Chemical Pretreatments Affecting Drying Characteristics of Chilli (cv. Huarou Yon)

One- (70°C) and two-temperature regimes (70 and 50°C) were used to dry chilli (Capsicum annuum cv. Huarou Yon) using a laboratory tray dryer compared to conventional sun drying. A pretreatment was done by soaking chilli in antibrowning solutions before drying. It was found that the drying rate of chilli soaked in chemical solutions was increased and the drying period of chilli was decreased. Page's model was found to fit well with the experiment for one- and two-temperature drying using least squares analysis. The highest value of the coefficient of determination (R² > 0.99), the lowest value of standard error of estimation (SEE < 0.00031), and the lowest value of the mean relative deviation (P < 10%) were obtained. The effective moisture diffusivities of chilli drying at 70°C and two-stage drying were between 6.01–7.22 × 10^?10 m²/s and 3.16–3.89 × 10^?10 m²/s, respectively. In contrast, the lowest value of effective moisture diffusivity of chilli was obtained by the conventional sun-drying method (0.597 × 10^?10 m²/s). The highest value of moisture diffusivity was observed for chilli soaked in sodium metabisulfite (NaMS) mixed with CaCl₂ solution for both one- and two-temperature regimes. The color of chilli was improved by using chemical pretreatments, in particular, chilli soaked in NaMS mixed with CaCl₂ solution.     

Investigation of the influence of the Reynolds number on extinction and reignition

In this study comparisons are made of the results of a series of simulations for different values of the Reynolds number, but with fixed Schmidt and Prandtl numbers (Sc=Pr=0.7) and identical chemistry and approximately identical large-scale dynamics and initial scalar geometry. The goal is the investigation of the influence of the change in the diffusive scales on local extinction and reignition in a diffusion flame. Extinction occurs when the fluctuations of the scalar dissipation rate at the stoichiometric value of the mixture fraction (χ_st) become larger than a threshold value (χ_q). The fluctuations of the scalar dissipation rate reach higher values with increasing Reynolds number, but the probability that χ_st>χ_q does not increase with Reynolds number at the two highest values of the Reynolds number studied. The latter effect is related to the lognormal nature of the PDF of the scalar dissipation rate. As the fluctuations of χ_st become increasingly larger than χ_q, extinction takes place faster and results in lower temperatures. Reignition, however, appears to take place approximately similarly in the different cases. The Reynolds number dependence of the average temperature of the stoichiometric surface is mostly due to the increase in extinguished area fraction of the stoichiometric surface. Although the amount of extinction increases as the Reynolds number is increased, the rate of increase appears to slow down with increasing Reynolds number.