Numerical Heat Transfer Attic Model Using a Radiant Barrier System

A two-dimensional, steady-state finite-element model was developed to simulate the thermal effects of the application of an attic radiant barrier system (ARBS) inside a ventilated residential attic. The attic is ventilated using the exhaust air from an evaporative cooler. The study uses a k-ε turbulent model to describe the velocity and temperature distributions in the attic. The ambient temperature and solar isolation densities on the outside inclined attic surfaces are used as driving functions for the model. The model also included the appropriate heat exchange modes of convection and radiation on these outside surfaces. Several recirculation zones were visually observed in the attic flow pattern. Also, the use of the ARBS seems to lower the heat transfer through the ceiling by 25–30%, but this effect decreases significantly as the outside ventilation rates are increased through the attic space. The 2D model revealed some interesting temperature distributions along the attic surfaces that could not have been predicted by the one-dimensional models. The lower emissivity ARBS seems to raise the temperature of the inclined attic surfaces as well as the temperature of the exhausted ventilation air.     

燃气辐射管换热器的结构优化与数值模拟

为解决W型燃气辐射管换热器排烟温度高的问题,设计了三种改进换热器性能的结构,采用ANSYS FLUENT软件进行数值模拟,得到了不同结构换热器的性能参数,如烟气出口温度、空气预热温度、压力损失、各换热面换热量和有无折流板的热阻变化.结果表明,中心空气管由一根φ79 mm粗管改为六根φ33 mm细管后换热量增加了57.6%,增设烟气双行程后换热量提高20.7%.增设密封折流板和多孔折流板后换热量分别增加了5.7%和5.3%,空气和烟气之间的热阻都降低了20%左右.多孔折流板的烟气压力损失比密封折流板低47.4%.      

Neutral temperature range in incubators: performance of equipment in current use and new developments

Low-birth-weight neonates should be nursed at thermoneutrality inside incubators. Thermoneutrality control is essential to enhance body growth and to reduce neonatal illnesses and mortality. Guidelines have been published to provide the thermoneutral range, but the recommendations did not always take into account all ambient and physiological parameters influencing thermoneutrality. In most marketed incubators, the heat supply is controlled through convective air flow (closed incubators) or through radiant power density (radiant warmer beds). The heating unit (on/off cycling or adjustable proportional control) is activated by an error signal calculated from the difference between a controlled temperature and a reference value preset by the clinician. The controlled variable can be either the incubator air or the skin temperature of the anterior abdominal region of the neonate. The neonate's size, thermal properties of the mattress and of incubator walls, air temperature and humidity, air velocity, incubator wall temperatures all influence the heat exchanges between the neonate and the surroundings, and, consequently, modify the obtention of thermoneutrality. Moreover, studies of the physiological mechanisms by which the neonate regulates body heat storage suggest that metabolic rate, behavior, vigilance level, nursing care, and heater control processes should also be taken into account. Little attention has been paid to these factors, and incubator performances are often disappointing. This article reviews the different factors that modify thermoneutral condition. An attempt is made to suggest new ways to design equipment incorporating these factors in algorithms controlling heater processes in order to reach the optimal thermal environment in which the neonate should be nursed.     

赣南地区低温地板辐射采暖效果研究

赣南地区属于夏热冬冷地区, 被列为非采暖区, 冬季室内热舒适性较差.由于各方面的原因, 人们对居住环境的要求越来越高, 迫切需要改善室内热舒适性.结合赣南地区冬季气候及地域特点, 研究低温地板辐射采暖的效果, 并与空调采暖进行对比.利用CFD理论分别对该采暖室在2种采暖方式下的室内热环境进行数值模拟, 分析室内空气温度场、湿度场, 并用PMV-PPD评价指标对室内热环境进行评定.研究表明, 与空调采暖相比低温地板辐射采暖:室内热环境更加舒适; 室内设计温度可降低2~3℃, 能节约15%的能量, 有利于节能环保.      

