Phase Changes In Mixtures Research Articles

Potential of organic Rankine cycle using zeotropic mixtures as working fluids for waste heat recovery

The performance of the ORC (organic Rankine cycle) systems using zeotropic mixtures as working fluids for recovering waste heat of flue gas from industrial boiler is examined on the basis of thermodynamics and thermo-economics under different operating conditions. In order to explore the potential of the mixtures as the working fluids in the ORC, the effects of various mixtures with different components and composition proportions on the system performance have been analyzed. The results show that the compositions of the mixtures have an important effect on the ORC system performance, which is associated with the temperature glide during the phase change of mixtures. From the point of thermodynamics, the performance of the ORC system is not always improved by employing the mixtures as the working fluids. The merit of the mixtures is related to the restrictive conditions of the ORC, different operating conditions results in different conclusions. At a fixed pinch point temperature difference, the small mean heat transfer temperature difference in heat exchangers will lead to a larger heat transfer area and the larger total cost of the ORC system. Compared with the ORC with pure working fluids, the ORC with the mixtures presents a poor economical performance.

Characteristics of amorphous complex formed between indomethacin and lidocaine hydrochloride

Indomethacin (IM) easily forms an amorphous complex with lidocaine (LC) by heat treatment. To know the mechanism involved in the formation of this complex, we studied temperature-dependent phase changes in mixtures of IM and lidocaine hydrochloride (LH), in which the cationic form of LC forms a salt with Cl−, in various molar ratios by using DSC and NMR. Although heating of the mixture of IM and LC (IM+LC), formed a eutectic mixture, that of IM and LH (IM+LH) did not, and IM in the IM+LH mixture was dissolved into fused LH. Cooling of the fused IM+LH showed the glass transition in all of the samples containing various amounts of IM, suggesting that fused IM+LH took a homogenous amorphous state (IM/LH) below its glass transition temperature, in contrast to the fused IM+LC, which formed the rubber state and/or glass state depending on the molar content of IM. The results of the NMR study showed that IM in IM/LH caused the electronic structure of LH to change in such a way as to become similar to that of LC, but this effect was limited. Hence, mode of interaction of LH with IM is different from that of LC with IM.

Phase evolution in V2O5-H3PO4-organic component systems during barothermal treatment

Data are presented on phase changes in mixtures of vanadium pentoxide and phosphoric acid during autoclaving in organic solvents in the presence of organic reductants.

Monte Carlo simulation of non-equilibrium segregation during crystal growth

Ising model simulations of the crystallization of two component mixtures have been performed for crystallization conditions both near and far from equilibrium. These simulations reproduce the phenomenon which has been termed ‘solute trapping’, where rapid crystallization results in crystals with concentrations which are far from equilibrium concentrations. Thermodynamic properties of Si doped with Bi have been used as a model alloy system in the simulations because there are extensive experimental results for these alloys. Simulations predict that crystallization far from equilibrium follows quite different rules from crystallization near equilibrium. This has significant implications for all first order phase changes in mixtures which take place under conditions which are far from equilibrium.

Shear-induced phase changes in mixtures

A thermodynamic theory to account for the behavior of liquid mixtures exposed to a shear is developed. One consequence of the theory is that shear-induced phase changes are predicted. The theory is based on a thermodynamics that includes specifically the shear rate in the formalism and is applied to mixtures by a straightforward modification of the corresponding states, conformalsolution approach. The approach is general but is used here for a mixture of Lennard-Jones particles with a Lennard-Jones equation of state as a reference fluid. The results are discussed in the context of the Scott and Van Konynenberg phase classification. It is shown that the influence of a shear does affect substantially the type of the phase behavior. Results from the model mixture are equated loosely with those from real polymeric liquids.