Modeling of the Equilibrium Moisture Content (EMC) of Tarragon (Artemisia Dracunculus L.)

The equilibrium moisture content of tarragon, Artemisia dracunculus L. (stem and leaf separately) was determined by using the saturated salt solutions method at three temperatures (25, 50 and 70°C) within a range of 5 to 90% relative humidity. Both adsorption and desorption methods were used for stem and leaf of two varieties: Russian and French tarragon. Experimental curves of moisture sorption isotherms were fitted by modified Henderson, modified Halsey, modified Oswin, modified Chung-Pfost and GAB equations and evaluated by residual sum squares, standard error of estimate and mean relative deviation. The modified Halsey and GAB equations were found to be the most suitable for describing the relationship among equilibrium moisture content, relative humidity and temperature. There was no significant difference between the equilibrium moisture content of the Russian and French tarragon

STUDY ON MECHANICAL PROPERTIES OF SUNFLOWER SEEDS

ABSTRACT Some physical and mechanical properties of sunflower seeds were studied. The measured parameters were linear dimensions, thousand grain mass, geometric mean diameter, sphericity, surface and projected area, volume, shape parameters (such as flakiness ratio and elongation ratio), true and bulk densities, porosity, angle of repose and static coefficient of friction of the Shamshiri variety in the moisture range from 6.3 to 20% (w.b.) using standard methods. Average rupture force, deformation and absorbed energy at rupture point of the sunflower seeds under compression as well as the extent of physical damage to seeds due to impact were also determined over a range of moisture contents between 1.8% and 20.3% (w.b). The results showed a variation of 14.32 to 31.00 mm for length, 4.73 to 9.82 mm for width and 2.36 to 6.67 mm for thickness of sunflower seeds. The values of the thousand grain mass, seed volume, true density, bulk density and porosity of sunflower seeds were between149. 81-167.77g, 99.05-628.9 mm3, 444.39-521.78 kg/m3, 269.06-275.57 kg/m3 and 39.09-47.18% respectively. The rupture force, deformation, and absorbed energy increased with increase in moisture content from 1.8 to 14.5%, while decreased with further increasing of moisture content from 14.5 to 20.3%. The mean value of percentage of physically damaged seeds increased from 2.75 to 10.81% with increasing the impact velocity from 40.8 to 62.3 m/s. In both impact orientations, the total damaged seeds increased with increase in impact velocity for all moisture contents of seeds

Quality, energy requirement and costs of drying tarragon (Artemisia dracunculus L)

Tarragon ( Artemisia dracunculus L.) is a favorite herbal and medicinal plant. Drying is necessary to achieve longer shelf life with high quality, preserving the original flavor. Essential oil content and color are the most important parameters that define the quality of herbal and medicinal plants. Hot air batch drying is the most common drying method for these plants but affects the essential oil content and color. The drying conditions affect essential oil content and color as well as the energy consumption and costs. Process engineers and farmers need to know how they have to dry to obtain the best quality. The objective of this work is to investigate the conditions for optimal drying in terms of quality, energy consumption and costs.Adsorption and desorption experiments were done to find the equilibrium moisture content and water exchange between the material and surrounding air during drying and storage at temperatures of 25ºC to 70ºC and relative humidities of 5% to 90%. Drying of tarragon leaves and chopped plants was investigated separately and the best model was selected from the drying equations in literature. The effect of drying temperature and relative humidity on the essential oil content and color change was studied. Experiments were done at temperatures of 40ºC to 90ºC and the optimal conditions were. Long‑term effects of the drying conditions were also investigated during the storage time. Material dried at 45, 60 and 90ºC was stored and the essential oil content and color of the material was measured after 15, 30, 60 and 120 days of storage. Drying at 45ºC was found as the best condition based on the changes of essential oil and color during drying and storage.Optimization of drying of tarragon was studied based on the results of the sorption isotherms, drying equations and the changes of essential oil content and color during drying and storage. Models were made for the drying process, energy consumption and cost calculation. The current conditions in The Netherlands andIranwere applied for various drying scenarios. The simulation model was run at selected ranges of temperature, humidity ratio, air speed and bed heights, with and without recirculation of the drying air. Considering the quality of dried material and costs, a temperature of 50ºC was found as the optimal temperature for drying tarragon. The costs per kg dried product was about three times higher for The Netherlands compared toIran. The recirculation is less important inIranbecause the ambient air has a higher drying potential and energy prices are lower

Modeling of desorption of Alfalfa (Medicago sativa) stems and leaves.

