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Instruments and analytical techniques are described for in-vehicle monitoring of amounts of air (void fraction) in engine coolant systems and for evaluating the performance of degas reservoirs. This method, based on electrical conductivity measurements of flowing air / coolant mixture, provides measurement, acquisition and display of coolant system temperature, pressure, flow rate, instantaneous void fraction and rate of air removal by degas bottle. Embedded temperature compensation equations are used for essentially real time display of the void fraction.

Solubility and viscosity predictions for solutions of a thermoplastic polymer with several supercritical gases indicate that significant viscosity reduction and solubility are achieved when the processing conditions are closely matched with the critical properties of the dissolved gas. For the solubility predictions, PVT behavior was modeled by the lattice theory based Sanchez - Lacombe equation-of-state (EOS). Viscosity was estimated by employing the Kelley - Bueche free volume theory coupled with the volumetric calculations of the EOS. Unlike conventional solvents, supercritical solvents add significant free volume to supercritical gas / polymer mixtures; this added free volume provides remarkable viscosity reduction. Viscosity reductions of up to two orders of magnitude are predicted for a supercritical gas / polymer system, compared to the undiluted polymer when the critical temperature for the supercritical gas is matched to the polymer processing temperature.