Thermo-flow characteristics and air flow field leading of the air-cooled condenser cell in a power plant

Special A-frame geometry of the air-cooled condenser cell and the complicated flow field at the exit of the axial flow fan bring on the air mal-distribution on the surface of the finned tube bundles and the deteriorated thermo-flow performances of a condenser cell. It is of benefit to the design and operation optimization of the direct dry cooling system in a power plant to investigate the thermo-flow characteristics of the condenser cell and propose the flow leading measures of cooling air. On the basis of the representative configuration of the air-cooled condenser cell in a 600 MW direct dry cooling power plant, the computa- tional models of the air side fluid and heat flows are built, in which the actual fan blade geometric details are considered. Various flow field leading ways of cooling air are presented and the thermo-flow characteristics in the A-frame condenser cell and through the finned tube bundles are compared. Results show that the flow field leading measures can result in the increased volumetric flow rate and heat rejection, thus bringing on the improved performance of the condenser cell. The improvement of thermo-flow oerformances depends upon the geometric details of the flow guiding device.

Air interaction around outdoor air-cooled condensers

In order to increase cooling or heating efficiency,a porous computational fluid dynamics（CFD）model is employed to predict the thermo-fluid status and optimize the placement of outdoor units.A full scale model is established to validate the accuracy of CFD simulation in terms of velocity and temperature distributions.The comparison between the measurement and the simulation shows a good agreement.By evaluating the condensers＇ sucked air temperature with CFD for three units installed in a row,it is found that the minimum separation distance among neighboring units is 0.2 m;a vertical wall should be apart from the unit line by at least 0.8 m;and large different operating pressures among units do not impact the flow rate and the heat transfer of the other units meaningfully.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

The Experimental Investigation of Recirculation of Air-Cooled System for a Large Power Plant

The paper introduces thermal buoyancy effects to experimental investigation of wind tunnel simulation on direct air-cooled condenser for a large power plant. In order to get thermal flow field of air-cooled tower, PIV experiments are carried out and recirculation ratio of each condition is calculated. Results show that the thermal flow field of the cooling tower has great influence on the recirculation under the cooling tower. Ameliorating the thermal flow field of the cooling tower can reduce the recirculation under the cooling tower and improve the efficiency of air-cooled condenser also.

GENOTOXIC EFFECT OF CIGARETTE SMOKE CONDENSATE (CSC) ON HUMAN DIPLOID CELL 2BS STRAIN

A series of bioassays such as sister chromatid exchange frequencies ( SCE.), chromosomal aberration ( CA ), micronuclel rate (MN) and cell-cycle delay have been used to detecting the genotoxic effect of cigarette smoke condensate (CSC) on human diploid cell 2BS strain. The results suggested that a higher SCE, ( 17. 0/ cell) was observed In 2BS cells treated with CSC at 100 μg/ml, as compared with 6. 9/cell of the background (P<0. 001). CA rate was significantly increased from 4% to 36% In cells treated with 10 μg/ml CSC (P< 0.001). MN rate varied from 9 -26‰ In cells treated with CSC compared to that of control (6‰). Meanwhile, the cell-cycle of cells was markedly delayed by CSC. The survival rate of 2BS cells declined to 59. 6% for treatment with CSC at 200 μg/ ml. There was a dose-effect response In SCE., CA, MN rate. We proposed that active oxygen might responsible for genotoxiclty of CSC on cells.

Influence of thermal flow field of cooling tower on recirculation ratio of a direct air-cooled system for a power plant

In order to get thermal flow field of direct air-cooled system,the hot water was supplied to the model of direct air-cooled condenser(ACC). The particle image velocimetery (PIV) experiments were carried out to get thermal flow field of a ACC under different conditions in low velocity wind tunnel,at the same time,the recirculation ratio at cooling tower was measured,so the relationship between flow field characteristics and recirculation ratio of cooling tower can be discussed. From the results we can see that the flow field configuration around cooling tower has great effects on average recirculation ratio under cooling tower. The eddy formed around cooling tower is a key reason that recirculation produces. The eddy intensity relates to velocity magnitude and direction angle,and the configuration of eddy lies on the geometry size of cooling tower. So changing the flow field configuration around cooling tower reasonably can decrease recirculation ratio under cooling tower,and heat dispel effect of ACC can also be improved.

Measures against the adverse impact of natural wind on air-cooled condensers in power plant

The natural wind plays disadvantageous roles in the operation of air-cooled steam condensers in power plant.It is of use to take various measures against the adverse effect of wind for the performance improvement of air-cooled condensers.Based on representative 2×600 MW direct air-cooled power plant,three ways that can arrange and optimize the flow field of cooling air thus enhance the heat transfer of air-cooled condensers were proposed.The physical and mathematical models of air-cooled condensers with various flow leading measures were presented and the flow and temperature fields of cooling air were obtained by CFD simulation.The back pressures of turbine were calculated for different measures on the basis of the heat transfer model of air-cooled condensers.The results show that the performance of air-cooled condensers is improved thus the back pressure of turbine is lowered to some extent by taking measures against the adverse impact of natural wind.

