Thermodynamic factor of quaternary mixtures from Kirkwood–Buff integration

Expressions for the thermodynamic factor matrix Γ of quaternary mixtures are derived in terms of Kirkwood–Buff integrals and implemented into the massively parallel simulation tool ms2. To assess these expressions, a liquid-like supercritical quaternary Lennard–Jones mixture is sampled throughout its entire composition range, employing molecular dynamics in the canonical ensemble. Good agreement is found between numerical chemical potential derivatives and the results from the present Kirkwood–Buff integral expressions. Moreover, the limits of the thermodynamic factor matrix for pure, binary and ternary subsystems are discussed.BMBF, 01IH16008E, Verbundprojekt: TaLPas - Task-basierte Lastverteilung und Auto-Tuning in der Partikelsimulatio

Design and test of a multi-coil helical evaporator for a high temperature organic Rankine cycle plant driven by biogas waste heat

A direct evaporator for a high temperature organic Rankine cycle (ORC) plant with toluene as a working fluid is designed and tested. The exhaust gas from a 800 kWe combined heat and power plant is cooled on the shell side of the present heat exchanger, while the working fluid is heated and evaporated within eight helically coiled tubes, constituting a tube bundle. A method to obtain optimal design parameters for this type of heat exchanger is presented, considering the heat source, the ORC and the available space at the test site. After manufacturing, the apparatus is tested to validate the design procedure, focusing on the employed heat transfer and pressure loss correlations on the shell side. It is shown that the predicted values of the overall heat transfer coefficient and the shell side Nusselt number are in good agreement with experimental data, showing a maximum deviation of 5.5%. The measured shell side pressure loss is slightly higher than the predicted value, indicating that the correlation underestimates the pressure loss coefficient by up to 7% at low Reynolds numbers, but has a good accuracy at higher Reynolds numbers. It is observed that it is essential to adjust the mass flow rate of the working fluid in each coil to obtain a homogenous vapor quality. A reliable operation of the direct evaporator with a maximum heat flow of 225 kW is shown

Reactive mass transfer around isolated bubbles rising in a thin-gap cell

International audienceThis study investigates reactive mass transfer around isolated bubbles of pure oxygen rising in a thin-gap cell filled with acetonitrile at rest. A colorimetric technique based on the bio-inspired copper(I) complex [Cu(TMG 2 tol)]OTf is used. The gap-and time-averaged dissolved oxygen concentration fields can be measured in the far-wake of the bubbles with 3 < d < 47 mm. The variations of the Sherwood numbers with the Peclet numbers show that the mass transfer results obtained are identical with the ones measured earlier with the copper(I) complex [Cu(btmgp)I]. This demonstrates the independency of mass transfer from the properties of the chemical system used. The results significantly enlarge the existing database, which is of great importance to establish robust scaling laws

Heterolepic β‐Ketoiminate Zinc Phenoxide Complexes as Efficient Catalysts for the Ring Opening Polymerization of Lactide

Zinc phenoxide complexes L1ZnOAr 1–4 (L1=Me2NC2H4NC(Me)CHC(Me)O) and L2ZnOAr 5–8 (L2=Me2NC3H6NC(Me)CHC(Me)O) with donor-functionalized β-ketoiminate ligands (L1/2) and OAr substituents (Ar=Ph 1, 5; 2,6-Me2-C6H3 2, 6; 3,5-Me2-C6H3 3, 7; 4-Bu-C6H4 4, 8) with tuneable electronic and steric properties were synthesized and characterized. 1–8 adopt binuclear structures in the solid state except for 5, while they are monomeric in CDCl3 solution. 1–8 are active catalysts for the ring opening polymerization (ROP) of lactide (LA) in CH2Cl2 at ambient temperature and the catalytic activity is controlled by the electronic and steric properties of the OAr substituent, yielding polymers with high average molecular weight (Mn) and moderately controlled molecular weight distribution (MWDs). 1 and 5 showed a living polymerization character and kinetic studies on the ROP of L–LA with 1 and 5 proved first order dependencies on the monomer concentration. Homonuclear decoupled 1H-NMR analyses of polylactic acid (PLA) formed with rac-LA proved isotactic enrichment of the PLA microstructure. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA