Experimental research on drying characteristics of PVC powder in a normal fluidized-bed dryer

For obtaining the drying curve of powder under fluidized drying, a normal fluidized-bed dryer is designed to study the drying kinetics of PVC （polyvinyl chloride） powder in the experiment. A new measure system is derived for drying dynamics testing. In the small fluidized-bed dryer, fluidization parameter of PVC powder is tested, and the operating air velocity can be chosen in the range of 0. 41 to 0. 55 m/s. Accordingly, the fluidized number Ua/Umf is from 1.24 to 1.67. A promising drying model is used to describe the drying process, and then the characteristic drying curve of PVC powder derived from a suspension method can be expressed as f = [-0. 622 6 ＋ 1. 254 6exp（2. 561 5Φ -0. 707 2） /[1 ＋ exp（2. 561 5Φ -0. 707 2）] Based on the experiments, the critical moisture content xc and the mass transfer coefficient K are determined to be 0. 02 kg/kg and 6. 0 × 10^-4 kg/（ m2 · s）, respectively. The experimental results in the small fluidized-bed dryer are similar to those of the real fluidized drying process, so the descried method can also be used in determining drying kinetics of powder materials such as PVC powder.

Experimental Investigation on Flow and Drying Characteristics of Impinging Stream Drying

Based on the experimental investigation of one-stage semi-circular impinging stream drying, the experiments with the two-stage semi-circular, as well as the vertical and semi-circular combined impinging stream drying were conducted. The variations of system pressure drop, the mean residence time of particles with the mass flow-rate ratio and air velocity etc, were determined. The influences of inlet air temperature, mass flow-rate ratio, initial moisture content of particles and air velocity etc. on drying characteristics were also studied. The results indicate that the vertical and semi-circular combined impinging stream drying can make full use of the advantages of both the vertical and semi-circular impinging stream drying. Reasonable mass flow-rate ratio, air velocity, and higher inlet air temperature should be used for less energy consumption and cost during drying process.

Drying Characteristic of Anchovy Fish

This paper focuses on the drying characteristic of anchovy fish （Anchovia engraulidae）. It is necessary to understand the drying behavior, quality of the products and time required to optimize the energy consumption of the process. The optimum velocity and temperature of drying air for good quality dried anchovy fish was determined. In average, the fish are 7 cm in length and 3.0-3.5 g in mass. Although some research on fish drying has been done, the study of drying of anchovy fish and its characteristic has not been well reported. The fish to be dried were arranged on 15 × 15 cm2 tray in the drying chamber of 17 × 30 cm2. The hot air of 40 -70 ℃ was delivered parallel to the tray with the velocity of 0.6 and 0.9 m s-1. It is found that thermal conductivity （k） and specific heat （cp） of anchovy fish are function of the moisture content （MC）. The higher moisture content results in higher thermal conductivity and specific heat. Critical water content is also found in this experiment as well as the optimum drying condition. Drying rate period of anchovy fish will change from the constant drying rate period to the falling drying rate period when critical moisture content is about 48.8%-50.3% （wet basis）. At these experiments, there is no case-hardening, even at temperature of 70 ℃. To achieve the optimum result, the drying process should be implemented in three steps, drying process at 70 ℃ for 150 min followed by drying at 50℃ for 100 min, and finally drying at 40℃ till achieving equilibrium moisture content. This research will contribute to improvement of drying method to achieve good quality of dried fish.

Effects of Modulation Methods on the Drying Characteristics and Nutritional Quality of Medicago sativa Hay

Two-year-old Medicago sativa at budding initial stage was taken as research materials.Five methods were used to make green hay,including flatting stems ＋ spraying 2.5% K2CO3,flatting stems,sun curing,drying in shade and drying under 105 ℃ condition（CK）.Besides,effects of different green hay making methods on dry characteristics and nutritional quality of M.sativa green hay were studied,and a comprehensive evaluation of M.sativa green hays was conducted.Results showed that,except CK,the drying rates in other making methods were all fast at first,and then slow down.Both of drying under 105 ℃ condition and flatting stems ＋ spraying K2CO3 could speed up drying rate and reduce nutritional losses of green hay.Sun curing could also speed up drying rate,but it could not maintain the quality of green hay.The results of Grey Relational Analysis on five green hay making methods indicated that CK had the best comprehensive performance,followed by green hays made by flatting stems ＋ spraying K2CO3.Therefore,flatting stems ＋ spraying K2CO3 was a quick and easy method to make green hay,and it was worth to be recommended in practical production.

Characteristics of Dry and Wet Climate in Shandong Province Based on Standardized Precipitation Index

Based on the monthly precipitation data of 116 meteorological stations in Shandong Province during 1970-2021,standardized precipitation index(SPI)was calculated,and the methods of linear fitting,mutation test and Morlet wavelet analysis were used to analyze the change trend and temporal and spatial distribution characteristics of SPI index in the past 52 years.The results show that there were more normal years in Shandong Province,and the frequency reached 38.46%.There was severe drought in the 1980s and more wet years after 2003.SPI index showed an upward trend in spring,summer and winter but a weak arid trend in autumn.In addition,intense dry weather was more frequent in summer.Spatially,the climate was normal or humid in most areas of Shandong Province.The regions with more wet years were located in the central and northeast Shandong and the peninsula,while the climate was normal in the southwest and north of Shandong.The areas with more dry years were mainly located in the northwest of Shandong Province.There was mainly local and global drought in Shandong Province,and the arid area showed a decreasing trend.In the past 52 years,Shandong Province experienced quasi-4 times of alternation between dry and wet climate.The long period of 21 a was the first main period,and the climate would be still wet in Shandong Province in the future.In terms of mutation,the climate in Shandong Province became humid after 2003,and 2003 was the mutation point.After the abrupt change,the climate changed from gradually drying to wetting.

