Synthesis of titanium dioxide precursor by the hydrolysis of titanium oxychloride solution

[EN] This communication focuses on the development of an approach to improve the synthesis of [Ti8O12(H2O)24]Cl8.HCl.7H2O crystals which is one of the precursor for titanium dioxide TiO2 particles. This study provides a significant improvement in crystallization kinetics with a production rate increased by a factor nineteen by intensifying heat and mass transfers compared to the process in a close vessel. This enhancement was made possible by the development of a new reactor to control the heat and mass transfers involved. In parallel with the experimental set-up, a numerical model representative of the transfer phenomena was initiated. The first numerical results are encouraging and present a good agreement with the measurements.The authors acknowledge financial support from the French Agence Nationale de la Recherche (ANR) under reference ANR-12-EMMA-0023 (Nano-OxTi project).Le Bideau, P.; Richard-Plouet, M.; Glouannec, P.; Magueresse, A.; Iya-Sou, D.; Brohan, L. (2018). Synthesis of titanium dioxide precursor by the hydrolysis of titanium oxychloride solution. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1333-1340. https://doi.org/10.4995/IDS2018.2018.75811333134

Parametric Study and Long-term Prediction of the Production of a Solar Water Heaters Installation

In order to increase the contribution of solar thermal energy in moderately exposed locations, it is necessary to study solar installations and optimise their design. A parametric analysis was carried out on a solar installation in a European climate, consisting of 16 water-in-glass evacuated tube collectors connected to their storage unit. The purpose of the installation is to prepare large quantities of hot water at 85°C twice a day to prepare feed for a calf rearing farm. The arrangement of half of the collectors in series and half in parallel makes this solar installation suitable for this application. The orientation and the inclination were studied for four different European cities to determine their effects on the energy supplied. The results show that location and orientation have a great impact, especially in the cities with higher solar irradiance. Having solar water heaters facing south with a 45° tilt angle allow the solar installation to maximise its production for three locations. Studying the ratio of the energy supply to the energy demand is an interesting way to show the performance of the solar installation. The developed dynamic numerical model will help design the solar energy production in challenging weather conditions where the reduction of fossil energy consumption can be optimised

Estimating thermal properties of phase change material from heat flux measurements

International audienceAn inverse analysis is applied to estimate the effective heat capacity and thermal conductivity of phase change material (PCM) as function of temperature. A sequential work in two distinct parts was adopted here which consists in the estimation of the thermal properties of the PCM in the solid and liquid states in a first step and completed by the characterization of the phase change in a second step. The effective heat capacity is judiciously parameterized as temperature dependent function to take into account the phase change phenomenon and its two solid and liquid phases. An experimental setup was built to collect the heat fluxes and temperatures histories around and inside a one dimensional sample of PCM. First the experimental data were used to estimate thermal conductivity and specific heat both at solid and liquid state and later combined with the developed inverse analysis to estimate the specific heat function over the phase change transition. Obtained results are compared to those obtained with the DSC facilities and an acceptable agreement between the two approaches is observed. The experiment was found to be well designed and the collected measurements trustworthy and complementary to handle this important estimation problem

In-situ assessment of a solar vacuum tube collectors installation dedicated to hot water production

In order to improve the contribution of solar thermal energy in moderately insolated regions, solar installations have to be optimized and their heating capacity has to be proven. In this aim, an in-situ thermal performance investigation was carried out on a solar installation of 24 “Water-in-Glass” evacuated tube collectors coupled to their storage unit in a northwest European climate. The aim of the installation is to provide a calf-breeding farm with an intermittent supply of water at 80 °C. The particularity of this solar installation is the specific arrangement of this kind of solar water heater in series and in parallel. Instrumentation was implemented to understand and establish energy balances. An analysis was carried out on four sequences representative of each season. The results show that despite mostly unfavorable sky conditions, the solar installation was capable of providing from 12 to 67% of energy needs for these four sequences

HYGRO-THERMAL BEHAVIOUR OF POROUS BUILDING MATERIAL SUBJECTED TO DIFFERENT EXTERNAL TEMPERATURE AND HUMIDITY CONDITIONS

This work is focused on the behaviour of a block of cement mortar, subjected to variable external temperature and humidity conditions. The porous building material sample is fitted inside a box, in which a heat exchanger is connected to a thermostatic bath. Three sequences of measurement are considered: (i) the response of the sample, when variations of temperature are applied; (ii) the air ranging between the exchanger and the non-isolated face of the mortar is continuously humidified, by injecting of sprayed water; (iii) the effect of simultaneously variation on temperature and humidity. A mathematical model representative of heat and mass transfer, in multiphasic medium (cement mortar), is developed in order to confront experimental and numerical results. Displacements of moisture and temperature fronts are observed and discussed. This study would enable us to understand the hygro-thermal behaviour of construction walls, to make an adequate design according to the climatic parameters and thus to improve the control of the energy used for heating

