The Application and Simulation of Fuzzy Adaptive PID in Household Heating Metering System

After heat is metered in each house unit,the heating system is regulated by variable flow.The temperature of the return w ater is controlled to regulate the flow to realize the temperature regulation.According to the characteristics of the temperature control w ith big inertia,pure time-delay and degeneration,a fuzzy adaptive PID controller is designed w ith the advantages of the fuzzy control and PID algorithm,and the simulation model is established according to the characteristics of heating metering system.Simulation results show that the fuzzy adaptive PID controller proposed has small overshoot,short oscillation cycle,high precision and strong anti-jamming capability in comparison w ith conventional PID controller,w hich could meet the requirement of the dynamic and steady-state performance of the heating process.

Formation of Face‑Centered Cubic Phase in Ti35 Alloy Under In Situ Heating Transmission Electron Microscopy

A thermally induced hexagonal close-packed(HCP)to face-centered cubic(FCC)phase transition was investigated in anα-type Ti35 alloy with twinned structure by in situ heating transmission electron microscopy(TEM)and ab initio calculations.TEM observations indicated that the HCP to FCC phase transition occurred both within matrix/twin and at the twin boundaries in the thinner region of the TEM film,and the FCC-Ti precipitated as plates within the matrix/twin,while as equiaxed cells at twin boundaries.The crystallographic orientation relationship between HCP-Ti and FCC-Ti can be described as:{111}FCC//{0002}HCP and<110>FCC//<1210>HCP.The HCP to FCC phase transition was accomplished by forming an intermediate state with a BB stacking sequence through the slip of partial dislocations.The formation of such FCC-Ti may be related to the thermal stress and temperature.Ab initio calculations showed that the formation of FCC-Ti may also be related to the contamination of interstitial atoms such as oxygen.

Paraffin–CaCl_(2)·6H_(2)O dosage effects on the strength and heat transfer characteristics of cemented tailings backfill

The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem.Paraffin–CaCl_(2)·6H_(2)O composite PCM was prepared in the laboratory.The composition,phase change latent heat,thermal conductivity,and cemented tailing backfill (CTB) compressive strength of the new material were studied.The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software.The results showed the following:(1) The new paraffin–CaCl_(2)·6H_(2)O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl_(2)·6H_(2)O.(2) The calculation formula of the thermal conductivity of CaCl_(2)·6H_(2)O combined with paraffin was deduced,and the reasons were explained in principle.(3) The“enthalpy–mass scale model”was applied to calculate the phase change latent heat of nonreactive composite PCMs.(4)The addition of the paraffin–CaCl_(2)·6H_(2)O composite PCM reduced the CTB strength but increased its heat absorption capacity.This research can give a theoretical foundation for the use of heat storage backfill in green mines.

The Heat Transfer Coefficients of the Heating Surface of 300 MWe CFB Boiler

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

Study on the Influence of Piloti on Mean Radiant Temperature in Residential Blocks by 3-D Unsteady State Heat Balance Radiation Calculation

Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.

A calculation method of the sensible heat flux by sodar

During the second course of USA - PRC joint air sea interaction experiment in 1986, the temperature structure parameters CT2 were measured by sodar over the Western Pacific Ocean. Based on similarity theory, a method is discussed to calculate the sensible heat flux over the ocean in unstable stratification. Becausehumidity is great over the ocean, so we have to consider the influence of water vapor structure parameter Ce2and the correlation coefficient betweene and T on the calculation of sensible heat flux using CT2 profiles measured by sodar. A new formula is suggested in terms of parameterization. The sensible heat flux calculated by sodar measurements is compared with that by bulk transfer method, and the results agree well.

Waste heat recovery from hot steel slag on the production line:Numerical simulation,validation and industrial test

Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.

