基于运行参数的加热器疏水端差简易计算模型

传统的加热器疏水端差应达值计算是在具备详细结构参数和运行参数的基础上通过理论计算得出,而实际计算中不同加热器结构参数的搜集比较困难。对于结构参数一定的加热器,通过计算加热器各运行参数对疏水端差的影响,建立了一种新的只考虑运行参数的加热器疏水端差计算模型。利用660MW和300MW机组卧式加热器运行参数验证结果表明,该模型精确度高,计算简单,有利于快速计算加热器疏水端差应达值。     

直接空冷凝汽器仿真模型的研究

充分考虑凝汽器结构参数和工质物性参数对传热过程的影响,运用工程模块化建模方法,建立了直接空冷凝汽器各单元凝结换热及整体压力计算的动态仿真模型.基于STAR-90仿真支撑平台,开发了相应的模型算法.建立了某200 MW直接空冷机组凝汽器系统的整体仿真模型,对在不同负荷下的静态仿真精度以及各种扰动下的动态特性进行验证,表明该模型能满足工程应用要求.     

回水温度变化对热网加热器动态特性影响分析

将热网加热器的过热段、凝结段和疏冷段统一为整体,并考虑热网加热器本身的蓄热能力,将循环水温度突变作为扰动,通过求解动态数学模型来求解扰动下的热网加热器循环水出口温度、热网加热器抽汽流量和热网加热器内饱和温度等参数的变化趋势,得出热网加热器由动态扰动到重新回归静态的变化过程。最终,通过动态过程的稳定时间的长短来分析热网加热器中各参数平衡速度的快慢。     

锅炉蒸发系统动、静态特性一体化计算方法

该文建立了锅炉蒸发系统热力过程动、静态特性的一体化模型。利用该一体化计算模型既可进行锅炉蒸发系统的动态过程分析，又能够完成锅炉蒸发系统的静态校核计算，同时还可以确定出锅炉蒸发受热面中热力参数的动态、静态分布情况。     

锅炉参数变化时汽轮机系统的仿真算法

采用实时仿真算法对锅炉-汽轮机系统动态特性进行了整体性模拟。首先建立了详尽的汽轮机各部件动态数学模型和热力系统流量网络计算模型，特别是除氧器、表面加热器和凝汽器的通用动态数学模型；然后，将汽轮机系统动态模型与锅炉系统动态模型连接为整体仿真模型，并进行仿真。该文还列出了锅炉某些参数变化时汽轮机系统几个关键基本参数仿真结果。对电站锅炉-汽轮机系统的整体性模拟可以对运行人员进行更加全面的指导，并且为进行单元机组的瞬态性能计算，进而修正稳态性能计算结果奠定了基础。图12参3     

基于Dymola平台的超超临界二次再热机组切除高压加热器动态仿真

为了分析某660 MW超超临界二次再热燃煤机组快速响应动态特性,基于Modelica/Dymola平台建立了高精度二次再热机组动态仿真模型。为了验证模型的可靠性和精确性,将仿真结果与不同负荷下设计数据进行比较发现,模型在不同负荷下的静态误差均在±5%以内。针对目前灵活性运行对电网负荷快速响应要求,模拟机组在分别切除4个高压加热器后负荷的瞬态响应特性,并具体分析了切除1号高压加热器对汽轮机抽汽以及锅炉主要受热面烟气侧与蒸汽侧动态特性的影响,获得了切除高压加热器后汽轮机抽汽变化动态过程和发电功率快速响应情况,以及锅炉烟气侧与蒸汽侧的参数变化动态过程。模拟结果表明：切除4个高压加热器均可以有效增加机组瞬时电负荷,分别可以达到29.8,15.6,8和6 MW,快速发电功率增加持续时间达到1 100,100,130和250 s,说明切除高压加热器可以改善二次再热燃煤机组对电网自动发电控制(AGC)的快速响应特性。     

锅炉过热系统动、静态特性一体化计算方法

该文建立了锅炉过热系统热力过程动、静态特性的一体化计算模型。利用这一体化计算模型既可以进行锅炉过热系统的动态过程分析，又能够完成锅炉过热系统的静态校核计算，同时还可以确定出锅炉过热系统热力参数的动、静态分布情况。     