The equilibrium moisture content of agricultural products is necessary to optimize drying process and helps to keep the quality of the product during the period of storage. The main aim of this research was to find the best model which could define well, the exchange of moisture between alfalfa (Medicago sativa) and the surrounding air. The desorption isotherms of alfalfa (stem and leaf) were determined separately by using the saturated salt solutions method at three temperatures (25, 50 and 70 °C) within a range of 5–90% relative humidity. Experimental curves of desorption isotherms were fitted to modified equations of Henderson, Halsey, Oswin and Chung-Pfost as well as the GAB model and then evaluated visually by using residual plots and also by some statistical error parameters. The modified Halsey model was found to be the most suitable for describing the relationship between equilibrium moisture content, relative humidity and temperature

Selection of a Relevant Mathematical Model for Drying of Tomato Slices Using Solar Dryer

In this research, solar drying of a thin layer of tomato slices was evaluated. The experiments were carried out at the air velocities of 0.5 and 1.0 m s-1 and thicknesses of 3, 5 and 7 mm. In order to find the most suitable form of thin layer drying model, nine different mathematical drying models were fitted to the experimental data to determine the pertinent coefficients of each model. The goodness of the fit was determined by calculating and comparing the values of the correlation coefficient (R^2 ) Root mean square error (RMSE) and chi-square (χ^2) for all models. The Page model with R^2=0.9974 ,χ^2=0.01351 , RMSE=0.002 showed the best fit

Long-term effects of drying conditions on the essential oil and color of tarragon leaves during storage

The effect of storage on the essential oil content and color of French Tarragon (Artemisia dracunculus L.) leaves is studied. Tarragon leaves were dried at temperatures 45, 60 and 90 °C with, respectively, the relative humidity levels 17%, 7% and 2.5%. At 60 °C also a relative humidity level of 18% was applied. The air velocity was constant at 0.6 m/s. Oil content and color were measured for the fresh and dried leaves just after drying as well as after storage during 15, 30, 60 and 120 days. The essential oil compounds of the material were isolated by the hydro-distillation method and analyzed by GC¿FID as well as GC¿MS. A Chroma meter was used to measure the color of the samples. The results showed a reduction of the oil content and changed color parameters during the storage period. The largest changes of the essential oil content (about 50% after 30 days) and color expressed by the hue value was found for the material dried at 90 °C. Drying at 45 °C resulted in the smallest quality change

Modeling of the equilibrium moisture content (EMC) of Miscanthus (Miscanthus x giganteus)

The desorption isotherms of miscanthus, Miscanthus x giganteus (stems and leaves) were determined separately by using the saturated salt solutions method at three temperatures (25, 50 and 70 degrees C) within a range from 5 to 90% relative humidity. Experimental curves of desorption isotherms were fitted to Modified Henderson, Modified Halsey, Modified Oswin and Modified Chung-Pfost models and evaluated by Residual Sum of Squares (RSS), Standard Error Estimation (SEE) and Mean Relative Deviation (MAD) methods. The Modified Oswin model was found to be the most suitable for describing the correlation between equilibrium moisture content, relative humidity and temperature

Investigation of one-dimensional heat flow in a solarflat plate collector with sun tracing system

