Impact of Cattaneo-Christov Heat Flux in the Nanofluid Flow over an Inclined Permeable Surface with Irreversibility Analysis

This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of a heat source/sink and thermal stratification. To gauge the energy loss during the process, an irreversibility analysis is also performed. A numerical solution to the envisaged problem is obtained using the bvp4c package of MATLAB. Graphs are drawn to assess the consequences of the arising parameters against the associated profiles. The results show that an augmentation in the magnetic field and nanomaterial volume fraction results in an enhancement in the temperature profile. A strong magnetic field can significantly reduce the fluid velocity. The behavior of the Skin friction coefficient against the different estimates of emerging parameters is discussed. .

血清HMGB1、CCL20、HSP27水平与慢性牙周炎患者牙周病变程度的相关性分析

目的探讨血清高迁移率族蛋白1(HMGB1)、CC趋化因子配体20(CCL20)、热休克蛋白27(HSP27)水平与慢性牙周炎(CP)患者牙周病变程度的相关性。方法选取2021年9月至2023年8月在新乡医学院第一附属医院诊治的60例CP患者纳入观察组,根据1∶1原则,另选取同期牙周健康者60例纳入对照组。比较两组及不同牙周病变程度CP患者血清HMGB1、CCL20、HSP27水平,分析各指标水平与CP牙周病变程度的相关性及联合诊断价值,并分析不同血清水平患者发生CP的危险度。结果观察组血清HMGB1、CCL20、HSP27水平高于对照组(P<0.05);不同牙周病变程度CP患者血清HMGB1、CCL20、HSP27水平比较:轻度<中度<重度,且各指标水平与牙周病变程度均呈正相关(P<0.05);入院时HMGB1、CCL20、HSP27水平联合诊断CP的曲线下面积(AUC)为0.905,最佳诊断敏感度为91.67%,特异度为88.33%,约登指数0.800,且各指标高水平患者发生CP的危险度是低水平的1.105倍、1.034倍、1.105倍(P<0.05)。结论HMGB1、CCL20、HSP27在CP患者血清中呈异常高表达,各指标水平与牙周病变程度均呈正相关,且联合检测对CP具有较高诊断价值,可作为临床诊断CP、评估牙周病变程度的有效指标。

Significance of Nanoparticles Aggregation with Cattaneo-Christov Heat Flux on the Water and Ethylene Glycol Mixture Based MWCNTs-Nanofluid Flow over a Stretching Cylinder

This work aims to analyze the flow of electrically conducting MWCNTs-nanofluid over a stretching cylinder with the aggregation and non-aggregation effects of nanoparticles. The working fluid comprised a combination of water and ethylene glycol, with volumetric proportions of (50:50) considered. Convective boundary constraints and modified Fourier law are implemented in heat transmission assessment. The mathematical flow model is formulated in the form of PDEs and is transformed into ODEs via similarity transformation. Numerical outcomes will be obtained with the use of the bvp4c technique and will be displayed with the help of graphs and tables. The results show that the surface drag coefficient is enhanced in the case of aggregation of nanoparticles whereas heat transfer rate is enhanced in the non-aggregation effect of nanoparticles. Furthermore, the temperature distribution enhances the increasing values of particle volume fraction in the case of aggregation effects of nanoparticles whereas temperature distribution lowers in the case of non-aggregation effect of nanoparticles. .