Influences of Lateral Double-Layered Deflectors on Cooling Performance of Air-Cooled Condenser

The cooling performance of air-cooled condenser(ACC)is susceptible to adverse impacts of ambient winds.In this work,three kinds of lateral double-layered deflectors installed under the ACC platform are proposed to weaken the unfavorable effects of cross winds.Through CFD simulation methods,the main parameters of thermo-flow performances of a 2×660 MW direct dry cooling system are obtained,by which it can be concluded that the deflectors can effectively reduce the inlet air temperatures while enhance the mass flow rates of upwind fans due to the guiding effect,especially at high wind speeds,while the improvement of cooling capacity of ACCs in the 0°wind direction is weak.The inclined-vertical deflectors are superior to others in performance improvement of ACCs for all cases,which can reduce the turbine back pressure by 12.15%when the wind speed is 12 m/s,so they can be applied to the performance enhancement of ACCs under windy conditions in practical engineering.

Performance Assessment of Air-Cooled Steam Condenser with Guide Vane Cascade

Ambient wind has an unfavourable impact on air-cooled steam condenser(ACSC) performance. A new measure to improve ACSC performance is proposed by setting a diffusion type guide vane cascade beneath the ACSC platform. The numerical models are developed to illustrate the effects of diffusion type guide vane cascade on ACSC performance. The simulation results show that this vane cascade can cause the increases in coolant flows across almost all fans due to its diffusion function and lower flow resistance. Meanwhile, the guide vane cascade also decreases the fan inlet temperatures because of the uniform flow field around the condenser cells. Comparing with the case without guide device, the overall heat transfer efficiency is increased by 11.2% for guide vane cascade case under the condition of 9 m/s. The heat transfer efficiency firstly enhances and then decreases with decreasing stagger angle of guide vane under a certain wind speed. The optimum stagger angle corresponding to the maximum heat transfer efficiency is about 65.5°. The heat transfer efficiency always enhances as increasing vane cascade height, and a vane cascade with 20 m to 30 m height may be suitable to the ACSC as considering the cost.

Tannin Nanoparticles(NP99)Enhances the Anticancer Effect of Tamoxifen on ER+Breast Cancer Cells

Recently,natural substances in the form of nanoparticles are increasingly being used in different field,particularly in medicines to enhance their beneficial effects in treatment and prevention.Cancer cells of the breast(MCF-7)have been chosen to be examined and treated in vitro with conventional drug Tamoxifen(Tam)and tannin nanoparticles extract(NP99)individually or in combination.MTT reagent has been applied to assess the cell viability and propagation percentage,DNA fragmentation and mRNA relative expression of apoptotic genes to study the cell death pathway.The results showed that Tam and tannin NP99 triggered cytotoxic activity towards the MCF7 cell.They reduce the viability and induced high potent repressive activity on cell proliferation percentage and induced apoptosis as indicated by rising the percentage in DNA fragmentation.Effect of NP99 extract exhibited its effect in a dose and time-varying.The combined treatment of Tam and NP99 were much more efficient than individual drugs.It could be concluded that NP99 is considered a promising natural anticancer agent as a new tool in therapeutic strategies.

Exciton Condensates and Superconductors-Technical Differences and Physical Similarities

We review several recent theoretical and experimental results in the study of exciton condensates. This includes the present experimental advances in the study of exciton condensates both using layers and coupled bilayers. We will shortly illustrate the different phases of exciton condensates. We focus especially on the Bardeen-Cooper-Schrieffer-like phase and illustrate the similarities to superconductors. Afterwards, we want to illustrate several recent advances and proposals for measuring the different phases of superconductors. In the remainder of this short review, we will provide an outlook for the possibilities and complications for future technical applications of exciton condensates.

