In the high-humidity, hot-summer-cold-winter(HSCW) zone of China, the moisture buffering effect in the envelope is found to be significant in optimum insulation thickness. However, few studies have considered the effe...In the high-humidity, hot-summer-cold-winter(HSCW) zone of China, the moisture buffering effect in the envelope is found to be significant in optimum insulation thickness. However, few studies have considered the effects of indoor moisture buffering on the optimum insulation thickness and energy consumption. In this study, we considered the energy load of an exterior wall under moisture transfer from the outdoor to the indoor environment. An optimum insulation thickness was obtained by integrating the P1-P2model. A residential building was selected for the case study to verify the proposed method. Finally, a comparison was made with two other widely used methods, namely the transient heat transfer model(TH) and the coupled heat and moisture transfer model(CHM). The results indicated that the indoor moisture buffering effect on the optimum insulation thickness is 2.54 times greater than the moisture buffering effect in the envelope, and the two moisture buffering effects make opposing contributions to the optimum insulation thickness. Therefore, when TH or CHM was used without considering the indoor moisture buffering effect, the optimum insulation thickness of the southern wall under one air change per hour(1 ACH) and 100% normal heat source may be overestimated by 2.13% to 3. 59%, and the annual energy load on a single wall may be underestimated by 10.10% to 11.44%. The decrease of airtightness and the increase of indoor heat sources may result in a slight reduction of optimum insulation thickness. This study will enable professionals to consider the effects of moisture buffering on the design of insulation thickness.展开更多
To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals wit...To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals with solid humidity conditioning materials(HCM).On this basis,a coupled anti-condensation regulation strategy between the NRCT and the fresh air system was constructed,which utilizes the moisture buffering effect of the HCM to extend the condensation time,and reserves sufficient time for active intervention of personnel and feedback adjustment of the fresh air system.Then,the indoor air parameters are restored to normal design values as a result of the fresh air system.Meanwhile,the HCM releases the adsorbed water vapor,thereby enabling the completion of the desorption process.Using numerical simulation methods to study each step of the anti-condensation regulation strategy,the results indicate that the NRCT can effectively prevent condensation,and it can ensure that condensation does not occur within 20 min after the window is opened,even under extreme weather conditions.Moreover,the anti-condensation effect improves with the thickness increase of the HCM.However,when ensuring the prevention of condensation while expecting the best moisture adsorption effect,there is an optimal value for the thickness of the HCM.Increasing the fresh air supply volume can enable the HCM to complete the desorption process more quickly.In the final steady-state operation process,the HCM can continue to release moisture,achieving sustainable utilization of the HCM.In actual operation,the operational duration of the fresh air system during the moisture desorption process can be regulated by tracking the relative humidity of the outlet to ensure that the HCM completes the adsorption and desorption cycle.This anti-condensation regulation strategy can provide effective guarantee for the non-condensing operation of radiant cooling terminals.展开更多
To address the limitations of current urban building energy modeling(UBEM),which often neglects moisture effects,we developed a comprehensive roadmap for modeling urban heat and moisture flows.This effort included dev...To address the limitations of current urban building energy modeling(UBEM),which often neglects moisture effects,we developed a comprehensive roadmap for modeling urban heat and moisture flows.This effort included developing an urban-scale whole-building heat and moisture transfer(HAMT)model that considers wind-driven rain,integrated with a microclimate model known as Urban Weather Generator(UWG).The proposed model was validated through analytical and comparative cases of whole-building hygrothermal performance analyses from the Annex 41 Project.The integrated whole-building and microclimate HAMT models were applied to a real urban building to assess the impact of moisture on annual energy predictions in a hot-humid region of Shanghai.The results show that incorporating moisture effects into the UBEM increases the annual cooling energy demand by 22.11%(5.92% owing to latent heat loads)and the annual heating loads by 6.06%,resulting in a 19.73%increase in the total annual energy loads.Additionally,the outer wall surface temperature decreases during and after rainfall events,with maximum decreases of 3.23℃ in winter and 8.80℃ in summer.Therefore,integrating moisture effects into UBEM is crucial,particularly in humid regions.展开更多