Experimental Study on the Hygrothermal Behavior of a Coated Sprayed Hemp Concrete Wall

Hemp concrete is a sustainable lightweight concrete that became popular in the field of building construction because of its thermal and environmental properties. However; available experimental data on its hygrothermal behavior are rather scarce in the literature. This paper describes the design of a large-scale experiment developed to investigate the hygrothermal behavior of hemp concrete cast around a timber frame through a spraying process; and then coated with lime-based plaster. The equipment is composed of two climatic chambers surrounding the tested wall. The experiment consists of maintaining the indoor climate at constant values and applying incremental steps of temperature; relative humidity or vapor pressure in the outdoor chamber. Temperature and relative humidity of the room air and on various depths inside the wall are continuously registered during the experiments and evaporation phenomena are observed. The influence of the plaster on the hygrothermal behavior of hemp concrete is investigated. Moreover; a comparison of experimental temperatures with numerical results obtained from a purely conductive thermal model is proposed. Comparing the model with the measured data gave satisfactory agreement

Design of Polyhydroxyalkanoate (PHA) Microbeads with Tunable Functional Properties and High Biodegradability in Seawater

Abstract Commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The properties of the beads reveal that the elaboration process enables the formation of spherical particles, that the crystallinity of the former polymer is not altered during the process and that the surface roughness of the particles can be tuned by changing the nature of the lateral chain in the PHA structure, in good correlation with its crystalline behavior. The mechanical properties of the different PHA beads are also found to be intimely linked with the crystalline content of the beads, with modulus varying between 1 to 7 GPa. All these properties are also governing the degradation behavior of these materials, as tested under marine environment. With a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content, these results emphasize the interest in developing PHA materials with tunable functions and degradation properties

Preparation of Lignosulfonate-Based Carbon Foams by Pyrolysis and Their Use in the Microencapsulation of a Phase Change Material

International audienceCurrently, further research on the valorization of lignin is needed to shift biorefineries from a conceptual basis to profitable practice. Providing global warming is a major concern as well, the use of lignin as the sole precursor to elaborate materials with thermal energy storage (TES) applications is especially welcomed in the search for new sustainable solutions. To this end, the preparation of on demand macroporous carbon foams from calcium lignosulfonate (CaLS) by pyrolysis is described herein, and their capability to microencapsulate phase change materials (PCMs) dedicated to the passive refrigeration of buildings by TES is further assessed as a proof of concept. The as-produced CaLS-based foams were found to be efficient containers for this purpose, displaying any appreciable leakage of PCMs. Furthermore, the thermal properties of the final materials were satisfactory as well, showing that the support does not affect the PCM performance negatively. Considering the process to produce such materials is not only straightforward but also relies on an inexpensive, widely available carbon precursor, it is expected that it serves as a starting point for pilot studies in TES projects

Emulsion-templated pullulan monoliths as phase change materials encapsulating matrices

International audienceEmulsion-templated pullulan monoliths encapsulating butyl stearate as bio-based phase change material (PCM) were synthesized. Pullulan was crosslinked with sodium trimetaphosphate (STMP) under alkaline aqueous conditions leading to an interconnected porous network. The influence of the drying process on the obtained composite material morphology was studied indicating freeze-drying as the most effective technique. Differential Scanning Calorimetry (DSC) studies allow to assess that encapsulation of butyl stearate onto pullulan matrix does not alter its phase change thermal properties. This new one-step encapsulating approach appears as efficient and cost-effective and is expected to find a broad development in energy storage applications

Toughened PS/LDPE/SEBS/xGnP ternary composites: morphology, mechanical and viscoelastic properties

In this work, we have developed super tough ternary polymer blends and composites composed of polystyrene (PS), low-density polyethylene (LDPE), polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) and exfoliated graphene nanoplatelets (xGnP). A 50/50 composition of PS and LDPE was selected for making the binary blend. The addition of xGnP in the binary blend reduces the tensile strength, elongation at break and tensile toughness considerably due to the unfavorable interactions existing between PS, LDPE, and xGnP. On the other hand, the mechanical properties of PS/LDPE binary blends are considerably improved by the addition of SEBS at the expense of modulus. The best results were obtained for a 33/33/33 (PS/LDPE/SEBS) composition. Further, different concentrations of xGnP were incorporated in the ternary blend with 33/33/33 composition. Interestingly, the composites show a significant improvement in mechanical properties especially for 2.91 wt% xGnP modified ternary blend. The DMA studies revealed that the stress with in the ternary composites are minimum when compared with binary blends and their composites. The variation in the phase morphology of the binary blends by the addition of SEBS and xGnP is responsible for the dramatic changes in mechanical and viscoelastic properties. This study validates large improvement in mechanical properties of the PS/LDPE polymer blends by the careful selection of SEBS and xGnP. Keywords: Polystyrene, Low-density polyethylene, Polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, Exfoliated graphene nanoplatelets, Toughened plastic