Performance of air conditioners with a gas-liquid separation condenser and one-tank laminated evaporator

In this study, a parallel flow condenser and laminated evaporator for an automotive air-conditioning system were modified to improve performance. Gas-liquid separation type condensers, in which the condenser and receiver drier are integrated, and one-tank laminated type evaporators were developed, and their performances were investigated experimentally using HFC-134a. Heat transfer characteristics in the condenser are examined by means of air temperature, air velocity entering the condenser and inlet pressure of the refrigerant; heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, flow rate of air, outlet pressure of refrigerant and superheat. Pressure drops for both evaporator and condenser are also measured, and correlations for pressure drop are derived for the condenser and evaporator, respectively. Air velocity and mass flow rate of the refrigerant have a significant effect on the overall heat transfer coefficient, and flow pass is not significantly influenced by the cooling capacity of the condenser. The overall heat transfer coefficient of the evaporator increases as air flow rate, air temperature and relative humidity increases.     

Experimental study on performance of automotive air conditioning system using R-152a refrigerant

Recently, as climate changes have manifested worldwide, every country is making efforts to prevent ozone depletion and global warming. In the automotive industry, R-134a refrigerant is widely used in air conditioning systems because it has zero ozone depletion potential (ODP). Unfortunately, its global warming potential (GWP) is high. Therefore, alternative refrigerants are needed as a replacement for R-134a. R-152a is considered to be one of the better alternative refrigerants due to zero ODP and low GWP. In this paper, the performance of an automotive air conditioning system using R-134a and one using R-152a are compared experimentally at the bench level. The experimental apparatus simulated a real automotive air conditioning system consisting of a cabin and engine room structure. The cooling capacity, condensing capacity, coefficient of performance (COP) and power consumption characteristics of the automotive air conditioning system are evaluated by changing the air velocity entering the condenser and the compressor rotation speed with the optimized refrigerant charge amount. Also, the performance of the R-152a system was investigated by changing the thermostatic expansion valve which is set of values. The results of this study show that the R-152a system is slightly better than the R-134a system, not only under driving conditions but also under idling condition. R-152a refrigerant thus shows promise as an alternative refrigerant to replace the current standard, R-134a, in automotive air conditioning systems.     

基于平行流蒸发器结霜问题的试验研究及解决方案

平行流蒸发器具有紧凑、高效的特点,在汽车空调中使用得越来越多。但其存在冷凝水排放不畅、制冷剂在扁管内分配不均等问题,在高湿情况下易发生结霜现象。本文针对某平行流蒸发器,在不改动空调系统其它部件的前提下,通过调整蒸发器本身结构、温度传感器位置及温度区间,实现了无结霜、出风温度均匀,空调系统性能得以提高。     

HFC1061汽车驾驶室内空调系统的设计

空气调节系统的设计目标就是要使室内空气的温度，湿度和流速等项指标保持在一定的范围内。详细介绍了ＨＦＣ１０６１汽车驾驶室内空调系统的结构和工作原理，通过冷，热负荷的计算，成功地设计了该车的空调系统。     

汽车空调系统工作原理及故障诊断

作为汽车的重要组成部分,空调系统一直都在汽车中扮演着重要角色。驾驶员可以借助空调系统,对车内环境(如温湿度等)进行调节,既可提高车内人员舒适度,还可消除附着在挡风玻璃的雾气,避免影响驾驶员的视线。但是经过长时间使用以后,汽车空调系统不可避免地会出现各种问题。文章首先对空调系统的运行原理进行了简单描述,然后分别介绍了空调系统制冷量不足、不制冷以及制冷效果时好时坏三种情况下的故障诊断。     

二甲醚用作汽车空调制冷剂的实验研究

根据二甲醚的热物理性质对二甲醚的制冷循环性能进行了分析,并在R134 a汽车空调系统上对二甲醚的制冷性能进行了测试。结果表明:由于二甲醚的气相和液相黏度都比较小,使用二甲醚作为制冷剂可以减小系统的阻力,有利于系统制冷性能的提高。二甲醚可以直接灌注式替代R134 a,但会造成蒸发器出口过热度降低,需对膨胀阀弹簧预紧力进行调整,才能充分发挥二甲醚的制冷性能。     

汽车排气系统的流场分析与优化

给出了某汽车排气系统一维非定常流动的气体动力学方程组和三维模拟数学模型.建立了该汽车排气系统与发动机的联合模型,并利用此模型得到了排气系统进口温度、质量流量、密度等参数.以此作为边界条件,利用三维CFD软件对该汽车排气系统流场进行了模拟,找到了影响排气系统背压的关键结构并进行了优化.结果表明,模拟结果与试验结果吻合性良好,优化后排气系统背压由40.5 kPa降至30 kPa.     

