Abstract ：

The distributed parameter models of counter flow and cross flow plate fin heat exchanger (PFHE) are constructed to investigate their thermodynamic characteristics. In practical application, the cold end of PFHE may be directly connected to the cold equipment. Therefore, the effect of longitudinal heat conduction (LHC) under different thermal boundary conditions set on two ends of the separating plates (SPs) is investigated based on the model of counter flow PFHE. It is found that LHC effect transmits the effect of boundary condition on two ends of the SPs into the inner domain of PFHE. The LHC effect on the heat transfer performance of PFHE is positive when setting appropriate boundary condition on two ends of the SPs. When considering LHC, compared with the adiabatic boundary conditions on two ends of the SPs, the effectiveness of constant wall temperature boundary conditions increases by 31.7 ∼ 35.8 %, and the effectiveness of constant heat flux boundary conditions increases by 22.8 %. The model of cross flow PFHE is used to investigate the effect of configuration and operation parameters on the heat transfer amount and the pump power. The cross flow PFHE is optimized to arrive at the maximization of heat transfer amount per unit pump power (HTPUP). In the three-stream cross flow PFHE studied, the heat transfer amount almost doesn't change when the xz projected area is maintained and one projected length (z side length) is changing. The pump power is the lowest and the HTPUP is the largest when z side length of PFHE (z side is the flow direction of the fluid with large mass flowrate) is 0.15 ∼ 0.2 m. © 2022 Elsevier Ltd

Keyword ：

Effectiveness; Heat transfer amount; Longitudinal heat conduction; Plate fin heat exchanger; Pump power

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Abstract ：

通过计算赤泥中所含金属氧化物与盐酸反应的吉布斯自由能,论证了两步盐酸酸浸提钪工艺的可行性。为使钪离子有高浸出率,同时与其他金属有较高的分离率,在二次酸浸中采用2.5 mol/L左右的低浓度盐酸开展了正交实验。使用Design-Expert 8.0软件对试验数据进行了分析,讨论了温度、时间、液固比、盐酸浓度对赤泥中各主要金属离子浸出的影响,建立了相应的多项式关联模型。确定的二次酸浸的最佳操作条件组合为:浸出温度为70℃,浸出时间为70 min,液固比为6,盐酸浓度为2.5 mol/L,在此条件下钪浸出率超过80%,铁、锆、钛等主要杂质离子浸出率维持在较低水平。

Keyword ：

赤泥 吉布斯自由能 盐酸浸出 正交实验

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Abstract ：

In order to improve the flow and heat transfer performance of 2 K sub-atmospheric pressure plate-fin heat exchanger, a new type of corrugated-serrated fin is proposed by combining corrugated and serrated fin. The Lw number is defined as a new structural parameter to describe the new type of fin. The numerical model of flow and heat transfer in the fin channels takes into account the influence of low temperature conditions with variable physical properties and has been fully verified by experimental data. Numerical investigation is performed to study the thermohydraulic characteristics of serrated fin, corrugated fin and corrugated-serrated fin. Meanwhile, three performance evaluation criteria Colburn factor j, friction factor f and TE-factor are used to qualitative compare their flow, heat transfer and overall thermo-hydraulic performance. The results reveal that the heat transfer performance of new corrugated-serrated fins is the best. Colburn factor j of the new fins increases by 19.97%-38.22% compared with corrugated fin, and increases by 25.09%-33.83% compared with serrated fin. The flow performance of the corrugated-serrated fin is slightly worse, but the overall thermo-hydraulic performance is better, especially at low Reynold number. Besides, the effects of various structural parameters on the thermohydraulic characteristics of the corrugated-serrated is obtained. The conclusions provide theoretical guidance on the design of 2 K sub-atmospheric plate-fin heat exchanger.

Keyword ：

Corrugated-serrated fin Numerical investigation Plate-fin heat exchanger Superfluid helium cryogenic system

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Abstract ：

The comprehensive performance of serrated fins in plate-fin heat exchanger (PFHE) under cryogenic condition is analyzed based on fluid-structure interaction (FSI). On the foundation of response surface methodology (RSM) and sobol sensitivity analysis, the effects and interaction effects of fin height, fin space, fin thickness and fin interrupted length on flow resistance, heat transfer and stress are analyzed quantitatively. The contour results show that, compared with the pressure stress, the thermal stress is very low and the high stress mainly locates in the regions of keen-edged geometric structure, and the highest stress is in the regions connecting two rows of fins. The sensitivity analysis results show that the effect of fin interrupted length on j factor is the most significant and the interaction effect of fin space and fin interrupted length is the most obvious. The effect of fin thickness on f factor or the maximum stress is the most significant and the interaction effect of fin thickness and fin space is the most obvious. By implementing Multi-Objective Genetic Algorithm (MOGA), the serrated fin structure is optimized comprehensively and a set of Pareto-optimal points are obtained. Compared with the original structure, the JF factor of optimized structure 1, 2 and 3 increases by 8.8%, 4.4% and 9.6%, and the maximum stress decreases by 29.6%, 42.3% and 21.1%, respectively. The MOGA based on RSM offers theoretical guidance for design optimization of PFHE. © 2020 Elsevier Ltd

Keyword ：

Fins (heat exchange) Fluid structure interaction Genetic algorithms Heat resistance Heat transfer Indium plating Pareto principle Plates (structural components) Sensitivity analysis

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Abstract ：

This study investigated the corrosion resistance of graphene/waterborne epoxy composite coatings in CO2-satarated NaCl solution. The coatings were prepared by dispersing graphene in waterborne epoxy with the addition of carboxymethylcellulose sodium. The structure and composition of the coatings were characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared and Raman spectroscopies. The corrosion resistance of the composite coatings was investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Composite coatings with more uniform surfaces and far fewer defects than blank waterborne epoxy coatings were obtained on 1020 steel. The 0.5 wt% graphene/waterborne epoxy composite coating exhibited a much lower corrosion rate and provided better water resistance properties and long-term protection than those of the blank epoxy coating in CO2-satarated NaCl solution.

Keyword ：

carbon steel CO2 corrosion coating graphene

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Abstract ：

The effects of geometrical parameters of serrated fin in plate-fin heat exchanger (PFHE) on entransy-dissipationbased thermal resistance (EDTR) caused by heat transfer (R-ht) and fluid friction (R-ff ) are investigated by design of experiment(DOE) and response surface methodology (RSM) in this paper. The results show that the fin height, fin interrupted length and fin space are positively correlated with R-ht, while the fin thickness and PFHE length are negatively correlated with R-ht. R-ff is far larger than R-ht, for about an order of magnitude, and R-ff increases almost linearly with the increase of Re when geometric parameters are fixed. R-ff increases with fin thickness and PFHE length, and decreases with fin height, fin interrupted length and fin space. Furthermore, Multi-objective Genetic Algorithm (MOGA) is carried out. Compared with the original design, R-ht of optimal structure 1 and 2 obtained based on two objectives of minimizing R-ff and minimizing R-ht reduces by 27.9% and 41.2%, respectively, and R-ff reduces by 65.3% and 55.8% respectively. Compared with the optimal results based on traditional objective functions (maximize j and minimize f), R-ht and R-ff obtained based on EDTR objective functions reduce by an average of 37.6% and 30.3% respectively, and the JF factor of EDTR optimal results increases by an average of 10.1%.The results show that the optimization results based on EDTR objective functions are better than that based on traditional objective functions for serrated fin in PFHE.

Keyword ：

Entransy-dissipation-based thermal resistance Multi-Objective Genetic Algorithm Plate-fin heat exchanger Response surface Serrated fin

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Abstract ：

Image inpainting is one of the most important problems in the field of image algorithm, and it is also an effective preprocessing method for many other image applications. In this paper, we suggest an image decontamination method which is mainly used to remove mesh stains and also provide a data set for this task. To our knowledge, this work is the first attempt to solve this kind of problem. Specifically, the proposed method is composed of two phases: we first remove the mesh stains with an Improved Conditional Generative Adversarial Network, and then utilize a Semantic Network to fine tune the details. Experiments demonstrated that this two-stage model can remove the mesh stains. Results show that our method significantly out-performs existing methods and achieves superior inpainting results on challenging cases. © 2013 IEEE.

Keyword ：

Image enhancement Knowledge representation Mesh generation Semantics Semantic Web

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Abstract ：

The condensation characteristic of R1234ze(E) inside an inclined circular tube (D = 4.57 mm) were numerically investigated. The mass flux covered from 300 to 800 kg.m(-2)S(-1) and the inclination angle varied from -90 degrees to 90 degrees. The inclination effects on film distribution, local film thickness, local heat transfer coefficient and velocity profile were detailed presented. Inclining the tube has a negligible effect on heat transfer coefficients at high mass fluxes and vapor qualities, but may cause an increase or decrease in heat performance when decreasing the mass flux and vapor quality. At the same inclination angle, slightly higher heat transfer coefficients were observed for the down-flow configuration. Increasing the inclination angle would thicken the film thickness of thin film region while reducing the film thickness of stratification region, which affected local heat transfer performance. Compared with heat transfer coefficients, the pressure gradients were more sensitive to the inclination angle. The local pressure gradients generally increased with the inclination angle for down-flow configuration. While the reverse was true for up-flow configuration. The simulated heat transfer coefficients and pressure gradients were compared with predictions of well-known correlations. The pressure drop models developed for horizontal tubes were not able to precisely predict the data of inclined tubes.

Keyword ：

Condensation Heat transfer Inclination Pressure drop R1234ze(E)

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Abstract ：

The effects and interaction effects of fin height, fin space, fin thickness and fin interrupted length on flow resistance, heat transfer and stress of plate fin heat exchanger (PFHE) on cryogenic condition are analyzed quantitatively, based on computational fluid dynamics (CFD), fluid structure interaction (FSI), response surface methodology (RSM) and sobol sensitivity analysis. The stress distribution in serrated fin structure shows that the large stress is mainly distributed in the regions of keen-edged geometric structure such as weld joint region and the region connecting two rows of fin. The sensitivity analysis results reveal that j factor is the most sensitive to fin interrupted length, and f factor and maximum stress are most sensitive to fin thickness. The sobol sensitivity analysis results show that, for j factor and maximum stress, it is sufficient to investigate the first-order sensitivity indices and high-order sensitivity is weak. For f factor, it is necessary to consider the second-order sensitivity, especially for fin space and fin thickness. Based on above analyses, by combining with Multi-Objective Genetic Algorithm (MOGA), the serrated fin structure is optimized from perspective of two objectives (maximizing JF factor and minimizing maximum stress) and three objectives (maximizing j factor, minimizing f factor and minimizing maximum stress). In general, the optimization results based on two objectives are more intuitive, and they offer a smaller solution space. An original point is optimized, the results reveal that, compared with original point, JF factor of optimized point 1 increases by 17.8% without changing maximum stress, while maximum stress of optimized point 2 decreases by 50.0% without changing JF factor.

Keyword ：

Cryogenic condition Multi-objective genetic algorithm Optimization Plate-fin heat exchanger Response surface Serrated fin Stress analysis

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Abstract ：

In this paper, the condensation characteristic of R1234ze(E) in horizontal circular, square and triangle channels were numerically investigated. The detailed liquid-vapor interfaces, local film thickness and stream traces were presented for better understanding the condensation process in circular and non-circular tubes. Under the same hydraulic diameter, the void fraction in square and triangle tubes was lower than that in circular tubes at the same vapor quality. The square tube exhibited higher heat transfer coefficients than that of the circular tube, while the triangle tube showed similar heat transfer performance with the circular tube. The tube shape had no significant effects on the pressure gradients. The gravity played a dominant role in local film distribution in the circular tube, but was almost negligible in the square tube. Both the surface tension and gravity played an important role in film distribution in the triangle tube. The number and structure of vortexes in the square and triangle tube were very different from that in the circular tube. The tube shape has a significant effect on the liquid phase velocity at different circumference positions. Under the same external perimeter, either the heat transfer coefficients or the pressure gradients of the square or triangle tube were larger than that of the circular tube. The numerical data of heat transfer coefficients and pressure gradients were also compared with the predicted values from the available well-known correlations. The results of this paper are important for the industrial applications of alternative refrigerants. © 2018 Elsevier Ltd

Keyword ：

Alternative refrigerant Condensation characteristics Condensation patterns Condensation process Heat transfer performance Liquid-vapor interface Square Triangle

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