The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significan...The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significance for recognizing the spatial-temporal pattern of Asian monsoons in the past and predicting environmental change in the future. Nevertheless, the framework of the Holocene moisture variation and related mechanisms remain controversial, owing to complex hydroclimatic conditions triggered by the landform of the large mountain-arid basin. Here, we employed geochemical proxies from typical aeolian sand-palaeosol sequences in the Gonghe Basin, northeastern QTP, together with Optically Stimulated Luminescence(OSL) dating, to reconstruct the pattern of effective moisture variation and associated mechanisms in this region. Our results indicate that the regional effective moisture was at its lowest until 9–8 ka, and approached a maximum during 8–4/3 ka of the middle Holocene. Afterwards, the climate became relatively dry in general, but with a transient humid interval around 2–1 ka. Our geochemical evidence indicates that the dry early Holocene probably can be attributed to a strong winter monsoon forced by remnant ice sheet, combined with the high evaporation caused by solar insolation. Also, shifts of humid-dry are closely linked to the Asian summer monsoonal strength and therefore the balance of evaporation-precipitation in the middle and late Holocene. Thus, the pattern of the Holocene effective moisture variation is characterized as the ‘monsoon model’ in a closed intermontane arid and semi-arid basin near the western Asian monsoonal limit.展开更多
The accuracy of the knowledge of mass transfer parameters （effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient） in the case of frying food, is essential and important for designin...The accuracy of the knowledge of mass transfer parameters （effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient） in the case of frying food, is essential and important for designing, modeling and process optimization. This study is undertaken to develop an approach for determining mass transfer parameters during frying of spherical rice cracker in sunflower oil at 150, 170 and 190 ℃. These parameters were evaluated from the plots of dimensionless concentration ratios against time of frying. Effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient ranged between 1.24×10^-8 to 2.36×10^-8 m^2/s, 1.96 to 2.34 and 5.51×10^-6 to 9.70×10^-6 m/s, respectively. Effective moisture diffusivity and mass transfer coefficient were found to increase with an increasing frying temperature, whereas mass transfer Biot number decreased. An Arrhenius-type relationship was found between effective diffusivity coefficient and frying temperature.展开更多
Rice husk (biomass fuel) samples have been dried in drying oven and a series of drying curve for illustrating moisture migration of rice husk have been obtained. It is first research for rice husk drying,and it can pr...Rice husk (biomass fuel) samples have been dried in drying oven and a series of drying curve for illustrating moisture migration of rice husk have been obtained. It is first research for rice husk drying,and it can provide reference of fuel processing for different boilers which require rice husk with various water contents. In this paper,we apply Page equation to reflect the drying process and obtain drying characteristic curve,then analyze the drying law. Kinetic analysis of the results of moisture migration test has been done,after which, effective moisture diffusion coefficient,activation energy and drying kinetic equation of rice husk samples are obtained in test temperature range (80 - 130 ℃) . And these results show specific influence law of temperature for effective moisture diffusion coefficient.展开更多
The available literature revealed a gap in reporting the rough rice drying kinetics parameters under isothermal conditions, particularly for Arkansas medium- and long-grain varieties. Therefore, medium-grain (RO170112...The available literature revealed a gap in reporting the rough rice drying kinetics parameters under isothermal conditions, particularly for Arkansas medium- and long-grain varieties. Therefore, medium-grain (RO170112 and Titan) and the long-grain (Diamond and Wells) rough rice varieties were dried under isothermal conditions. The drying process occurred under 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C in a system emulating the thermogravimetric analyzer. Drying kinetics models were studied for four well-known models: Page, Newton, Logarithmic, and Henderson & Pabis. The drying kinetics constants were determined for the four studied models. The initial moisture content of rough rice was 28.2% db. Profound moisture reduction was observed during the first three hours of drying, followed by less moisture content reduction. The results showed that at the drying temperature of 100°C and after 6 hours of the drying process, the lowest moisture content reached 13.9% (db) for Titan rough rice. The drying rate of rough rice ranged between 7.41 and 2.01%/h during the first hour of drying under the studied temperature