Waste Heat Recovery from a Drier Receiver of an A/C Unit Using Thermoelectric Generators

Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer receiver(FDR)of an air conditioning(A/C)system,which would otherwise go to waste.The study aims to build a set of thermoelectric generators(TEG)to collect the waste heat of the FDR and generate low-power electricity.A novel electrical circuit with two transformers is designed and fabricated to produce a more stable voltage for operation and charging.The thermoelectric generator(TEGs)was installed on the FDR of the A/C unit.The test showed that climate conditions have a significant impact on the output power generated from the system.The results showed that the peak voltage recorded in the current study is 5.2 V per day(wet,cold,and wind weather)with an output power of 0.2 W.These values are acceptable for powering the load and charging a single battery with 3.5 V as the voltage increases battery 0.1 V/20 min charge.A case study of operating the emergency signs in a building was considered.The current heat recovery system is deemed to be easily installed and can be connected to a network of TEGs to produce more power.

Numerical simulation of gas-liquid two-phase jet flow in air-bubble generator

Air-bubble generator is the key part of the self-inspiration type swirl flotation machines,whose flow field structure has a great effect on flotation.The multiphase volume of fluid(VOF),standard k-ε turbulent model and the SIMPLE method were chosen to simulate the present model;the first order upwind difference scheme was utilized to perform a discrete solution for momentum equation.The distributing law of the velocity,pressure,turbulent kinetic energy of every section along the flow direction of air-bubble generator was analyzed.The results indicate that the bubbles are heavily broken up in the middle cross section of throat sect and the entrance of diffuser sect along the flow direction,and the turbulent kinetic energy of diffuser sect is larger than the entrance of throat sect and mixing chamber.

Influence of Different Vortex Generators on Heat Transfer in Direct Air-Cooled Condensers

通过数值模拟研究了矩形小翼、三角小翼、梯形小翼、柱面梯形翼、柱面三角翼和柱面矩形翼等6种涡流发生器分别安装于直接空冷凝汽器单排蛇形翅片扁管中的压降和换热性能。Re数在600~1800范围内,涡流发生器采用相同高宽比、尾高、攻角以及安装位置。结果表明：矩形小翼的换热及压降增大最多,Re=1729时,相比平直翅片分别增加了14.27%和18.32%。Re=1 729时,柱面梯形翼的压力损失比矩形小翼少4.7%,换热低1.5%。当以（j/j0）/（f/f0）1/3作为综合换热性能评价标准时,柱面梯形翼的综合换热性能最好。另外,考察了柱面梯形翼倾角的影响（0°、6°、12°、20°、24°和26°）,相同工况下,倾角为12°的柱面梯形翼换热最好（较平直翅片增强4.29%~14.1%）、压降最小（增大7.5%~12.8%）且综合换热性能最好。柱面梯形翼因其迎流面积与斜边长度的匹配以及流线型柱面,具有良好的强化传热效果以及较小的压降。

Millimeter Scale MEMS Air Turbine Generator by Winding Wire and Multilayer Magnetic Ceramic Circuit

This paper provides a new system and concept concerning to MEMS air turbine power generator. The generator was composed of the MEMS air turbine and the magnetic circuit. The magnetic circuit was fabricated by multilayer magnetic ceramic technology and achieved monolithic structure which included high permeability material and three di-mensional helical conductor patterns inside. Although the output power was micro watt class, some features were extracted by comparing to the simple winding wire type magnetic circuit. In the power density measurement, almost same output power density was extracted though the turn number of the winding wire type was more than that of monolithic type. Also the resistance of the conductor was quarter of the winding type. The maximum output voltage and the maximum power of the monolithic generator was 6.2 mV and 1.92 μVA respectively. The DC conductor resistance was 1.2 Ω. The energy density was 0.046 μVA/mm3. The appearance size of the monolithic type was 3.6, 3.4, 3.5 mm, length, width and height respectively.

Urban Surroundings Influence on Air Temperature in a Small Urban Area of Curitiba-Brazil

The formation of urban climates constitutes a distinctive system intrinsically linked to the urban environment. This study aims to delve into the impact of the urban environment on climatic variables. The Urban Weather Generator (UWG) algorithm was employed to generate climatic data, facilitating the creation of an epw climate file that corresponds to the urban characteristics surrounding the Centro Politécnico campus at the Federal University of Paraná (UFPR). Comprehensive analyses encompassing land use, occupancy patterns, albedo, surface absorption, anthropogenic heat, and architectural attributes were conducted. A comparative assessment between the UWG-derived air temperature values and meteorological station data revealed that the UWG effectively characterizes the air temperature patterns around the UFPR campus. The anticipated air temperature values consistently surpass the original dataset (SWERA), which was utilized as input, primarily during the hours from 3 p.m. to 7 a.m., showcasing the unmistakable urban heat island phenomenon.

