Impact of the Initial Flow Conditions on the Wetting Efficiency on a Flat Inclined Surface

The paper presents a numerical study of a liquid flow on a flat inclined surface using a 3-dimensional unsteady Eulerian multiphase model. Application of a VOF (Volume of Fluid) technique, a surface tracking method, allowed to reconstruct a flow structure and determine surface wettability revealing their dependence on the liquid flow rate. The critical Reynolds number value corresponding to the transition from the rivulet flow to the fully wetted surface was found to agree quite well with the reference literature data. Detailed calculations showed that the solution is sensitive to the initial conditions, i.e. it may change when the dry plate is replaced by a surface covered with a liquid film. Such a behaviour results from variation of the dynamic contact angle between the receding and the advancing contact angles corresponding to the dewetting and wetting conditions, respectively

Application of Different Low-Reynolds k-ɛ Turbulence Models to Model the Flow of Concentrated Pulp Suspensions in Pipes

AbstractIn the pulp and paper industry, the design of industrial equipment based on empirical correlations can be avoided using Computational Fluid Dynamics (CFD) tools. The present study aims at investigation of the turbulent pipe flow of concentrated Eucalyptus pulp suspension using the ANSYS FLUENT® CFD software package. The modelling strategy was a pseudo-homogeneous approach. The non-Newtonian behavior of the pulp suspension was introduced into the CFD code considering its viscosity as a function of a shear rate. Additionally, the existence of a water annulus at the pipe wall surrounding the core flow was taken into account. Four low-Reynolds k-ɛ turbulence models were selected in the present study aiming at describing the presence of a drag reduction effect. All the models used were able to reproduce the drag reduction effect. Additionally the Lam-Bremhorst model was modified taking into account alterations applied successfully by other authors for the turbulent flow of polymer solutions. A good correspondence between the peculiar S-shaped profile near the wall, for the dimensionless velocity, reported in literature for these systems and those obtained numerically was achieved. The approach followed was validated by comparing the numerical results of pressure drop with those from literature

Tłumaczenia tytułów filmów z Jamesem Bondem na język francuski, niemiecki i polski

The following article aims at the comparative analysis of the linguistic aspects of the movie title. The authors of the article analyzed 24 James Bond movie titles. The analysis includes the analysis of the relation between the original English titles and their counterparts in French, German and Polish. The research showed that the translators worked according to three patterns that are shown in the article. The authors also came to the conclusion that the translators of the analyzed titles mostly aimed at the functionality of translation

Process intensification for post combustion CO₂ capture with chemical absorption: a critical review

The concentration of CO₂ in the atmosphere is increasing rapidly. CO₂ emissions may have an impact on global climate change. Effective CO₂ emission abatement strategies such as carbon capture and storage (CCS) are required to combat this trend. Compared with pre-combustion carbon capture and oxy-fuel carbon capture approaches, post-combustion CO₂ capture (PCC) using solvent process is one of the most mature carbon capture technologies. There are two main barriers for the PCC process using solvent to be commercially deployed: (a) high capital cost; (b) high thermal efficiency penalty due to solvent regeneration. Applying process intensification (PI) technology into PCC with solvent process has the potential to significantly reduce capital costs compared with conventional technology using packed columns. This paper intends to evaluate different PI technologies for their suitability in PCC process. The study shows that rotating packed bed (RPB) absorber/stripper has attracted much interest due to its high mass transfer capability. Currently experimental studies on CO₂ capture using RPB are based on standalone absorber or stripper. Therefore a schematic process flow diagram of intensified PCC process is proposed so as to motivate other researches for possible optimal design, operation and control. To intensify heat transfer in reboiler, spinning disc technology is recommended. To replace cross heat exchanger in conventional PCC (with packed column) process, printed circuit heat exchanger will be preferred. Solvent selection for conventional PCC process has been studied extensively. However, it needs more studies for solvent selection in intensified PCC process. The authors also predicted research challenges in intensified PCC process and potential new breakthrough from different aspects