range of 40°C to 100°C. The drying rate was higher with the higher temperature levels during the first three hours. Among all the studied models, the Page, Newton, and Logarithmic models best fit 25%, 25%, and 50% of the twenty-eight studied cases. The challenge that arose from these results led to evolving a mathematical solution by joining the three models in one equation. The combined model showed the best fit for all the studied cases, with R<sup>2</sup> ranging between 0.9999 and 0.9954 for the medium- and long-grain rice varieties. Increasing the drying temperature increased the effective moisture diffusivity values. The highest effective moisture diffusivity of 18.104 × 10<sup>-9</sup> m<sup>2</sup>/s was obtained at the drying temperature of 100°C for medium-grain rice, Titan. The activation energy values ranged between 17.77 and 24.48 kJ/mol for the four rough rice varieties.展开更多
The fluctuation of a single lake level is a comprehensive reflection of water balance within the basin, while the regional consistent fluctuations of lake level can indicate the change of regional effective moisture. ...The fluctuation of a single lake level is a comprehensive reflection of water balance within the basin, while the regional consistent fluctuations of lake level can indicate the change of regional effective moisture. Previous researches were mainly focused on reconstructing effective moisture by multiproxy analyses of lake sediments. We carried out a series of experiments, including a transient climate evolution model, a lake energy balance model and a lake water balance model to simulate continuous Holocene effective moisture change represented by variability of virtual lake level in East and Central Asia.The virtual lake level, area, water depth and salinity are not equivalent to actual values, but we estimated relative changes of the regional effective moisture. We also explored the driving mechanisms of effective moisture change in different geographical regions. Our results indicated that gradually falling effective moisture during the Holocene in northern China was due to the combined effects of high lake evaporation caused by longwave and shortwave radiation, and low precipitation caused by reductions of summer solar insolation. A decline in effective moisture through the Holocene in the Tibetan Plateau and southern Central Asia resulted from decreased precipitation because of the weakening of the Asian summer monsoon. Increased precipitation induced by the strengthening of the westerly circulation contributed to the effective moisture rise during the Holocene in northern Central Asia.展开更多
Vacuum far-infrared radiation(VFIR)drying has recently received many attentions because of its effective and successful applications in drying some agricultural products.The VFIR drying of Radix Rehmanniae was conduct...Vacuum far-infrared radiation(VFIR)drying has recently received many attentions because of its effective and successful applications in drying some agricultural products.The VFIR drying of Radix Rehmanniae was conducted and Weibull distribution function was applied to fit the drying kinetics in this study.The results showed that the increase of radiation heater temperature and the decrease of chamber pressure could reduce drying time obviously.Compared with single diffusion equation,Weibull distribution function had higher precision to fit the drying curves of VFIR drying of Rehmanniae.The effective moisture diffusivity(Deff)increased with the increase of heater temperature and the decrease of pressure.Scanning electron telescope(SEM)analysis showed that more porous surface could be observed after VFIR drying,which is beneficial to enhance moisture diffusivity and drying rate as well.展开更多
The effects of long-term moisture changes on the migration,release,and bioavailability of selenium in soil are complex.Due to the lack of effective monitoring methods for precise quantification,its dynamic behavior is...The effects of long-term moisture changes on the migration,release,and bioavailability of selenium in soil are complex.Due to the lack of effective monitoring methods for precise quantification,its dynamic behavior is still unclear.Based on the DGT(Diffusive Gradients in Thin-films)technology,this study sets up three moisture control scenarios:continuous wet,wet-dry alternating,and continuous dry,and carries out a 6-month soil moisture control experiment.In the experiment,the DGT device collected the diffusion gradient data of soil selenium under different scenarios,and analyzed the migration characteristics of selenium in combination with the adsorption isotherm.Meanwhile,the release rate,migration coefficient,and bioavailability parameters of selenium are calculated by fitting the first-order kinetic model,further verifying the reliability and applicability of the DGT data.The experimental results demonstrate that under continuous wet conditions,the release rate of soil selenium reaches 1.85µg·cm^(-2)·h^(-1),with a migration coefficient of 0.012 cm^(2)·h^(-1)and a bioavailability parameter of 0.74;under wet-dry alternating conditions,they are 1.42µg·cm^(-2)·h^(-1),0.01 cm^(2)·h^(-1),and 0.68,respectively;under continuous dry conditions,the release rate of soil selenium is the smallest,at 0.88µg·cm^(-2)·h^(-1),with a migration coefficient of 0.004 cm^(-2)·h^(-1)and a bioavailability parameter of 0.5.The results of this experiment reveal the dynamic behavior of soil selenium under different moisture conditions and reflect the high efficiency of DGT technology in dynamic monitoring and quantitative analysis of soil selenium behavior,providing a scientific basis for the optimal management of rhizosphere soil selenium.展开更多
