Search results for "fluid"

Microcanonical Determination of the Interface Tension of Flat and Curved Interfaces from Monte Carlo Simulations

2012

The investigation of phase coexistence in systems with multi-component order parameters in finite systems is discussed, and as a generic example, Monte Carlo simulations of the two-dimensional q-state Potts model (q=30) on LxL square lattices (40<=L<=100) are presented. It is shown that the microcanonical ensemble is well-suited both to find the precise location of the first order phase transition and to obtain an accurate estimate for the interfacial free energy between coexisting ordered and disordered phases. For this purpose, a microcanonical version of the heatbath algorithm is implemented. The finite size behaviour of the loop in the curve describing the inverse temperature vers…

Atomistic Simulation of Transport Phenomena in Simple and Complex Fluids and Fluid Mixtures

2003

Computer simulations of fluids in thermal equilibrium can yield information on transport coefficients such as self—diffusion and interdiffusion coefficients, viscosity, and thermal conductivity. While the estimation of self—diffusion coefficients from the mean square displacements of the respective particles is rather straightforward, the estimation of other transport coefficients is less straightforward, and can be based on either an analysis of time correlation functions of the appropriate collective variables, or on nonequilibrium techniques where the linear response to appropriate perturbations is measured.

Experimental and Numerical Simulations of Flow and Heat Transfer in Heat Exchanger Elements Using Liquid Crystal Thermography

2004

Experimental and numerical investigation of heat transfer and fluid flow were conducted for classic heat exchanger elements (flat plate with fin-tubes in-line, staggered and with vortex generators) and corrugated-undulated ducts under transitional and weakly turbulent conditions. The dependence of average heat transfer and pressure drop on Reynolds number and geometrical parameters was investigated. Distributions of local heat transfer coefficient were obtained by using liquid crystal thermography and surface-averaged values were computed. Three-dimensional numerical simulations were conducted by a finite-volume method using a low-Reynolds number k-e model under the assumption of fully deve…

Membrane fluidity of stressed cells of Oenococcus oeni

2000

International audience; The determination of membrane fluidity in whole cells of Oenococcus oeni was achieved by membrane probe 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy measurements. The results demonstrated instantaneous fluidity variations with cells directly stressed during the measure. Heat (42°C) or acid (pH 3.2) shocks decreased the anisotropy values (fluidising effects), whereas an ethanol shock (10% ethanol, v/v) increased the membrane rigidity. The velocities of fluidity variation with non-adapted or adapted cells (incubation in inhibitory growth conditions) were compared. The adaptation of the cells to acid conditions had no effect on the membrane fluidity variation a…

Numerical study of the accuracy of temperature measurement by thermocouples in small-scale reactors

2018

Proper temperature measurement is imperative in any laboratory study if reliable data are to be obtained, particularly in the field of chemical kinetics. In this paper we analyze in silico some typical thermowell configurations used in small-scale reactors by coupling computational fluid dynamics (CFD) with conjugated heat transfer phenomena. This allows us to identify deviations in measurements arising from thermal radiation and self-conductivity in mid and high temperature ranges, in addition to radial temperature gradients. A novel design is proposed and optimized by additional simulation, showing potential for faster and more accurate temperature measurements.

An experimental investigation on the long-term compatibility of preheated crude palm oil in a large compression ignition diesel engine

2018

An experimental study was carried out on a large stationary compression ignition engine to evaluate the long-term compatibility and durability issues associated with the use of crude palm oil as fuel. Two different preheating temperatures (60 and 80 °C) were adopted to assess the potential improvements related to lower fuel viscosity. The results obtained, in terms of in-cylinder carbon deposits and engine wear, were compared with the results obtained using ordinary diesel fuel. For each fuel and preheating temperature, the engine was operated for 300 consecutive h, during which several engine lubricant samples were collected and analysed to determine soot and fuel contaminations, viscosity…

Flow and thixotropy of non-contaminating oil drilling fluids formulated with bentonite and sodium carboxymethyl cellulose

2007

Abstract A study has been made of low-contaminating oil drilling mud in water base, composed of bentonite, at concentrations in the range of 6–12% (w/w), and sodium carboxymethyl cellulose at two different concentrations. Flow analysis yielded an empirical formula indicating shear stress as a function of the formulation concentrations of bentonite and sodium carboxymethyl cellulose, stirring time and shear rate. To study the thixotropy of the different formulations the cycles' method has been used. Calculations were made of the thixotropic areas, obtaining a semi-empirical equation for these areas. The results are analyzed on the base of relative thixotropic area and total relative thixotro…

Traumatische spino-thorakale Liquorfistel

1995

Hydrothermal processes with REE enrichment in Fuerteventura carbonatites: evidences in accessory minerals

2021

Los diques carbonatíticos que afloran en la parte centro-occidental del Complejo Basal de Fuerteventura (Ajuy, Punta de la Nao), fueron afectados por el evento intrusivo mioceno responsable del metamorfismo de contacto y fusión parcial de parte del complejo alcalino-carbonatítico. Las características texturales, los procesos de formación de monacita enriquecida en LREE (La, Ce, Nd) en microfracturas que afectan a los cristales de zircón, evidencian interacciones de las carbonatitas con fluidos hidrotermales y removilización parcial de REE. El pirocloro es el principal mineral reservorio de tierras raras (suma REE=216694 ppm), con valores elevados de LREE (LaN=185816 y CeN=165209) respecto a…

Impact of sedimentology and diagenesis on the petrophysical properties of a tight oolitic carbonate reservoir. The case of the Oolithe Blanche Format…

2013

18 pages; International audience; The Oolithe Blanche Formation was studied in three quarries, located at the south-eastern edge of the Paris Basin (France). Heterogeneities in reservoir properties were assessed through a sedimentological, diagenetic and petrophysical study. The relationships between depositional settings, diagenesis and petrophysical properties were analysed using detailed petrographic studies, image analysis, Nano CTscans and petrophysical measurements. The carbonate reservoir pore network is mainly controlled by intraparticle microporosity which ensures the connectivity with interparticle meso- and macroporosity. Early cementation vs. early compaction processes (mainly g…