Sterowanie przepływem przy zastosowaniu strugi przeciwbieżnej

The paper presents the results of experimental analysis of the flowfield in slightly heated countercurrent round jets. The velocity measurements were carried out by means of hot-wire anemometry (a combined CTACCA system for temperature compensation). The instantaneous signals collected during the experiment were digitally processed and used for determination of the statistics of velocity and temperature fields including frequency characteristics. The results revealed that the fluid aspiration at the jet periphery significantly influences large-scale structures naturally existing in the flow and being responsible to a great extent for the mixing and entrainment in the free flow. The aspiration intensity was found as the key parameter deciding about the way the reverse flow either inhibits or enhance transport processes.W pracy zaprezentowano wyniki badań eksperymentalnych pola przepływu w lekko nieizotermicznych strugach przeciwbieżnych. Pomiary prędkości zostały przeprowadzone z użyciem 2-kanałowego układu termoanemometrycznego (układ stałotemperaturowy CTA z kompensacją temperatury kanałem stałoprądowym CCA). Sygnały pomiarowe zarejestrowane w trakcie eksperymentu były następnie poddane obróbce cyfrowej w celu uzyskania statystyk pól prędkości i temperatury, obejmujących również rozkłady widmowe turbulentnych fluktuacji. Uzyskane wyniki wykazały, iż zastosowanie przepływu zwrotnego na obrzeżach strugi głównej modyfikuje znacząco charakterystyki zorganizowanych struktur wirowych, występujących w przepływie w sposób naturalny i odpowiedzialnych w dużym stopniu za podsysanie czynnika z otoczenia oraz jego wymieszanie ze strugą główną. Obraz pola przepływu okazał się być silnie zależny od intensywności odsysania, która w zależności od poziomu może prowadzić do wytłumienia lub intensyfikacji procesów transportu promieniowego

Modelling the dynamics of flexible and rigid fibres

A particle-level simulation technique has been developed for modelling fibre suspension flow in a converging channel of a papermachine headbox. The fibre model is represented by a chain of elements connected together. The model was verified by the simulation of rigid fibre dynamics in a simple shear flow. The period of rotation was found to be in a very good agreement with theory and reference data. The model was then employed to simulate fibre motion in a converging channel of a papermachine headbox. Fibre suspension motion was resolved using two-step procedure. Velocity field was calculated by means of a commercial CFD code ANSYS Fluent with RSM turbulence model applied and used as an input to the in-house code allowing to simulate fibre dynamics. Results of the calculations were used to construct the fibre orientation probability distribution (FOPD) which was found to be consistent with available experimental data

Numerical analysis of CO₂ capture efficiency in post combustion CCS technology in terms of varying flow conditions

The paper deals with the computational fluid dynamics modelling of carbon dioxide capture from flue gases in the post combustion-capture method, one of the available carbon capture and storage technologies. 30% aqueous monoethanolamine solution was used as a solvent in absorption process. The complex flow system including multiphase countercurrent streams with chemical reaction and heat transfer was considered to resolve the CO2 absorption. The simulation results have shown the realistic behaviour and good consistency with experimental data. The model was employed to analyse the influence of liquid to gas ratio on CO2 capture efficiency

Diffusion of jets with annular counterflow and small diameter ratio

International audienceA new technique was proposed by Strykowski and Wilcoxon (SW) several years ago for improving mixing in axisymmetric jets. In their facility, a countercurrent flow was produced near the jet exit, giving rise to enhancement of the initial jet instabilities. The annular counterflow was created by applying suction to an annular collar placed around the jet nozzle. The authors studied jets exhausting from a nozzle with a large area contraction ratio and a large collar/jet diameter ratio (2). They have shown that the initial jet turbulent activity and diffusion are significantly increased by a strong counterflow. Such a dramatic increase of mixing was also observed in a tube jet with a small gap between the collar and the inner nozzle. These results have confirmed the interest of using counterflow for the control of jet mixing. The technique also seems very promising for applications to combustion. Recently, Asendrych and Drobniak investigated the thermal field of nonisothermal countercurrent jets