In view of the robot hand-eye calibration process of artificial time is long and the calibration of the problem of the great error. Based on the binocular measuring, this paper designs a robot ...hand-eye calibration method based on the depth of the camera. Depth of the calibration imaging camera and a point cloud model, By parallax of calibration feature points and depth value reflect the space relationship between the camera and import coordinate robot base coordinate system at the same time, the moment of hand-eye relation transforms. Experiments show that the calibration methods of plane error is less than 0. 40 mm, space error is less than 0. 46 mm, calibration time not more than 5 min. To verify the correctness and validity of the method, and improve the operational efficiency of the industrial robot calibration process.
Aiming at the problem of automatic optical detection of electronic street sign display quality defects, it is difficult to separate the reflection interference of the sun visor and the low contrast ...of the target area, This paper proposed a new threshold segmentation method based on area constraints. This paper constructed a bilateral filtering method using pixel frequency and time domain information to process the original image. This paper introduced an area constraint condition based on the histogram threshold segmentation method, and limit the threshold value range based on prior information. Finally this paper realized defective targets using image moments. The experimental results show that the method successfully realizes the real-time, fast and accurate detection of electronic street sign display quality defects, and provides an effective solution for the detection of electronic street sign defects.
•An 2D axisymmetric model of water vapor separation in the membrane was developed.•The permeation and the diffusion were considered in the transport model.•The water vapor concentration in the ...membrane layer exhibits layered distribution.•The amount of water vapor separation is less dependent on the feed humidity.•There is a critical transmembrane pressure for the water vapor transport.
A two-dimensional axisymmetric mathematical model was established to describe the pressure-driven water vapor separation in the hollow fiber composite membrane for air dehumidification. The developed transport model considered the permeation in the dense layer and the diffusion in the porous membrane substrate, in which the mass and momentum balance equations were coupled. The predicted results by the simulation model was consistent well with the experimental data. The velocity, pressure and concentration profiles and the mass transfer process in a single hollow fiber membrane were then solved and analyzed in detail, including the effects of feed velocity, feed humidity and transmembrane pressure on the dehumidification performance. The results show that the amount of water vapor separation (outlet humidity) is more sensitive to the medium feed velocity with the separation amount about twice than that of high and low velocities. The separated amount of water vapor by the membrane is less dependent on the feed inlet humidity. And the air dehumidification performance of the membrane could be realized effectively until the transmembrane pressure over a critical value, which is 1.0 bar in this model. The findings deliver an insight into the mass transport in the membrane-based dehumidification process, with the aims to provide a useful reference to the design, process optimization and module development using hollow fiber membrane.
► Experiments are performed at three microgap heat sinks which meet vapor confinement. ► Lower the microgap depth, better the performance is achieved. ► Higher local heat transfer coefficient is ...achieved at lower mass flux. ► Effect of heat flux on pressure drop increases as microgap dimension decreases. ► Smaller microgap maintains uniform wall temperature and lower temp fluctuation.
Two-phase microgap channel cooling concept has been recently proposed for cooling the heat sources directly in application of electronic devices thermal management. This concept is relatively new and more research should be carried out systematically to investigate the size effects of microgap channel on heat transfer and pressure drop mechanisms. In this study, local flow boiling phenomenon in different microgap sizes has been investigated experimentally. Experiments are performed in silicon based microgap heat sink having microgap of depth 190μm, 285μm and 381μm, using deionized water with inlet temperature of 86°C. The effects of mass flux and heat flux on heat transfer coefficient and pressure drop characteristics are examined by using three different mass fluxes 420kg/m2s, 690kg/m2s and 970kg/m2s and effective heat flux varying from 0 to 110W/cm2. An array of integrated micro-temperature sensors are used in this study to obtain the local temperatures and subsequently local heat transfer coefficients are determined. Apart from these experimental investigations, simultaneous high speed visualizations are conducted to observe and explore the mechanism of flow boiling in microgap channel. The results of this study show that flow boiling heat transfer coefficient is dependent on gap size, and the lower the gap size, higher the heat transfer coefficient. Moreover, it has been observed that confined slug and annular boiling are the dominant heat transfer mechanisms in microgap channels after the onset of nucleate boiling. Hence, local heat transfer coefficient increases significantly because of thin film evaporation during confined boiling at high heat flux. This study also evaluates the effectiveness of microgap cooling technology, to eliminate temperature gradient and hotspots.
The development of electric vehicles plays an important role in the field of energy conservation and emission reduction. It is necessary to improve the thermal performance of battery modules in ...electric vehicles and reduce the power consumption of the battery thermal management system (BTMS). In this study, the heat transfer and flow resistance performance of liquid cold plates with serpentine channels were numerically investigated and optimized. Flow rate (m˙), inlet temperature (Tin), and average heat generation (Q) were selected as key operating parameters, while average temperature (Tave), maximum temperature difference (ΔTmax), and pressure drop (ΔP) were chosen as objective functions. The Response Surface Methodology (RSM) with a face-centered central composite design (CCD) was used to construct regression models. Combined with the multi-objective non-dominated sorting genetic algorithm (NSGA-II), the Pareto-optimal solution was obtained to optimize the operation parameters. The results show that the maximum temperature differences of the cold plate can be controlled within 0.29~3.90 °C, 1.11~15.66 °C, 2.17~31.39 °C, and 3.43~50.92 °C for the discharging rates at 1.0 C, 2.0 C, 3.0 C, and 4.0 C, respectively. The average temperature and maximum temperature difference can be simultaneously optimized by maintaining the pressure drop below 1000 Pa. It is expected that the proposed methods and results can provide theoretical guidance for developing an operational strategy for the BTMS.
The pressure driven membrane-based air dehumidification technology is a promising energy-efficient technology for the air conditioning systems. To promote the engineering application of membrane ...dehumidification technology, factor significance analysis and multi-objective optimization of dehumidification membrane module were numerically investigated. Response surface method (RSM) was adopted to design the desired simulation cases and analyze the significance of five key factors, i.e., feed velocity, water vapor permeability coefficient, filling rate, fiber length, fiber diameter, on the membrane dehumidification characteristics. The second-order regression models of the dimensionless dehumidification amount per unit area (ma*) and the dehumidification rate (γ) were established based on the analysis of variance (ANOVA). It was found that the water vapor permeability coefficient has the most significant effect on γ and ma*. However, the dehumidification coefficient of performance (COP) and the frictional coefficient (f*Re) are hardly affected by the five independent factors. An average COP of 2.523 implies a good dehumidification efficiency of membrane module. As a multi-objective optimization method, the genetic algorithm was used for the membrane module optimization. The optimal solution represented by Pareto frontier is finally obtained in terms of γ and ma*. The optimized factor-level combination can be selected from the Pareto solution set according to the actual requirements of energy consumption and dehumidification efficiency.
•Response surface methodology was used to analyze the factor significance on module performance.•Multi-objective optimization of air dehumidification membrane module was conducted by the genetic algorithm.•The dehumidification coefficient of performance (COP) is almost unaffected by the module structural parameters.•High utilization efficiency of membrane area is obtained at low fiber diameters and medium filling rates.•Appropriate operating conditions can be selected from the Pareto solutions of γ and ma*.
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A hybrid air-conditioning system has been proposed by integrating an indirect evaporative pre-cooling unit. In the proposed system, the room exhaust air is employed in the indirect evaporative cooler ...(IEC) to pre-condition the ambient intake air. The mathematical formulation has been judiciously established for the pre-cooling IEC. The validation of the numerical model has been conducted by comparing the simulated results with the experimental data in terms of the outlet temperature and the heat flux along the heat exchanger surface. The pre-cooling performance of the IEC is theoretically investigated for the climate in representative cities selected from five different climate zones. The psychrometric illustration of the air conditioning variation has indicated that the ambient air can be pre-cooled and pre-dehumidified through the IEC. The possibility of water vapor condensation depends on the humidity ratio of the ambient intake air. The simulation result demonstrates the capability of the pre-cooling IEC to fulfill part of the cooling load of the ambient intake air resulting in a marked energy saving potential.
An accurate prediction for deep-buried ground heat exchangers (DBGHEs) is the premise for efficient utilization of geothermal energy. Due to the complexity of the geological composition spanning ...thousands of meters, the configuration of boundary conditions plays a critical role in evaluating DBGHE thermal performance. This paper proposed a three-dimensional model of full-scale DBGHE involving both conductive and convective heat transfer in aquifuge and aquifer layers. The constant inlet temperature and constant heating power boundaries in the DBGHE domain, and the surface–bottom temperature and heat flux boundaries in the rock-soil domain were examined. It was found that the differences in the performance prediction caused by different DBGHE boundary conditions were closely related to the system’s operating time. The relative differences in heat extraction amount and average borehole temperature of 2000 m DBGHE caused by the two inlet boundaries on the 30th day were, respectively, 19.5% and 18.3%, while these differences on the 120th day were decreased to 8.4% and 9.9%, respectively. It was found that the constant inlet temperature boundary was more appropriate than the constant heating power condition for estimating aquifer effects on the performance of DBGHE. For the rock-soil domain, the results showed that the heat extraction amount of DBGHE under the heat flux boundary was 12.6%–13.6% higher than that under the surface–bottom temperature boundary. Particularly, when considering the velocity change of groundwater in the aquifer, the relative difference in heat extraction amount increments caused by the two types of rock-soil boundaries can reach 26.6% on the 120th day. It was also found that the thermal influence radius at the end of a heating season was hardly affected by either the DBGHE inlet or rock-soil domain boundary conditions.
Gas membrane separation technology is widely applied in different industry processes because of its advantages relating to separation performance and economic efficiency. It is usually difficult and ...time consuming to determine the suitable membrane materials for specific industrial separation processes through traditional experimental research methods. Molecular simulation is widely used to investigate the microscopic morphology and macroscopic properties of materials, and it guides the improvement of membrane materials. This paper comprehensively reviews the molecular-level exploration of the dominant mechanism and influencing factors of gas membrane-based separation. The thermodynamics and kinetics of polymer membrane synthesis, the molecular interactions among the penetrated gases, the relationships between the membrane properties and the transport characteristics of different gases in the composite membrane are summarized and discussed. The limitations and perspectives of the molecular simulation method in the study of the gas membrane separation process are also presented to rationalize its potential and innovative applications. This review provides a more comprehensive reference for promoting the materials' design and engineering application of the gas separation membrane.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study aims to improve an H-Darrieus vertical-axis wind turbine (VAWT) by imposing a novel double-deflector design. A computational fluid dynamics (CFD) model was implemented to examine the ...aerodynamic characteristics of the VAWT with double deflectors. Geometrics factors related to the locations of the two deflectors were considered, and the orthogonal array based on the Taguchi method was constructed for CFD simulation. The CFD results were further provided as the training data for the artificial neural network (ANN) to forecast the optimal configuration. The results indicate that the performance of a VAWT with a double-deflector design could exceed that of a bare VAWT or that of one using a single deflector. The mean power coefficient for a bare VAWT is 0.37, although it could be much higher with a proper setup using double deflectors. The prediction of ANN analysis is consistent with the result of CFD simulation, in which the difference between the ANN prediction and CFD simulation is generally less than 4.48%. The result confirms the accuracy of the prediction of the optimal VAWT performance with a double-deflector design.
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