This study investigates the microwave drying kinetics of thin layer Mabonde banana variety(MBV)at power levels between 100 and 300 W.Six mathematical drying models:Wang and Singh,Verma,Two-term,Page,Two term exponenti...This study investigates the microwave drying kinetics of thin layer Mabonde banana variety(MBV)at power levels between 100 and 300 W.Six mathematical drying models:Wang and Singh,Verma,Two-term,Page,Two term exponential,and Logarithmic models were fitted to experimental drying data obtained from the study.The statistical consistency of the models was determined using statistical parameters including coefficient of determination,mean bias error,root mean square error,and reduced Chi square.Moisture migration from banana slices was described using the Fick’s diffusion model.The effective diffusivity was calculated.The results indicated that drying took place largely in the falling rate period.The time required to reduce the moisture of banana to a certain level was dependent on the microwave output,being the longest at 100 W and shortest at 300 W.The effective moisture diffusivity increased with increasing microwave power with values at 4.89×10^(-10),1.09×10^(-9) and 1.69×10^(-9) m^(2)/s at 100,200,and 300 W,respectively.The Wang and Singh model gave the best results for the description of thin layer drying of MBV.展开更多
This study investigated the drying kinetics of pork slice in infrared drying condition.Drying temperature,slice thickness and initial moisture content were selected as influencing factors on the drying characteristics...This study investigated the drying kinetics of pork slice in infrared drying condition.Drying temperature,slice thickness and initial moisture content were selected as influencing factors on the drying characteristics and drying rate of pork slice.Drying curves obtained from the experimental data were fitted to semi theoretical and/or empirical thin layer drying models.The effects of drying temperature and slice thickness on the model constants were evaluated by the multiple regression method.All the models were compared according to three statistical indexes,i.e.,root mean square error,chi-square and modeling efficiency.The slice thickness,drying temperature and initial moisture content have significant influences on the effective diffusivity coefficient of pork.The results showed that the drying rate of pork slices increased with the increases of drying temperature and initial moisture content.The decreases of slice thickness also led to an increase of drying rate.The Henderson and Pabis model can best describe the drying curves of pork.展开更多
The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system(ANFIS)and Artificial Neural Networks(ANNs)model for predicting the drying characteristics of potato,garlic and cantaloup...The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system(ANFIS)and Artificial Neural Networks(ANNs)model for predicting the drying characteristics of potato,garlic and cantaloupe at convective hot air dryer.Drying experiments were conducted at the air temperatures of 40,50,60 and 70C and the air speeds of 0.5,1 and l.5 m/s.Drying properties were including kinetic drying,effective moisture diffusivity(Deff)and specific energy consumption(SEC).The highest value of Deff obtained 9.76×10^-9,0.13×10^-9 and 9.97×10^-10 m^2/s for potato,garlic,and cantaloupe,respectively.The lowest value of SEC for potato,garlic,and cantaloupe were calculated 1.94105,4.52105 and 2.12105 kJ/kg,respectively.Results revealed that the ANFIS model had the high ability to predict the Deff(R^2=0.9900),SEC(R^2=0.9917),moisture ratio(R^2=0.9974)and drying rate(R^2=0.9901)during drying.So ANFIS method had the high ability to evaluate all output as compared to ANNs method.展开更多
In this study,drying characteristics of Syzygium cumini was experimentally investigated under the temperatures of 50°C,60°C and 70°C and the mathematical models were used to fit the drying of Syzygium c...In this study,drying characteristics of Syzygium cumini was experimentally investigated under the temperatures of 50°C,60°C and 70°C and the mathematical models were used to fit the drying of Syzygium cumini.Moisture transfered from Syzygium cumini was described by applying the Fick’s diffusion model and the effective moisture diffusivity was calculated.The temperature dependence of the effective moisture diffusivity for the drying of Syzygium cumini samples was described by an Arrhenius-type relationship with activation energy.Drying data were fitted to seven drying models,namely Lewis,Henderson and Pabis,Logarithmic,Twoterm,Page,Wang and Singh and modified Henderson and Pabis.The Logarithmic model was found as the best fitted model in describing the drying behavior of Syzygium cumini.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51978623 and 52076189)。