Introduction Drying is one of the most common methods for storing food and agricultural products. During drying process, free water that causes the growth of microorganisms and spoilage of products is removed from the product. There are several methods for drying of agricultural products. one of the most important methods of investment is drying by using sunlight. Iran is situated at 25- 43oE longitude and mean solar radiation is about 4.9 kwh.m-2.d-1. Because of the proper solar radiations in 95% of the agricultural areas in Iran, solar drying is widely used for drying of fruits and vegetables. The use of solar dryer causes saving in energy consumption and processing costs for drying of products in farms and gardens. Several researchers investigated heat transfer and heat flow in dryers. Selection of appropriate method was carried out for drying of agricultural products using heat pump. Experiments were done and mathematical relationships were estimated to obtain correlation parameters between Reynolds number and Nusselt number for the three cases of solar dryer (cabinet, indirect and combination).The best working conditions were determined for three types of solar collectors (flat, finned and corrugated). In this study, the process of heat transfer and heat transfer coefficient of a solar dryer with and without rotation of absorber plate was compared. Materials and Methods The experiments were conducted in Azarshahr, East Azarbayjan province, Iran in September 2014. Newton's law of thermodynamic was used to analyze the working condition of solar absorber. For this purpose the absorber plate was divided into four equal parts. According to the thermal equations and related boundary conditions as well as the relationship between heat transfer coefficient and the temperature gradient, equation 1 for the Nusselet number obtained: 1 Beside the relationship between Nusselt number and heat transfer coefficient is defined as equation 2: 2 Finally variation of total heat flow over the time at different surfaces of the collector is determined by using equation 3: 3 Two cases (solar panel with rotation and without rotation) were considered for testing. Data measuring was carried out for 9 hours from 8 to 17. The fluid flow rate was 0.0185m3.s-1. The dryer was installed in an environment with air temperature of 31.6 oC and 31.8 oC, with the air velocity of 0.58 m.s-1 and 0.54 m.s-1 and with the relative air humidity of about 21%and 21.5% at the first and second days, respectively. The dryer had an automatic temperature controller to fix the air temperature with an accuracy of ±0.1 oC. An anemometer Yk-2005AM model was used to regulate the required air velocity. The output data of the thermocouples was recorded by a digital thermometer (DL-9601A, Lutron) that was connected to a computer using RS232 cable and recorded the temperature at required point every an hour. The relative humidity of the ambient was measured every hour with a digital hygrometer (HT.3600, Taiwan), accuracy of 3%. By assembling controlling system with a DC motor, a precious photocell and a proper mechanism, the frame would rotate by the sun and followed solar radiation, therefore more solar energy produced in solar panel. Results and Discussion The results of the experiments showed that the heat transfer process increased in both cases from the early morning and reached to its maximum value around 12 to 14 o’clock. The trend was more homogeneous in the dryer by absorber plate without rotation due to the decline of the heat accumulation. The mean temperature rise in the solar dryer without rotation was 37oC and in the solar dryer with rotation was 54oC. Because of the rotation of solar plate, variations of solar radiation were low. Therefore, by rotation of the solar dryer panel the temperature rise was 27oC. The values of heat transfer coefficient in the solar dryer with rotation were decreased by the time. This reduction in the hours before noon is more than after noon. This is due to the reduction of the temperature gradient in the solar absorber plate. Also the results showed that heat transfer coefficient in the lower levels (S1 and S2) is more than higher levels (S3 and S4). Variations of the heat flow for the solar dryer with rotation is more than the other. Because in the first one, the absorber plate was followed the solar radiation and generated heat in the plate increases and the fan does not have the ability to discharge the generated heat. The total amount of heat transfer in absorber plate with rotation was 36.1% higher than the absorber plate without rotation. To increase the heat transfer from the dryer, design of the system to change air flow rate by increasing temperature, can increase the efficiency of the dryer. Conclusions In this study the performance of the absorber plate in a solar dryer in two cases with rotation and without rotation were compared. The results showed that by rotation of the solar absorber plate the output temperature of the collector rises about 27oC. Thermal fluctuation in the rotation solar plate is lower than the solar plate without rotation