نویسندگان
1 گروه مهندسی بیوسیستم، دانشگاه محقق اردبیلی
2 گروه مهندسی بیوسیستم، دانشگاه علوم کشاورزی و منابع طبیعی ساری
3 گروه مهندسی بیوسیستم، دانشکده کشاورزی دانشگاه تربیت مدرس
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction
Today, a high percentage of industrial dryers are convection dryers. Currently, most of the energy used for drying comes from fossil fuels, which have irreparable environmental damage. Solar energy is a clean and renewable energy used for the drying process since ancient times. Over time, various solar dryers were produced and investigated in research. Researches show that most of these dryers are convective and work based on the hot air-drying method. The refractance window dryers are a new generation of dryers with high-quality dried products. Like other dryers, the drying process in these dryers is energy-intensive. This research has tried to provide the energy needed to heat water in an RW dryer system by receiving solar energy through a PTC collector. An attempt has been made to study the drying kinetics of apple slices inside a combined solar dryer. The combined dryer included a refractance window dryer and PTC collector.
Materials and Methods
In this research, an attempt has been made to study the drying kinetics of apple slices inside the combined dryer included a refractance window dryer and a PTC collector. The drying experiments were divided into three categories. The first group of tests was related to the common drying method (RW), which was performed at three temperature levels (65, 75, and 85°C). To conduct tests in the first category, only city electricity was used to heat water. The second group of experiments was conducted as combined drying by solar energy (PRW). In this method, three temperature levels (65, 75, and 85°C) were used. Fick's second law was used to measure the effective diffusion coefficient. Mathematical models were used to describe the drying curves of the thin layer to investigate the drying kinetics. Experimental data obtained from the drying of apple slices were described using Logarithmic, Henderson and Pabis, Newton, Modified Page, and Midili models.
Results and Discussion
The drying time was 140-320 min in the first method, 160-260 min in the second method, and 240 min in the third method. In the first method, the results showed by increasing the temperature from 65 to 85°C, the drying time decreased by 56.25% (from 320 to 140 minutes) and by 38.46% (from 260 minutes to 160 minutes) in the second method. The fitting of the used models with the real data showed that all the used models had good accuracy in determining the process of exiting moisture from the apple slices. Among the investigated models, the Midili model was more accurate than other models due to having higher R2 and lower SSE and RMSE. The lowest and highest effective moisture diffusivity coefficients obtained in the experiments conducted by RW-65 and RW-85 methods as 8.93×10-13 and 4.82×10-12, respectively. Also, the effective moisture diffusion coefficient in the solar method was obtained as 1.74×10-12 in SRW.
Conclusion
In fitting the data with the Midili model, the mean values of R2, SSE, and RMSE were obtained as 0.963, 0.031, and 0.062, respectively. After the Midili model, modified Page, Henderson, logarithmic and Newton models were more accurate in describing the exit of moisture from the product, respectively. Also, the results showed with increasing the water temperature in the system, the effective moisture diffusion coefficient increases. The presented combined solar dryer has a good ability to dry the apple slices and reduced energy consumption compared to non-renewable resources.
Acknowledgment
This study has been conducted as an interior research project of the University of Mohaghegh Ardabili.
کلیدواژهها [English]
)