血清HSP70、CCR3水平对细菌性肺炎患儿病情评估的价值

目的 探讨血清热休克蛋白70(HSP70)、CC趋化因子受体3(CCR3)表达水平对细菌性肺炎患儿病情评估的临床价值。方法 选取2022年6月至2023年6月湖北医药学院附属国药东风总医院就诊的细菌性肺炎患儿113例作为研究对象,按照病情严重程度分为轻症组71例和重症组42例。收集2组患儿的性别、年龄、体重指数,并测定肺功能[呼吸频率(RR)、潮气量(VT)、达峰容积比(VPTEF/VE)]等临床资料。采集清晨空腹外周静脉血5 mL,采用酶联免疫吸附试验法检测血清HSP70、CCR3水平,利用受试者工作特征(ROC)曲线分析血清HSP70、CCR3水平对细菌性肺炎患儿的病情评估的预测价值;采用Pearson分析血清HSP70、CCR3水平与病情严重程度的关系。结果 2组患儿在性别、年龄、体重指数等一般资料比较,差异无统计学意义(P>0.05);重症组血清HSP70、CCR3与RR明显高于轻症组,VT、VPTEF/VE显著低于轻症组,差异均有统计学意义(P<0.05)。血清HSP70联合CCR3评估细菌性肺炎患儿的AUC为0.916,明显高于单独检测(Z=2.480,3.322,P<0.05)。细菌性肺炎患儿病情严重程度与血清HSP70、CCR3表达水平呈正相关(r=0.826,0.778,P<0.05)。结论 细菌性肺炎患儿血清HSP70、CCR3表达水平明显升高,与病情严重程度密切相关,可作为细菌性肺炎患儿病情严重评估的临床指标。

Darcy-Forchheimer flow of variable conductivity Jeffrey liquid with Cattaneo-Christov heat flux theory

The role of the Cattaneo-Christov heat flux theory in the two-dimensional laminar flow of the Jeffrey liquid is discussed with a vertical sheet. The salient feature in the energy equation is accounted due to the implementation of the Cattaneo-Christov heat flux. A liquid with variable thermal conductivity is considered in the Darcy-Forchheimer porous space. The mathematical expressions of momentum and energy are coupled due to the presence of mixed convection. A highly nonlinear coupled system of equations is tackled with the homotopic algorithm. The convergence of the homotopy expressions is calculated graphically and numerically. The solutions of the velocity and temperature are expressed for various values of the Deborah number, the ratio of the relaxation time to the retardation time, the porosity parameter, the mixed convective parameter, the Darcy-Forchheimer parameter, and the conductivity parameter. The results show that the velocity and temperature are higher in Fourier＇s law of heat conduction cases in comparison with the Cattaneo-Christov heat flux model.

3D Casson nanofluid flow over slendering surface in a suspension of gyrotactic microorganisms with Cattaneo-Christov heat flux

A mathematical model is proposed to execute the features of the non-uniform heat source or sink in the chemically reacting magnetohydrodynamic （MHD） Casson fluid across a slendering sheet in the presence of microorganisms and Cattaneo-Christov heat flux. Multiple slips （diffusion, thermal, and momentum slips） are applied in the modeling of the heat and mass transport processes. The Runge-Kutta based shooting method is used to find the solutions. Numerical simulation is carried out for various values of the physical constraints when the Casson index parameter is positive, negative, or infinite with the aid of plots. The coefficients of the skin factors, the local Nusselt number, and the Sherwood number are estimated for different parameters, and discussed for engineering interest. It is found that the gyrotactic microorganisms are greatly encouraged when the dimensionless parameters increase, especially when the Casson fluid parameter is negative. It is worth mentioning that th~ velocity profiles when the Casson fluid parameter is positive are higher than those when the Casson fluid parameter is negative or infinite, whereas the temperature and concentration fields show exactly opposite phenomena.

Cattaneo-Christov heat flux model for third-grade fluid flow towards exponentially stretching sheet

The Cattaneo-Christov heat flux in the two-dimensional （2D） flow of a third- grade fluid towards an exponentially stretching sheet is investigated. The energy equation is considered through thermal relaxation. Similarity transformations are accounted to obtain the ordinary differential systems. The converted non-dimensional equations are solved for the series solutions. The convergence analysis of the computed solutions is reported. The graphical results of the velocity and temperature profiles are plotted and elaborated in detail. The results show that the thermal relaxation enhances the temper- ature gradient while reduces the temperature profile.

