MACHRK is a computer program that calculates isentropic flow properties of mixtures of air and refrigerant R-134a (tetrafluoroethane), which are used in transonic aerodynamic testing in a wind tunnel at Langley Research Center. Given the total temperature, total pressure, static pressure, and mole fraction of R-134a in a mixture, MACHRK calculates the Mach number and the following associated flow properties: dynamic pressure, velocity, density, static temperature, speed of sound, viscosity, ratio of specific heats, Reynolds number, and Prandtl number. Real-gas effects are taken into account by treating the gases comprising the mixture as both thermally and calorically imperfect. The Redlich-Kwong equation of state for mixtures and the constant-pressure ideal heat-capacity equation for the mixture are used in combination with the departure-function approach of thermo thermodynamics to obtain the equations for computing the flow properties. In addition to the aforementioned calculations for air/R-134a mixtures, a research version of MACHRK can perform the corresponding calculations for mixtures of air and R- 12 (dichlorodifluoromethane) and for air/SF6 mixtures. [R-12 was replaced by R- 134a because of environmental concerns. SF6 has been considered for use in increasing the Reynolds-number range.]

This program was written by Ray Kvaternik of Langley Research Center. For further information, access the Technical Support Package (TSP) free on-line at under the Software category. LAR-17095-1

NASA Tech Briefs Magazine

This article first appeared in the January, 2006 issue of NASA Tech Briefs Magazine.

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