Thermal behavior of latent thermal energy storage unit using two phase change materials: Effects of HTF inlet temperature

This work presents a numerical study of the thermal behavior of shell-and-tube latent thermal energy storage (LTES) unit using two phase change materials (PCMs). The heat transfer fluid (HTF) flow through the inner tube and transfer the heat to PCMs. First, a mathematical model is developed based on the enthalpy formulation and solved through the governing equations. Second, the effects of HTF inlet temperature on the unsteady temperature evolution of PCMs, the total energy stored evolution as well as the total melting time is studied. Numerical results show that for all HTF inlet temperature, melting rate of PCM1 is the fastest and that of PCM2 is the slowest; increasing the HTF inlet temperature considerably increases the temperature evolution of PCMs. The maximum energy stored is observed in PCM2 with high melting temperature and high specific heat; heat storage capacity is large for high HTF inlet temperature. When the HTF inlet temperature increases from 338 K to 353 K, decreasing degree of melting time of PCM2 is the biggest from 1870 s to 490 s, which reduces about 73.8%; decreasing degree of melting time of PCM1 is the smallest from 530 s to 270 s, which reduces about 49.1%

Softening of over-dried "Deglet-Nour" dates to obtain high-standard fruits: impact of rehydration and drying processes on quality criteria

The postharvest hydrothermal treatment of date palm fruit was studied in order to enhance the quality and consumer acceptance of 'Deglet Nour' hard dates, because these dates are unfit for direct consumption. Hot water hydration was performed by soaking at 25, 45, and 65 degrees C and convective hot air drying at 35, 45, 60, 75, and 85 degrees C at various levels of air humidity. Numerous quality parametersi.e., texture, color, moisture and sugar contentswere investigated. Artificial maturation due to the softening of texture and the equilibration of sugars was achieved using the hydration pretreatment. A 6-h soaking at 45 degrees C could be the best option to obtain a product of highest quality, but the moisture content would exceed that required for safe storage. Drying and quality tests led to the selection of a pretreatment step of soaking at 30 degrees C for 8h, followed by drying at an intermediate temperature (60 degrees C) as the optimum condition to obtain a final product of high quality with the standard moisture content of 0.35kg/kg d.b

Étude du traitement thermique à l’eau chaude en vue d’amélioration de la qualité des dattes sèches

An experimental study of the rehydration, by hot water impregnation, of Deglet-Nour dates was made in order to improve the quality of dry dates. To this end several parameters of quality were simultaneously tested: moisture content, sugars, texture and color in order to allow a good appreciation of the final product. Various samples were rehydrated with 25, 45 and 65°C in solutions of ultrapure water sweetened to 0, 10 and 20 Brix. The obtained results highlighted a complementary maturation by hydrant and sugar inversion. The phenomenon of diffusion water-date was accelerated by the increase in the temperature of steeping but this one was slowed down by the increase in concentration of the sweetened solutions and the sugar losses in the steeping solution were negligible. Among several invested operating conditions, steeping with 30°C, during about eight hours, was selected as optimal treatment for a better quality of the final product. In order to restore the standard moisture content allowing a safe storage, a complementary drying operation can be proposed.Une étude expérimentale de la réhydratation, par imprégnation à l’eau chaude, de la datte Deglet-Nour a été faite en vue d’améliorer la qualité des dattes sèches. A cet effet plusieurs paramètres de qualité ont été testés simultanément : humidité, sucres, texture et couleur afin de permettre une bonne appréciation du produit fini. Différents échantillons ont été réhydratés à 25, 45 et 65°C dans des solutions d’eau pure sucrées à 0°, 10° et 20° Brix. Les résultats obtenus ont mis en évidence une maturation complémentaire par prise en eau et inversion de sucres. Le phénomène de diffusion eau-datte a été accéléré par l’augmentation de la température de trempage mais celui-ci a été freiné par l’augmentation de concentration des solutions sucrées et les pertes de sucres dans la solution de trempage étaient négligeables. Parmi plusieurs conditions opératoires investies, le trempage à 30°C, pendant environs huit heures, a été choisi comme traitement optimal pour un produit fini de meilleure qualité. Afin de restituer au produit sa teneur en eau normale pour un stockage sain, une opération complémentaire de séchage peut être proposée

Dynamic performance of fuel cell power module for mobility applications

Fuel cell powered vehicles have been developed as another alternative to internal combustion engine powered vehicles for some applications including passenger cars, buses, trains, motorcycles, forklifts, electric wheelchairs, electric trolleybuses, medical carts, military engines, personal sports craft, mobility devices and other self propelled equipment. Up to now, many researches have focused on the development of the power module in the Fuel cell vehicles (FCVs) and the components of these systems such as membranes, bipolar plates, and electrodes. However, our work in this study focuses on operating the integrated fuel cell power module system efficiently for various operating conditions such as pressure, relative humidity and operating modes. In our validation we have utilized PEMFC single cell, with active area geometry 16 cm2 and of 120 cm2 . Some results obtained in our study shown significant performance indicators for PEMFC stack (composed of 2 cells and 4 cells in a series) at different humidification level

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed