Effect of Ultrasonic Reflection Echo during Polymer Mixing Process

2010 ◽  
Vol 156-157 ◽  
pp. 1644-1648
Author(s):  
Chin Chi Cheng ◽  
Shao Chung Cheng ◽  
Chi Huang Lu

The objective of this study is to investigate the effect of ultrasonic reflection echo during polymer mixing process in the internal mixer. Phase change from solid to liquid, partially melted pellets, and distributing progress of CaCO3 powder during the melting process of low density polyethylene (LDPE) and the mixing process of the melted LDPE with a calcium carbonate (CaCO3) powder were successfully monitored by ultrasound. Melting and mixing completions were determined when ultrasonic reflection echo reached its upper stable level. The mixing period was proportional to the mass of added CaCO3 powder. The mean peak value of ultrasonic reflection L2f echo at the upper stable level decreased when the total amount of added CaCO3 powder increased. The presented ultrasonic technique can be utilized to optimize the melting and mixing processes, reduce cost and evaluate melting and mixing quality.

1992 ◽  
Vol 114 (1) ◽  
pp. 63-71 ◽  
Author(s):  
W. A. Eckerle ◽  
H. Sheibani ◽  
J. Awad

An experimental study was conducted to investigate the mixing processes downstream of a forced mixer. A forced mixer generates large-scale, axial (stirring) vorticity, which causes the primary and secondary flow to mix rapidly with low loss. These devices have been successfully used in the past where enhanced mixing of two streams was a requirement. Unfortunately, details of the mixing process associated with these lobed forced mixers are not well understood. Performance sensitivity to design variables has not been documented. An experiment was set up to investigate the mixing processes downstream of a mixer. Air flow was independently supplied to each side of the forced mixer by separate centrifugal blowers. Pressures were measured at the entrance to the lobes with a pitot-static probe to document the characteristics of the approaching boundary layer. Interior mean and fluctuating velocities were nonintrusively measured using a two-component laser-Doppler velocimetry (LDV) system for velocity ratios of 1:1 and 2:1. The wake structure is shown to display a three-step process where initially secondary flow was generated by the mixer lobes, the secondary flow created counterrotating vortices with a diameter on the order of the convolute width, and then the vortices broke down resulting in a significant increase in turbulent mixing. The results show that the mean secondary motion induced by the lobes effectively circulated the flow passing through the lobes. This motion, however, did not homogeneously mix the two streams. Turbulent mixing in the third step of the mixing process appears to be an important element in the enhanced mixing that has been observed with forced mixers. The length required for the flow to reach this third step is a function of the velocity ratio across the mixer. The results of this investigation indicate that both the mean secondary motion and the turbulent mixing occurring after vortex breakdown need to be considered for prediction of forced mixer performance.


Author(s):  
Wayne A. Eckerle ◽  
Hamdi Sheibani ◽  
Jean Awad

An experimental study was conducted to investigate the mixing processes downstream of a forced mixer. A forced mixer generates large scale, axial (stirring) vorticity which causes the primary and secondary flow to mix rapidly with low loss. These devices have been successfully used in the past where enhanced mixing of two streams was a requirement. Unfortunately, details of the mixing process associated with these lobed forced mixers are not well understood. Performance sensitivity to design variables has not been documented. An experiment was set up to investigate the mixing processes downstream of a mixer. Air flow was independently supplied to each side of the forced mixer by separate centrifugal blowers. Pressures were measured at the entrance to the lobes with a pitot-static probe to document the characteristics of the approaching boundary layer. Interior mean and fluctuating velocities were nonintrusively measured using a two-component Laser Doppler Velocimetry (LDV) system for velocity ratios of 1:1 and 2:1. The wake structure is shown to display a three step process where initially secondary flow was generated by the mixer lobes, the secondary flow created counter-rotating vortices with a diameter on the order of the convolute width, and then the vortices broke down resulting in a significant increase in turbulent mixing. The results show that the mean secondary motion induced by the lobes effectively circulated the flow passing through the lobes. This motion, however, did not homogeneously mix the two streams. Turbulent mixing in the third step of the mixing process appears to be an important element in the enhanced mixing that has been observed with forced mixers. The length required for the flow to reach this third step is a function of the velocity ratio across the mixer. The results of this investigation indicate that both the mean secondary motion and the turbulent mixing occurring after vortex breakdown need to be considered for prediction of forced mixer performance.


2010 ◽  
Vol 44-47 ◽  
pp. 127-131
Author(s):  
Chuan Sheng Wang ◽  
Shan Hu Li ◽  
Hui Guang Bian ◽  
Zhuang Zhi Xue

VIC mixer was a new type mixing equipment, and both had internal mixer's and open mixer's advantages. Meshing clearance of VIC mixer can be changed in the mixing process at any time by the eccentric bearing. The meshing clearance can be changed at different stages of the mixing process to adjust the different mixing formula and process. Through the experiments we had found that VIC mixer have a good mixing temperature control, cooling efficiency and low peak value in power when the meshing clearance is small. When the meshing clearance is large there is a high feeding speed, energy utilization efficiency and dispersion.


2015 ◽  
Vol 815 ◽  
pp. 14-18
Author(s):  
P. Santhiya ◽  
S.T. Sam ◽  
H. Kamarudin ◽  
S. Ragunathan ◽  
N.Z. Noriman ◽  
...  

The properties of blends made from low density polyethylene (LDPE) with various concentration of jackfruit seeds flour (JSF) with the presence of citric acid (CA) were investigated. The JSF content was varied from 0 to 20 wt%. The JSF were blended with LDPE by using an internal mixer (Brabender) at a temperature of 150°C. The test was carried out by using differential scanning calorimetry (DSC), with heating temperature of 100C/min. The crystallinity had improved with the presence of CA. However, the crystallinity slightly reduced with the increasing JSF content and further increased with the presence of CA.


