Paraffin waxes are becoming increasingly attractive especially on thermal energy storage field. The crystallization process, considered as a major thermal discharging approach, has a significant impact on the thermal performances of paraffin wax. This study aims to comprehend the mechanism of paraffin wax crystallization under non-isothermal conditions by means of Differential Scanning Calorimetry (DSC). Jeziorny and Mo models were applied to reveal the morphology of paraffin wax crystals. Moreover, the non-isothermal crystallization activation energy was calculated through Kissinger and Friedman methods, respectively. Investigations show that the used kinetics models gratifyingly fitted the experimental data, providing crystallization kinetic parameters such as crystallization rate, half-life time (t1/2) as well as the required cooling rate for a designated relative crystallinity. Furthermore, it was found that the average Avrami exponent value is close to 2 which indicates that the crystals are one-dimensional with needle-like morphologies.
Nowadays, latent heat storage is becoming an imperative in building sector since it plays a crucial role in conserving energy through controlling the thermal comfort level. In this field, different storage systems based on phase change material show great performances in terms of energy saving, leading to a significant improvement of occupant thermal comfort. In this work, the thermal behavior and energy efficiency of a residential house incorporating various phase change materials (RT18HC, RT21HC, RT25HC, and RT28HC) in Mediterranean climate region were investigated via numerical simulations. EnergyPlus software was used to analyze the thermal performance of phase change materials applied to the interior wall surfaces of a simplified building model in El Jadida city. The integration of different single and double phase change material layers has been evaluated based on various concepts such as the average temperature fluctuation reduction and the monthly energy saving. The study showed that low melting point phase change material outperforms in terms of heating load, while phase change material with high melting temperature favors the cooling performance. Moreover, the results show that double-layer systems formed by two distinct phase change materials exhibit higher performance than a single phase change material layer throughout the whole year. The annual energy saving rate reaches 41.42% and 55.41% when using single and double phase change material layers, respectively. Finally, we opted for an optimum double-layer system for lower energy consumption in the selected city.
Phase change materials (PCMs) show a good capability in absorbing massive heat when undergoing phase change, which have great potential to be incorporated into building envelopes to enhance indoor thermal comfort by preventing heat penetration into buildings and reducing energy requirements. In this work, a deep analysis of PCM enhanced-walls model has been conducted in six representative climate regions of Morocco: El Jadida, Fez, Marrakesh, Ifrane, and Errachidia. More in detail, numerical simulations were carried out to assess the thermal behavior and energy performance of a residential building integrated with four different PCMs. The results showed that the effectiveness and selection of PCMs strongly depend on local weather where they are applied, characteristics of HVAC systems, PCM layer thickness, and position. Furthermore, with reference to each climate zone, the appropriate PCM leading to the lowest annual energy consumption was identified. The findings show that PCMs are particularly suitable for Mediterranean climates, which a promising annual energy saving of about 41% was obtained. While, the lowest value was recorded in Errachidia city reveals that the integration of PCM has little effect in desert climate zone. As for the other climates considered, values of about 28% to 31% were achieved in the studied house model.
This paper addresses an experimental investigation of the microinjection molding process through three increasing sections of polyoxymethylene (POM) stepped parts. High and low levels of mold temperature and injection velocity were defined to evaluate the relationship between machine settings, melting and crystallization properties, morphology formation, and shrinkage. The internal morphology of parts showed a mix of structures, from the mold surface towards the core region of each section. Differential scanning calorimetry (DSC) tests highlighted the difficulty of concluding the relationship between the melting temperatures, the processing conditions, and the position of the samples within the mold. The skin‐layer crystallinity declines with increasing part‐step thickness, while the crystallinity degrees of intermediate and core layers are sensitive to the thermal gradients. It was also observed that crystallinity rises along with increasing thickness, benefiting from further polymer chain relaxation and perfection. The unsymmetrical mold cavity results in substantial differences in shrinkage. High shrinkage occurs across the thickness direction due to fast material solidification. The experimental results were supported by the calculated shear rates and temperature fields at the end of the mold‐filling phase. This work yields new insights into comprehending the intricate flow and thermal properties of stepped micropart geometries, which are widely encountered in the plastics manufacturing industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.