Application of machine learning to develop a real-time air-cooled condenser monitoring platform using thermofluid simulation data

A data-driven surrogate model is proposed for a 64-cell air-cooled condenser system at a power plant.The surro-gate model was developed using thermofluid simulation data from an existing detailed 1-D thermofluid network simulation model.The thermofluid network model requires a minimum of 20 min to solve for a single set of in-puts.With operating conditions fluctuating constantly,performance predictions are required in shorter intervals,leading to the development of a surrogate model.Simulation data covered three operating scopes across a range of ambient air temperatures,inlet steam mass flow rates,number of operating cells,and wind speeds.The surrogate model uses multi-layer perceptron deep neural networks in the form of a binary classifier network to avoid ex-trapolation from the simulation dataset,and a regression network to provide performance predictions,including the steady-state backpressure,heat rejections,air mass flowrates,and fan motor powers on a system level.The integrated surrogate model had an average relative error of 0.3%on the test set,while the binary classifier had a 99.85%classification accuracy,indicating sufficient generalisation.The surrogate model was validated using site-data covering 10 days of operation for the case-study ACC system,providing backpressure predictions for all 1967 input samples within a few seconds of compute time.Approximately 93.5%of backpressure predictions were within±6%of the recorded backpressures,indicating sufficient accuracy of the surrogate model with a significant decrease in compute time.

Boosting Cu(In,Ga)Se_(2)Thin Film Growth in Low-Temperature Rapid-Deposition Processes:An Improved Design for the Single-Heating Knudsen Effusion Cell

The Knudsen effusion cell is often used to grow high-quality Cu(In,Ga)Se_(2)(CIGS)thin film in coevaporation processes.However,the traditional single-heating Knudsen effusion cell cannot deliver complete metal selenides during the whole deposition process,particularly for a low-temperature deposition process,which is probably due to the condensation and droplet ejection at the nozzle of the crucible.In this study,thermodynamics analysis is conducted to decipher the reason for this phenomenon.Furthermore,a new single-heating Knudsen effusion is proposed to solve this difficult problem,which leads to an improvement in the quality of CIGS film and a relative increase in conversion efficiency of 29%at a growth rate of about 230 nmmin1,compared with the traditional efficiency in a lowtemperature rapid-deposition process.

An Influencing Factor - Water-Filter Ratio on Heat Resistance of Condensate Polishing Filter Material in Water

In air-cooled condenser, high temperature condensing water m summer which approaching and exceed 60＊ C, which may result in filter materials degradation and release impurities. This paper discusses an influencing factor, water-filter ratio （soaking solution and filter quality ratio）, on leachable dissolution rate and filter material degradation rate m high temperature water. The UV absorption at 254nm （A254） and the exchange capacity ware measured after heat test as composite indicators. In addition, the Wends of A254 variation with heating time were measured in different water-filter ratio. The stability is probably due to the effect of water-filter ratio. This has been further borne out that, water-filter ratio increases, leachable concentration decreases exponentially and tends to a fLxed value.

A Creation Model from the Gell-Mann Standard Model to the Creation of Bio Cells: Based on the Assumption of Homogeneous 5D Space-Time Universe

In this paper, we briefly go over the homogeneous 5D model field theory: from the 5D space-time inception, to its quantum field solutions given in terms of Higgs vacuum, filled with magnetic monopole bose fields of all energies. Then through the space dimension reduction projections, the Gell-Mann standard model was obtained as well as a quantum to Classical connection was made via introducing Bose distribution to the monopoles to obtain the Perelman entropy and Ricci Flow mappings. This provided us a picture to the creation of Astronomical objects, from galaxies to stars and planets. This method of splitting the monopole energy into ranges is extended to show that below the basic rest mass range of the electron and Quark, it still can be applied to explaining for the creation of the chemical elements periodic table. But perhaps the most interesting is in the lowest hundreds of Hz energy range, obtained from yet another 3 fold space symmetry breaking, into 2D × 1D, producing bio nitrogenous bases composed of 3 Carbon 12 in hexagon structures, due to preservation of the 1D monopole standing waves of this low frequencies. From that by imposing gauge changes the monopole states into DNA spectra. Since such spectra states retain the DLRO, it induces formation of charge carriers periodicity in a spherical bio cell.. It was then argued that due to cell’s surface proteins, the structure must contain partial filled VB, with “p” state hole density, and empty CB, separated from VB by a positive band gap. Such band structures resemble known HTC Cuprate ceramics. Since the HTC goes through a Superconductivity transition via the simultaneous bose exciton condensation, providing a Coulomb pressure, which reduces the band gap substantially, and induces the ODLRO transition of the hole density. The same obviously applies to the bio cells. Because of the near continuous exciton levels generated, a matching to the DNA spectra then can always occur by selective choices of proteins on the cell surface. Judging from a numerical study, we did years ago on YBCO, with doping. We found with a large enough VB hole density, the exciton induced superconducting gap can easily lead to Tc in the room temperature range. In fact by EMF excitation can increase the exciton pressure and trigger the ODLRO transition Tc upward. In fact, numerical results then suggest there do exist coherent EMF spectra from three key elements: Water, Carbon and Hydrogen, together with Oxygen, as studied over the years by numerous people, starting from Schrödinger to most recently Geesink.

