新型流化床换热器的研讨

流化床换热器是基于流化床热交换理论所研究的一种新型换热器,此种换热器特别适用于烟气中的粉尘较多且为气一液换热的余热回收。文中介绍了流化床的原理和特点,流化床换热器的换热原理以及流化床换热器的换热系数的计算方法等等。     

热轧工作辊换热系数的遗传算法优化模型

边界热交换系数的确定是热轧工作辊高精度温度场计算的关键参数.分析了热轧工作辊的热边界条件,建立了实用的轧辊温度场模型,采用改进的遗传算法--新的适应值标定方法对工作辊关键换热参数进行优化.仿真和实验结果表明,该优化模型实用可靠,可用于生产实践中工作辊换热系数的确定.     

Surface Temperature Change of U75V 60 kg/m Heavy Rail During Heat Treatment

The U75V 60 kg/m heavy rail samples were heated to 900 ℃ in a resistance furnace for a fixed duration of 50 min. Under this condition, the samples were austenitized totally. Then, the samples were dragged out of furnace and cooled for 25 s in the open air. After that, the samples entered into the air spraying channel, and were cooled from the top and both sides by compressed air. During this period, main technical parameters were changed such as the distance between spray nozzles and surface of rail head, air pressure, air spraying time and air temperature. So under laboratory condition, optimal heat-treating parameters of U75V 60 kg/m heavy rail were determined as the distance between spray nozzles and surface of rail head of 15 mm, air pressure of 0.26 MPa, cooling time of 80 s, and air temperature of 28 ℃. The surface temperature at different positions of heavy rail was measured before and after heat treatment, and the temperature changing law was determined. The self tempering occurred on the surface of rail head after heat treatment, and the tempering temperature became the largest (about 3 min) after heat treatment, separately 528, 524 and 536 ℃ at the center, top fillet and bottom fillet of rail head. The heavy rail was cooled in open air after heat treatment; during this period, the temperature gap on the surface of heavy rail became smaller and smaller, and was reduced to zero when being cooled for 20 min.     

Balance mathematical model for the heat regime of cold rolling of electrical steel strips in a reversing mill

A mathematical model is developed to describe the heat regime of a reversing cold-rolling mill that takes into account the substantial differences between the heat processes occurring in reversing and continuous mills. Model and heat balance equations are used to calculate the strip temperature in passes and the temperature and the heat profile of rolls as functions of the rolling regime parameters and the heat-transfer coefficients that characterize the heat exchange between a strip, rolls, and lubricant-cooling agents and depend on the cooling system parameters of a mill. The model can be used to find a heat regime favorable for achieving the required final magnetic properties of electrical steel. The efficiency of the factors affecting the heat regime in rolling is studied.     

移动床固体颗粒绕流顺排圆管的过程

工业中常用带埋管的移动床来加热或冷却固体颗粒物料,其过程涉及颗粒流与管壁间的复杂传热,而颗粒绕流圆管的流动过程对其传热效果起着决定性作用.为简化描述颗粒的流动过程,通过分析颗粒绕流圆管的特性,建立了拟漏斗流模型,并给出了模型所需颗粒绕流圆管描述参数的取值范围,模型可用以求取颗粒绕流圆管的速度场和时长等参数.建立了埋管移动床实验系统,考察了颗粒绕流顺排管束的过程;同时利用离散单元法(DEM)对该过程进行数值模拟,获得了颗粒绕流圆管的流动过程,并利用移动床实验结果对比验证了离散单元法数值模拟结果;最后,对比了基于拟漏斗流模型的计算结果和离散单元法数值模拟结果,并根据此结果对拟漏斗流模型的描述参数进行了确定.      

Scar traction appliance for a patient with microstomia: a clinical report

This clinical report illustrates how an active traction appliance was made for a patient with severe microstomia by attaching custom-made lip retractors to an orthodontic headgear. A steady, light tensile force was imparted to the lips with the elastic bands between the retractors and the headgear.     

