Transport property measurements

Figure 1 Phase diagram of TTF-TCNQ derived by transport properties measurements,...

The vast majority of accurate transport-property measurements have been performed on molecularly simple pure fluids under conditions close to ambient pressure and temperature. As one moves away from this set of circumstances, the amount of available information decays rather rapidly and its accuracy declines dramatically. 

The three transport properties of the greatest concern are the viscosity, thermal conductivity and mass-diffusion coefficients. In each case, although measurements had been conducted over a period of at least 150 years, it was not until around 1970 that techniques of an acceptable accuracy were developed for the relatively routine measurement of any of these properties. There is ample evidence in the literature of very large discrepancies among measurements made prior to that date. One reason for these discrepancies lies in the conflicting requirements that, to make a transport-property measurement, one must perturb an equilibrium state but, at the same... 

However, it is still necessary to consider whether it is possible to perform easily all transport-property measurements that industry requires. Let us assume that we need to measure only three properties at just 10 temperatures and 10 pressures, for 15 pure fluids and all their possible multicomponent mixtures, at five compositions in the liquid and gas phases. Then, the total number of measurements required is of the order of 10 (3x10x10x32766x5x2). If one further assumes that one can perform three measurements per day, then it is obvious that even for the above program of measurements, 90.000 man-years will be required and it considered only 15 materials from among the set of several thousand involved routinely in industry. It is clear that measurement alone cannot serve the industrial appetite for transport property data. Nevertheless, accurate measurements will continue to be vital for the verification of theory and the validation of predication. 

It seems clear from the rejection and ultrafiltration data that there is no appreciable protein adsorption on the cellulosic fibers. The transport properties measured in saline are of good predictive value for both serum and BSA experiments. 

In crystalline semiconductors, the investigation of electronic transport properties (measured as a function of temperature or electric or magnetic field strength) can provide information on the scattering mechanism, carrier concentration and mobility, Fermi-level position, etc. Yet none of these latter quantities is obtained directly from the experiment Theoretical models for the transport are fitted to the experiment data to obtain transport parameters. The validity of both transport theories and transport parameters is checked by the quality of the fit and by a comparison of parameters obtained from different transport experiments. 

L. A. Woolf, Insights into solute-solute-solvent interactions from transport property measurements with particular reference to methanol-water mixtures and their constituents. Pure Appl. Chem., 57 (1985), 1083. 

Aziz, R.A., Janzen, A.R., Moldover, M.R. Ab initio calculations for helium a standard for transport property measurements. Phys. Rev. Lett. 74, 1586-1589 (1995)... 

Yanl] XRD, magnetic and transport properties measurements 4.2-400 K / Cr2peS4... 

Although transport property measurements, like thermoelectric power, specific heat, etc., are important in the critical and insulating regimes, they are not as sensitive as the low temperature conductivity and MR. The linear temperature dependence of thermoelectric power and a linear term in the specific heat (which are typical for metallic systems) have been observed in the insulating regime too. As the system moves into the insulating side the hopping contribution to thermoelectric power (5 dominates over the metallic... 

Ferry A, Doeff MM, DeJonghe LC (1998) Transport property measurements of polymer electrolytes. Elecuochim Acta 43(10-11) 1387-1393... 

Transport property measurements are normally reported in terms of the measured state variables of temperature, pressure and composition. Density is not usually measured at each state point but is instead obtained from an equation of state formulation. It is crucial to consider the uncertainty in the density which is calculated by the equation of state. As in the case for the transport property correlations, the uncertainty in the fluid density is not uniform over the entire PVT x) surface (Younglove 1982). The uncertainty in the fluid density in the critical region is almost certainly larger than it is in the dilute-gas limit or near the phase boundaries far from the critical point Chapter 8 discusses equations of state and their importance in the analysis of transport properties. 

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