Conception of an apparatus for pressure, density, and temperature measurements in the critical region of pure fluids in Spacelab

A multicell arrangement, allowing isochoric pressure, density and temperature measurements, in the critical region of pure fluids in order to establish their thermodynamic properties in the absence of gravity, is described. The knowledge of these properties is a prerequisite for obtaining correct equations of state and strongly affects the dimensioning of chemical engineering processing plants. Fundamental aspects of measuring thermodynamic data in the critical region are discussed and applied to the Spacelab environment. The layout of the apparatus, its temperature control, and the instrumentation for density and pressure measurements are described.