热处理炉直接控制系统的模拟研究

以炉膛能量平衡方程和工件、炉围和台车的热传导方程为基础，建立了热处理炉数学模型，实现了热处理全过程，即空炉、加热、保温和冷却四个阶段的数学描述。模型的炉膛辐射热交换部分采用了全交换面积的概念，有效减少了重复计算。以炉子模型作为软件平台，研究了热处理炉的直接数字控制(DDC)系统，整定了各阶段的PID参数，在此基础上实现了热处理过程及其控制系统的离线模拟。     

An equivalent square field formula for determining head scatter factors of rectangular fields

A simple formula is derived for the calculation of an equivalent square field that gives the same head scatter factor as a given rectangular field. This formula is based strictly on the configuration of a medical linear accelerator treatment head. The geometric parameters used are the distances between the target and the top of each field-defining aperture. The formula accounts for both the effect of field elongation and the collimator exchange effect. This method predicts the output to within 1% accuracy for both open and wedged fields and does not require any new measured data other than the field size dependence of head scatter for a range of square field sizes. Interestingly, the formula we derived has the same format as the formula that was empirically obtained by Vadash and Bj?rngard [Med. Phys. 20, 733-734 (1993)].     

热管技术回收低温烟气余热的经济性分析和计算

针对酸露点附近的换热问题,采用热管换热技术来减低排烟温度,建立换热和经济性评价的数学模型,计算不同排烟温度下的设备投资和经济收益,并对投资回收期及新增部分经济指标等参数进行分析和讨论。提出一种新的经济性指标来考虑设备的经济性．可为不同排放温度下余热回收设备的选择和设计提供参考。     

A holographic study of variations in bone deformations resulting from different headgear forces in a macerated human skull

The effects of headgear on maxillary displacement and the resulting growth modifications are not completely understood, especially regarding the complex relationships between initial and secondary skeletal reactions on one hand and the influence of the direction and magnitude of the applied force on the other. The aim of the present investigation was to study, by means of holographic interferometry, the initial bone displacement occurring in response to headgear traction applied at different force magnitudes and in different directions. Orthopedic forces of 560 grams and orthodontic forces of 354 grams were stimulated on a macerated human skull. The forces came from from high-, straight-, and low-pull headgear traction directed above, through, and below the center of resistance of the maxillary first permanent molars. Immediate skeletal changes were recorded by laser holography. Initial displacements of the maxilla and zygomatic arch in both horizontal and vertical planes were evaluated on frontal and lateral holograms. In most cases, both force magnitudes caused substantial displacements in both planes, albeit to different extents. Complex bending, and rotational, translational, and relative displacements were observed. The direction of displacement did not strictly coincide with that of the applied force. The results of this study indicate that both orthodontic and orthopedic headgear traction may lead to complex initial three-dimensional skeletal displacement in directions not always corresponding with the direction of the applied force.     

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%.      

气淬高炉熔渣冷却凝固相变特性仿真

为了探究实际喷吹参数对渣珠内部凝固换热过程产生的影响,研究了不同喷吹速率和渣珠粒径参数下、高炉渣珠落到冷渣器时、渣珠内部温度场及固液相变规律,获得了不同气淬参数对高炉渣气淬渣珠冷却过程中换热情况的影响。结果表明,气淬高炉熔渣能够加快渣珠表层凝固形成固态渣壳,但是整个凝固过程并不均匀。随着喷吹速率的增大,渣珠凝固速度增快,渣壳形成时间缩短;粒径越小,渣珠换热速度越快,发生完全凝固时间越短。1 723 K出渣温度、350 m/s喷吹速率、粒径3 mm渣珠落入冷渣器时能够获得最快凝固速率,形成完整渣壳,同时节约能耗。     

Human calorimetry in sealed hermetic enclosures

The paper gives the results of an experimental assessment of personal biocalorimeter and calorimetric garment. The paper is addressed to biologists, physiologists and physicians investigating heat exchange and thermal regulation of the human body as well as to thephysicists developing calorimetric theories and methods. It presents theoretical concepts underlying direct calorimetry of a suited man and contains a block-diagram of the biocalorimeter that was used to examine energy parameters of the human body, including metabolic rate, heat production, heat release and heat balance. The data obtained were statistically treated and heat effects were characterized by empiric expressions. It was for the first time in medical practice that the personal calorimeter and calorimetric garment made it possible to accumulate information on the thermal state of the human body. This information helps to diagnose the health condition of man, to standardise environmental parameters in aviation, space and such like suits and to automatize their maintenance in experimental and real life situations.     