Hot Air Generator Using Natural Convection Flow in a Heated Channel

Hot air producing is one of the most important engineering applications in recent years.It is a technique used in various thermodynamic systems,such as home heating systems,food dryers.One of the main problems impeding the spread of hot air producing technology is the lack of homogeneity of the heat flow coming from hot air generators as well as an inadequate flow rate.The most of the existing hot air generators require to be supported by systems that can increase the low volumetric flow and the air temperature of these generators,through increasing the speed of the flow of air emitted or lifting the drawer Heat,which contributes to raising the overall cost.However,to improve the thermal and dynamic quality of the hot air flow produced by the generator,a numerical investigation of the free convection flow inside two different configurations is presented in this thesis.The primary objective of this work is to predict the behavior of the flow inside tow configurations,the first one consists of a vertical cylinder with heated walls,and the second configuration is an open-ended vertical cylinder with a hot disc placed at the entrance(configuration A,configuration B).This work characterizes through the examination of this flow,the variables that control an air emission with high flow rate and a high and homogeneous temperature to represent the appropriate criteria that should be respected to obtain a hot air generator overcoming the previously mentioned constraints.Furthermore;the results of this work show the influence the boundary conditions and Rayleigh number on the resulting flow.

Experimental assessment of a new salt aerosol generator for measuring efficiency of automotive air filters

Generation of polydisperse KCl aerosol with a new salt aerosol generator was investigated.Special attention was paid on particles with diameters between 3 and 10 μm.The main improvement consists of the different routes of KCl solution droplets.In traditional generators,the solution droplets travel through one cylinder;while in the case analyzed here,after spray atomization,the droplets travel through two cylinders in series.The first cylinder was fed with warm air and the second one with cold air.In such way,the complete evaporation of the water from the droplets can be ensured.The influencing factors of the generated aerosol size distribution were investigated.The data measured show that the concentration of generated aerosol becomes higher both increasing the flow rate of the KCl solution injected in the first cylinder and increasing the concentration in the solution.The temperature of solution influences mainly the generation of smaller KCl particles(0.3-3 μm).The amount of hot air used in the generation process increases the concentration of larger KCl particles(>3 μm) while cold air does not have the same effect.The aerosol generator is able to generate KCl aerosol stably.This instrument can be used effectively for testing air filters for automotive.

Analyses of an air conditioning system with entropy generation minimization and entransy theory

In this paper,based on the generalized heat transfer law,an air conditioning system is analyzed with the entropy generation minimization and the entransy theory.Taking the coefficient of performance（denoted as COP） and heat flow rate Qout which is released into the room as the optimization objectives,we discuss the applicabilities of the entropy generation minimization and entransy theory to the optimizations.Five numerical cases are presented.Combining the numerical results and theoretical analyses,we can conclude that the optimization applicabilities of the two theories are conditional.If Qout is the optimization objective,larger entransy increase rate always leads to larger Qout,while smaller entropy generation rate does not.If we take COP as the optimization objective,neither the entropy generation minimization nor the concept of entransy increase is always applicable.Furthermore,we find that the concept of entransy dissipation is not applicable for the discussed cases.

Correlation Dimension in Fault Diagnosis of 600 MW Steam Turbine Generator

GP algorithm of correlation dimension computation is ameliorated which overcomes the shortage of traditional one. Improved process of GP algorithm takes the influence of temporal correlative pairs of points on correlation dimension into account and promotes the computational efficiency prominently. Iterative SVD method is applied to remove the influence of noise on the result of correlation dimension. The faults of steam flow turbulence and oil film disturbance which occur in 600 MW Steam Turbine Generator are analyzed and whose correlation dimensions are computed. More distinct quantitative index than FFT is gained to distinguish two faults and it’s of little importance to apply correlation dimension to study the influence of various factors on steam flow turbulence fault for nonexistence of convergent floor in correlation integral curve, which presents a new way to learn the operational function of large capacity steam turbine generator and carry out comprehensive condition monitoring.

