OPTIMIZE, UPGRADE OR INVEST IN A NOVEL DRYER? – A BRICK FACTORY CASE STUDY

Drying has an enormous impact on the quality of final masonry clay elements. The accumulated knowledge about modeling the drying process, as well as the registered progress in computing the coupling between the heat and mass transfer during the last decade has reached the applicative industrial level. The available novel commercial drying solutions have dropped the drying cycle to 5 hours for hollow clay products and up to 9 hours for clay blocks of large size and weight. The ability to speed up the drying process also strongly depends on the properties of the raw materials. The decision on optimization of the existing dryer and its upgrade or investment in a novel drying facility must be experimentally validated. Results of the one-month monitoring and analysis of the production process in one Serbian brick factory including the material and energy balances are given in this paper. Based on the collected data, raw material limitations and costs of the novel dryer the existing tunnel dryer upgrade and the minimization of the "false" ambient air into the dryer are proposed.

Leaves drying kinetics of the species Zanthoxylum sprucei (Rutaceae) and Melampodium divaricatum (Asteraceae)

The study of the drying of the plants is important for the extraction methods of the active principles, since it provides benefits both for the efficiency and for the stability. The objective of this research is to study the drying kinetics of the leaves of Zanthoxylum sprucei (Rutaceae) and Melampodium divaricatum (Asteraceae) species from the Manabí province. Eight empirical models derived from Fick's law with adjustment and the STATISTICA software as modeler was used. The model was made by applying the ORIGIN Pro fit curve. The kinetic results were obtained experimentally in a laboratory scale tunnel dryer with a temperature of 40°C, at 1 atm of pressure and a speed air of 8.47 m.s-1. To determine the model that best fits the experimental data, it relies on the correlation coefficient (R2), mean square error (ERMS) and chi-square (X2). The mathematical model that best describes the drying process is the logarithmic for Zanthoxylum sprucei and the Wang and Singh model for Melampodium divaricatum.

Dynamic Modelling and Performance Optimization-Based Sliding Mode Control of Process Drying in a Convective Tunnel Dryer

In this work, we thoroughly investigate the use of sliding mode control for nonlinear systems, specially its application for the control of dryer designed for drying food products. A dynamic model of the drying process has been developed, experimental measurements presented in this paper are established for different values of drying air temperature and drying air velocity. Two scenario of sliding mode control applied to the hybrid tunnel dryer has been assessed through simulations. At first, a nonlinear sliding mode control with first order sliding surface was tested. In front of the insufficient performance of this control in terms of the presence of chattering phenomenon and static error, it was decided to apply a nonlinear sliding mode control with PI sliding surface. Simulation results show that this latter control approach can obtain excellent control performance with no chattering problem, reducing of static error and a good tracking of trajectory.

Dynamic Modelling and Performance Optimization-Based Sliding Mode Control of Process Drying in a Convective Tunnel Dryer

In this work, we thoroughly investigate the use of sliding mode control for nonlinear systems, specially its application for the control of dryer designed for drying food products. A dynamic model of the drying process has been developed, experimental measurements presented in this paper are established for different values of drying air temperature and drying air velocity. Two scenario of sliding mode control applied to the hybrid tunnel dryer has been assessed through simulations. At first, a nonlinear sliding mode control with first order sliding surface was tested. In front of the insufficient performance of this control in terms of the presence of chattering phenomenon and static error, it was decided to apply a nonlinear sliding mode control with PI sliding surface. Simulation results show that this latter control approach can obtain excellent control performance with no chattering problem, reducing of static error and a good tracking of trajectory.

Design, Fabrication and Performance Evaluation of Solar Tunnel Dryer for Ginger Drying

