The mass and heat transfer process through the door seal of refrigeration

As one of the main reasons causing leakage heat load in a refrigerator,mass and heat transfer through refrigerator door seal is of great importance to be studied.In this paper,a model is presented for numerical simulation of mass and heat transfer process through refrigerator door seal,and an experiment apparatus is designed and set up as well for comparison.A two-dimensional model and tracer gas method are used in simulation and experiment,respectively.It can be found that the relative deviations of air infiltration rate between the simulated results and experimental results were less than 1%,and the temperature difference errors at two special points of the door seal were less than 2.03℃.In conclusion,the simulated results are in good agreement with the experimental results.This paper initially sets up a model that can accurately simulate the heat and mass transfer through the refrigerator door seal,and the model can be used in refrigerator door seal optimization research in the follow-up study.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Evaluating the treatment of E-waste──a case study of discarded refrigerators

Disassembly and recycling of E-waste creates a series of environmental problems. The selection of a technologically reliable, environmentally friendly, economically affordable and socially acceptable recycling technology for E-waste is a significant question. This study establishes a Monte-Carlo mathematical model of cost minimization, given the constraints of environmentally sound handling of the e-waste, in the context of Crystal Ball risk assessment and evaluation software. By following the streams of the different treatment processes, which consist of various technologies including disassembly, recycling and disposal, the econom-ics of various possibilities were identified and the optimal recycling technology proposed. The key factors of the proposed scenarios were determined by using sensitivity analysis. The results of this study show that, for discarded refrigerators, the operating life span plays the key role. The model supports maintenance and resale of the short lived refrigerators. For the longer lived refrigerators material recycling is recommended by the model. Sensitivity analysis shows that purchase cost, plastic sale price, condenser sale price and disassembly costs are the main effects. This study provides a significant technical support for policy making in E-waste management.

Breakdown characteristics of CF4 and CF4/N2 hybrid gas in refrigeration temperature range

Common insulation gas cannot normally work in refrigeration temperature range(153-243 K), especially in extremely cold regions. To solve this problem, this essay uses cubic equation combined with two-parameter model in theorem of corresponding states to estimate dew-point of hybrid gas. The influence of temperature on mixing ratio is studied by using van der Waals equation. The result shows that the mixing ratio is stable during temperature-fall period. Insulation property of CF_4 and CF_4/N_2 in refrigeration temperature range is studied through self-designed low-temperature test system. The result shows when the density of hybrid gas is invariable, temperature changing has less influence on breakdown voltage, and when the mixing ratio is 20%, CF_4/N_2 is the greatest potential hybrid gas.

PVTxSTUDYOFBINARYSYSTEMR22／R152aWITHBURNETTMETHOD

This paper reports the PVT x properties of R22/R152a system in the ranges of temperature from 298.15K to 353.15K and pressure from 0.288 MPa to 1.288 MPa. Sixty seven PVT x measurements for three compositions, i.e., 0.2712, 0.4094 and 0.7911 mole fraction of R22, have been measured along 16 isotherms. The uncertainties of temperature and pressure measurements are less than ±0.01K and ±500 Pa respectively. The reliability of the experimental measurements is confirmed by the CSD equation.

Water Production by Condensation of Wet Air

It is now assumed that climate warming is effective and noticeable. It not only leads to a lack of water that is increasing in desert areas, but it must be kept in mind that the inhabitants of the villages located in the geographical areas whose access to water is difficult, make binding efforts to gain access to water. This article proposes to present the possibility of obtaining water by the condensation of the water vapors of the air by applying the thermodynamic processes of the humid air as well as those of the refrigerating installations. In fact, atmospheric air contains suspended water vapors. When this steam cools below its rose point, there is condensation if water vapors and liquid water or ice appears. It was obtained a quantity of condensed vapors in a refrigeration facility. This amount is directly proportional to the refrigeration power whose efficiency can be improved by the use of photovoltaic energy given the reduced financial cost of this energy. This seems to be a hope among the possible solutions to be considered for the resolution of the water issue.

电臂尺寸和安装条件对热电模块力学性能的影响

针对热电制冷模块中热电臂尺寸对模块整体热应力场的影响,以C-31106型热电制冷模块为研究对象,建立由31对热电偶组成的热-电-力学耦合多物理场模型.采用有限元仿真方法,考虑钎料层的存在并引入表征黏塑性材料的Anand修正本构方程,建立3种安装条件下的热电模型,分析不同电流下热电臂高度和截面边长对热电模块温度场和力学性能的影响规律.结果表明,当热电臂处于最佳高度时,在给定范围内热电臂截面边长越大,越有利于提高热电模块力学可靠性,当工作电流为2.6 A,截面边长从0.99 mm增加到1.09 mm时,冷、热端的最大von Mises应力分别减小了74.67%和22.60%.对模块冷端和热端分别采用固定约束和机械压装的安装方式可有效提高热电模块的力学可靠性,当采用上述安装方式时,冷、热端的最大von Mises应力相比两端只采用固定约束的安装方式分别减小了48.76%和74.02%.

"一平台、三路径"中职制冷专业建设与实践——以天津市第一商业学校为例

“一平台”是对接国际行业标准,搭建制冷维修行业良好操作培训平台。“三路径”是构建“国际视野,一专多能”师资成长路径;构建“标准对接,资源共享”教材建设路径;构建“育训并举,课证融通”人才培养路径。本文旨在为相关院校的制冷专业在专业教育教学改革、提高教育教学质量、实现培养目标等方面提供借鉴。

多冷媒非均质人工冻结壁弹塑性应力分析

【目的】受制冷媒介温度差异以及被冻地层与冻结管距离差异的影响,多冷媒联合双排管冻结壁的非均匀性较为显著,为了合理评价该类冻结壁的安全性,需开展考虑非均质性的多冷媒人工冻结壁弹塑性应力分析。【方法】选取距离1/4管距处的冻结壁作为特征截面,将该截面上的温度分布曲线等效成三段一次函数形式,并将冻结壁视为随温度成线性变化的非均质材料,分别基于4种冻土屈服准则,推导得出多冷媒联合双排管非均质冻结壁弹塑性应力解析表达式。基于该解析表达式,对多冷媒冻结壁的受力特性进行计算,并将该计算结果与均质冻结壁计算得出的结果进行对比。【结果和结论】研究发现:(1)在盐水-二氧化碳联合双排管冻结壁中,径向应力随着相对半径r的增加而上升,环向应力在不同冻结区间(Ⅰ、Ⅱ、Ⅲ)表现出不同的变化趋势。(2)基于均质冻结壁计算理论,弹性极限状态的冻结壁的环向应力最大值出现在冻结壁内侧,弹塑性状态的冻结壁的环向应力最大值出现在弹塑性分界面处,塑性极限状态的冻结壁的环向应力最大值出现在冻结壁最外侧;而基于非均质冻结壁计算理论,冻结壁环向应力最大值始终出现在冻结壁分区界线(r=2)处。(3)在考虑非均质特性后,冻结壁的弹性极限承载力降低1.8%,而塑性极限承载力提高8.1%。在弹塑性状态下,对应相同塑性区相对半径,非均质冻结壁具有更高的承载力,且这种现象随着塑性区相对半径的增大而愈发明显。研究成果对富水地层多冷媒联合冻结帷幕的设计具有重要的参考价值。

熔体纺丝纤维的磁热性能与磁制冷应用研究进展

本文对熔体纺丝合金纤维的磁热性能和磁制冷应用的研究进展进行了综述,总结了不同种类具有磁热性能的合金纤维在磁场驱动下能够产生的磁熵变最大值、半高宽和磁制冷能力。概述了熔体纺丝法的基本原理和操作过程,以及小尺寸纤维形态在实际磁制冷机中的应用优势,并重点介绍了将合金制备成纤维形态能够解决大块合金中存在的相关问题,描述了不同种合金纤维产生磁热效应的原理,阐明了纤维相变特征对制冷温度区间、磁熵变及磁热效应的影响机制,最后总结了合金纤维在活性蓄热器中的制冷功率和性能系数的研究情况,简述了将小尺寸合金纤维大批量应用于实际磁制冷装置以解决该类装置制冷效率低、制冷功率小的可行性。