奥拓轿车的空调系统

奥拓轿车是近几年国内出现的新车型，其空调系统设计合理，性能可靠，调温能力强。它的空调系统主要由压缩机，冷凝器，贮液干燥器，膨胀阀，蒸发器等组成，空调系统的控制元件主要有：制冷开关，彭风开关，放大器，高压开关，恒温器和加速断裂开关等，对各部件的结构和功用进行了详细的介绍。     

Performance characteristics of a supplementary stack-cooling system for fuel-cell vehicles using a carbon dioxide air-conditioning unit

In fuel-cell-powered vehicles, the fuel-cell system requires a thermal-management subsystem to dissipate heat released during the reaction of hydrogen with oxygen. When the stack generates power at a high rate, a large amount of heat is also generated. If cooling by the radiator is insufficient, a supplementary stack-cooling system is needed to maintain a safe operating temperature. In this study, the performance of a CO₂ air-conditioning unit for stack cooling was investigated under various conditions, and the relationship between cabin cooling and stack cooling was also studied. The coefficient of performance (COP) increased from 1.9 to 2.4, with an increase in cabin-air inlet flow rate from 0 to 8 m³/min. When the air-conditioning unit was turned off, the cooling capacity of the stack cooler was increased; correspondingly, as the cabin-cooling capacity was increased, that of the stack cooler decreased. With an increase in ambient-air inlet temperature from 38°C to 45°C, the COP decreased by 24%. Additionally, both the stack-cooling capacity and cabin-cooling capacity were decreased by about 12% and 16%, respectively, due to reduced heat transfer in the gas cooler as the ambient air inlet temperature was increased. It is expected that the experimental results can serve as a resource in designing a stack-cooling system using a CO₂ air-conditioning unit to enhance stack power generation and efficiency.     

热带沙漠气候环境汽车空调系统的开发

阐述热带沙漠气候环境下汽车空调制冷性能的研究,对热带沙漠气候环境下整车空调系统的舒适性温度指标进行分析探讨;并以某车型出口迪拜的空调系统改进性开发为实例,从系统架构、性能指标、部件布置和试验验证等方面行介绍。     

不同进出风口方式下汽车流场模拟研究

汽车进出风口对汽车空气动力学特性有重要的影响。利用CATIA建立了三种不同进出风口的汽车模型,利用CFD方法研究不同进出风口对汽车流场的影响。采用三维不可压缩雷诺平均方程N～S方程采用RNG k-ε湍流模型,利用二阶迎风差分格式获得控制体积界面上的物理量,应用SIMPLEC算法进行迭代计算,对汽车流场进行模拟仿真,并将结果进行对比分析。研究结果表明：汽车前端只有一个进风口的情况下,发动机迎风面的高压区偏上,并且高压区的压力明显低于增加辅助进风口的情况。将三种情况下仿真得出的发动机舱内散热所需的冷却空气量与实际所需要的空气量对比,结果显示,汽车前端只有一个进风口的情况不能满足发动机舱内的散热需求,而其余两种情况能够满足散热需求。     

Air flow trajectory and surge avoidance of centrifugal compressor under variable pressure operation of automotive fuel cells

The compressor of an automotive proton exchange membrane fuel cell requires severe dynamic performance under normal driving patterns. Because the air flow demand of the automotive fuel cell requires steep increase/decrease, it is very important to understand the air flow trajectory of the centrifugal compressor to avoid the compressor surge. In this study, a simulation model of an automotive fuel cell system with a dynamic compressor was developed to investigate the proper trajectory of air flow rate on a performance map of an air compressor. The dynamic response of the compressor shows that the cathode inlet and exit valves have a significant effect on surge evolution. In particular, the results showed that a proper combination of valve opening areas is required to avoid compressor surge. In this study, the original two valve approach was reduced to a single cathode exit valve control with fixed cathode inlet orifice. A surge rejection algorithm was also developed, based on the comparison of surge protection envelope pressure with actual measured pressure. The results show that surge evolution is effectively avoided by controlling the cathode exit valve.     

颗粒捕集器喷油助燃再生旋流式燃烧器流场特性分析

颗粒捕集器喷油助燃再生燃烧器内的流场分布对气流组织及油气混合有重要影响,而供风形式是燃烧器内流场特性的主要影响因素之一.为了在燃烧室内形成稳定持续的回流,促进油气混合进程,分别采用双矩形口切向供风和直片式轴向旋流器供风两种供气形式,设计等入口截面面积的两种供风系统结构,并在相同发动机排气和补气条件下对燃烧器冷流场进行仿真分析.分析结果表明,两种供风形式均能形成可回流到油气混合室端面的中心回流区,轴向旋流器供风时的中心回流区的长度、最大回流速度、突扩位置的重附着区长度分别比双矩形口切向供风时大8.11%,5.63%和9.59%,且轴向旋流器供风时的湍动能大于双矩形口切向供风.对比结果显示,利用轴向旋流器供风更有利于促进混合过程的进行,对气流的组织更合理.     

