CALCULATION OF THERMOPHYSICAL PROPERTIES OF SLAB LASER MULTI-COMPONENT GAS MEDIUM

Subject of Research. The paper presents a method for calculation of thermal conductivity and viscosity of the gaseous slab laser medium. The method is based on the use of the known properties of its components. Thermal conductivity determination is necessary for mathematical and thermal modeling in the process of thermal mode development. The main feature of the proposed technique is application versatility and the possibility to obtain effective characteristics with sufficient accuracy for complex composition gases containing more than two components. Method.The calculation approach lies in consistent application of the Lindsay-Bromley and Wilke formulas for binary gas to the components of the mixture depending on their molar concentration. The component selection order is due to the smallest variance of the calculated values from the reference data. Main Results. The method was verified by comparison of the calculated and experimental data for three-component mixtures. It was found that viscosity measurement error does not exceed 1.5 % with an average deviation of less than 1 %. The average deviation of the values in the case of thermal conductivity is much higher, but the measurement error does not exceed 5 %. For the most frequently used composition of CO2, N2, Xe, and He mixture as a slab laser medium, the thermal properties were calculated for the minimum and maximum concentrations of carbon monoxide arising during operation. The tables show step-by-step application of the method and the dependence of thermal conductivity on temperature. There is a strong increase in thermal conductivity in the range of operating temperatures (more than twice). For example, at room-temperature range (300 K) it is equal to 0.067 W/(m·K), at 800 K it reaches 0.137 W/(m·K). This difference creates a significant non-uniformity of gas medium temperature field and affects drastically the laser stability. Practical Relevance.The results obtained can find practical application in the development of slab lasers and can be used to eliminate power drops and stabilize the operation of existing lasers providing the regulating process for the component concentrations of the gas composition.