文摘In the high-humidity, hot-summer-cold-winter(HSCW) zone of China, the moisture buffering effect in the envelope is found to be significant in optimum insulation thickness. However, few studies have considered the effects of indoor moisture buffering on the optimum insulation thickness and energy consumption. In this study, we considered the energy load of an exterior wall under moisture transfer from the outdoor to the indoor environment. An optimum insulation thickness was obtained by integrating the P1-P2model. A residential building was selected for the case study to verify the proposed method. Finally, a comparison was made with two other widely used methods, namely the transient heat transfer model(TH) and the coupled heat and moisture transfer model(CHM). The results indicated that the indoor moisture buffering effect on the optimum insulation thickness is 2.54 times greater than the moisture buffering effect in the envelope, and the two moisture buffering effects make opposing contributions to the optimum insulation thickness. Therefore, when TH or CHM was used without considering the indoor moisture buffering effect, the optimum insulation thickness of the southern wall under one air change per hour(1 ACH) and 100% normal heat source may be overestimated by 2.13% to 3. 59%, and the annual energy load on a single wall may be underestimated by 10.10% to 11.44%. The decrease of airtightness and the increase of indoor heat sources may result in a slight reduction of optimum insulation thickness. This study will enable professionals to consider the effects of moisture buffering on the design of insulation thickness.
基金supported by the National Natural Science Foundation of China[No.52276179]the Natural Science Foundation of Jiangsu Province[No.BK20231425]。
文摘To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals with solid humidity conditioning materials(HCM).On this basis,a coupled anti-condensation regulation strategy between the NRCT and the fresh air system was constructed,which utilizes the moisture buffering effect of the HCM to extend the condensation time,and reserves sufficient time for active intervention of personnel and feedback adjustment of the fresh air system.Then,the indoor air parameters are restored to normal design values as a result of the fresh air system.Meanwhile,the HCM releases the adsorbed water vapor,thereby enabling the completion of the desorption process.Using numerical simulation methods to study each step of the anti-condensation regulation strategy,the results indicate that the NRCT can effectively prevent condensation,and it can ensure that condensation does not occur within 20 min after the window is opened,even under extreme weather conditions.Moreover,the anti-condensation effect improves with the thickness increase of the HCM.However,when ensuring the prevention of condensation while expecting the best moisture adsorption effect,there is an optimal value for the thickness of the HCM.Increasing the fresh air supply volume can enable the HCM to complete the desorption process more quickly.In the final steady-state operation process,the HCM can continue to release moisture,achieving sustainable utilization of the HCM.In actual operation,the operational duration of the fresh air system during the moisture desorption process can be regulated by tracking the relative humidity of the outlet to ensure that the HCM completes the adsorption and desorption cycle.This anti-condensation regulation strategy can provide effective guarantee for the non-condensing operation of radiant cooling terminals.
基金support from the National Natural Science Foundation of China(52478031).
文摘To address the limitations of current urban building energy modeling(UBEM),which often neglects moisture effects,we developed a comprehensive roadmap for modeling urban heat and moisture flows.This effort included developing an urban-scale whole-building heat and moisture transfer(HAMT)model that considers wind-driven rain,integrated with a microclimate model known as Urban Weather Generator(UWG).The proposed model was validated through analytical and comparative cases of whole-building hygrothermal performance analyses from the Annex 41 Project.The integrated whole-building and microclimate HAMT models were applied to a real urban building to assess the impact of moisture on annual energy predictions in a hot-humid region of Shanghai.The results show that incorporating moisture effects into the UBEM increases the annual cooling energy demand by 22.11%(5.92% owing to latent heat loads)and the annual heating loads by 6.06%,resulting in a 19.73%increase in the total annual energy loads.Additionally,the outer wall surface temperature decreases during and after rainfall events,with maximum decreases of 3.23℃ in winter and 8.80℃ in summer.Therefore,integrating moisture effects into UBEM is crucial,particularly in humid regions.