Molybdenum disulfide and magnesium oxide nanoparticle performance on micropolar Cattaneo-Christov heat flux model

This article intends to illustrate the Darcy flow and melting heat transmission in micropolar liquid.The major advantage of micropolar fluid is the liquid particle rotation through an independent kinematic vector named the microrotation vector.The novel aspects of the Cattaneo-Christov(C-C)heat flux and Joule heating are incorporated in the energy transport expression.Two different nanoparticles,namely,MoS2 and MgO,are suspended into the base-fluid.The governing partial differential equations(PDEs)of the prevailing problem are slackening into ordinary differential expressions(ODEs)via similarity transformations.The resulting mathematical phenomenon is illustrated by the implication of fourth-fifth order Runge-Kutta-Fehlberg(RKF)scheme.The fluid velocity and temperature distributions are deliberated by using graphical phenomena for multiple values of physical constraints.The results are displayed for both molybdenum disulphide and magnesium oxide nanoparticles.A comparative benchmark in the limiting approach is reported for the validation of the present technique.It is revealed that the incrementing material constraint results in a higher fluid velocity for both molybdenum disulphide and magnesium oxide nanoparticle situations.

Melting effect and Cattaneo-Christov heat flux in fourth-grade material flow through a Darcy-Forchheimer porous medium

The melting phenomenon in two-dimensional(2 D)flow of fourth-grade material over a stretching surface is explored.The flow is created via a stretching surface.A Darcy-Forchheimer(D-F)porous medium is considered in the flow field.The heat transport is examined with the existence of the Cattaneo-Christov(C-C)heat flux.The fourth-grade material is electrically conducting subject to an applied magnetic field.The governing partial differential equations(PDEs)are reduced into ordinary differential equations(ODEs)by appropriate transformations.The solutions are constructed analytically through the optimal homotopy analysis method(OHAM).The fluid velocity,temperature,and skin friction are examined under the effects of various involved parameters.The fluid velocity increases with higher material parameters and velocity ratio parameter while decreases with higher magnetic parameter,porosity parameter,and Forchheimer number.The fluid temperature is reduced with higher melting parameter while boosts against higher Prandtl number,magnetic parameter,and thermal relaxation parameter.Furthermore,the skin friction coefficient decreases against higher melting and velocity ratio parameters while increases against higher material parameters,thermal relaxation parameter,and Forchheimer number.

Mathematical modeling of mixed convective MHD Falkner-Skan squeezed Sutterby multiphase flow with non-Fourier heat flux theory and porosity

In a wide variety of mechanical and industrial applications,e.g.,space cooling,nuclear reactor cooling,medicinal utilizations(magnetic drug targeting),energy generation,and heat conduction in tissues,the heat transfer phenomenon is involved.Fourier’s law of heat conduction has been used as the foundation for predicting the heat transfer behavior in a variety of real-world contexts.This model’s production of a parabolic energy expression,which means that an initial disturbance would immediately affect the system under investigation,is one of its main drawbacks.Therefore,numerous researchers worked on such problem to resolve this issue.At last,this problem was resolved by Cattaneo by adding relaxation time for heat flux in Fourier’s law,which was defined as the time required to establish steady heat conduction once a temperature gradient is imposed.Christov offered a material invariant version of Cattaneo’s model by taking into account the upper-connected derivative of the Oldroyd model.Nowadays,both models are combinedly known as the Cattaneo-Christov(CC)model.In this attempt,the mixed convective MHD Falkner-Skan Sutterby nanofluid flow is addressed towards a wedge surface in the presence of the variable external magnetic field.The CC model is incorporated instead of Fourier’s law for the examination of heat transfer features in the energy expression.A two-phase nanofluid model is utilized for the implementation of nano-concept.The nonlinear system of equations is tackled through the bvp4c technique in the MATLAB software 2016.The influence of pertinent flow parameters is discussed and displayed through different sketches.Major and important results are summarized in the conclusion section.Furthermore,in both cases of wall-through flow(i.e.,suction and injection effects),the porosity parameters increase the flow speed,and decrease the heat transport and the influence of drag forces.

CoO_(x)/CC复合电极的制备及其电化学性能

为了改善金属氧化物的导电性和循环性能,采用电化学沉积和热处理方法制备氧化钴/碳布(CoO_(x)/CC)复合电极,通过SEM、XRD和电化学工作站等方法对复合电极的微观形貌组成和电化学性能进行表征和测试.结果表明:①CoO_(x)/CC复合电极表面形成了由大片层构成的棒状晶体,在一定程度上保持了钴基金属有机骨架(Co-MOF)模板原有的结构;②复合电极表面成分为Co、CoO和Co_(3)O_(4)的混相;③作为锂离子电池电极,CoO_(x)/CC复合电极在0.5 mA/cm^(2)的电流密度下,具有较高的面积比容量,为8.5 mAh/cm^(2);④CoO_(x)/CC复合电极循环稳定性良好,面积比容量除首次衰减13%外,基本保持不变.