Effects of air movement in a hot air dryer on the drying characteristics of colored potato (Solanum tuberosum L.) using computational fluid dynamics

The flow fields of hot air in the dryer for drying colored potatoes of which characteristics are highly sensitive to the temperature were simulated using computational fluid dynamics(CFD)simulation.The local air velocity decreased as the distance from the flow inlet increased.The mass and heat transfer coefficients increased from 0.666×10^(-2) m/s to 1.711×10^(-2) m/s,and 6.555 W/(m^(2)·K)to 16.834 W/(m^(2)·K),respectively,as the air velocity increased from 0.207 m/s to 1.567 m/s at 60°C.The drying simulation model using the heat and mass transfer model made accurate predictions.The thermal properties of colored potato,such as the thermal conductivity and specific heat,decreased significantly from 0.440 W/(m·K)to 0.034 W/(m·K)and 3906.45 J/(kg·K)to 2198.52 J/(kg·K),respectively,as the moisture content decreased from 78% to 5%.With the variable thermal and physical properties,the heat transfer simulation model made accurate predictions of the hot-air drying characteristics for the colored potatoes,and the RMSE values for all cases were(1.85±0.27)℃.

Study of Kinetic Characteristics for Drying Rice Husk

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.

Experimental and Theoretical Analysis of the Impinging Stream Drying

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.

Effects of Mechanical Sowing and Transplanting on Characteristics of Dry Matter Production in Middle-season Hybrid Rice

To clarify the effects of mechanical sowing and transplanting on dry mat- ter production of middle-season hybrid rice, a two-factor split plot design was used to study the effects of different sowing and transplanting methods and their interac- tion with the seedling number per hill or seeding time on dry matter accumulation, distribution and transformation of F You 498, a middle-season hybrid rice variety, under field conditions in 2012 and 2013. The results showed that there was a marked effect of the sowing and transplanting methods and their interaction with the seedling number per hill or seeding time on dry matter accumulation, distribution and transformation. The total population dry matter accumulation of the treatments with mechanical direct seeding （MDS） and machine-based transplanting （MT） was lower than that of the treatment with traditional manual transplanting （TMT）. How- ever, MDS had higher dry matter accumulation and accumulating rate in the joint- ing-earing stage,and maintained higher stem-sheath exportation, export rate and transformation than MT and TMT; MT had higher dry matter accumulation and ac- cumulating rate in the heading-maturity period than MDS and TMT. Moreover, the treatments with low seedling number per hill or early seeding enhanced the assimi- lation of dry matter after heading,the ratio of dry matter accumulation after earing to biomass yield and the contribution rate of dry matter accumulation after earing, and a reasonable early sowing was favorable to increase the harvest index of middle- season hybrid rice under mechanical sowing and transplanting conditions.

Vibration transmissibility characteristics of smart spring vibration isolation system

The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

Theoretical and Experimental Studies on Low-Temperature Adsorption Drying of Fresh Ginger

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.

Innovative superheated steam impingement blanching(SSIB)enhances drying rate and quality attributes of line pepper

Blanching is an essential step before processing of agricultural products as it can inactivate enzymes that cause undesirable changes.In current work the effects of superheated steam impingement blanching(SSIB)time and temperature on drying characteristics and red pigments content of line pepper were investigated.Results showed that after a 3-min SSIB pretreatment at 110℃ the pepper epidermis covered with wax coat was damaged.In addition,the drying time was extensively decreased and the loss of red pigments of dried products was reduced.Results showed that the whole drying process took place in the falling rate period,which indicated that diffusion was the dominant physical mechanism governing moisture movement in the samples.Therefore,the second Fick’s law of diffusion was used to determine the effective moisture diffusivity(Deff)of line pepper,which increased from 1.193×10^-10 to 3.128×10^-10 m^2/s with increasing of the drying temperature and air velocity.The drying activation energy(Ea)of pretreated samples was 34.31 kJ/mol,which decreased by 3% compared with the non-pretreatment group.The findings of this work indicate that SSIB is very promising pretreatment technique as it not only enhances drying process but also improves bioactive substance preservation of red pepper.

Drying kinetics of technical specified rubber

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.

Drying of Flowing Liquid Film on Rotating Disk

Recently,development of high technology has been required for the formation of uniform thin film in manufacturing processes of semiconductor as the precision instruments become more sophisticated.A method called spin coating is often used for spreading photoresist on a wafer surface and drying photoresist film.In spin coating process,photoresist is uniformly spread on the wafer surface by centrifugal force caused by rotating wafer.However,it is a serious concern that streaky lines,which are caused by spiral vortices,appear on the wafer surface and prevent the formation of uniform film in the case of high rotating speed.On the other hand,in the case of low rotating speed,a small hump of the film is formed near the wafer edge.The main purpose of this study is to make clear the drying characteristics of the flowing liquid film on the rotating wafer.Temperature distribution of the flowing liquid film is captured by an infrared thermal video camera and radial gradient of the film temperature is introduced in order to evaluate the drying characteristic of the flowing film under steady state condition.Effects of the flow rate of the liquid film on the film temperature are investigated.The film temperature gradually decreases in the radial direction in all cases.At low rotating speed,the radial gradient of the film temperature is almost constant widely.On the other hand,at high rotating speed,the radial gradient of the film temperature takes a certain maximum value.It is found that the location of the gradient peak corresponds with the transition region of the air boundary layer,in which spiral vortices swirl,and shifts to the inner side of the disk with an increase of the liquid flow rate.