基金This study was supported by the Strategic Priority Research Program of Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road (Grant No. XDA 2009000001)the National Natural Science Foundation of China (Grants No. 41977393 and 41671204)
文摘The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significance for recognizing the spatial-temporal pattern of Asian monsoons in the past and predicting environmental change in the future. Nevertheless, the framework of the Holocene moisture variation and related mechanisms remain controversial, owing to complex hydroclimatic conditions triggered by the landform of the large mountain-arid basin. Here, we employed geochemical proxies from typical aeolian sand-palaeosol sequences in the Gonghe Basin, northeastern QTP, together with Optically Stimulated Luminescence(OSL) dating, to reconstruct the pattern of effective moisture variation and associated mechanisms in this region. Our results indicate that the regional effective moisture was at its lowest until 9–8 ka, and approached a maximum during 8–4/3 ka of the middle Holocene. Afterwards, the climate became relatively dry in general, but with a transient humid interval around 2–1 ka. Our geochemical evidence indicates that the dry early Holocene probably can be attributed to a strong winter monsoon forced by remnant ice sheet, combined with the high evaporation caused by solar insolation. Also, shifts of humid-dry are closely linked to the Asian summer monsoonal strength and therefore the balance of evaporation-precipitation in the middle and late Holocene. Thus, the pattern of the Holocene effective moisture variation is characterized as the ‘monsoon model’ in a closed intermontane arid and semi-arid basin near the western Asian monsoonal limit.
文摘The accuracy of the knowledge of mass transfer parameters （effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient） in the case of frying food, is essential and important for designing, modeling and process optimization. This study is undertaken to develop an approach for determining mass transfer parameters during frying of spherical rice cracker in sunflower oil at 150, 170 and 190 ℃. These parameters were evaluated from the plots of dimensionless concentration ratios against time of frying. Effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient ranged between 1.24×10^-8 to 2.36×10^-8 m^2/s, 1.96 to 2.34 and 5.51×10^-6 to 9.70×10^-6 m/s, respectively. Effective moisture diffusivity and mass transfer coefficient were found to increase with an increasing frying temperature, whereas mass transfer Biot number decreased. An Arrhenius-type relationship was found between effective diffusivity coefficient and frying temperature.
文摘Rice husk (biomass fuel) samples have been dried in drying oven and a series of drying curve for illustrating moisture migration of rice husk have been obtained. It is first research for rice husk drying,and it can provide reference of fuel processing for different boilers which require rice husk with various water contents. In this paper,we apply Page equation to reflect the drying process and obtain drying characteristic curve,then analyze the drying law. Kinetic analysis of the results of moisture migration test has been done,after which, effective moisture diffusion coefficient,activation energy and drying kinetic equation of rice husk samples are obtained in test temperature range (80 - 130 ℃) . And these results show specific influence law of temperature for effective moisture diffusion coefficient.
文摘The available literature revealed a gap in reporting the rough rice drying kinetics parameters under isothermal conditions, particularly for Arkansas medium- and long-grain varieties. Therefore, medium-grain (RO170112 and Titan) and the long-grain (Diamond and Wells) rough rice varieties were dried under isothermal conditions. The drying process occurred under 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C in a system emulating the thermogravimetric analyzer. Drying kinetics models were studied for four well-known models: Page, Newton, Logarithmic, and Henderson & Pabis. The drying kinetics constants were determined for the four studied models. The initial moisture content of rough rice was 28.2% db. Profound moisture reduction was observed during the first three hours of drying, followed by less moisture content reduction. The results showed that at the drying temperature of 100°C and after 6 hours of the drying process, the lowest moisture content reached 13.9% (db) for Titan rough rice. The drying rate of rough rice ranged between 7.41 and 2.01%/h during the first hour of drying under the studied temperature range of 40°C to 100°C. The drying rate was higher with the higher temperature levels during the first three hours. Among all the studied models, the Page, Newton, and Logarithmic models best fit 25%, 25%, and 50% of the twenty-eight studied cases. The challenge that arose from these results led to evolving a mathematical solution by joining the three models in one equation. The combined model showed the best fit for all the studied cases, with R<sup>2</sup> ranging between 0.9999 and 0.9954 for the medium- and long-grain rice varieties. Increasing the drying temperature increased the effective moisture diffusivity values. The highest effective moisture diffusivity of 18.104 × 10<sup>-9</sup> m<sup>2</sup>/s was obtained at the drying temperature of 100°C for medium-grain rice, Titan. The activation energy values ranged between 17.77 and 24.48 kJ/mol for the four rough rice varieties.
