| Summary: | <p>The paper investigates an influence of helium fraction (light gases) on the Prandtl number value for binary and more complex gas mixtures.</p><p>It is shown that a low value of the Prandtl number (Pr-number) results in decreasing a temperature recovery factor value and, respectively, in reducing a recovery temperature value on the wall (thermoinsulated wall temperature) with the compressive gas flow bypassing it. This, in turn, allows us to increase efficiency of gasdynamic energy separation in Leontyev's tube.</p><p>The paper conducts a numerical research of the influence of binary and more complex gas mixture composition on the Prandtl number value. It is shown that a mixture of two gases with small and large molecular weight allows us to produce a mixture with a lower value of the Prandtl number in comparison with the initial gases. Thus, the value of Prandtl number decreases by 1.5-3.2 times in comparison with values for pure components (the more a difference of molar mass of components, the stronger is a decrease).</p><p>The technique to determine the Prandtl number value for mixtures of gases in the wide range of temperatures and pressure is developed. Its verification based on experimental data and results of numerical calculations of other authors is executed. It is shown that it allows correct calculation of binary and more complex mixtures of gases</p><p>For the mixtures of inert gases it has been obtained that the minimum value of the Prandtl number is as follows: for helium - xenon mixtures (He-Xe) makes 0.2-0.22, for helium - krypton mixtures (He-Kr) – 0.3, for helium - argon mixes (He-Ar) – 0.41.</p><p>For helium mixture with carbon dioxide the minimum value of the Prandtl number makes about 0.4, for helium mixture with N2 nitrogen the minimum value of the Prandtl number is equal to 0.48, for helium-methane (CH4) - 0.5 and helium – oxygen (O2) – 0.46.</p><p>This decrease is caused by the fact that the thermal capacity of mixture changes under the linear law in regard to the mass concentration of components while the viscosity and heat conductivity change under more complicated laws. Just this mismatch leads to having the local minimum for the Prandtl number value.</p>
|
|---|