Drying paddy with low-pressure superheated steam(LPSS)can effectively increase theγ-aminobutyric acid content in paddy.This study aimed to investigate the characteristics and mathematical models(MMs)of thin-layer dry...Drying paddy with low-pressure superheated steam(LPSS)can effectively increase theγ-aminobutyric acid content in paddy.This study aimed to investigate the characteristics and mathematical models(MMs)of thin-layer drying of paddy with LPSS.The experimentally obtained data werefitted by nonlinear regression with 5 MMs commonly used for thin-layer drying to calculate the goodness of fit of the MMs.Then,the thin-layer drying of paddy with LPSS was modeled with two machine learning methods as a Bayesian regularization back propagation(BRBP)neural network and a support vector machine(SVM).The results showed that paddy drying with LPSS is a reduced-rate drying process.The drying temperature and operating pressure have a significant impact on the drying process.Under the same pressure,increasing the drying temperature can accelerate the drying rate.Under the same temperature,increasing the operating pressure can accelerate the drying rate.The comparison of the model evaluation indexes showed that 5 common empirical MMs(Hederson and Pabis,Page,Midilli,Logarithmic,and Lewis)for thin-layer drying can achieve excellent fitting effects for a single experimental condition.However,the regression fitting of the indexes by calculating the coefficient(s)of each model showed that the empirical MMs produce poor fitting effects.The BRBP neural network-based model was slightly better than the SVM-based model,and both were significantly better than the empirical MM(the Henderson and Pabis model),as evidenced by a comparison of the training root mean square error(RMSE),testing RMSE,training mean absolute error(MAE),testing MAE,training R2,and testing R2 of the Henderson and Pabis model,the BRBP neural network model,and the SVM-based model.This results indicate that the MMs established by the two machine learning methods can better predict the moisture content changes in the paddy samples dried by LPSS.展开更多
The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and...The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and the mean residence time of particles, and the influence of various factors on drying characteristics were studied. A mathematical model of granular material drying in a semi-circular impinging stream dryer was proposed, in which the flow characteristics as well as the heat and mass transfer mechanisms were considered. Reasonable numerical methods were used to solve the equations. Under various conditions, the calculated results agree well with the experimental data. The unsteady-state drying dynamic equation, as well as the variations of drying rate and moisture content versus time were obtained. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate semi-circular stage number and curvature radius, flow-rate ratio, air velocity, and higher inlet air temperature should be used for enhancing the drying process.展开更多
Edible fungi are rich in nutrition,but they are susceptible to spoilage,and often prolonged by drying.RF and microwave energy drying have the advantages of short drying time,high energy efficiency and good process con...Edible fungi are rich in nutrition,but they are susceptible to spoilage,and often prolonged by drying.RF and microwave energy drying have the advantages of short drying time,high energy efficiency and good process control.However,to develop an effective dielectric drying method,it is important to understand dielectric properties,the major factor characterizing the interaction between the electromagnetic energy and the food.At present,there is a lack of research on dielectric properties of edible fungi.In this study,a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters.The dielectric parameters were observed at different temperatures(25–85°C)for edible fungi powder with moisture content ranging from 5 to 30%wet basis over a frequency range of 1–3000 MHz.The relationship between the dielectric properties and frequency,temperature,and moisture content were obtained via regression analysis.Further,the dielectric penetration depth was calculated,and the effects of frequency,moisture content,and temperature on the penetration depth were also analyzed.The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature,while they decreased with increasing frequency.At high moisture content and temperature,the increase in dielectric properties was slightly larger than that at low moisture content and temperature.The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies.The penetration depth decreased with an increase in temperature,moisture content,and frequency.It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale,whereas microwave energy could be employed for drying edible fungi on a small scale.展开更多
The working principle of low-temperature adsorption drying and the advantages of its application for biological materials drying were introduced in this paper. By using fresh ginger as the drying material, the effects...The working principle of low-temperature adsorption drying and the advantages of its application for biological materials drying were introduced in this paper. By using fresh ginger as the drying material, the effects of temperature and relative humidity on its drying characteristics were examined. The results show that the drying rate increases with the temperature increasing or the humidity decreasing. The drying time to the equilibrium is almost the same under different humidity conditions, but low equilibrium moisture content can be acquired under low humidity. The shrinkage characteristics of fresh ginger were also studied. The change of its surface appearance during the drying process was characterized by the new Charged Coupled Device （CCD） and the Environmental Scanning Electron Microscopy （ESEM） technique. A mathematical model of drying dynamics was set up according to the experiments.展开更多
This paper reports the study of crumb rubber drying in different experimental designs.It is important to understand the characteristics of crumb rubber drying in order to formulate a better drying strategy that could ...This paper reports the study of crumb rubber drying in different experimental designs.It is important to understand the characteristics of crumb rubber drying in order to formulate a better drying strategy that could give higher energy efficiency.Four experiments were carried out with constant heat at maximum 100℃ and a stainless steel container was used to hold the sample of crumb rubber under study.The surface temperature profile of the rubber was investigated using two types of drying methods,normal hot air drying and vacuum drying.It was found that when the sample was dried,external surface temperature for drying with hot air dryer was higher than vacuum dryer.The results showed the evolution of temperature profile was not in good agreement with the prediction which revealed that there was no temperature gradient within the drying samples.The energy consumption for vacuum drying was higher compared to hot air drying,where there was a difference of 0.7079 MJ/kg H2O evaporated for drying temperature at 100℃.The best fit model generated from the experimental data was the modified Henderson and Pabis model and the highest effective diffusivity obtained was 5.243×10^-9m^2/s heating by vacuum oven at 90℃ under zero atmospheric pressure.展开更多