基于 SPH 方法的空调进气口进水量分析及优化

由于雨刮臂摆动频次与导水槽及空调外循环进风口结构不匹配等因素，部分车型在淋雨工况下，有水滴甚至水流沿空调进风口进入空调系统，导致空调出现异味，甚至有水渗漏进入乘客舱，出现严重的感知质量问题。采用 SPH 方法，考虑雨刮臂运动、车身姿态及气流效应工况下，借助 PreonLab 软件仿真，复现某车型淋雨场景下的水管理质量问题，通过在空调外循环进风口位置增加挡板，显著减少了溅入空调箱的雨水量，并在实车淋雨试验中得到验证。方法能在车辆开发阶段发现并整改车辆在淋雨场景下的流通路径设计不合理等问题，可改变目前车辆淋雨场景水管理质量控制主要依托实车测试的现状，也可应用于车辆水管理的其他性能质量的控制，如涉水、雨污等。     

基于往复流风冷的动力锂电池热仿真正交分析

随着电动汽车销量的增加,动力电池的热安全问题日益受到关注,电池温度过高会影响电池的性能,严重时会导致热失控的发生。为研究锂电池的放电特性,探究不同因素对电池组往复流风冷散热的影响规律,基于外接UDF的Fluent仿真计算,利用正交试验,分析了入口风速、冷却空气温度、往复流周期三个参数对电池温度分布的影响规律。研究结果表明往复流周期对电池组温度分布均匀性的影响最大,入口风速对电池组最高温度影响最大,而冷却空气温度影响则相对较小。在此基础上,进一步获得了往复流散热性能的最优匹配参数。     

汽车空调系统与发动机冷却系统的耦合分析

建立汽车空调系统与发动机冷却系统数学模型,对两系统进行耦合计算,与实验结果对比表明:仿真与实验结果吻合较好,能够满足工程设计的需要。     

汽车空调系统浅谈

随着人们对于汽车乘坐舒适性要求的不断提高,汽车空调得到长足发展,本文对汽车空调的定义、发展历程、工作特点做了说明,并按照动力源和结构形式的不同对其进行了分类,最后着重介绍了汽车空调系统组成及工作过程,介绍结构、工作情况时做到图文并茂,条理清晰,通俗易懂。     

采用车厢底部出风的变频热泵空调在低温地区大巴车辆上的应用研究

纯电动大巴空调冬季制热是目前行业普遍关注的焦点问题,受大巴空调厂家技术影响,大部分电动空调热泵制热在环境温度0℃左右将无法启动,所以目前行业冬季制暖主要采用燃油炉或PTC加热方式。燃油炉与PTC加热能耗高,严重影响整车续航里程。热泵大巴空调可实现-15℃正常热泵制热,补气增焓技术可实现-25℃正常热泵制热。另外,在冬季制热时,暖风从上部的风道往下吹,大部分热风下不去,造成了车厢上部温度高,脚部温度过低,非常影响舒适性。通过从上部风口引一些风道到脚部的方式,提高车厢底部的热风循环,提高车厢热泵制热的舒适性,从而验证了大巴车厢底部出风对热泵空调制热效果的影响。综合上述,对热泵空调在低温地区冬季热泵制热效果及节能效果进行对比测试,通过对比热泵空调和电加热器的温升速率、耗电量和舒适性等参数,可得知热泵空调升温速度快、温控精度高、耗电量少,变频热泵空调更舒适、更节能。     

TBM施工引水隧洞降温技术研究

TBM施工时,岩温和机械发热所产生的大量热量会导致隧洞内的温度环境恶化,TBM掘进面附近的温度控制是影响连续长距离掘进的重要因素之一。为制定合理的TBM施工段降温措施,采用传热学理论,对采用压入式独头通风的TBM施工隧洞内的温度分布规律进行研究,并以引汉济渭岭北段TBM 5#斜井工区为例进行验证。通过引入空调工程中焓值的概念,确定TBM隧洞人工降温的冷负荷,对常见的降温措施进行对比讨论,进而确定TBM施工隧洞的降温措施。研究表明： 隧洞内的空气温度与隧洞壁温、通风风温、通风风量、盾构的发热功率、隧洞周长、通风长度、风管侧壁传热系数和隧洞侧壁的换热系数等参数有关;对于TBM掘进面附近高温、高湿的环境,只能采取人工制冷降温措施进行降温     

汽车空调整车环境模拟试验室热湿负荷及主要参数的计算

利用状态空间法对环境模拟试验室各围护结构的热负荷进行了精确的计算，同时对空调机组的制冷量、风量及加湿设备的加湿量进行了计算。通过所建立的汽车空调环境模拟试验室进行了长安汽车2种工况的实车测试．结果表明该环境模拟试验室的设备选型是合理的。