Improving Air-Cooled Condenser Performance in Combined Cycle Power Plants

It has been recognized in recent times that air-cooled condensers (ACCs) are environmentally preferable to the traditional water-cooled condensers for rejecting heat in combined-cycle power plants (CCPPs). However, a drawback of ACCs is that their performance can decline with increasing ambient air temperature. A new approach is proposed in this paper that has the potential to alleviate this drawback of ACCs. In this approach, a chilled-water thermal energy storage system (TES) is used to precool the inflow air to the ACC whenever the ambient air temperature increases above the design air inlet temperature. The temperature of the TES system is maintained by an absorption refrigeration system (ARS) driven by low-quality waste heat from the CCPP. A process model integrating the CCPP with the ARS and the TES has been developed to optimize the volume of the TES. A 500?MW CCPP with steam turbine net output of 170.9?MW was chosen to evaluate the application of this approach for a power plant to be located in southern New Mexico. This analysis showed that a tank volume of 4,500?m3 will be required to maintain the air temperature at the inlet to the ACC at the design value of 20°C throughout the year. Simulations under ambient air temperatures up to 40°C indicated that the proposed system is capable of maintaining the rated net power output of the plant with minimal fluctuations. Simulations also showed that TES tank volume is most sensitive to the design air inlet temperature to the ACC—an increase of this temperature by 1°C can result in at least 25% reduction in the volume.     

圆坯连铸结晶器热流研究

 对圆坯连铸结晶器平均热流和局部热流进行了研究。分析了拉速、电磁搅拌电流和弯月面波动等工艺参数对结晶器局部热流(高热流区热流)和平均热流的影响。结果表明：拉速为14~26 m/min,搅拌电流在200~320 A时,局部热流与平均热流变化趋势不完全一致。局部热流对工艺参数反应敏感,传热极不均匀;平均热流不能完全反映局部热流的变化,局部热流能更及时地反映坯壳的凝固情况。     

辐射直接交换面积数论网格法与Monte-Carlo法的比较研究

针对辐射直接交换面积,分别用数论网格法与Monte-Carlo法进行了比较计算。结果表明,与Monte-Carlo法相比,数论网格法具有计算速度快,计算精度高及使用方便等优点。     

基于正交法扁双P型辐射管仿真模拟及结构优化

在扁形双P型辐射管的基础上,研究了扁双P型辐射管的中心管的等效半径、支管的等效半径、中心管和支管间距、管长等结构尺寸对辐射管性能的影响.通过建立正交试验方案对辐射管结构尺寸以及燃烧器喷口结构位置进行优化.结果表明,影响辐射管表面温差的最明显因素依次:中心管与支管的间距、中心管等效半径、管长和支管等效半径;影响辐射管辐射功率的明显因素依次:管长、中心管等效半径、中心管与支管的间距和支管的等效半径.上下空气喷口与左右空气喷口大小比例在7:3和9:1比较接近,辐射管的性能参数最好;左右空燃气喷口间距为50 mm,上下空气喷口间距在60 mm的情况下辐射管表面的温度不均匀系数最小,为0.058.      

HTAC辐射管在燃气真空热处理炉中的应用

概要介绍了HTAC辐射管技术，并阐述了其结构和特点，以及蓄热式辐射管燃气真空炉结构和特性。     

矿井通风热湿提取与资源化利用方法

矿井热湿风流中储存有大量低位热能和水汽,导致井下工作环境恶劣,乏风直排造成了大量资源浪费。因此,矿井通风热湿提取与资源化利用是解决深井热害和矿井低碳转型发展的重要途径之一。受地面大气状态参数和井下热湿源的影响,井巷热湿风流参数随时间变化,实时掌握井巷热湿风流转变特征是精准提取矿井风流中低位热能的关键。本文基于热湿风网实时解算,确定了矿井关键热湿节点分布规律及变化特征;建立了冷凝热湿提取计算模型,研发了热湿风流低位冷凝余热提用技术,形成了制冷–除湿联合的低位热能原位利用系统;提出了矿井乏风集中式和关键节点分布式热湿提取与资源化利用方法,并对提热收水效果进行了实例分析,为矿井低位热能提取利用和热害治理提供了理论基础和建设思路。      