33%硫酸镁湿热敷预防PICC机械性静脉炎的效果

目的观察33%硫酸镁湿热敷预防外周留置中心静脉导管(PICC)致机械性静脉炎的效果。方法将80例行PICC的鼻咽癌患者随机分为治疗组40例和对照组40例,两组均给予常规护理,治疗组于PICC置管后4小时给予33%硫酸镁局部湿热敷,30min/次,2次/d,连续5d。观察两组机械性静脉炎的发生率。结果治疗组静脉炎发生率为10.00%,对照组发生率为27.50%,两者比较,差异具有统计学意义(P<0.05)。结论应用33%硫酸镁溶液进行湿热敷能降低PICC致机械性静脉炎的发生率。

CC型一次表面传热与阻力特性试验研究

介绍了一次表面的发展及目前国内外研究的状况,采用单吹瞬变法对自行设计的3种CC（Cross Corrugated）型一次表面进行传热与阻力特性的试验研究。建立了数学模型,由数值解求得流体的出口温度与时间及传热单元数NTU间的函数关系。通过配比,获得了换热表面在测定工况下的NTU值。首次获得该3种CC表面的j和f的试验关联式。j因子和f因子均随Re的增加而逐渐下降,符合紧凑表面传热性能和阻力性能的一般规律。经误差分析,所提供的试验关联式的拟合误差不大于15%,具有足够的工程精度。关联式的使用条件是Re=120~800,换热面当量直径为1.2~1.4 mm,交错角45~75°。采用综合评价因子j/f对3种表面的性能进行了分析,结果表明,宽高比较大的型面具有较佳的综合性能。所得数据还与国内外其他学者的数值模拟结果进行了比较,试验数据与数值模拟的结果基本符合。

GCr15轴承钢方坯连铸轻压下工艺优化与实践

为提高GCr15轴承钢连铸坯均质化水平,改善内部裂纹、缩孔等缺陷,通过实物计算坯壳厚度生长比例、钢种热属性测试,设计浇注过程大压下和联合轻压下试验,监控浇注过程铸坯表面温度和拉矫机工作状态等方法,优化轻压下工艺。结果表明,连铸轻压下合理的起始位置R为42%~45%,为获得更优低倍质量,200 mm×200 mm、240 mm×240 mm、300 mm×340 mm三种规格连铸轻压下起始位置较原工艺后置1~3 m;以200 mm×200 mm GCr15为例,增加铸坯压下量,由1.25 mm/m提高到2.5 mm/m,可减轻铸坯轻压下裂纹,显著改善铸坯Y-Z纵向低倍成分和组织均匀性,轧材中心碳偏指数普遍达到0.97~1.03,实现了既不产生明显轻压下裂纹、又能改善中心偏析和V型偏析缺陷的目标。

Analytical study of Cattaneo–Christov heat flux model for a boundary layer flow of Oldroyd-B fluid

We investigate the Cattaneo-Christov heat flux model for a two-dimensional laminar boundary layer flow of an incompressible Oldroyd-B fluid over a linearly stretching sheet. Mathematical formulation of the boundary layer problems is given. The nonlinear partial differential equations are converted into the ordinary differential equations using similarity transformatioris. The dimensionless velocity and temperature profiles are obtained through optimal homotopy analysis method （OHAM）. The influences of the physical parameters on the velocity and the temperature are pointed out. The results show that the temperature and the thermal boundary layer thickness are smaller in the Cattaneo-Christov heat flux model than those in the Fourier＇s law of heat conduction.