基金supported by the National Natural Science Foundation of China (Grant No. 41822708)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20100102)the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (Grant No. 2019QZKK0202)。
文摘The fluctuation of a single lake level is a comprehensive reflection of water balance within the basin, while the regional consistent fluctuations of lake level can indicate the change of regional effective moisture. Previous researches were mainly focused on reconstructing effective moisture by multiproxy analyses of lake sediments. We carried out a series of experiments, including a transient climate evolution model, a lake energy balance model and a lake water balance model to simulate continuous Holocene effective moisture change represented by variability of virtual lake level in East and Central Asia.The virtual lake level, area, water depth and salinity are not equivalent to actual values, but we estimated relative changes of the regional effective moisture. We also explored the driving mechanisms of effective moisture change in different geographical regions. Our results indicated that gradually falling effective moisture during the Holocene in northern China was due to the combined effects of high lake evaporation caused by longwave and shortwave radiation, and low precipitation caused by reductions of summer solar insolation. A decline in effective moisture through the Holocene in the Tibetan Plateau and southern Central Asia resulted from decreased precipitation because of the weakening of the Asian summer monsoon. Increased precipitation induced by the strengthening of the westerly circulation contributed to the effective moisture rise during the Holocene in northern Central Asia.
基金the National Natural Science Foundation of China(Grant No.U1404334)the College Young Teachers Development Program of Henan province(Grant No.2015GGJS-048)the Science and Technology Project of Henan Province of China(Grant No.12A210005 and 14B550005)。
文摘Vacuum far-infrared radiation(VFIR)drying has recently received many attentions because of its effective and successful applications in drying some agricultural products.The VFIR drying of Radix Rehmanniae was conducted and Weibull distribution function was applied to fit the drying kinetics in this study.The results showed that the increase of radiation heater temperature and the decrease of chamber pressure could reduce drying time obviously.Compared with single diffusion equation,Weibull distribution function had higher precision to fit the drying curves of VFIR drying of Rehmanniae.The effective moisture diffusivity(Deff)increased with the increase of heater temperature and the decrease of pressure.Scanning electron telescope(SEM)analysis showed that more porous surface could be observed after VFIR drying,which is beneficial to enhance moisture diffusivity and drying rate as well.
文摘The effects of long-term moisture changes on the migration,release,and bioavailability of selenium in soil are complex.Due to the lack of effective monitoring methods for precise quantification,its dynamic behavior is still unclear.Based on the DGT(Diffusive Gradients in Thin-films)technology,this study sets up three moisture control scenarios:continuous wet,wet-dry alternating,and continuous dry,and carries out a 6-month soil moisture control experiment.In the experiment,the DGT device collected the diffusion gradient data of soil selenium under different scenarios,and analyzed the migration characteristics of selenium in combination with the adsorption isotherm.Meanwhile,the release rate,migration coefficient,and bioavailability parameters of selenium are calculated by fitting the first-order kinetic model,further verifying the reliability and applicability of the DGT data.The experimental results demonstrate that under continuous wet conditions,the release rate of soil selenium reaches 1.85µg·cm^(-2)·h^(-1),with a migration coefficient of 0.012 cm^(2)·h^(-1)and a bioavailability parameter of 0.74;under wet-dry alternating conditions,they are 1.42µg·cm^(-2)·h^(-1),0.01 cm^(2)·h^(-1),and 0.68,respectively;under continuous dry conditions,the release rate of soil selenium is the smallest,at 0.88µg·cm^(-2)·h^(-1),with a migration coefficient of 0.004 cm^(-2)·h^(-1)and a bioavailability parameter of 0.5.The results of this experiment reveal the dynamic behavior of soil selenium under different moisture conditions and reflect the high efficiency of DGT technology in dynamic monitoring and quantitative analysis of soil selenium behavior,providing a scientific basis for the optimal management of rhizosphere soil selenium.