HTAC辐射管在燃气真空热处理炉中的应用

概要介绍了HTAC辐射管技术，并阐述了其结构和特点，以及蓄热式辐射管燃气真空炉结构和特性。     

Estimating Regional Evapotranspiration Using Remote Sensing: Application to Sone Low Level Canal System, India

Remote sensing-derived spectral data have been used in the past to partition net radiation, soil heat, and sensible heat fluxes for estimating latent heat flux as a residual of surface energy balance, and thus regional evapotranspiration. Attempts to provide a simplified procedure for estimating sensible heat flux at a regional scale have not been successful because of the relatively strong dependence of the heat transfer coefficient on the land–atmosphere boundary condition. This paper presents a remote sensing-based procedure to estimate the sensible heat flux incorporating the local meteorological conditions, and in turn to determine the regional evapotranspiration. The model utilizes satellite-derived surface albedo, surface temperature, and leaf area index along with a very few agrometeorological data as inputs. The proposed procedure has been tested on a part of the Western Yamuna Canal system, India, and is found to be computationally simple as well as stable. For a well-watered wheat crop, the average evapotranspiration by the proposed model is estimated to be 2.05?mm?d?1 on January 30, 1996, whereas it is estimated to be 1.89?mm?d?1 using the Penman-Monteith equation, indicating a difference of less than 10%. The model is subjected to sensitivity analysis for uncertainties in the observed wind velocity and the computed leaf area index (by ±20%) to estimate sensible heat flux. Results reveal that the percentage change in mean sensible heat flux for the image is less than 5% in all cases, thus indicating the acceptability of the model against the uncertainties. Further, the model has been applied to three sets of Landsat-TM data covering the Sone Low Level Canal system, India, to demonstrate its usefulness in evaluating water delivery performance.     

直接控制系统参数的模型法研究

直接控制系统的参数离线整定的主要困难在于无法确定受控系统的响应。本文以能量平均方程和热传导方程为基础,建立了较为严密的炉子简化模型,作为调试环境,首次尝试实现了PID参数的离线预调试,它对于实际在线研究有参考价值,并可成为直接控制系统CAI的蓝本。同时以全交换面积为基础提出了热电偶计算公式,该公式解除了炉转为辐射零热流面的假设条件,具有更一般的意义。     

连退炉用U型辐射管内无焰燃烧的数值模拟

钢铁冶金用连续退火炉中通常使用辐射管对工件进行间接加热,这不仅保证被加热工件受热均匀,还能不影响其表面质量.但同时,由于辐射管内燃烧空间有限,极易产生局部高温区,这会影响被加热产品质量,而且高温会导致NOx 大量生成,此外,较大的壁温差异所产生的热应力会使管壁遭到蠕变破坏,缩短其使用寿命.因此,为了优化辐射管的性能,基...     

分级气体成分对燃气辐射管热过程影响的数值模拟及研究

采用现有的双P型辐射管进行燃烧实验,并进行相应的CFD仿真对比,结果显示NO_x体积分数的数值计算与试验结果误差最大为3.6%,其他参数的偏差均在1%以内.将空气分级的理念应用于双P型辐射管,设计一种带支管的分区分级燃气辐射管,并对其流动和传热特性进行仿真研究.结果表明:支管通入空气量占总空气量的25%时,辐射管壁面温差最大,热效率最高;支管通入燃气量为20%时,辐射管壁面温差最小,壁面温度均匀性最好;支管以相同空燃比同时通入空气和燃气,且支管通入空燃气量为总燃气量的25%时,整个辐射管内气体温度分布最均匀;支管通入空燃气量占总气体量从5%增加到35%的过程中,壁面温差先降低后缓慢增加,支管通入燃气量为20%时辐射管壁面温差最小.      