小型风力机叶片电加热融冰功率的影响因素

电加热融冰技术作为解决风力机叶片覆冰最为行之有效的方法,有必要对融冰功率的影响因素进行研究分析。为此以小型风力机覆冰叶片为研究对象,建立了叶片电加热融冰数值计算模型,阐述了数值求解过程;进而定义了临界融冰功率和限时融冰功率,并给出了相应的计算过程;通过对旋转叶片进行人工覆冰试验并获得冰型,仿真分析了覆冰程度、环境温度、合成风速、叶片攻角、允许融冰时长等因素对融冰功率的影响。结果表明:限时融冰功率随着允许融冰时长的增加而减小,但认为允许融冰时长4~6min为宜;融冰功率随着覆冰程度的增加而减小;环境温度与融冰功率呈现负线性关系;合成风速与融冰功率呈现正相关;融冰功率随叶片攻角的增加整体呈现先增加后减小的规律,且在0°~4°之间出现最大值;限时融冰功率相较于临界融冰功率高1~2 kW/m^(2)。该文结果可为实际风力机叶片电加热融冰系统的运行与设计提供一定的帮助。

含端壁涡轮导叶红外测温的误差影响机理研究

由于涡轮叶片所处的工作环境复杂,受到壁面及燃气辐射干扰,导致测温十分困难。为进一步分析涡轮叶片表面在端壁影响下的温度分布情况,采用数值模拟结合自定义编程的方式进行了含端壁涡轮导叶的温度误差验证计算。利用自定义编程对经典同心球模型进行了角系数,有效辐射等可靠性验证计算,验证方法可靠。基于该方法进行了端壁与涡轮导叶各网格单元的角系数,叶片表面间的辐射换热计算,输出涡轮导叶的表面辐射特性分布,运用玻耳兹曼定律反推导出该工况涡轮导叶所受到的辐射能流分布情况;计算分析了不同误差影响机理下,含端壁的涡轮导叶温度误差分布情况,探明了热辐射环境下对叶片表面辐射特性的影响。结果表明:当进口黑体辐射温度在1 400~1 800 K之间,进口辐射强度是对叶片换热影响最大的因素;利用有效辐射和所计算的误差分布可知,进口辐射温度影响区域主要是叶片前缘区域,最大计算误差不超过2.82%;通过有效辐射及误差分布可见,出口黑体辐射温度的变化对于涡轮导叶的影响较小,受温度影响区域也主要为叶片前缘区域,最大计算误差不超过2.35%;叶片表面发射率与温度成正相关,当叶片表面发射率增大时,叶片表面温度随之均匀升高,在真实工况下,叶片材料物性的改变较小,在发动机设计中可以近似忽略由于叶片温度变化导致物性参数改变带来的影响。

不锈钢表面Al/Cu涂层制备与第一性原理计算

为了研究Al/Cu涂层中金属间化合物的生成顺序和形成机理,在304不锈钢基体表面制备了Al/Cu涂层。对试样进行热处理使得Al/Cu涂层原位反应生成金属间化合物,随后测试了涂层的高温抗氧化性能。采用第一性原理计算Al-Cu金属间化合物的焓、熵、吉布斯自由能和热容等数据。将热力学和扩散动力学相结合,提出有效生成自由能模型来预测化合物在Al/Cu界面的生成顺序。结果表明:Al/Cu涂层中首先形成Al_(2)Cu相,在Al/Cu界面处出现了AlCu相,加热时间增加至20 h后出现了富Cu的Al_(4)Cu_(9)相。由第一性原理计算得出,Al-Cu金属间化合物的形成顺序为Al_(2)Cu→AlCu→Al_(4)Cu_(9),与实验结果一致。此外,氧化实验结果表明,涂层具有良好高温抗氧化性能。

轴向柱塞泵热特性及热力学建模实验研究

针对轴向柱塞泵在高压和高速工况下发热过快的问题,对柱塞泵热特性和热力学建模进行了仿真分析与实验研究。首先,在摩擦副发热理论基础上,考虑了泵内油液搅动摩擦与轴承摩擦发热源,研究了柱塞泵内发热机理和传热分析的热特性理论;然后,根据柱塞泵部件复杂和固流态域区分度高的特点,阐述了所采用的控制体积法原理,将泵划分为5个控制体积后,建立了以各个控制体温度变化为导向的热力学模型;最后,采用光纤光栅温度传感器和蓝牙无线温度传感器,针对不同的控制体节点设计了传感器封装结构和布置方法,共同组成了轴向柱塞泵在线热监测系统,并进行了在不同压力条件下的对照实验,对理论模型进行了有效性验证与分析。研究结果表明:对比实验和仿真结果,模型温度变化与实际误差值在5%左右,验证了该模型能准确地反映和预测泵热力学变化过程。该结果为柱塞泵热力学状态监测提供了故障诊断基础,并为液压系统热管理系统设计提供了理论基础和设计依据。

