平壁三角形直肋装置肋化热阻系数曲线图

提供了工程计算用的平壁三角形直肋装置肋化热阻系数曲线图。从图上可清楚地看出肋基厚、肋高和肋间距对肋装置传热性能的影响 ,有助于最佳尺寸的确定 ,简化传热计算。     

梯形肋片管表面温度的试验与计算

以几种不同形状的梯形肋片管为研究对象 ,通过建立试验台 ,模拟了肋片的多种工况 ,得到了肋片的实际温度分布 ,继而从理论上对肋片的温度和传热量进行了推导计算 ,最后 ,对两者进行了对比 ,并分析了结果     

肋片几何参数对表冷器除湿性能影响的数值分析

对表冷器除湿性能进行数值计算,选取5个影响表冷器除湿性能的参数:肋片高度、肋片厚度、肋片间距、风速、冷壁温度。重点研究肋片结构参数对表冷器除湿性能的影响。采用正交方法进行实验设计,比较极差大小后发现,影响表冷器除湿性能的结构参数大小依次为肋片厚度、肋片间距、肋片高度,所占权重分别为54.97%、39.79%、5.24%;通过计算各个因素对表冷器除湿性能的显著性水平,得到肋片厚度对表冷器除湿性能有显著性影响。     

梯形剖面圆形肋片管温度场的研究

提出了一种新的梯形剖面肋片管沿肋高（即沿肋根致肋端方向）温度分布计算方法,实测结果表明这一计算方法有较高精度,实验同时显示了沿肋宽方向（即沿肋片的厚度方向）的温度分布不均匀性,对环肋结构优化有重要参考作用。     

交错内肋微通道的流动和传热特性研究

为了研究带有交错内肋微通道的流动和传热特性,采用数值模拟的方法分析了肋片的形状对微通道热力性能的影响,对比了矩形肋、菱形肋、三角形肋和圆形肋4种不同形状内肋结构的微通道和光滑矩形微通道的热力性能。结果表明：矩形肋、菱形肋、三角形肋和圆形肋微通道的努塞尔数Nu都大于光滑矩形微通道的努塞尔数Nu,最大值分别为光滑矩形微通道的2.59,2.71,2.90和2.48倍;肋片对微通道的传热特性具有显著的强化作用,这是由于流体在交错内肋的后方产生涡流,实现整个流场的全局强化传热,极大提升微通道传热特性;交错内肋的应用也增大了通道的摩擦系数,矩形肋、菱形肋、三角形肋和圆形肋微通道摩擦系数的最大值分别为光滑矩形微通道的8.66,7.96,17.50和5.96倍。     

肋片的强化传热和调温作用

本文阐述了肋片强化传热的原理；分析了肋片最佳形状和尺寸确定的计算式；提出了肋片在强化传热、调节壁温中的正确布置方法。     

采暖散热器肋片结构优化

通过对采暖散热器肋片的散热状况分析，建立了散热器肋片传热过程的物理和数学模型。     

直肋片最佳肋片厚度的理论关系式

本文从追求整个肋壁最大传热量出发,证明了肋片传热面最佳肋片厚度的存在,并得到了确定最佳肋片厚度的理论关系式。     

辐射对流条件下肋片散热的数值计算和结构优化

本文利用matlab对一种矩形肋片进行了散热数值计算 ,以金属热强度为结构优化的目标函数 ,通过对计算结果的分析得出了此种肋片的最佳肋高尺寸 ,同时 ,认为利用matlab来解决这类肋片优化问题是非常方便的。     

DG130／9．8-1型锅炉省煤器改造

本文针对锅炉省煤器磨损和传热问题，对采用螺旋肋片省煤器在设计中诸多因素进行分析，同时结合平果铝热电厂群2炉改造工程项目阐述了螺旋肋片省煤器的应用情况。这种螺旋肋片省煤器具有较高的传热效率，可有效地解决磨损问题，提高锅炉效率和使用率，是省煤器改造中较佳选择方式。     

Thermal performance assessment of turbulent channel flows over different shaped ribs

