No abstract

Mastering the process of drying the palm heart (Jomare) requires knowing their isothermal sorption. The purpose of this work is the experimental determination of the palm heart sorption isotherms. the gravemitric method of saturated saline solutions is used at three different temperatures (40, 50 and 60 °C) with a water activity extending from 0.067 to 0.85. The equilibrium was obtained after about 10 days. Four mathematical models have been used (LANGMUIR, GAB, modified BET and Peleg) to model and predict hygroscopic behavior during drying and storage. After smoothing and optimization of these models on the basis of the statistical processing of the obtained data, the results shows that the GAB and modified BET models best match the sorption isotherms. The isosteric desorption heats for the heart of palm are calculated using the Clausius-Clapeyron equation. Through this study, an expression has been proposed that allow the prediction of the thermodynamic properties of the palm heart. The results of this research can be used to determine characteristic drying curves and to have optimal storage conditions.

The effect of drying temperature and the application of ultrasound on drying kinetics of Lawsonia inermis (henna) leaves and the extraction of lawsone from the dried samples was addressed. Indeed, henna leaves were dried with and without the application of ultrasound (21.7 kHz, 30.8 kW/m3) at 40, 50 and 60 °C with a constant air velocity (1 m/s). As expected, both the increase of temperature and the application of ultrasound decreased the drying time and increased the rate of extraction of the lawsone. The values of the effective diffusion coefficients obtained were used to quantify this influence showing the value increases with higher drying temperature and the application of ultrasound. Moreover, the influence of temperature was quantified by the estimation of the activation energy from an Arrhenius-type equation (46.25 kJ/mol in the case of drying without ultrasound application and 44.06 kJ/mol in the case of ultrasonically-assisted drying). Regarding the influence of studied variables on lawsone extraction yield, the higher is the temperature, the lower is the yield, probably linked with lawsone degradation reaction due to thermal treatment. On the contrary, the application of ultrasound improved the extraction yield mainly at the lower drying temperature tested of 40 °C.

This paper seeks, as a part of Algerian policy, to encourage the reconstruction of the ground in order to achieve economic reconstruction and the safety of inhabitants and the environment. The study focuses on the hygrothermal behaviour of compressed and stabilised earth blocks that can be used in different climate zones, like the south of Algeria, where the temperature is up to 50°C in summer, and the coastal towns, where humidity exceeds 80%. Accordingly, an experimental study has been conducted to determine the influence of temperature on the sorption isotherms for compressed and stabilised earth blocks stabilised with 6% of cement. The sorption isotherms were measured at temperatures of 10, 23, 30, 40 and 50°C. Twelve equations have been fit to the experimental isotherms to find the one that gives the best agreement. An experimental model was then developed based on the Oswin model describing the dependence of temperature on the sorption characteristics of compressed and stabilised earth blocks. The results show a significant influence of the increase in temperature on the hygrothermal behaviour, in particular a reduction of 11% in the equivalent water content between 10°C and 50°C.

During a forced convection sun drying and storage operation, the equilibrium water content of a product to be dried is critical. These figures are frequently derived using isothermal sorption curves. The calculation of isotherms is a necessary step in determining the distribution and intensity of water connections in products. for that this paper concentrates on the experimental determination of the adsorption-desorption isotherms for various temperatures (40, 50, and 60℃) of the Nicotiana Tabacum L plants. From which we had established the relationship between the water activity and the water content in the product. However, the aforementioned determination was carried out by the static gravimetric method. Eight saturated salt solutions have been utilized in applications such as (KOH, KCl, MgCl2, MgNO3, K2CO3, BaCl2, K2SO4, and NaCl). Hygroscopic equilibrium was completed after 13 days for temperature 40℃, 11 days for 50℃, and 9 days for 60℃. The overall experimental sorption curves are summarized by six models (HENDERSON, modified HALSEY, OSWIN, GAB, modified BET, and PELEG). The sorption isotherms built using the Clausius–Clapeyron equation were used to determine the net isosteric temperatures of desorption and adsorption of Nicotiana Tabacum L. The results for the adsorption-desorption isotherms found are type III according to IUAPC. Following the smoothing of the experimental results by different used models, it was found that the models of GAB and Peleg allow having the lowest mean relative errors and correlation coefficient.