Thermoelastic solutions for thermal distributions moving over thin slim rod under memory-dependent three-phase lag magneto-thermoelasticity

Abstract

Enlightened by the Caputo fractional derivative, the present study deals with a novel mathematical model of generalized thermoelasticity to investigate the transient phenomena due to the influence of magnetic field and moving heat source in a rod in the context of three-phase lag (TPL) theory of thermoelasticity. Both ends of the rod are fixed and heat insulated. Employing Laplace transform as a tool, the problem has been transformed into the space-domain and solved analytically. Finally, solutions in the real-time domain are obtained by applying the inverse Laplace transform. Numerical calculation for stress, displacement, and temperature within the rod is carried out and displayed graphically. The effect of moving heat source speed on temperature, stress, and temperature is studied. It is found from the distributions that the temperature, thermally induced displacement and stress of the rod are found to decrease at large source speed. For the better understanding of the effect of moving heat source on all the distributions, three animations are added.     

竖直恒温面自然对流边界层不稳定性研究

在无扰动、随机式扰动以及正弦式扰动下,通过对竖直恒温面处状态Ra为1.328×10^9、Pr为6.24的自然对流进行模拟,探索了热边界层的不稳定性和共振强化自然对流换热。结果表明:(1)竖直自然对流边界层上游位置的随机式扰动对热边界层的影响主要体现在稳定阶段;(2)该状态下的竖直自然对流边界层的特征频率为15 067,且相比于无扰动状态,频率为15 067的正弦式扰动能在竖直恒温面处提高5.15%的换热量;(3)在竖直自然对流边界层上游位置加入特征频率的正弦式扰动,竖直恒温面处的局部努塞尔数Nu均出现明显波动,且波动随着边界层高度的增加而增大。     

Heat Transfer Enhancement by Using Copper–Water Nanofluid Flow Inside a Pin Channel

Influences of simultaneous utilization of pin channel and copper–water nanofluid on performance of plate-fin heat exchangers were experimentally explored and compared with results obtained for the base fluid flow inside a plain channel. Experimental results clearly indicate that compared with the plain channel, the pin channel significantly improves the thermal-hydraulic performance of the plate-fin heat exchanger, about 38%. In addition, the heat transfer coefficient as well as pressure drop are increased by using the nanofluids instead of the base fluid. Noticeable average performance factor of 1.65 is obtained for the simultaneous utilization of pin channel and nanofluid inside the plate-fin heat exchanger.     

水流损失和热补偿共同作用对增强型地热系统(EGS)产能影响的研究

基于青海共和盆地-3705m地热田实测数据,结合流固耦合传热理论并运用Comsol软件,建立了离散型裂隙岩体流体传热模型。考虑水流损失和热补偿共同作用,模拟得到了开采过程中上、下岩层(盖层和垫层)为绝热不渗透、传热不渗透、渗透传热时,储层(上、下岩层和压裂层)温度场的变化特征,分析了产出流量、水流损失、产出温度、产热速率的变化规律。研究结果表明:采热过程中产出流量始终小于注入流量;产出流量增幅速率先增大后减小,最后趋于稳定,前3a产出流量增幅超过总增幅量的3/4;忽略水流损失,将高估产热速率,采热初期甚至达到考虑水流损失时产热速率的3倍以上;考虑水流损失,产热速率呈先快速上升再趋于稳定后逐渐下降的趋势,最优开采时间为3a^11a;研究上、下岩层对产出温度的影响,仅考虑传热,采热寿命延长5.43%,同时考虑渗流传热时,采热寿命延长2.71%;采热前9a,水流损失占主导作用,即流入上、下岩层水流损失对产热速率的影响高于热补偿效应,开采10a后,热补偿效应占主导作用;同时考虑水流损失和热补偿效应得到的产热速率变化规律与实际工程更为符合,建议选择低渗透能力的上、下岩层延长增强型地热系统(EGS)运行时间。     

The Impacts of Crystalline Structure and Different Surface Functional Groups on Drug Release and the Osseointegration Process of Nanostructured TiO2