U型辐射管加热装置的性能分析

实验研究了U型辐射管加热装置的性能。确定了实行烧嘴分级燃烧的配风板和配风环的结构形式。研究认为,分级燃烧不仅能保证燃料的完全燃烧,改善辐射管的表面温度分布,而且还可有效抑制NOx的生成,高效换热器可提高热回收效率。结构优化后的辐射管加热装置在使用时可使辐射管表面温差控制在65-81℃,烟气中NOx（11％O2）含量小于70×10^-6,换热器的温度效率大于42％。     

The effect of climatic factors on the onset of acute myocardial infarction]

The results of the single-relative analysis on the three climatic factors of air temperature, pressure and relative humidity to the attack of acute myocardial infarction in Shenyang city located in the cold Northeastern China area, showed that the attack was more frequent in summer time with high temperature, humidity and low air pressure. The attack was positively related to temperature (r = 0.7463 P < 0.01) and humidity (r = 0.6466 P < 0.01) while is negatively related to air pressure (r = -0.7300 P < 0.05). And specifically, in Shenyang area the incidence was obviously increased with average temperature > 20 degrees C, air pressure < 1010, and relative humidity > 70%. Patients should reduce the activities in high or low temperature environment. Proper precautions should be taken well in advance to avoid the attack on the patients in a particular season. And different nursing measures should be taken in different seasons to comply with changes of climate, for averting the attacks caused by the climate.     

带烟气回流W型辐射管热过程数值模拟

基于商业软件FLUENT同时,采用RNG k-ε模型和非预混燃烧模型,建立了带烟气回流W型辐射管燃烧器的燃烧及传热的三维数学模型,对辐射管内湍流和燃烧状况进行了模拟,并得到了出口NOx排放的计算结果;通过与相应实验数据的对比,验证了模型的可靠性.分析了辐射管内流体流动,传热和燃烧的特征,研究了燃气流量及空气预热温度对辐射管使用性能的影响;结果表明:燃气流量的提高,会增大辐射管壁面温度的不均匀性,而提高预热温度则相反;两者与辐射管加热能力呈正相关,但都会使得出口烟气内的NOx含量增大.     

Gas Turbine Power Augmentation by Overspray Inlet Fogging

The power output of a gas turbine (GT) is highly affected by ambient temperature. A higher ambient temperature will result in a lower power output, due to reduced inlet air density and mass flow rate. Therefore, GT power loss can be recovered by cooling the inlet air. Due to compression with intercooling, overspray inlet fogging (wet compression) can increase power more than using only evaporative inlet cooling. It can also be used to recover aircraft thrust loss due to high ambient temperature operation, or to boost takeoff thrust. This paper is focused on the effects of adding an overspray inlet fogging system to an existing GT power plant. Simulation runs were made for adding an overspray inlet fogging system to a GE 7111EA GT engine to compare with the baseline case (28.2°C, 75.7% relative humidity). Power augmentation using evaporative and overspray inlet fogging can range from 1.85 to 16.8?MW, which amounts to a 2.5–22.4% power increase. Moreover, the net efficiency is also increased by 1.62%. Therefore, overspray inlet fogging is capable of both boosting the GT power and improving the efficiency. Results from this study can be used as a guideline for GT power augmentation by overspray inlet fogging.     

提高亚包晶钢板坯拉速对结晶器传热的影响

通过对提高亚包晶钢AQ钢种230 mm×1200 mm板坯拉速试验过程中结晶器冷却水参数、铜板测温等数据进行适时记录,并与数学模型及ANSYS商业软件相结合,研究了提高拉速对结晶器平均热流、局部热流、铜板温度场以及坯壳厚度的影响。结果表明,拉速由1.3m/min提高到1.5m/min时,平均热流增加0.1 MW/m²左右,宽边弯月面区域局部热流增加0.13 MW/m²,但均在合理范围内,这与采用高碱度高结晶温度的试验保护渣有关;结晶器窄/宽面平均热流比超过0.9,应适当减少结晶器锥度;宽面坯壳厚度平均减薄4 mm左右,应严格控制结晶器传热强度,以保证连铸工艺稳定和铸坯质量。