基于静态凝聚法的蜂窝芯轴向变胞元非均匀排布优化

为了有效改善蜂窝结构的强度与刚度,提出利用静态凝聚法实现变胞元的几何参数和非均匀排布同时优化的方法。根据卡氏定理,推导胞元的等效弹性模量和泊松比;沿轴向均匀划分蜂窝芯为若干列子结构,利用有限元法得到子结构的刚度矩阵;采用静态凝聚法建立超单元刚度矩阵,依据超单元节点编号装配获得蜂窝芯的整体刚度矩阵;计算蜂窝芯在剪切载荷作用下的结构变形,并与ANSYS结果比较分析。以子结构的个数以及胞元的夹角、夹板宽与斜壁长之比为设计变量,胞元的等效弹性模量最大和蜂窝芯的变形最小为设计目标,利用改进的粒子群算法进行优化并研究蜂窝芯优化前后的静、动态特性变化规律。结果表明:变胞元非均匀排布优化后,最大的位移、应力、应变均明显减小,且激励频率等于第二阶固有频率时振动最为强烈。研究结论可为蜂窝结构变胞元排布的优化设计提供指导。

人结直肠癌细胞周期各时相中双微体存在形式及复制分离时期的分析

目的探究双微体(Double minute chromosomes,DMs)在肿瘤细胞周期各时相内的主要存在形式,明确DMs的复制、分离时相。方法通过无血清饥饿法阻滞人结直肠癌细胞COLO 320DM周期进展后,取花萼海绵体诱癌素A(Calyculin-A)诱导间期细胞以染色质超前凝集制备核型样本。用秋水仙素处理COLO 320DM细胞以获取有丝分裂(M)期细胞进行核型分析。在普通光学显微镜下观察并拍摄DNA合成前期(G1期)、DNA合成后期(G2期)、M中期、M后期和M末期核型,并统计DMs数量。结果DMs在G1期、M后期和M末期时相细胞中主要以单体形式存在;在G2期和M中期时相细胞中主要以双体形式存在。结论单体型DMs在S期发生复制后由单体转变为双体,双体型DMs在M后期完成分离并由双体转变为单体。

Facile access to C-N bonds via unexpected side reactions of Knoevenagel condensation and their application in high-efficiency organic solar cells

The construction of C-N bonds is of great importance in the fields of biology,medicine,chemistry and materials science.Here,the replacement of organic base from pyridine to piperidine in the Knoevenagel condensation process unexpectedly yields a series of novel organic molecules containing C-N bonds.Interestingly,the synthesis method does not require any external transition-metals catalysis,and photo-/electro-catalysis.Additionally,when the new compound 1b is added as a third component to a well-known binary system of PM6:Y6,the efficiency of the organic solar cell is significantly improved,resulting in an outstanding efficiency of 18.0%,which is one of the highest values reported to date for PM6:Y6-based ternary organic solar cells.

Application of self-adaptive temperature recognition in cold-start of an air-cooled proton exchange membrane fuel cell stack

The Self-adaptive control of the temperature can achieve the start of fuel cell at different operating temperatures, which is very important for the successful cold-start of the air-cooled PEMFC. The temperature distribution characteristics during the cold-start process were analyzed based on adaptive temperature recognition control in this paper. Preheating model and cold-start model were established and the optimal balance between the hot air flow rate and the temperature required to promote a uniform temperature distribution in the stack was explored in the preheating stage. Finally, the non-equilibrium mass transfer, as well as the temperature rise in the catalyst layer and gas diffusion layer with different current densities, were analyzed in the start-up stage. The results indicate that the air-cooled PEMFC stack can be successfully started up at -40 ◦C within 10 min by means of external gas heating. The current density and air velocity have significant impacts on the temperature of aircooled PEMFC stack. Dynamic analysis of air-cooled PEMFCs and real-time monitoring are suitable for machine learning and self-adaptive control to set the operation parameters to achieve successful cold start. Optimize the matching of load current and cathode inlet speed to achieve thermal management in low temperature environment.

干细胞聚合体构建方法与牙再生应用现状

牙缺损和牙缺失是口腔健康领域常见的临床问题,传统的治疗方法如义齿和种植体仍存在诸多局限性。近年来,随着干细胞研究和组织工程技术的发展,再生医学为牙再生与修复提供了新的希望。其中,间充质凝聚是器官形态发育中的关键初期事件,基于其原理,体外工程化构建的干细胞聚合体已被成功应用于牙髓、牙本质、牙周等多种组织的再生修复。本文将从干细胞聚合体的理论基础、构建方法以及其在牙再生领域的应用现状进行探讨,旨在为进一步理解干细胞聚合体的生物学基础及其在牙再生领域的应用提供理论支持和实验指导。