文摘Drying paddy with low-pressure superheated steam(LPSS)can effectively increase theγ-aminobutyric acid content in paddy.This study aimed to investigate the characteristics and mathematical models(MMs)of thin-layer drying of paddy with LPSS.The experimentally obtained data werefitted by nonlinear regression with 5 MMs commonly used for thin-layer drying to calculate the goodness of fit of the MMs.Then,the thin-layer drying of paddy with LPSS was modeled with two machine learning methods as a Bayesian regularization back propagation(BRBP)neural network and a support vector machine(SVM).The results showed that paddy drying with LPSS is a reduced-rate drying process.The drying temperature and operating pressure have a significant impact on the drying process.Under the same pressure,increasing the drying temperature can accelerate the drying rate.Under the same temperature,increasing the operating pressure can accelerate the drying rate.The comparison of the model evaluation indexes showed that 5 common empirical MMs(Hederson and Pabis,Page,Midilli,Logarithmic,and Lewis)for thin-layer drying can achieve excellent fitting effects for a single experimental condition.However,the regression fitting of the indexes by calculating the coefficient(s)of each model showed that the empirical MMs produce poor fitting effects.The BRBP neural network-based model was slightly better than the SVM-based model,and both were significantly better than the empirical MM(the Henderson and Pabis model),as evidenced by a comparison of the training root mean square error(RMSE),testing RMSE,training mean absolute error(MAE),testing MAE,training R2,and testing R2 of the Henderson and Pabis model,the BRBP neural network model,and the SVM-based model.This results indicate that the MMs established by the two machine learning methods can better predict the moisture content changes in the paddy samples dried by LPSS.
基金Supported by the State Key Fundamental Research Plan of China (No. G20000263) and the Director Foundation of Institute of Engineering Thermophysics, Chinese Academy of Sciences.
文摘The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and the mean residence time of particles, and the influence of various factors on drying characteristics were studied. A mathematical model of granular material drying in a semi-circular impinging stream dryer was proposed, in which the flow characteristics as well as the heat and mass transfer mechanisms were considered. Reasonable numerical methods were used to solve the equations. Under various conditions, the calculated results agree well with the experimental data. The unsteady-state drying dynamic equation, as well as the variations of drying rate and moisture content versus time were obtained. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate semi-circular stage number and curvature radius, flow-rate ratio, air velocity, and higher inlet air temperature should be used for enhancing the drying process.
基金support provided by the National Key R&D Program of China(No.2018YFD0400200)China National Natural Science Foundation(No.31601484)Jiangsu Agricultural Scientific and Technological Self-Innovation Foundation[CX(18)3037].
文摘Edible fungi are rich in nutrition,but they are susceptible to spoilage,and often prolonged by drying.RF and microwave energy drying have the advantages of short drying time,high energy efficiency and good process control.However,to develop an effective dielectric drying method,it is important to understand dielectric properties,the major factor characterizing the interaction between the electromagnetic energy and the food.At present,there is a lack of research on dielectric properties of edible fungi.In this study,a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters.The dielectric parameters were observed at different temperatures(25–85°C)for edible fungi powder with moisture content ranging from 5 to 30%wet basis over a frequency range of 1–3000 MHz.The relationship between the dielectric properties and frequency,temperature,and moisture content were obtained via regression analysis.Further,the dielectric penetration depth was calculated,and the effects of frequency,moisture content,and temperature on the penetration depth were also analyzed.The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature,while they decreased with increasing frequency.At high moisture content and temperature,the increase in dielectric properties was slightly larger than that at low moisture content and temperature.The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies.The penetration depth decreased with an increase in temperature,moisture content,and frequency.It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale,whereas microwave energy could be employed for drying edible fungi on a small scale.
文摘The working principle of low-temperature adsorption drying and the advantages of its application for biological materials drying were introduced in this paper. By using fresh ginger as the drying material, the effects of temperature and relative humidity on its drying characteristics were examined. The results show that the drying rate increases with the temperature increasing or the humidity decreasing. The drying time to the equilibrium is almost the same under different humidity conditions, but low equilibrium moisture content can be acquired under low humidity. The shrinkage characteristics of fresh ginger were also studied. The change of its surface appearance during the drying process was characterized by the new Charged Coupled Device （CCD） and the Environmental Scanning Electron Microscopy （ESEM） technique. A mathematical model of drying dynamics was set up according to the experiments.
基金The authors wished to acknowledge the contributions made by Sphere Corporation Sdn Bhd,University Of Nottingham–Malaysia Campus(UNMC)for their financial support.
文摘This paper reports the study of crumb rubber drying in different experimental designs.It is important to understand the characteristics of crumb rubber drying in order to formulate a better drying strategy that could give higher energy efficiency.Four experiments were carried out with constant heat at maximum 100℃ and a stainless steel container was used to hold the sample of crumb rubber under study.The surface temperature profile of the rubber was investigated using two types of drying methods,normal hot air drying and vacuum drying.It was found that when the sample was dried,external surface temperature for drying with hot air dryer was higher than vacuum dryer.The results showed the evolution of temperature profile was not in good agreement with the prediction which revealed that there was no temperature gradient within the drying samples.The energy consumption for vacuum drying was higher compared to hot air drying,where there was a difference of 0.7079 MJ/kg H2O evaporated for drying temperature at 100℃.The best fit model generated from the experimental data was the modified Henderson and Pabis model and the highest effective diffusivity obtained was 5.243×10^-9m^2/s heating by vacuum oven at 90℃ under zero atmospheric pressure.