两类实用的单相受热管集总参数动态修正模型

通过惯性补偿的方法,对锅炉单相受热管的两类常用的集总参数模型进行动态修正,得到两类高精度的集总参数动态修正模型;该两类修正模型均能较好地反映热工对象的分布参数特性,既适用于全工况高精度实时仿真培训系统研究,又适用于电站全程控制系统仿真研究。两类修正模型均具有建模简单、计算方便及使用性强特点,有较广泛的工程应用前景。图６参５     

汽轮机叶片三维有限元模型的建立及静态与动态应力分析

为了获得汽轮机叶片更为真实详细的应力状态，建立三维实体模型并采用合适的有限元模型进行分析是非常必要的。本文给出了完成叶片三维应力分析所必须的三个步骤并提供了相应的方法：叶片三维有限元计算网格的自动生成，合适的静态与动态应力有限元分析模型的建立，有限元分析结果的后处理方法。文中最后还使用本文提供的方法分析了一个汽轮机末级长叶片和五片成组叶片的静态与动态应力，计算结果与实验数据进行了对比，表明了计算模型的精确度以及应力分析系统的工程实用性。     

人工神经元网络在汽液物性参数拟合中的应用

在热能系统的模拟与综合中,必须首先解决物性参数的计算问题。本文分析了现有物性参数的一些常用计算方法,提出了利用人工神经元网络对具有静态特性的物性参数进行拟合的计算机方法。在简单介绍人工神经元网络,特别是BP算法的基础上,通过对饱和水蒸汽的物性参数进行拟合的实例分析,认为人工神经元网络对于具有静态特性的饱和水蒸汽的物性参数具有很好的拟合效果,非常适合于实际的工程应用,对于其它具有静态特性的气体或液体的物性参数拟合也有参考价值。     

MIXED CONVECTION IN A CHANNEL WITH POROUS MULTIBLOCKS UNDER IMPOSED THERMAL MODULATION

This study is made of an enhancement of a mixed-convection heat transfer in a channel containing multiple porous blocks heated from below. The heat flux from the most upstream heater varies in a sinusoidal form, while other heaters have a constant heat flux. The Brinkman-Forchheimer-extended Darcy model and two-equation energy model are adopted to characterize the flow and temperature fields inside porous regions. The explicit effect of thermal modulation at the upstream heater is examined by acquiring comprehensive numerical solutions. The heat transfer enhancement is pronounced at the far downstream heaters when resonance is realized. The resonance frequency is close to the characteristic frequency of the system, which scales with the time for the main stream to travel from a heater to a neighboring heater. The evolutions of flow and temperature fields are exemplified to provide physical interpretations. The effects of pore density and of porous block height are reported. The benefit of heat transfer augmentation, as opposed to the increased friction factor, is assessed to justify the use of thermal modulation in the upstream heater.     

Thermal behavior of a porous electric heater

The performance of a proposed porous electric heater is investigated. The porous heater exchanges heat with the working fluid through its large volumetric surface area. As a result, it produces lower surface temperature as compared with the conventional heater for the same imposed heating power. Two mathematical models are presented to describe the thermal behavior of both heaters. Axial diffusion is included in the governing equation of the solid conventional heater. The predictions of both models are compared at different operating conditions where it is found that porous heaters have much better thermal performance than the conventional heaters.     

Design and Analysis of Infrared Heating with Overlapping Heater Array Scheme for Industrial Application

A recently developed infrared (IR) local heating method is fairly effective to reduce springback of advanced high strength steel in manufacturing processes of car chassis. Although parabolic heaters, consisting of an IR lamp located on the focus of a parabolic reflector, can reduce springback in stamping processes, non-negligible temperature changes are generated in the heated area. For this reason, an improved heater has been required for the IR heating method. In this work, an overlapping heater array is designed to solve the problem of the parabolic heater for the IR local heating method. The overlapping heater array can reduce the temperature change in the heated area. In the overlapping heater array, the parabolic heaters are connected in series. The connected parabolic heaters are then placed on both sides of a thin sheet metal and intersected to reduce the temperature change. In order to design a more efficient overlapping heater array, a simple design parameter was employed. The numerical and experimental verifications have shown that the overlapping heater array drastically reduces the temperature change in the heated area.     