Heat Transfer Analysis in Cooling System of Hydropower’s Generator

Cooling process of power plant generator is handled via air-cooled radiators in which the cooling water is supplied from lake with its water temperature varies from season to season. In this study, the effect of temperature fluctuations of cooling water entering the cooling system has been examined via analysis of energy (NTU method) and exergy. The exergy analysis has been done by definition of efficiency coefficient for exergy of cooling media (water) and heating media (air). Besides, the effect of changing the cooling water temperature and flow rate entering the radiators on the cooling system performance has been studied. The results revealed the generator cooling system performance level held sufficient till the temperature of inlet water was kept under 293 k (20°C). On one hand, when the temperature of cooling water at the inlet rises to 12°C, the rate of heat exchange at radiators falls up to 34.3%. On the other hand, by water temperature passing the 12°C limit, the efficiency of cooling media exergy falls to 78% leading to efficiency rise in radiators’ heating media exergy level to 61%. According to the results of this study, changing flow rate of cooling media up to 40% gives rise to the efficiency coefficient of radiators’ cooling media exergy level to about 18.7%. While it does not affect the efficiency level of energy at radiators, the flow rate rise of cooling media may not be considered as a way to give rise to efficiency level of radiators.

Absolute Orientation of Molecules with Competing Hydrophilic Head Groups at the Air/Water Interface Probed with Sum Frequency Generation Vibrational Spectroscopy

建设性或破坏光谱在在在和频率产生(SFG ) 的接口上下面向的分子的组之间的干扰系列提供这些分子的组的绝对取向的直接大小。这条简单途径能被采用讯问除在 SFG 研究使用复杂绝对阶段测量以外的绝对分子的取向。我们在 p-cyanophenol ( PCP )使用了 CN 组是的分子内部阶段标准，并且我们由测量 PCP ， 35DMHBN ，和 26DMHBN 解决方案的混合物的水的表面的 SFG 系列在空气/水接口在 3,5-dimethyl-4-hydroxy-benzonitrile ( 35DMHBN )和 2,6-dimethyl-4-hydroxy-benzonitrile ( 26DMHBN )测量了 CN 组的 SFG 领域的阶段。结果证明 35DMHBN 让它的 CN 组指进水的阶段；当时 26DMHBN，类似于 PCP，让它的 CN 组指离开水的阶段。为在空气 / 水接口的 35DMHBN 和 26DMHBN 分子的 CN 组的 tilt 角度在 25 °附近是从接口正常的 45 °。这些结果在竞争因素的详细平衡的理解上提供了卓见，例如极的头组，氢结合和恐水病的效果的 solvation，等等，在在空气 / 水接口影响绝对分子的取向上。

气隙静偏心故障对永磁风力发电机定子绕组振动的影响

端部绕组振动是导致绝缘磨损和退化的关键因素之一,综合分析永磁风力发电机气隙静偏心故障前后定子端部绕组的振动特性。首先,推导正常情况和气隙静偏心故障下的气隙磁通密度,得到端部绕组的电磁力表达式;然后,基于电磁-结构耦合模型,得出绕组电磁力、应力应变等力学响应特性;最后,实测3 kW故障模拟发电机在正常和气隙静偏心故障情况下的定子绕组振动响应。实验结果与理论分析、有限元计算结果基本吻合。结果表明:气隙磁通密度随偏心程度的增加而增大(气隙减小处),随偏心故障加剧端部绕组电磁力/振动增大,绕组电磁力/振动以偶倍频为主。另外,直线段绕组和端部绕组的连接处为振动磨损危险位置。

自动飞行员复诵指令生成方法研究

为了提高效率,降低培训成本并推广使用计算机来取代管制模拟机中的飞行员席位,采用集成学习的策略来生成飞行员复诵指令。选用5个大规模预训练语言模型进行微调,并使用K折交叉验证来筛选出性能较好的4个模型作为基础模型来构建集成学习模型。所构建的集成学习模型在管制指令数据集上取得在本领域中的最优效果。在通用的ROUGE(recall-oriented understudy for gisting evaluation)评价标准中,取得R_(OUGE-1)=0.998,R_(OUGE-2)=0.995,R_(OUGE-L)=0.998的最新效果。其中,R_(OUGE-1)关注参考文本与生成文本之间单个单词的匹配度,R_(OUGE-2)则关注两个连续单词的匹配度,R_(OUGE-L)则关注最长公共子序列的匹配度。为了克服通用指标在本领域的局限性,更准确地评估模型性能,针对生成的复诵指令提出一套基于关键词的评价标准。该评价指标准基于管制文本分词后的结果计算各个关键词指标来评估模型的效果。在基于关键词的评价标准下,所构建模型取得整体准确率为0.987的最优效果,对航空器呼号的复诵准确率达到0.998。