In implantable materials, surface topography and chemistry are the most important in the effective osseointegration and interaction with drug molecules. Therefore, structural and surface modifications of nanostructured titanium dioxide (TiO₂) layers are reported in the present work. In particular, the modification of annealed TiO₂ samples with —OH groups and silane derivatives, confirmed by X-ray photoelectron spectroscopy, is shown. Moreover, the ibuprofen release process was studied regarding the desorption-desorption-diffusion (DDD) kinetic model. The results proved that the most significant impact on the release profile is annealing, and further surface modifications did not change its kinetics. Additionally, the cell adhesion and proliferation were examined based on the MTS test and immunofluorescent staining. The obtained data showed that the proposed changes in the surface chemistry enhance the samples’ hydrophilicity. Moreover, improvements in the adhesion and proliferation of the MG-63 cells were observed.     

Experimental study of transient heat transfer characteristics of single-phase natural convection in multidimensional porous bed with volumetric heat generation

Natural convection in an internally heated porous bed of height and diameter of 450 mm and 500 mm, respectively, and superposed with the fluid layer has been experimentally investigated. The onset of natural convection in the bed is indicated by change in the rate of temperature rise within the bed. An empirical model based on local Nusselt number and local Rayleigh number has been developed. A comparison of the present model with the models in literature is made to draw out the differences between the local heat transfer of large multidimensional beds and the average heat transfer of small beds.     

Ground states of two-component attractive Bose–Einstein condensates I: Existence and uniqueness

We study ground states of two-component Bose–Einstein condensates (BEC) with trapping potentials in ${\mathbb{R}}^2$, where the intraspecies interaction $(?a_1,?a_2)$ and the interspecies interaction ?β are both attractive, $i.e$, $a_1$, $a_2$ and β are all positive. The existence and non-existence of ground states are classified completely by investigating equivalently the associated $L^2$-critical constraint variational problem. The uniqueness and symmetry-breaking of ground states are also analyzed under different types of trapping potentials as $\beta \nearrow {\beta }^{?}=a^{?}+\sqrt{(a^{?}?a_1)(a^{?}?a_2)}$, where $0<a_i<a^{?}:={6w6}_2^2$ ($i=1,2$) is fixed and w is the unique positive solution of $\mathrm{\Delta }w?w+w^3=0$ in ${\mathbb{R}}^2$. The semi-trivial limit behavior of ground states is tackled in the companion paper [12].     

热源塔热泵系统夏季工况优化运行实验研究

由于热源塔在冬夏季工况下的换热能力存在较大差异,按冬季工况设计的热源塔热泵系统,在夏季工况下运行时存在换热能力过剩的问题,影响系统性能。为解决上述问题,本文构建了热源塔热泵系统,实验研究了其冬夏季工况的性能差异。在此基础上,对夏季工况下的优化运行进行了实验研究,结果表明,通过调节空气和溶液流量,将热源塔的逼近度和冷幅分别控制在3.5℃和4.3℃,可使得系统性能系数由3.6提升至3.9,并对其节能机理进行了分析。     

Monte Carlo study of the critical and the compensation behaviors of the double perovskite Sr2CrIrO6

The phase diagrams and magnetic properties of double perovskite $S{r}_{2}CrIr{O}_6$ have been studied by using Monte Carlo simulation based on the heat bath algorithm. The ground-state diagrams of the compound $S{r}_{2}CrIr{O}_6$ have been calculated for different combinations of system parameters. The diagrams obtained are very rich and they give an idea of all the most stable configurations. The effects of the exchange interactions and the crystal field on the phase diagrams and magnetic properties of the system have been examined. A number of interesting phenomena have been observed such as the compensation temperature, the first and second order phase transitions, the critical triple point and the terminal critical point.     

Experimental Performance of a Solid Heat Exchanger with Tree-Like Flow Passages

System performance of a solid single-fluid compact heat exchanger with tree-like flow passages has been experimentally examined. The results, presented in the form of commonly defined dimensionless parameters, demonstrate that system performance can be characterized in a mode similar to traditional compact heat exchanger designs. Pressure forces were found to dominate inertia forces at low Reynolds numbers. Correlations of the Euler number, Nusselt number, Colburn factor, and friction factor as a function of Reynolds number were utilized to compare system performance to traditional two-fluid compact heat exchangers.