基于灰色-层次理论的热水器综合评价研究

对几种常用综合评价方法进行了分析,提出运用灰色理论和层次分析理论联合建立综合评判模型.从安全性、经济性和使用性3个方面确定了热水器的评价指标体系,并运用新建的综合评判模型对4个不同类型的热水器产品的综合性能进行了评价.结果表明太阳热水器综合性能最佳.     

Three-Dimensional Study of Natural Convection in a Horizontal Channel With Discrete Heaters on One of Its Vertical Walls

Three-dimensional natural convection in a horizontal channel with an array of discrete flush-mounted heaters on one of its vertical walls is numerically studied. Effects of thermal conductivities of substrate and heaters and convection on outer sides of the channel walls on heat transfer are examined. The substrate affects heat transfer in a wider range of thermal conductivities than do the heaters. At lower heater thermal conductivities a higher heat portion is transferred by direct convection from the heaters to the adjacent coolant. However, higher substrate conductivity is associated with higher heat portion transferred through the substrate. The innermost heater column is found to become the hottest heater column due to the lower coolant accessibility. The heat transfer in the channel is strongly influenced by convection on the outer sides of the channel walls. Correlations are presented for dimensionless temperature maximum and average Nusselt number.     

Three-dimensional numerical simulation of natural convection in an inclined liquid-filled enclosure with an array of discrete heaters

A three-dimensional (3-D) numerical model is developed to investigate the effects of inclination on the heat transport processes in a liquid-filled rectangular enclosure of finite size. The interactions of flows tangential and normal to the heater surfaces in an inclined enclosure cause a slight oscillation in Nusselt number. Inclination has little effects on the average heat transfer characteristics except configurations close to the conduction case with heaters on top leading to a sharp decrease in Nusselt number. The critical Rayleigh number of 1708 is also observed in the present study regardless of inclinations. Heat transfer from discrete heaters is non-uniform. Maximum Nusselt number occurs at the heater leading edge and decreases towards the trailing edge. Correlations for the row average Nusselt number vs. Rayleigh number at various inclination angles are presented. By taking the average of the discrete heater array, the numerical results compared well with the empirical correlations obtained from a single heater plate in literature.     

Comparative study of three thermosyphon solar water heaters made of flat-plate collectors with different absorber configurations

The paper presents a comparative study of three solar water heaters made of flat-plate collectors with different absorber configurations. The performance of the three solar water heaters is assessed under the same conditions. The collectors have the same surface area and are glazed. The theoretical model for each collector type, with the transient effects taken into account, is based on a control volume. By considering a small element of the collector in each case and the storage tank, six partial differential equations were developed for each solar water heater and were solved numerically for a cloudy day. This study shows that the thermal performance obtained with the solar water heater using the absorber-pipe lower bond configuration in the solar collector is always greater than the two others. These results showed that the solar water heater made of the absorber-pipe lower bond configuration is more efficient than the other systems.     

Performance study of thermosyphonic circulation solar water heaters using packed bed collectors

In the present investigation the performance behaviour of thermosyphonic circulation solar water heaters using packed bed collectors has been analysed. Iron chips, gravels and stones have been used as packing materials. Average tank water temperature, collector as well as system efficiency and mony pay-back for these packed bed solar water heaters are compared with those for solar water heater using a plane collector. Experimental results reveal that the performance of solar water heater improves appreciably by packing its collector with packing material. Among the packed-bed solar water heaters tested the iron chips packed-bed solar water heater gives the overall best performance.     

Bubble nucleation on micro line heaters under steady or finite pulse of voltage input

Nucleation temperatures on micro line heaters under steady voltage input were measured precisely by obtaining the I-R (current-resistance) characteristic curves of the heaters having dimensions of 50 μm in length, 3 or 5 μm in width, and 0.583 μm in thickness. The bubble nucleation temperature on the heater with 3 μm width is higher than the superheat limit, while the temperature on the heater with broader width of 5 μm is considerably less than the superheat limit. The nucleation temperature under a finite voltage pulse input was also measured for 5-μm width heater. The nucleation temperatures were also estimated by using the molecular cluster model for bubble nucleation on the cavity free surface with effect of contact angle. The bubble nucleation process was observed by a microscope/35 mm camera unit with a flash light of μs duration.