Background The performance of a solar tunnel dryer for drying ginger was investigated through a series of experiments. Two axial flow fans with a power rating of 28W, supply voltage of 220V, and powered by a 50W PV module were used to supply hot air to the drying chamber. Results and discussion The dryer has been put through no-load and load tests with solar PV powered fans. Solar radiation, dry air temperature, ambient temperature, relative humidity (RH), and air velocity were recorded at five solar tunnel dryer positions by dividing the 8.5-meter-long solar tunnel dryer into four equal parts every thirty minutes. When the solar radiation was altered between 540 and 820 W/m2, the hot air temperature at the collector output rose from 34°C to 65.5°C for an 8-hour operation in the no-load state. At loading operation circumstances, average maximum temperatures of 30°C at 9:00 AM and 77°C at 13:00 PM were achieved. In 24 hours (3 solar days), the solar tunnel drier was able to reduce the moisture content of sliced ginger from 90.4 % to 11.8 percent (wet basis). Open sun drying, on the other hand, takes 40 hours (5 solar days) to obtain the same wet basis condition. With a solar collector area of 6 m2. Conclusions Eight experiments have been conducted at no-load and full-load conditions. The drying air temperature varied from 34.0°C to 65.5°C at the collector outlet. The drying time decreases as the collector area increases, whereas the drying efficiency and time savings increase. Furthermore, the gingers were totally sheltered from rain, insects, and dust while drying in the solar tunnel dryer, resulting in high-quality dried gingers. The dryer could be utilized in rural locations where there is no access to energy because the fans are driven by a solar module. The solar tunnel dryer showed a net saving in drying time of 40% over open sun drying.

Drying kinetics and thermodynamic analysis of tomato in a tunnel dryer

In this study, drying kinetics and thermodynamic analysis of tomato were conducted in a tunnel dryer. Drying experiments were performed at three temperatures (100, 115, and 130 °C) and an air velocity of 1.45 m/s. From the drying curves, only a falling rate period was observed. Under these conditions, a characteristic drying curve was determined. It is observed that at the 40 minutes of the drying process, the outlet gas enthalpy achieved a maximum value that is very close to the inlet value and remained constant until the end of the process. Entropy exhibited similar behaviour to enthalpy. The maximum value of the exergy efficiency curve corresponds to the maximum value observed within the drying rate curves. This maximum value represents the stage when the available energy is efficiently used in moisture removal. As the drying rate decreases the available energy is started to be less employed.

Effect of Different Drying Methods on the Drying Kinetics of Fermented Cardaba Banana Peels

Cardaba banana peels (Musa acuminata) were fermented for three days and dried using solar dryer, open sun and tunnel dryer. Nonlinear regression analysis was used to fit in the experimental data. Moisture drying was investigated using Fick’s second law. Statistical tools such as coefficient of determination (R2), reduced chi square (χ2), Mean Bias Error (MBE) and Root Mean Square Error (RMSE) were used to test the reliability of the model. Sample dried in sun had single falling rate pattern whereas samples in solar and tunnel dryer exhibited a second falling rate pattern. The values of R2 ranged from 0.872 - 0.989, χ2(1.4E-34 - 0.0624), MBE (-0.0067 - 0.0491) and RMSE (1.1E-17 - 0.2247). Effective moisture diffusivity for samples dried in solar, tunnel and sun were 2.92 E-11m2/s, 1.98 E-11m2/s and 1.09 E-11m2/s, respectively. The energy of activation in the process was 64.9kJ/mol. Page model best described drying behavior of the samples.Keywords: Fermentation, banana peels, drying, models, diffusivity, activation energy

Experimental Studies of Drying Pineapple with An Active Indirect Solar Tunnel Dryer in Malaysia

Abundant sunshine and tropical climate of Malaysia have made pineapple a suitable fruit to be grown in this country. However, to have longer shelf-life, lighter weight for transportation and less storage space, drying of pineapple has been a common preservation method in this country. Open-sun drying used to be most common method of preserving agricultural products. Nevertheless, due to the disadvantages of open sun drying method, solar drying technology has become an alternative method of drying vegetables, fruits, spices, herbs etc. The main purpose of this paper is to evaluate the performance of active solar tunnel dryer (ASTD) for drying sliced pineapples. The air circulation system in this dryer is based on forced convection system. In active solar tunnel dryer inlet airflow temperature was gained by corrugated absorber plate. During the experiment minimum, maximum and average of absorber thermal efficiency were 13.1% and 24.4%, and 19.8 % respectively. The inlet temperature range was between 260C to 380C, the escalated temperature range was between 340C to 750C on the absorber outlet. Relative humidity (RH) experienced changes due to irradiance intensity, the RH reduced when passed through the absorber plate. The average inlet humidity was 54% while average outlet humidity was 36%. During 9 hours of drying process, pineapple moisture content reduced from 89% to 12.5% and its weight decreased from 5 kg to 0.6 2kg. The peak sun hours were 5.7 hours, and loading density was 1.51 kg/m2.