculations were performed using ANSYS bundled software. Due to the negligible effect of thermal flows from the thruster unit on the thermal state of PSU, thermal simulations of the thruster unit and the PSU were performed separately. The aluminum thermostatically controlled mounting flange, located above the gas-discharge chamber presents the boundary. All PSU’s structural elements in the computer model are simulated as simple geometric forms, such as cylinders or parallelepipeds with appropriate geometrical dimensions. The total heat emission in the PSU unit from all its constituting elements is taken equal to 66.4 W. This value corresponds to the operating mode of a low-power radio frequency ion thruster. To intensify maximally the heat removal by radiation, the emissivity factor of 0.9 was attributed to all external surfaces of the PSU unit components. To maximize radiant heat removal, the outer surfaces of elements of PSU were modeled with the emissivity of 0.9. To increase the conductive heat exchange, a partial PSU components’ potting (gersil) was performed. The calculation used the real thermal contact between adjacent surfaces with corresponding values of thermal junction resistance. A series of calculations was conducted for various the compound’s thermal resistance values from 1.2 to 2.7 W/(m·K). The figure below shows the dependence of the temperature of the most heated component of the structure under various thermal conductivity coefficients of the compound. The requirements for the thermal conductivity of the compound for filling the PSU’s PCBs were determined. When using materials with thermal conductivity exceeding 1.7 W/(m·K), it is possible to ensure the permissible temperature of electronic components at a temperature of the mounting flange reaching 50°C. Dependence of the maximum PSU’s temperature on the coefficient of thermal conductivity of the compound The developed physico-mathematical model can be employed at the stage of the ion thruster preliminary designing.