Measurement and simulation validation of numerical model parameters of fresh concrete

Abstract In the numerical simulation of the macroscopic flow of the concrete, it can optimize the performance indicators of the screw conveyor and improve the uniformity of the material to be discharged in the batch production. The discrete element method is effective. The accuracy of physical parameters of this method is a key issue for the reliability of the simulation results of concrete. In this study, we measured the parameters describing the interaction between gravel, mortar, as well as between these two materials and the wall (steel). The experimentally determined parameters include the particle density, size, shape, coefficient of restitution, coefficients of static, and rolling friction. The cohesion coefficient of mortar particles for batch time was obtained by comparing the spread diameter and flow time in V-funnel experiments and simulation. After these calibration steps, the DEM parameters were validated by comparison of the mass flow rate and driving power by the batch production of screw conveying in simulations and experiments. The calculated results are proved to be close to the experimental data, which demonstrates that the measured DEM parameters are of sufficient accuracy to be used in the simulation of concrete flow performance (mass flow rate, energy consumption) in the screw conveyors.

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Thermal Characteristics Analysis on Multi- Heat Pipe Induced Heat Exchanger

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.b1034.1292s219 ◽

2019 ◽

Vol 9 (2S2) ◽

pp. 143-147 ◽

Cited By ~ 1

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Heat Pipe ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Cold Water ◽

Hot Water ◽

Working Fluid ◽

Physical Parameters

In this investigation of multi heat pipe induced in heat exchanger shows the developments in heat transfer is to improve the efficiency of heat exchangers. Water is used as a heat transfer fluid and acetone is used as a working fluid. Rotameter is set to measure the flow rate of cold water and hot water. To maintain the parameter as experimental setup. Then set the mass flow rate of hot water as 40 LPH, 60LPH, 80 LPH, 100LPH, 120 LPH and mass flow rate of cold water as 20 LPH, 30 LPH, 40 LPH, 50 LPH, and 60 LPH. Then 40 C, 45 ºC, 50 ºC, 55 C, 60 ºC are the temperatures of hot water at inlet are maintained. To find some various physical parameters of Qc , hc , Re ,, Pr , Rth. The maximum effectiveness of the investigation obtained from condition of Thi 60 C, Tci 32 C and 100 LPH mhi, 60 LPH mci the maximum effectiveness attained as 57.25. Then the mhi as 100 LPH, mci as 60 LPH and Thi at 40 C as 37.6%. It shows the effectiveness get increased about 34.3 to the maximum conditions.

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Dynamic characteristic analysis of vertical screw conveyor in variable screw section condition

Science Progress ◽

10.1177/0036850420951056 ◽

2020 ◽

Vol 103 (3) ◽

pp. 003685042095105

Author(s):

Jianming Yuan ◽

Mingzhi Li ◽

Fangping Ye ◽

Zhenhui Zhou

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Volume Fraction ◽

Particle Volume Fraction ◽

Screw Conveyor ◽

Characteristic Analysis ◽

Particle Volume ◽

Flow Rate Increase ◽

Particle Feeding

Vertical screw conveyors are used widely in industry for elevating bulk materials over relatively short distances, but the problem of insufficient feeding and low conveying efficiency always exist in the vertical conveying process. In this paper, a vertical screw conveyor with variable screw section is presented, and the characteristics of vertical screw conveyor are investigated under the variable screw sections using discrete element method (DEM). The results show that the particle volume fraction in the inlet and the mass flow rate increase in the condition of variable screw section, and the screw rotational speed has a significant influence on mass flow rate. It is evident that the design of variable screw section provides an effective way in improving the particle feeding rate and the conveying efficiency.

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Modeling and Simulation of Multistage Microcompressor With Passive Microvalves for Micro Coolers

ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2016-7934 ◽

2016 ◽

Author(s):

Shawn T. Le ◽

Hisham Hegab

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

High Frequency ◽

Pressure Ratio ◽

Model Parameters ◽

Negative Effect ◽

Frequency Threshold ◽

Gap Height ◽

Operation Frequency

A cascaded multistage (2-stage) micro gas compressor in series is investigated through a lump model simulation to determine its feasibility in increasing compressor performance. A dynamic model of the micro gas compressor which consists of a unimorph piezoelectric diaphragm and passive micro check valves is presented and simulated with a Matlab Simulink® tool. Simulation is implemented for a 1 and 2-stage microcompressor design. Finite element analysis (FEA) is used to determine the lump model parameters from the fluid-structure interaction (FSI) between the microvalve and gas flow dynamics. FSI model parameters are extracted and developed as a lump model equation for Simulink® numerical computation. Dynamic simulations confirm that there is an increase in pressure ratio for a multistage microcompressor when compared to a single stage, which is achievable with passive microvalves. However, there are negative effects of using passive microvalves at high frequency. Frequency response results gathered from simulation shows that mass flow rate through the microvalve decreases above the frequency threshold ∼1 kHz for our design. This is in two parts due to a smaller gap height opening of the microvalve plate at high frequency and the reverse flow leakage. Both losses in mass flow rate from the microvalves decrease the total flow rate of the microcompressor above ∼1 kHz. Increasing actuation frequency below the ∼1 kHz threshold increases the flow rate of the microcompressor in the design. Therefore, it is concluded that the maximum flow rate of the microcompressor increases with increasing operation frequency, but becomes limited by the negative effect of the microvalve at a high frequency threshold due to the attenuation of the microvalve gap height. Although flow rate is affected, maximum pressure ratio of the microcompressor is still achievable at various frequency range, assuming the stroke volume of the pump chamber is constant throughout all frequency ranges. Multistage simulations show that the operation frequency ratio between each stage can have some negative effect in achieving the maximum theoretical pressure ratio.

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Study of the Greitzer Model for Centrifugal Compressors: Variable Lc Parameter and Two Types of Surge

Energies ◽

10.3390/en13226072 ◽

2020 ◽

Vol 13 (22) ◽

pp. 6072

Author(s):

Filip Grapow ◽

Grzegorz Liśkiewicz

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Linear Trend ◽

Oscillation Amplitude ◽

Pressure Oscillation ◽

Tuning Parameter ◽

Model Parameters ◽

Model Compressor ◽

Best Fit

In this paper, the Greitzer surge model was systematically analysed with the model compressor duct length Lc as the tuning parameter. The surge phenomenon is known to induce a serious risk to centrifugal compressor operation. The two-dimensional Greitzer model is a well-established way of modelling this dangerous instability, but the determination and changes of the model parameters are still being discussed. In this paper an automated procedure determines the Lc value providing the best fit with the experimental data has been presented. The algorithm was tested on five valve positions and revealed that the best fit was obtained for different Lc values following a linear trend against the mass flow rate. The study has also shown that the Greitzer model has two solutions for a given pressure oscillation amplitude: one similar to the deep surge (low Lc) and one similar to the mild surge (low Lc). This suggests that this model can be used to simulate both types of the phenomenon known from the experimental analyses. The study proposes the dimensionless average pressure as the parameter allowing to distinguish which surge cycle was observed at a given instance. Past papers were analysed to observe the surge type that appeared in different experiments. It was found that most researchers obtained low Lc surge. The results show that both deep and mild surge could be simulated with the Greitzer model. It also revealed that the Lc should not be treated as a constant value for a given machine and that it changes with the mass flow rate.

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