基金the financial support to AOO from the Research Fund Project No.SARDF/14/FST/01the Work Study Programme of the University of Venda,Thohoyandou,South Africa.
文摘This study investigates the microwave drying kinetics of thin layer Mabonde banana variety(MBV)at power levels between 100 and 300 W.Six mathematical drying models:Wang and Singh,Verma,Two-term,Page,Two term exponential,and Logarithmic models were fitted to experimental drying data obtained from the study.The statistical consistency of the models was determined using statistical parameters including coefficient of determination,mean bias error,root mean square error,and reduced Chi square.Moisture migration from banana slices was described using the Fick’s diffusion model.The effective diffusivity was calculated.The results indicated that drying took place largely in the falling rate period.The time required to reduce the moisture of banana to a certain level was dependent on the microwave output,being the longest at 100 W and shortest at 300 W.The effective moisture diffusivity increased with increasing microwave power with values at 4.89×10^(-10),1.09×10^(-9) and 1.69×10^(-9) m^(2)/s at 100,200,and 300 W,respectively.The Wang and Singh model gave the best results for the description of thin layer drying of MBV.
基金the National Natural Science Foundation of China(No.61663039)Natural Science Foundation of Ningxia Hui Autonomous Region(No.NZ1648)the Natural Science Funds of Ningxia University(ZR15010).
文摘This study investigated the drying kinetics of pork slice in infrared drying condition.Drying temperature,slice thickness and initial moisture content were selected as influencing factors on the drying characteristics and drying rate of pork slice.Drying curves obtained from the experimental data were fitted to semi theoretical and/or empirical thin layer drying models.The effects of drying temperature and slice thickness on the model constants were evaluated by the multiple regression method.All the models were compared according to three statistical indexes,i.e.,root mean square error,chi-square and modeling efficiency.The slice thickness,drying temperature and initial moisture content have significant influences on the effective diffusivity coefficient of pork.The results showed that the drying rate of pork slices increased with the increases of drying temperature and initial moisture content.The decreases of slice thickness also led to an increase of drying rate.The Henderson and Pabis model can best describe the drying curves of pork.
文摘The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system(ANFIS)and Artificial Neural Networks(ANNs)model for predicting the drying characteristics of potato,garlic and cantaloupe at convective hot air dryer.Drying experiments were conducted at the air temperatures of 40,50,60 and 70C and the air speeds of 0.5,1 and l.5 m/s.Drying properties were including kinetic drying,effective moisture diffusivity(Deff)and specific energy consumption(SEC).The highest value of Deff obtained 9.76×10^-9,0.13×10^-9 and 9.97×10^-10 m^2/s for potato,garlic,and cantaloupe,respectively.The lowest value of SEC for potato,garlic,and cantaloupe were calculated 1.94105,4.52105 and 2.12105 kJ/kg,respectively.Results revealed that the ANFIS model had the high ability to predict the Deff(R^2=0.9900),SEC(R^2=0.9917),moisture ratio(R^2=0.9974)and drying rate(R^2=0.9901)during drying.So ANFIS method had the high ability to evaluate all output as compared to ANNs method.
文摘In this study,drying characteristics of Syzygium cumini was experimentally investigated under the temperatures of 50°C,60°C and 70°C and the mathematical models were used to fit the drying of Syzygium cumini.Moisture transfered from Syzygium cumini was described by applying the Fick’s diffusion model and the effective moisture diffusivity was calculated.The temperature dependence of the effective moisture diffusivity for the drying of Syzygium cumini samples was described by an Arrhenius-type relationship with activation energy.Drying data were fitted to seven drying models,namely Lewis,Henderson and Pabis,Logarithmic,Twoterm,Page,Wang and Singh and modified Henderson and Pabis.The Logarithmic model was found as the best fitted model in describing the drying behavior of Syzygium cumini.
