Effect Of Drying Air Temperature Research Articles

Experimental Performance of a Thermoelectric Heat-Pump Drying System for Drying Herbs

In this study we investigated thermoelectric (TE) heat-pump drying of laurel clock vine leaves, and the effect of drying-air temperature on the characteristics of the leaves. The TE drying system comprised four TE modules each with its own rectangular fin heat sink. The hot side of each TE module was fixed to its own heat sink; the cold sides were fixed to heat-pipe heat sinks and a drying chamber. The drying time depended on drying-air temperature. The heating capacity and coefficient of performance (COP) increased as the current supplied to the TE modules was increased. Calculated COP for the entire TE heat-pump drying system were 1.28 and 0.81 for drying-air temperatures of 50 and 40°C, respectively.

Effect of Drying Air Temperature on the Quality of Essential Oil from Mikania glomerata

This study aimed to evaluate the influence of drying air temperature on the content of essential oil extracted from guaco. The drying tests were performed in an experimental fixed-bed dryer, which contains 4 perforated trays with upward air flow. Treatments consisted of five temperatures for the drying air (ambient air and air heated to 40, 55, 70 and 85oC), with three repetition, using 850 g of fresh guaco leaves. Guaco leaves were dried until reaching a final moisture content of approximately 10% w.b. The drying air velocity was 0.5 m s -1 . Essential oil extraction was performed by hydrodestilation, using Clevenger equipment. Results of the essential oil content showed that the drying air temperatures from 55 to 85oC did not statistically influence the essential oil content. The chromatographic profile of the essential oil presented changes as a function of the drying treatment when compared with the in natura plant (control).

Effects of Drying Air Temperature on the Structural Properties of Garlic Evaluated During Drying

Second order phase transitions may occur in foodstuffs during the convective drying process. These transitions involve physicochemical changes, which influence both structural properties and drying behavior. The aim of this study was to examine the effects of drying air temperature and the second order phase transition of garlic on the changes in particle density, apparent density, apparent porosity, effective diffusivity, and cracking produced during drying. Garlic slices were dehydrated at three air temperatures (40, 50, and 60°C). The moisture content (X), inside temperature (Ti), surface temperature (Ts), apparent (ρb) and particle (ρp) densities of garlic slices were measured during drying. Porosity (ϵ) was calculated based on the data collected for ρp and ρb. Glass transition temperatures (Tg) and micrographs were obtained for both raw and dehydrated garlic. A critical point in the intersection of Ti, Ts, and Tg was found; this point was identified as a second order phase transition. Diffusivity and slope changes in ρb, ρp, and ϵ with respect to moisture content were found to be related to this critical point. Experimental data for ρb, ρp, and ϵ was fitted to a nonlinear equation with three exponential terms with respect to moisture content, with an R2 > 0.85. Less dense products were found to be more porous, with more cracking, higher moisture diffusivity, and lower Tg at the end of the drying process.

The Effect of Drying Air Temperature and Humidity on the Drying Kinetic of Kenaf Core

Drying kinetics of kenaf core was investigated in a Low Temperature and Humidity Chamber Test. The drying experiments were carried out at temperature of 45, 50 and 55°C and air relative humidity of 10, 20 and 30% using a constant air velocity of 1.0 m/s. The moisture content data at various drying air conditions were converted to moisture ratio and plotted against time to obtain the drying curves for each experimental data. The curves were fitted to eight different thin layer drying models to determine a suitable model for drying of kenaf core. The fit quality of the models was evaluated based on their coefficient of determination (R2), reduced chi-square (χ2) and root mean square error (RMSE). Among the eight models, Two Term model is the best model for describing the drying behavior of kenaf core. The drying air temperature gave more significant effect on the drying kinetic of kenaf core compared to the drying air relative humidity under the experimental conditions studied.

Avaliação do vigor de sementes de carambola em função da secagem e do armazenamento

Neste estudo se avaliaram os efeitos imediato e latente da temperatura do ar de secagem no vigor das sementes de carambola, em condições controladas de laboratório. O vigor foi estimado por meio do índice de velocidade de germinação (IVG) e do tempo médio de germinação (t médio). Os testes de secagem foram realizados em secador protótipo de camada delgada a 30, 34 e 38 °C, empregando-se fluxo tangencial de ar seco de 1,123 kg s-1 m-2. O efeito latente das condições de secagem sobre o vigor foi determinado armazenando-se as sementes durante 45, 60, 90, 180 e 270 dias, a 15 °C. Não se observou efeito imediato significativo da secagem para nenhuma das temperaturas avaliadas, sobre o vigor das sementes estimado, tanto pelo IVG quanto pelo t médio. Em relação ao efeito latente, a melhor qualidade fisiológica estimada pelo maior IVG foi obtida para a temperatura de secagem de 38 °C e período de armazenamento de 180 dias. Os maiores valores do vigor estimados pelo menor t médio, independentemente da temperatura de secagem, foram obtidos para os períodos de armazenamento de 90 e 270 dias; portanto, os dois testes de vigor estudados devem ser utilizados com cautela na avaliação da qualidade fisiológica de lotes de sementes de carambola.

PH—Postharvest Technology: Effects of Drying Air Temperature and Humidity on Stress Cracks and Breakage of Maize Kernels

Samples of a single commercial maize hybrid were dried in a thin-layer dryer at four different air temperatures (40, 60, 80 and 100°C) and two levels of humidity (air saturation temperature of 5 and 25°C). The dried samples were subject to stress crack analysis and, after a tempering stage, were tested for breakage susceptibility. Stress cracking and breakage susceptibility both increased with drying temperature. Air humidity had no significant effect on either measure but higher drying air humidity resulted in a much longer drying time at the lowest air temperature (40°C).

Ginseng Drying - The Effect of Drying Air Temperature and Humidity upon Quality

Ginseng roots were dried in an incomplete block design of four temperatures and two relative humidity levels. Dried roots were then evaluated by ginseng buyers for color, size, and quality. The average root mass was determined for each treatment, and the color of samples from each treatment was evaluated using the Hunter colorimeter. The drying temperatures and humidities used in the study produced minor differences in measured color parameters. However, buyer evaluations of root color and quality were not significantly different for any treatment. In addition, there was no significant correlation among buyer ratings, and the buyer ratings did not significantly correlate with measured color or root mass parameters. Drying time decreased with increasing temperature, but was not affected by the relative humidity treatments.