Demonstration projects and sustainable housing

Because of the complicated structure of the built environment, it is frequently difficult to obtain good results on sustainable development projects. In The Netherlands, the Dutch government have used a range of new steering instruments which have cleverly enabled innovation to take place within a market economy. This imaginative governmental process uses covenants, network management and above all, demonstration projects to assess the feasibility of innovation. The authors describe the process and consider examples from energy efficient and sustainable housing, highlighting the importance of clear targets.     

Examen de l'influence d'une activation sur un coke de saccharose basse temperature par des methodes de resonance magnetique

The nuclear dynamic polarization method (NDP) was used for a determination of the nature of the interactions between the nuclei of liquids or gases adsorbed on a saccharose charcoal and its paramagnetic centers. Various chemical processes of activation used by different authors to increase the adsorbing surface unfortunately modify the electronic properties of the charcoal (vanishing of the paramagnetic centers). A new method of preparation of a low temperature active charcoal is described. E.P.R. experiments made on this charcoal lead to the conclusion that this new process does not modify fundamentally its paramagnetic properties. NDP investigations on molecules adsorbed on such charcoal show a molecular sieve effect, hence an increase of the porosity. Furthermore, such experiments made with various fluorine compounds show a scalar interaction between charcoal electrons and fluorine nuclei, that does not exist between electrons and protons. Differences between effects for various molecules are also investigated.     

Study of the strength of very young concrete as a function of the amount of hydrates formed—influence of superplasticizer

The strength of microconcretes has been measured at the end of mixing and for some hours afterwards. At the same time, measurements of the heat of hydration have been made. During the ‘dormant period’ the hydration, slight as it is, produces in fact an increase in strength: the flocculated structure of the fresh cement paste can explain the immediate reinforcement of the bonds as soon as hydration begins. When a superplasticizer is used, besides the well-known hydration delay, the beginning of hydration does not signify now that the strength increases: no doubt this is a consequence of the dispersion of the structure by the admixture. After the setting, the filling of pores is easier with a dispersed structure than with a flocculated one, because of the better distribution of the cement particles: a sample with superplastizcier, to attain the same strength, will need less hydrates than a plain sample.     

Mixing characteristics in the torus reactor

The hydrodynamic characteristics of propeller-induced toroidal flow in a loop reactor were investigated by performing an RTD analysis. The experimental determination of circulation time allows the calculation of the mean axial velocity with respect to the rotational speed of the impeller. RTD measurements are interpreted with the aid of the dispersion plug flow model, and it is shown that axial dispersion is relatively weak in the torus reactor. The mixing time was also determined experimentally and related to the circulation time. A direct relationship between mixing time and axial dispersion coefficient has been established, leading to a correlation for the mixing time in a torus reactor.     

Effect of Ultra-high-pressure Homogenization on Structure and on Rheological Properties of Soy Protein-stabilized Emulsions

ABSTRACT: An ultra high-pressure homogenizer (20 to 350 MPa) was used to realize fine food emulsions stabilized by soy proteins. The first aim of the work was to understand how dynamic high-pressure processing affects soybean globulin conformation. Then, the effect of homogenizing pressure on the emulsions structure and rheology was investigated. High-pressure homogenization caused denaturation of proteins due to strong mechanical forces and high temperatures encountered in the valve. Droplet sizes of emulsions were greatly reduced with high-pressure homogenization and Newtonian liquid emulsions were converted into shear-thinning emulsion gels by homogenization at pressures above 250 MPa. Hydrophobic interactions between proteins were supposed to cause the gel-like network structure of emulsions.     

Computational analysis of geometrical factors affecting experimental data extracted from hydrogen permeation tests: III – Comparison with experimental results from the literature

The membrane thickness is one of the major parameters affecting hydrogen diffusion during electrochemical permeation tests. In this work, we study the effects of membrane thickness by comparing experimental results from the literature with a numerical analysis by finite element method (FEM). We consider the effects of a palladium coating or an oxide layer on the diffusion through α-iron, and we also studied the effects of an oxide layer on the diffusion through martensitic steels. Our model allows us to match the experimental data and determine the initial subsurface hydrogen concentration, trap densities, and the diffusivity of the layer. However, we had to consider the effects of the mechanical polishing on hydrogen trap densities and concentrations to ensure a reasonable correlation. The balance between the effects of trapping and the oxide layer are finally discussed; while hydrogen trapping increases the effective subsurface concentration, the oxide layer decreases its value.     

Evaluation of temperature field and heat flux by inverse analysis during steel strip rolling

Knowledge of the temperature field in the roll is a critical factor of modern, high-speed rolling mills. In this paper, an inverse analytical method is developed to determine the temperature field and especially the temperature (and heat flux) at the surface of the roll by measuring the temperature with a thermocouple (fully embedded) at only one point inside the roll. Iterative methods are not studied because short computation times are desired. Some assumptions are done to resolve analytically the unsteady heat equation, taking into account the restrictions of the measurement system (e.g., measurement according to successive times). The solution is validated by comparing the outputs of the method and prescribed analytical temperature fields. Good agreement is obtained. Noise sensitivity is estimated by adding artificial random numbers to the inputs. Good accuracy is observed. A 10% error of the temperature sensor depth is also considered and does not compromise the method. On the other hand, the computation time (around 0.05 s by cycle) is studied to rapidly optimise the industrial parameters during the rolling process.     

High capacity multicomponent hydrogen storage materials: Investigation of the effect of stoichiometry and decomposition conditions on the cycling behaviour of LiBH4–MgH2

LiBH₄–MgH₂ is an attractive reversible hydrogen storage system, it combines two high capacity hydrides (18.3 and 7.6 wt.%, respectively) and the concerted dehydrogenation reaction has a smaller enthalpy change than either species on its own. The latter effect leads to a destabilisation of the hydrided products and results in a lowering of the dehydrogenation temperature. In situ neutron diffraction experiments have been undertaken to characterise the mechanism of decomposition of the LiBD₄–MgD₂ system, with an emphasis on investigating the synergistic effects of the components during cycling under various conditions. This study compares the effect of stoichiometry of the multicomponent system on the cycling mechanism. Results show that LiBD₄–MgD₂ in a 2:1 molar ratio can be reversibly dehydrogenated under low pressures of hydrogen or under vacuum, contrary to earlier reports in the literature, although the reaction was only partially reversed for the 2:1 mixture decomposed under vacuum. This work shows that the reaction pathway was affected by dehydrogenation conditions, but the stoichiometry of the multicomponent system played a minor role.     

Mass transfer at the electrodes of the ‘falling-film cell’

In the falling-film cell the electrolyte flows as a thin film in the channel between an inclined plane plate and a sheet of expanded metal which work as electrodes. The present work gives the mass transfer coefficients at both electrodes; the experimental variables are the electrolyte flow-rate, the angle of inclination of the channel and the interelectrode distance. The results allow three different flow regimes to be characterized. At low flow rates, there exists a particular regime where capillary effects are present; in this regime the mass transfer coefficient decreases with increasing flow rate, which is interesting from the point of view of possible industrial electrolytic applications.Nomenclature b width of the inclined channel - D diffusion coefficient - d interelectrode distance - e _m mean film thickness - Grashof number, based ond - Grashof number, based onL - ¯k overall mass transfer coefficient, defined by Equation 9 - L electrode length - Q _v volumetric flow rate - volumetric flow rate per unitQ _vl width of channel - Reynolds number - Schmidt number - Sherwood number, based ond - Sherwood number, based onL - mean velocity of the liquid film - inclination angle of the channel with respect to the horizontal - kinematic viscosity of them electrolyte