超临界CO_(2)印刷电路板换热器热工水力特性研究

对于超临界CO_(2)布雷顿循环中的印刷电路板换热器,其复杂结构与工作介质的特殊物理性质将导致集总参数方法出现较大的计算误差。为提升印刷电路板换热器的换热参数的计算精度,本文基于Modelica语言,采取分节点建模方法,开发了印刷电路板换热器的热工水力特性计算程序,对其稳态运行时的换热参数进行了分析。结果表明:印刷电路板换热器的通道内超临界CO_(2)的对流换热系数沿流动方向发生显著变化。与设计值相比,分节点计算程序的最大相对误差小于3%,计算精度相比于集总参数方法显著提升,因此有必要采取分节点计算方法以提高计算精度。研究结果可为超临界CO_(2)布雷顿循环系统中印刷电路板换热器的设计和仿真提供参考。

基于插片散热器的某功放单元设计

设计一款可在室内机房环境条件下工作,总热耗约为2700 W,结构紧凑、散热方式简单、散热效果良好,可安装在19寸机柜内的功放单元。依据该功放单元工作原理、内部器件布局、热耗,综合考虑散热与结构要求,设计一种采用组合插片散热器强迫风冷的方案。通过功放模块和电源分组固定安装在分层的3个插片散热器上,同时与设备侧壁形成完整的风道的方式,实现了功放单元的强迫风冷散热;并对该设备进行了热传导与散热理论计算,同时运用仿真软件建立模型,进行数值分析。数值仿真结果显示,该功放单元正常工作热交换达到平衡状态时,功放模块外壳最高温度为64.2℃,满足设计要求。通过实物样机验证了该功放单元基于组合插片散热器结构设计方案的可行性,以及计算、仿真方法的合理性、正确性。

复合绝缘子无溢流覆冰增长数值模拟及自然覆冰试验验证

绝缘子覆冰对电力系统的安全可靠运行构成了严重威胁。目前,主要从试验角度定性解释伞裙结构对绝缘子覆冰形态、覆冰量的影响,少有基于覆冰增长机理的冰形数值模拟研究。因此以FXBW-35/70为研究对象,基于流体力学和热力学原理,计算分析了绝缘子表面冻结系数和对流换热系数的变化规律,建立了绝缘子无溢流覆冰增长三维数值模型,并进行了自然覆冰试验验证。结果表明,冻结系数随着温度、水滴直径和液态水含量的升高而降低;对流换热系数随着风速的增大而增大。绝缘子无溢流覆冰增长方向与位置有关,杆径覆冰主要沿径向增长,而伞裙边缘覆冰沿径向和轴向2个方向增长。模型计算得到的绝缘子覆冰特征参数与试验的误差均在15%以内,验证了模型的有效性。

太阳能真空集热管热损分析与试验研究

基于热平衡法提出了一种动态热平衡热损计算方法,并进行了验证,同时分析了环境温度、进口温度、流量对真空集热管热损的影响。结果表明,热损随着环境温度的降低、进口熔盐温度的升高和熔盐质量流量的降低而增大;当辐照强度在700 W/m2以上时,真空集热管获得的热量大于热损并能稳定工作,说明槽式光热电站在东南沿海等太阳能资源相对不足的地区有一定的适用性。

夏热冬冷地区动态传热保温设计室外典型气象参数确定方法

GB50176-2016《民用建筑热工设计规范》中围护结构外墙保温设计采用稳态方法,但夏热冬冷地区由于特有的建筑运行模式,使外墙传热方向发生逆转,故稳态方法难以满足冬季室内热环境水平提升的实际需求。提出一种基于动态传热的冬季外墙保温设计室外计算温度确定方法,探究室外干球温度和太阳辐射逐时波动的最不利组合,将保温设计的目标由“日”提升到“时”。基于典型城市2007-2017年逐时气象数据,以外墙内表面温度的累计不保证天数作为热工设计指标,将累计不保证天数恰好不为0(指各朝向外墙内表面温度低于室内基本热舒适条件下所能允许温差的天数)时作为典型日挑选的依据,并将典型日出现频率最高的日期作为室外计算温度选取的依据,获得冬季保温设计典型日,并获得了典型日计算时长的影响。可为夏热冬冷地区围护结构外墙保温设计室外计算参数的挑选提供理论支撑。