Incidence of asystole in electroconvulsive therapy in elderly patients

We hypothesize that selective brain cooling (SBC) can occur in hyperthermic humans despite the fact that humans have no carotid rete, a vascular structure that facilitates countercurrent heat exchange and that is located at the base of the skull in some mammals. We postulate that an increase in emissary and angular ocular venous flows contributes to SBC. The efficiency of SBC is increased by evaporation of sweat on the head and by ventilation through the nose. A body position that increases the intravenous pressure gradient across the skull increases emissary flows and hence enhances the efficiency of SBC. The validity of using tympanic temperature as an index of brain temperature is also postulated.     

基于遗传算法的工作辊温度场参数优化模型

针对热连轧机工作辊热辊形计算中温度场模型的热交换等参数难以确定的问题 ,建立了基于遗传算法的参数优化模型 ,可以解决复杂条件下的热参数的求解问题。利用优化参数计算的轧辊温度场与实际测量结果一致。     

空分设备换热器设计及温差选取

介绍了一般空分设备换热系统的设计软件环境,同时对空分设备的换热阻力设计,对气体、液体以及气液混合物的换热及换热器温差选取进行了详尽的阐述。随着空分行业的蓬勃发展,研究并合理地分析应用空分换热系统对提升行业设计能力有重大意义。     

内翅片管换热器传热性能实验研究

以内翅片管作为换热器传热元件，通过实验方法对其传热性能进行研究。在考虑了内翅片使管内传热面积增大，传热性能提高这一特点，经过反复实验，回归出了内翅片管传热的准则方程式。并对与内翅片管结构和特点相近的内插管，在外型尺寸相同、实验条件相同的前提下，进行了传热性能实验研究和比较。     

A case of bilateral optic neuropathy and recurrent transverse myelopathy associated with perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA)

The purpose of this study was to evaluate skeletal and dental effects of bionator headgear combination appliances on patients in development period with Class II, division 1 malocclusion. The comparison of computerized X-ray cephalometric measurements between the 26 treated children and 26 untreated children was made. The results showed that ANB angle was significantly reduced and horizontal mandibular growth development tended to be normal in the treated group. It was suggested that the bionator headgear combination appliance can restrain the maxillary growth early and promote the forward mandibular growth which contribute the functional jaws correction.     

Comprehensive Mathematical Model and Optimum Process Parameters of Nitrogen Free Blast Furnace简

According to different energy utilization in different regions, blast furnace is divided into raceway zone, bottom heat exchange zone （BHZ）, thermal reserve zone （TRZ）, and top heat exchange zone （THZ）, and a mathe- matical model of nitrogen free blast furnace （NF-BF） is established. The optimum process parameters of two kinds of nitrogen free blast furnaces are calculated by the new mathematical model. The results show that for the nitrogen free blast furnace with a single row of tuyeres, the optimum process parameters are coke ratio of 220 kg/t, coal ratio of 193 kg/t, and volume of recycling top gas of 577 m3/t; for two rows of tuyeres, the process parameters are coke ratio of 202 kg/t, coal ratio of 211 kg/t, volume of recycling top gas in upper area of 296 m3/t, and volume of recy- cling top gas in lower area of 295 ma/t. Energy balances are reached in different regions. Theoretical combustion temperature （TCT） in raceway zone is largely affected by different processes, and a lower TCT should be adopted for the single row of tuyeres, but for two rows of tuyeres, a higher TCT should be maintained. Compared with tradi- tional blast furnace, in NF-BF, the emission of CO2 would be reduced by 45.91% and 49.02G for a single row of tuyeres and two rows of tuyeres, respectively, and combined with CO2 sequestration technology, zero emission of CO2 could be realized.     

间壁式固体散料余热回收器的开发

分析了固体产品及废渣等余热回收的必要性,设计开发了固体散料余热回收装置.介绍了该热回收器的结构特点及其应用.同时,应用Fluent软件模拟对比了热回收器管内放置强化传热插件前后的换热过程,验证了插件的强化换热效果.