针对连续暴露因素的广义倾向评分方法在环境健康领域中的应用

目的介绍针对连续暴露因素的广义倾向评分(GPS)方法原理,探索其在环境健康领域中的应用,为测量环境健康风险提供有效工具。方法利用北京市“空气污染与人群健康队列研究”基线调查数据(2017—2018年),评价针对连续暴露因素的GPS方法在大气污染对健康效应估计中的应用效果。结果应用针对连续暴露水平的GPS方法后,不同暴露水平人群的混杂因素均衡性得到明显改善。PM_(2.5)暴露每增加10μg/m^(3),高血压患病的风险增加比例从原来的10.3%上升到11.9%。结论针对连续暴露水平的GPS方法在一定程度上为大气污染与健康的关联研究提供更准确的流行病学证据。

高炉煤气的CCPP发电系统运行特性分析

以燃用高炉煤气的燃气蒸汽联合循环发电系统为研究对象,分析了燃气轮机进气温度、负荷和排烟温度及汽轮机负荷之间的关系。当燃气轮机进气温度低于-16℃时,汽轮机负荷降低12 MW;当燃气轮机进气温度超过20℃时,燃气轮机最高负荷约105 MW,比额定负荷低4 MW。燃气轮机进气温度过高或过低均会使系统的经济性变差。采取加热或冷却的措施维持燃气轮机进气温度在合理范围,可实现燃气蒸汽联合循环发电系统经济运行。

轴径向静态偏心故障下外转子永磁发电机电磁转矩特性分析

对外转子永磁发电机轴径向静态偏心故障下的电磁转矩特性进行了理论解析、仿真计算和实验验证。首先,在考虑齿槽效应影响条件下,引入磁导修正系数ε(θ),推导出轴径向静态偏心前后气隙磁密表达式,并考虑绕组分布情况,构建一种新型的永磁发电机轴径向静态偏心故障下相电流数学模型,在此基础上得到轴径向偏心下电磁转矩解析表达式。其次,通过有限元仿真计算得到外转子永磁发电机轴径向静态偏心下的电磁转矩波动特性。最后,在一台外转子永磁发电机上通过故障模拟实验实例印证了解析分析和仿真计算结果。结果表明:相较于正常情况,径向偏心时,电磁转矩以直流、二倍频、四倍频成分为主,随着偏心程度的加剧,电磁转矩的直流、二倍频、四倍频成分幅值将随着增大;轴向偏心时,电磁转矩谐波成分不变,随着偏心程度的加剧,各谐波成分幅值将随着减小。对外转子永磁发电机气隙偏心故障分析的一个重要补充,对此类问题的现场检测和鉴定具有参考价值。

大规模飞机排班问题研究综述

飞机排班是航班计划的关键环节,直接影响民航运输的安全和经济效益。随着中国机队规模的稳步扩张,大规模飞机排班问题的研究愈发迫切;然而,早期基于连接网络或时空网络的机型指派模型及侧重运营收益、维修需求或鲁棒性的飞机排班问题模型,在问题规模、约束条件数量等方面往往受限,不能满足大规模飞机排班需求。本文在分析各类排班问题关联性和局限性的基础上,归纳了大规模一体化飞机排班问题的模型及其求解算法,分析了各算法的适用范围、优势和不足,并发现:分阶段排班模型无法保证全局最优解,一体化飞机排班模型更具有实际意义;精确算法理论上可保证求得最优解,但运算复杂、耗时长、模型分解难度大;启发式算法计算速度快,步骤简单,但无法保证求解的质量和算法的稳定性。在此基础上,进一步提出了未来大规模一体化飞机排班问题的研究方向:①问题建模方面,可在优化航线网络结构的同时,综合考虑航线需求、时间均衡调度和个性化机组指派等因素,建立一体化飞机排班集成模型,以解决现有模型的局限性;②问题求解方面,可以将Benders分解和列生成算法相结合,将整个问题分解为相对简单的主问题和子问题的组合,减少求解难度;也可将精确算法和启发式算法相结合,在保证求解精度的前提下尽量减少运算耗时,提高求解效率。