垂直管内高质量流速超临界CO_(2)换热特性

利用已有的流动传热实验数据,对不同湍流模型预测超临界CO_(2)(S-CO_(2))传热能力进行了评价及选取,确定了SST k-ω湍流模型为最优模型。分析了入口温度、热流密度、质量流速、浮升力和流动加速效应对内径为10mm的垂直加热管内S-CO_(2)的对流传热特性的影响。结果表明:在一些工况条件下Bu<10^(-5)、Bu^(*)<5.6×10^(-7)和K_(v)<3×10^(-6)并不满足,表明浮升力和流动加速度效应并不能解释高质量流速下的数值模拟结果。基于超临界类沸腾理论,建立了垂直加热管内S-CO_(2)类沸腾传热模型,并阐述了S-CO_(2)传热恶化现象,径向方向上S-CO_(2)热物性和湍流的详细分布表明超临界传热受类气膜的厚度、类气膜的热性质和近壁区湍流动能的影响很大,成功解释了SCO_(2)在高质量流速下的传热机理。最后引入超临界沸腾数SBO,提出了适用高质量流速的传热关联式。

含盐液滴运动传热传质特性及其影响因素

船舶在极地等气候寒冷恶劣的海上环境航行时,海水飞沫易导致其上层结构结冰,严重时对船舶航行及室外环境作业安全造成威胁。准确预测海水飞沫结冰,对确保极地区域安全作业具有重要意义。海水飞沫结冰和纯水飞溅结冰的主要区别在于盐度对结冰的影响,对于结冰问题,通常将海水飞沫简化为含盐的液态水滴(即含盐液滴,简称液滴)。数值模拟是研究含盐液滴结冰的重要手段,含盐液滴运动-传热传质过程是其结冰数值模拟的关键环节,决定了液滴撞击特性及与结冰相关的撞击液滴的物理量。本文在SHIPICE传热模型的基础上,提出了含盐液滴在运动过程中考虑质量损失及盐度变化的传热传质耦合模型;基于NNW-ICE平台,发展了拉格朗日框架下含盐液滴运动-传热传质耦合数值计算方法并开发了相应计算程序,实现了含盐液滴运动-传热传质过程的模拟;探究了含盐液滴运动-传热传质过程中的关键影响因素,系统分析了不同来流速度、温度、相对湿度和液滴粒径条件下的传热传质效应,为进一步发展含盐液滴结冰数值计算方法奠定了基础。

余热回收型吸收式制冷循环系统的能效优化研究

在21世纪的能源利用领域,随着化石燃料的过度开采和资源紧张,人们不断寻找着一种高效、可持续的能源利用方式。面对这样的挑战,能源的回收和高效利用显得尤为关键。基于此,提出一种溴化锂吸收式制冷系统,该系统专门用于回收低温能源和工业废热等余热回收。首先,通过使用溴化锂水溶液的状态方程以及水和蒸汽的状态方程,建立了数学模型,以获取系统热力计算所需的状态参数;其次,将最大化性能面积比作为目标函数进行优化设计,明确了不同工作条件下各个热力学参数与系统性能之间的内在联系,计算了系统中各环节热力参数;最后,通过仿真分析的方法,对制冷系统中的关键参数进行了深入探讨,重点考察了那些可能对系统性能产生显著影响的因素,包括但不限于吸收剂浓度、循环泵速和热交换器效率等。结果表明:所设计的系统将热力系数提高了11.32%,同时总换热面积下降了1.82%。该系统成功地回收了废热并实现了制冷效果,展示了广泛的应用前景。

耦合海水淡化的船舶柴油机排气净化装置设计

为综合高效实现船舶柴油机烟气废热回收海水淡化以提升尾气净化率,本文以KincaidB&W6L90GE型船舶柴油机为研究对象,提出一种耦合海水淡化的船舶柴油机废气高效净化技术,介绍了耦合海水淡化的船舶柴油机排气净化技术原理,理论设计计算耦合海水淡化的船舶柴油机废气净化系统的蒸发段和冷凝段,得到烟气余热回收制淡系统蒸发段和冷凝段的换热系数分别为42.29W/(m^(2)·℃)和1067.42W/(m^(2)·℃)、换热面积分别为517.31m^(2)和38.26m^(2),该系统整体尺寸为Φ6m,总高度为6.452m,并进一步得到船舶烟气净化系统整体尺寸为Φ4.0m,总高度为9.66m,完成了系统的整体尺寸设计计算和结构布置。