2013 ◽  
Vol 477-478 ◽  
pp. 217-220
Author(s):  
Wen Bo He ◽  
Yuan Wang ◽  
Xiao Yan Gong

A pulsatile circulation system has been built to simulate aortic blood flow. The system has both upstream and downstream compliances and resistances to simulate the elasticity and resistances of blood circulation system. Influences of the compliances and resistances on the pulsatile pressure waveforms have been systematically studied using this system. We found that in absence of the compliances and the downstream resistance, it results in an oversize negative pulsation to the pressure waveforms. The downstream resistance hardly affects the structure of the pressure waveforms, whereas the mean amplitude of pressure increases along with the downstream resistance. The compliance can reduce the peak value of the pressure, which is unrelated to the location of the compliance but related to the elasticity in the system. With fixed upstream system elasticity, the pressure waveform is more stable.


2020 ◽  
Vol 35 (4) ◽  
pp. 1427-1445
Author(s):  
Ewan Short

AbstractForecasters working for Australia’s Bureau of Meteorology (BoM) produce a 7-day forecast in two key steps: first they choose a model guidance dataset to base the forecast on, and then they use graphical software to manually edit these data. Two types of edits are commonly made to the wind fields that aim to improve how the influences of boundary layer mixing and land–sea-breeze processes are represented in the forecast. In this study the diurnally varying component of the BoM’s official wind forecast is compared with that of station observations and unedited model guidance datasets. Coastal locations across Australia over June, July, and August 2018 are considered, with data aggregated over three spatial scales. The edited forecast produces a lower mean absolute error than model guidance at the coarsest spatial scale (over 50 000 km2), and achieves lower seasonal biases over all spatial scales. However, the edited forecast only reduces errors or biases at particular times and locations, and rarely produces lower errors or biases than all model guidance products simultaneously. To better understand physical reasons for biases in the mean diurnal wind cycles, modified ellipses are fitted to the seasonally averaged diurnal wind temporal hodographs. Biases in the official forecast diurnal cycle vary with location for multiple reasons, including biases in the directions that sea breezes approach coastlines, amplitude biases, and disagreement in the relative contribution of sea-breeze and boundary layer mixing processes to the mean diurnal cycle.


2018 ◽  
Vol 1 (2) ◽  
Author(s):  
Weiwei Lin

Objective (1)Through the blood physiological and biochemical tests during the altitude training, to analyze the body function of swimmers in this stage.(2) Through the individual lactate threshold tests before and after the altitude training,to analyze the effects of altitude training. Methods Eight swimmers took a 26-day altitude training session.The individual lactate threshold test was carried out by the Swedish Monak839E power cycle progressive loading method before and after the training;During the altitude training period, 5ml of the subjects' elbow vein was extracted and tested on an empty stomach and in a quiet state every Monday morning. Results (1)When swimmers reached the plateau, the hemoglobin value was indistinguishable from the plain(male 156.2±7.01,female 135.7±8.75g/L),From the hemoglobin value (male 154.03 + 5.67, female 134.23 + 9.66g/L), there was a decrease in both male and female in the second week.But hypoxia stimulated red blood cell production, and the body itself was gradually adapting to the training load.Thus, the hemoglobin value of the third week (male 157.17 + 3.7, female 141.93 + 10.06g/L) was significantly improved, and higher than the level of the first week.During the altitude training period, the mean value of male’s blood testosterone was 474.33 + 97.06ng/dl, and the female’s blood testosterone was 33.67 + 17.25ng/dl.Male’s blood testosterone was lower than the mean of the national team, because the study participants were youngers who were not fully developed and had shorter training years.There were different trends in blood testosterone value between male and female. Male’s blood testosterone values during the Monday morning of these three weeks were 479.67±76.25、492.33±83.61、451±153.41ng/dl respectively.female’s blood testosterone values during the Monday morning of these three weeks were 29.33±21.83、32±23.26、39.67±9.29ng/dl respectively.These further indicated that this altitude training plan was more suitable for male with shorter training years, and the body had certain fatigue accumulation, but the decrease range was within a reasonable range.However, the increase of blood testosterone per week in female indicated that the training stimulation depth was not enough, and the potential of athletes should be further explored.According to the changes of creatine kinase, the sensitivity of male to the change of altitude training intensity was also shown, and the highest value of creatine kinase was 731U/L in the first week.(2) From the value of the individual lactate threshold before and after altitude training, no matter male or female,the change was not obvious, but was generally improved, this may be the altitude training adopted the pattern of three and a half weeks, training time was short.Secondly, as a professional athlete, the "plastic space" gradually decreased with the extension of the training years.Most of the peak blood lactate occurred in 1-3 minutes of recovery period.and the average value increased from 8.96 + 1.86mmol/L before altitude training to 9.99 + 1.47mmol/L.Among them, the peak value of male’s blood lactate was increased from 8 + 2.22mmol/L before the altitude training to 10.91 + 1.43mmol/L, and there was a significant difference in the peak of blood lactate before and after the altitude training.However, the peak value of female’s blood lactate was decreased from 9.92 + 0.79mmol/L before the altitude training to 9.07 + 0.88mmol/L. This was mainly due to the fact that a member of the swimmers had caused the result, and this swimmer’s enduring lactate level was lower than the one before the plateau. Conclusions The altitude training generally improved athletes’ training ability, but based on factors such as training age, gender, should be targeted according to the individual situation of each athlete training plan, so as to achieve more from less.


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