Dynamics of Sutterby fluid flow due to a spinning stretching disk with non-Fourier/Fick heat and mass flux models

The magnetohydrodynamic Sutterby fluid flow instigated by a spinning stretchable disk is modeled in this study.The Stefan blowing and heat and mass flux aspects are incorporated in the thermal phenomenon.The conventional models for heat and mass flux,i.e.,Fourier and Fick models,are modified using the Cattaneo-Christov(CC)model for the more accurate modeling of the process.The boundary layer equations that govern this problem are solved using the apt similarity variables.The subsequent system of equations is tackled by the Runge-Kutta-Fehlberg(RKF)scheme.The graphical visualizations of the results are discussed with the physical significance.The rates of mass and heat transmission are evaluated for the augmentation in the pertinent parameters.The Stefan blowing leads to more species diffusion which in turn increases the concentration field of the fluid.The external magnetism is observed to decrease the velocity field.Also,more thermal relaxation leads to a lower thermal field which is due to the increased time required to transfer the heat among fluid particles.The heat transport is enhanced by the stretching of the rotating disk.

CC板通道入口效应对传热特性和阻力特性的影响

选取低Reynolds数k-ε湍流模型,采用数值模拟的方法计算了不同Reynolds数下入口效应和CC板通道单元体传热特性、阻力特性的关系。数值模拟的结果表明:入口效应的存在使得CC板通道前3个单元体的湍流强度显著变大,在第4个单元体之后入口效应对传热特性的影响可以忽略;随着Reynolds数的增加,由于CC板通道入口处湍流强度增加的程度逐渐变小,入口效应对传热效果的强化能力下降;随着Reynolds数的增加,入口段和充分发展段的摩擦阻力系数均有所下降;此外,由于入口效应的存在,CC板通道入口段的摩擦阻力系数比充分发展段高20%左右。

双抽热电机组–抽背热电机组双机联合运行特性及优化研究

为挖掘混合类型热电联产机组的节能潜力、降低发电成本,通过EBSILON软件搭建60MW双抽(double-extraction condensing unit,CC)-抽背(extraction condensing unit with a high back-pressure,CB)热电联产机组的仿真模型,研究该联合机组的运行特性并建立基于可解释增强机和鸟群算法的双抽-抽背热电联产机组负荷优化模型,最后以典型日热电负荷优化任务为例,给出双机热电负荷优化结果。结果表明:当保持双抽机组的中压流量不变,存在中压流量极限值10.39t/h,使低压流量与电功率的运行区域只受到最大主蒸汽流量、最小凝汽量以及最小主蒸汽流量的限制;存在中压流量极限值59.26t/h,使运行区域只受最大主蒸汽流量和最小凝汽量限制;当双机总中压流量一定时,双抽-抽背机组的联合运行区域可以用极限工况即抽背机组承担最大中压流量,双抽机组承担剩余中压流量来近似表示。该优化方法与热电负荷平均分配方案对比,典型日可以降低1148.58GJ热耗,发电标准煤耗率由212.10g/(kW·h)降低为209.05g/(kW·h),可以节省标煤3.05g/(kW·h)。

超临界CO_(2)及其混合物在竖直圆管内的传热特性数值研究

碳捕捉、运输和储存(CCS)对实现碳中和具有重要意义。以超临界CO_(2)、超临界CO_(2)+CH_(4)混合物(CH_(4)摩尔分数分别为1%、3%、5%)及超临界CO_(2)+N_(2)混合物(N_(2)摩尔分数分别为1%、3%、5%)为工质,在工质质量流速为300~600 kg/(m^(2)‧s)、热流密度为80~100 kW/m^(2)、入口压力为8~10 MPa的条件下,研究了超临界CO_(2)及超临界CO_(2)混合物在竖直圆管内的流动换热过程。结果表明,随着工质中CH_(4)和N_(2)摩尔分数的降低,工质的换热系数峰值逐渐升高,且其对应的温度逐渐升高;工质的换热系数随着质量流速的增大而增大,且质量流速越大,换热系数变化幅度越大;随着入口压力的增大,工质的换热系数峰值有所降低,且其对应的温度逐渐升高;湍动能、浮升力及定压比热容与超临界CO_(2)及其混合物换热强化密切相关。

连铸结晶器弯月面区域传热模拟

用体积控制法对连铸结晶器弯月面区域的温度场进行了数值模拟，然后用鹿岛制铁所的一整套原始数据进行验证计算，计算输出为温度场分布、凝壳表面温度、凝壳厚度、渣圈形状、渣缝隙宽度等数值结果。温度场的进一步分析表明，弯月面部分凝固是铸坯表面振痕形成的根本原因。