Electrolyte and temperature effects in a rising bubble

In this work, the rise characteristics of a single H₂ bubble, in the ellipsoidal regime, in (i) water, (ii) single electrolyte (2 M, 4.5 M NaCl) solution and (iii) various concentrations of electrolyte mixture (up to 6.4 M of 1:5 weight fraction NaCl-NaClO₃), have been studied, at temperatures up to 80°C. Our results...

De lerende als rode draad: Weten wat de (werkende) student nodig heeft

Het permanent najagen van kennis en vaardigheden voor onze persoonlijke en professionele ontwikkeling zal ons steeds meer veranderen in levenslang lerenden. Maar wat houdt 'een leven lang ontwikkelen' precies in, en welke rol kunnen universiteiten daarin spelen?

Impact of flocculant addition in oil recovery from multiphasic fermentations

Emulsion formation is a major concern when dealing with multiphasic fermentations. Flocculants can be used together with other demulsification techniques to improve oil recovery in multiphasic fermentations. In this paper, the impact of adding flocculants during a multiphasic fermentation with 10 wt% dodecane, to destabilize the broth...

Jumping to a better world: An agent-based exploration of criticality in low-carbon energy transitions

Understanding the possible transition pathways of the energy system requires the integration of human behaviour in energy system models. In order to model the influence of actor behaviour we have developed ACT (Agent-Based Model of Critical Transitions), an agent-based model inspired by an existing conceptualisation of critical transitions....

Fluidization dynamics of cohesive Geldart B particles. Part II: Pressure fluctuation analysis

The increase of inter-particle cohesive force greatly changes the fluidization dynamics, finally leading to the partial or complete failure of fluidization. However, few studies concern such transition process. This paper investigates the fluidization dynamics of Geldart B particles with a wide-range of cohesive force by analyzing the in-bed...

A mechanistic model for oil recovery in a region of high oil droplet concentration from multiphasic fermentations

Multiphasic fermentations where an organic phase is spontaneously formed or when it is added for product removal are commonly used for production of valuable compounds. The turbulent conditions and the presence of surface-active compounds (SACs) during fermentation create a stable emulsion difficult to separate. A gas bubble/oil droplet...

Particle image velocimetry measurements of a thermally convective supercritical fluid

Abstract: The feasibility of particle image velocimetry (PIV) in a thermally convective supercritical fluid was investigated. Hereto a Rayleigh–Bénard convection flow was studied at pressure and temperature above their critical values. The working fluid chosen was trifluoromethane because of its experimentally accessible critical point. The...

Electrolyte effects on recirculating dense bubbly flow: An experimental study using X-ray imaging

In this work, the effect of an electrolyte (up to 2 M of NaCl dissolved in water) on a homogeneous dense bubbly flow, in an airlift bubble column, is studied using nonintrusive techniques. X-ray and high-speed imaging are used to investigate the bubble size distribution, the local and the global gas-fraction profiles. The major effect of the...

X-ray computed tomography of cavitating flow in a converging-diverging nozzle

Cavitation is a complex multiphase phenomenon, where the production of vapor bubbles leads to opaqueness of the flow. While it is nearly impossible to visualize the interior of the cavitation region with visible light, we show that with X-ray computed tomography it is possible to obtain the time-averaged void fraction distribution in an...

Automated feedback on viewing skills lowers accident involvement

The risk of being involved in an accident in the first year after licensing is greater for novice drivers who passed their driving exam the first time than for novice drivers who failed their first driving exam. Enhanced training programmes can shorten the duration of training and can raise the passing rate on the first exam, but can also...

Inter-compartment interaction in multi-impeller mixing: Part II. Experiments, sliding mesh and large Eddy simulations

Steady state multiple reference frame-RANS (MRF-RANS) simulations frequently show strong over-predictions of the mixing time in single-phase, multi-impeller mixing tanks, which is sometimes patched by ad hoc tuning of the turbulent Schmidt-number. In Part I of this work, we experimentally revealed the presence of macro-instabilities in the...

An experimental parametric study on natural circulation BWRs stability

A parametric study on the stability performance of a prototypical natural circulation BWR is performed with the downscaled GENESIS facility. The GENESIS design is based on fluid-to-fluid modeling and includes an artificial void reactivity feedback (VRF) system for simulating the neutronic-thermal-hydraulic coupling. In this work a more...

Characteristics of turbulent heat transfer in an annulus at supercritical pressure

Heat transfer to fluids at supercritical pressure is different from heat transfer at lower pressures due to strong variations of the thermophysical properties with the temperature. We present and analyze results of direct numerical simulations of heat transfer to turbulent CO2 at 8 MPa in an annulus. Periodic streamwise conditions are imposed so...

Concurrent audio-visual feedback for supporting drivers at intersections: A study using two linked driving simulators

A large portion of road traffic crashes occur at intersections for the reason that drivers lack necessary visual information. This research examined the effects of an audio-visual display that provides real-time sonification and visualization of the speed and direction of another car approaching the crossroads on an intersecting road. The...

Turbulence attenuation in simultaneously heated and cooled annular flows at supercritical pressure

Heated or cooled fluids at supercritical pressure show large variations in thermophysical properties, such as the density, dynamic viscosity and molecular Prandtl number, which strongly influence turbulence characteristics. To investigate this, direct numerical simulations were performed of a turbulent flow at supercritical pressure (CO2 at 8...

Investigation of rehomogenization in the framework of nodal cross section corrections

Few-group cross sections used in nodal calculations derive from standard energy collapsing and spatial homogenization performed during preliminary lattice transport calculations, that implicitly assume an infinite array of identical fuel-assemblies. The infinite-medium neutron flux used for cross section weighting does not account for...

Natural convection driven heat transfer in fluids with strongly variable properties: A particle image velocimetry study

The High Performance Light Water Reactor (HPLWR) is one of the six innovative nuclear energy systems proposed by the Generation IV International Forum. The use of water at supercritical pressure as the coolant in the HPLWR allows a significative increase of the thermal efficiency of the power plant, a reduction in size and complexity of the...