Experiments are conducted to assess turbulent forced convection heat transfer and friction loss behaviors for air flow through a constant heat flux channel fitted with different shaped ribs. The rib cross-sections used in the present study are triangular (isosceles), wedge (right-triangular) and rectangular shapes. Two rib arrangements, namely, in-line and staggered arrays, are introduced. Measurements are carried out for a rectangular channel of aspect ratio, AR = 15 and height, H = 20 mm with single rib height, e = 6 mm and rib pitch, P = 40 mm. The flow rate is in terms of Reynolds numbers based on the inlet hydraulic diameter of the channel in a range of 4000 to 16,000. The experimental results show a significant effect of the presence of the ribs on the heat transfer rate and friction loss over the smooth wall channel. The in-line rib arrangement provides higher heat transfer and friction loss than the staggered one for a similar mass flow rate. In comparison, the wedge rib pointing downstream yields the highest increase in both the Nusselt number and the friction factor but the triangular rib with staggered array shows better thermal performance over the others.     

Two-dimensional-numerical investigation on the influence of first rib distance from the entrance of channel on Nusselt number and pressure drop

Enhancing the heat transfer coefficient in heat sinks can be achieved by surface modification techniques. Although the addition of ribs increases heat transfer capacity, it also increases pressure drop, lowering the channel's thermohydraulic performance (THP) factor. Rib research began a decade ago, with the majority of studies focusing on new rib designs or factors such as relative roughness pitch, relative roughness height, channel width, and channel height (geometric optimization) to improve THP. The goal of this study is to investigate the influence of the positioning of the first rib from the channel entrance on the Nusselt number, pressure drop, and THP factor with a simple design that could be manufactured easily. Three distinct rib designs are evaluated with rib positioning from the channel entrance, rib thickness, pitch, and Reynolds number as the parameters. It was found that the fluid starts settling up at the ribs as the ribs are moved closer to the channel entry point, thus increasing the pressure drop and reducing the fluid velocity. For the proposed design and dimensions, the Nusselt number increases by 3%–5%, and the pressure drop lowers by 4%–14% when the first rib is placed away from the channel entrance.     

综采工作面冒顶和片帮的控制研究

工作面顶板冒漏和煤壁片帮会影响到煤炭的正常回采工作和作业人员的安全,以3302综采工作面为例,分析了该工作面冒顶和片帮的主要原因,并提出了相应的控制方法及措施,从而有效预防工作面顶板冒漏和大面积煤壁片帮现象发生。     

Thermal performance characteristics of a micro-combustor with swirl rib fueled with premixed hydrogen/air

Outer wall temperature and exergy efficiency of micro-combustor are very essential in determining micro-thermophotovoltaic energy conversion effectiveness. In this study, a swirl rib was designed to improve the thermal efficiency of micro-combustor since a swirl flow can be formed when the hydrogen/air mixture passes through the swirl rib, which increases the residence time and turbulence intensity of the mixture. Effects of position, height, spacing, and shape of the swirl rib on the thermal performance of a cylindrical micro-combustor were investigated numerically. The thermal performance shows different trends with the variation of these geometric parameters, and an optimum mean outer wall temperature of 1260 K is obtained at the distance between the inlet and the rib of 7 mm, the rib height of 1.2 mm and the rib spacing of 0.5 mm, but this optimum setting triggers the large pressure drop that impedes further improvement of the micro-combustor performance. To minimize this effect, three rip shapes including rectangle, trapezoid and inversed trapezoid was designed. The results show that the micro-combustor with trapezoidal rib presents better thermal performance. This study provides theoretical guidance for the optimal design of the hydrogen-fueled micro-combustor.     

电场作用下肋表面电对流现象的可视化研究

电场可强化池态沸腾换热已经得到研究者的普遍认可.以往研究者主要针对光滑表面、加热管或加热线表面的电场强化换热进行研究.在光滑表面增加肋结构可以改变加热面附近的电场分布,从而影响加热面的换热效果.以R113作为实验工质,搭建了可视化的池沸腾实验台,采用高速摄像机记录了肋高为2 mm的加热面在电场作用下的电对流现象.实验发现,电对流随着施加电压的升高而增强,电对流加速了加热面附近流体的混合,破坏了热边界层,使得加热面温度降低从而强化了换热.     

Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm². High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.     

Thermal characterization of turbulent flow in a channel with isosceles triangular ribs

The article presents an experimental investigation on turbulent heat transfer and friction loss behaviors of airflow through a constant heat-fluxed channel fitted with different heights of triangular ribs. The rib cross-section geometry used in the present study was isosceles triangle. Two rib arrangements, namely, in-line and staggered arrays, were introduced. Measurements were carried out for a rectangular channel of aspect ratio, AR = 10 and height, H = 30 mm with three uniform rib heights, e = 4, 6 and 8 mm (e/H = 0.13, 0.2 and 0.26) and one non-uniform rib height, e = 4,6 mm (e/H = 0.13,0.2) alternately for a single rib pitch, P = 40 mm. The flow rate in terms of Reynolds numbers based on the inlet hydraulic diameter of the channel was in a range of 5000 to 22,000. The experimental results show a significant effect of the presence of the ribs on the heat transfer rate and friction loss over the smooth wall channel. The uniform rib height performs better than the corresponding non-uniform one. The in-line rib arrangement provides higher heat transfer and friction loss than the staggered one for a similar mass flow rate. In comparison, the largest e/H rib with inline array yields the highest increase in both the Nusselt number and the friction factor values but the lowest e/H rib with staggered array provides the best thermal performance.     

Numerical investigation on the performance of proton exchange membrane fuel cells with channel position variation

Such factors as mole fractions of species, water generation, and conductivity influence the performance of proton exchange membrane fuel cells (PEMFCs). The geometrical shape of the fuel cells also should be considered a factor in predicting the performance because this affects the species' reaction speed and distribution. Specifically, the position between the channel and rib is an important factor influencing PEMFC performance because the current density distribution is affected by the channel and rib position. Three main variables that decide the current density distribution are selected in the paper: species concentration, overpotentials, and membrane conductivity. These variables should be considered simultaneously in deciding the current density distribution with the given PEMFC cell voltage. In addition, the inlet relative humidity is another factor affecting current density distribution and membrane conductivity. In this paper, two channel‐to‐rib models, namely, channel‐to‐channel and the channel‐to‐rib, are considered for comparing the PEMFC performance. Thorough performance comparisons between these two models are presented to explain which is better under certain parameters. A three‐dimensional numerical PEMFC model is developed for obtaining the current density distribution. Water transfer mechanism because of electro osmotic drag and concentration diffusion also is presented to explain the PEMFC performance comparison between the two models. Copyright © 2012 John Wiley & Sons, Ltd.     

Turbulent forced convection flow inside inward-outward rib corrugated tubes with different rib-shapes

The thermal and hydrodynamic behaviors of forced convection turbulent flow inside the corrugated tube are investigated numerically. The ribs of corrugated tube are distributed in inward-outward arrangement simultaneously and alternately (referred as IOCT). Three roughness shapes of the corrugated tube are examined; rectangular, semicircular, and trapezoidal ribs. The computational model is validated through comparison with the predicted results with correlated and experimental ones of related works. The performance of IOCT is compared thermally and hydrodynamically with that of the inward-rib corrugated tube (ICT), outward-rib corrugated tube (OCT) and smooth tubes. The results reveal that the heat is exchanged effectively by employing IOCT than utilizing OCT but with extra pumping power losses. At the maximum Re, it is found that the heat transfer of IOCT is 17.7% higher than that of OCT, and utilizing IOCT instead of ICT results in a reduction of friction factor by about 27.2%. Also, IOCT exhibits a lower friction factor and pressure drop penalty than that imposed by ICT. Also, roughness shapes have an insignificant effect on the thermal and hydrodynamic performances of IOCT for the same rib geometrical parameters. Furthermore, the influence of variation pitch-to-diameter ratio is also examined for various rib shapes of IOCT.