减小喉罩型号改善通气效果的临床观察

目的探讨减小喉罩型号改善通气效果的临床观察。方法选取喉罩固定翼距门齿距离>3 cm的男性患者60例为研究对象,随机分为试验组和对照组,每组30例。比较试验组(3号喉罩)与对照组(4号喉罩)的通气优良率、FOB理想位置比例、气道峰压差及2组喉罩置入后的密封压、套囊内压、漏气率,比较2组喉罩远端与食道入口距离,观察2组喉罩拔出时带血丝情况,术后24 h咽部并发症发生情况(包括术后咽痛、声嘶)及咽痛持续时间。2组患者设置的呼吸参数相同。结果试验组喉罩置入后通气成功率、FOB理想位置置入比例及通气效果优良率提高,漏气率值降低,密封压值提高,喉罩远端距食道入口距离较对照组减小,术后咽部并发症发生率较对照组低,差异均有统计学意义(P<0.05)。结论对于喉罩固定翼距门齿距离>3 cm的患者,通过减小喉罩型号,使喉罩放置理想位置比例增加,通气优良率升高,漏气率降低,密封压值提高,咽部并发症降低,可改善喉罩通气效果,安全有效。

等离子体发生器导流板结构优化研究

高效滤芯是空气净化器的关键部件,当空气净化器中流向高效滤芯部分的送风不均匀时,会导致滤芯利用率较低,从而影响滤芯的过滤性能.为提高滤芯的使用效率进而改善装置的净化性能,可以在风机和高效滤芯之间放置导流型等离子体发生器,利用发生器的导流板使送风气流更均匀的吹向滤芯.为探究适宜的导流板结构参数,采用数值模拟的方法对不同结构参数导流板下的流动过程进行分析,通过对比滤芯使用率和送风均匀性等指标,给出适宜的导流板长度和张开角度设计方案.研究结果表明,对于本文研究的净化器尺寸,导流板设计长度为100 mm、张开角度为10°时的送风更均匀.优化后的尾部导流板结构简单、设计合理、使用方便,分散了送风气流的方向,更有利于提高后端高效滤芯的利用率和使用寿命.

大气污染与耳鼻咽喉急性疾病发病的时间序列分析

目的分析大气污染与耳鼻咽喉急性疾病发病的关系。方法回顾性收集2013至2018年杭州市主城区4家大型三级综合性医院(杭州市第一人民医院、浙江省中西医结合医院、杭州市中医院、杭州市第三人民医院)耳鼻咽喉急性疾病(包括急性扁桃体炎、急性会厌炎、急性喉炎、急性鼻-鼻窦炎、急性中耳炎)的门急诊量,并获取同时期该地区大气污染及气象参数数据。采用R统计软件建立广义相加模型,研究不同大气污染物浓度对耳鼻咽喉急性疾病门急诊量的影响,根据季节、年龄分层分析研究不同大气污染物浓度与门急诊量的关系。结果2013至2018年杭州市主城区耳鼻咽喉急性疾病门急诊总量333254人次,日均门急诊量为152人次。颗粒污染物(PM2.5、PM10)日均浓度每增加10μg/m^(3),在滞后第4天时对耳鼻咽喉急性疾病门急诊量的影响效应最大;气态污染物(SO2、NO2)日均浓度每增加10μg/m^(3),分别在滞后第4天、滞后第6天效应最大。单大气污染物模型中:年龄分层分析显示,在就诊的不同年龄亚组中,5~14岁年龄亚组中各大气污染物浓度与门急诊量的相关性最为明显,PM2.5、PM10、SO2、NO2浓度每升高10μg/m^(3),其效应排序为:NO2>SO2>PM10>PM2.5,RR值分别1.07(95%CI:1.05~1.09)、1.05(95%CI:1.03~1.07)、1.04(95%CI:1.02~1.05)、1.03(95%CI:1.02~1.05);季节分层分析显示,冷季(11月至4月)中大气污染物对耳鼻咽喉急性疾病门急诊量增加的影响强于暖季(5月至10月)(P<0.05)。在双大气污染物模型中,大气双污染物与耳鼻咽喉急性疾病门急诊量的相关性均有统计学意义(均P<0.05)。结论2013至2018年杭州市主城区大气污染物浓度升高与人群耳鼻咽喉急性疾病门急诊量增加相关,且具有滞后效应。耳鼻咽喉急性疾病的发病冷季效应强于暖季,5~14岁儿童的影响效应最为显著。这对制定耳鼻咽喉急性疾病的防治策略有重要参考价值。