LNG取样技术标准化探讨

我国大型液化天然气(LNG)接收站和中小型LNG工厂迅猛发展,LNG质量检测取样需求增多,取样是否具有代表性影响LNG组成分析结果,因此取样技术至关重要。为了研制适应各种类型LNG场站使用的取样技术国家标准,通过对国内外LNG取样技术及标准进行调研分析,结合实际应用情况和应用效果,指出了我国现行国家标准GB/T 20603—2006存在的问题,并提出了解决方案和修订建议:即将标准名称改为《冷冻轻烃流体液化天然气的取样》,增加间歇取样方法和点样取样方法。在LNG接收站推荐采用连续法和间歇法,与国际标准ISO 8943:2007保持一致,有利于我国LNG进口结算;在小型LNG工厂、LNG加气站等小型场站推荐采用点样取样法,满足小型LNG场站取样需求。

低露点控制技术研究进展

低露点控制技术是指通过去除或降低空气中的水分或其他成分,使得空气在温度下降时不会产生液态水滴。该文综述冷冻除湿、溶液除湿、膜除湿和转轮除湿等技术的原理、特点和应用领域,分析各种技术在不同工况下能够实现的露点控制极限,以及空间密封性对于低温下露点控制的重要性。该文指出,低露点控制技术在多个领域都有着广泛的应用前景,但在低温领域的研究尚需深入,通过不同技术手段的结合与优化,将有望实现更低露点的控制,促进这些领域的发展和提升产品质量。

基于PSYPRO露点水势的土体吸力测量方法研究

土体吸力测量对岩土工程稳定性评估至关重要,实时准确量测土体从饱和状态到干燥状态的吸力变化一直是非饱和土力学领域的研究热点和难点。露点水势技术是一种新型土体吸力测量方法。详细介绍了PSYPRO露点水势仪的工作原理以及所需要调试参数的意义,并结合标定试验和蒸发试验给出了PSYPRO露点水势仪测量土体不同吸力区间的最优参数设置推荐。先利用不同浓度NaCl溶液对PST-55湿度计进行标定试验并得到了校正系数,随后开展室内土体蒸发试验,并使用PST-55湿度计和ML3土体含水率传感器分别测量干燥过程中土体吸力和含水率变化,验证了露点水势技术用于土体吸力实时连续监测的可行性和准确性。

基于冰浆制冷的标准冷源及不确定度分析

房间空调器制冷量的计量结果在不同焓差室间不一致的问题仍困扰着中国空调行业,是国际贸易中容易引发纠纷的计量学问题,亟待研究可对焓差实验室进行标定的标准冷源。在研究国内外房间空调器几种主流的制冷量计量方法以及标准冷源研究现状的基础上,结合对冰浆制冷物理过程的深入理解,提出基于冰浆制冷的标准冷源装置,包括冰浆制备系统和换热系统两大部分。对其进行实验研究及制冷量不确定度分析,验证该标准冷源装置是否具备标定焓差实验室的能力。实验结果表明:在焓差室室外侧为0℃,室内侧为标准制冷工况,m=70 g/s下该标准冷源装置输出制冷量的相对不确定度可以达到1.2%,约为空气焓值法的1/3,可作为标准冷源对焓差室的制冷量测量结果进行标定,有助于提高制冷行业的国际竞争力。

多制冷站负荷分配调度策略研究

研究中央空调多制冷站冷源系统的负荷分配调度策略。利用制冷站实测数据,首先采用带指数遗忘的最小二乘法对制冷站的能耗模型进行参数辨识,建立多制冷站群控系统的能耗模型。在此基础上,以多制冷站系统能耗最低为目标,在满足末端冷负荷需求前提下,利用改进的野狗优化算法(Improved Dingo OptimizationAlgorithm,IDOA)优化了多制冷站负荷分配策略。在实际系统上进行的测试表明:提出的制冷站负荷优化控制策略较原运行方式在最大制冷季可单日节能8.88%,温差最大季可单日节能11.14%。

R1234yf新能源汽车空调电子膨胀阀测试系统研制

针对目前国内现有电子膨胀阀测试系统偏差大、测试范围小、耗能大,研制了一种新型R1234yf新能源汽车空调电子膨胀阀测试系统,该测试系统利用制冷剂节流后气相经压缩机加压、液相经制冷剂循环泵加压,两相充分混合后进入冷凝器,利用排气节流阀直接控制被测电子膨胀阀阀后压力。依据汽车热管理国家标准对该测试系统进行了可行性及热力性能分析,并与实际制冷方法、液环法测试系统冷凝热负荷及耗功总和进行对比。结果表明:该系统利用两相环法,可以减少冷凝后的冷凝热量,通过排气节流阀控制被测阀后压力,取消蒸发器,提高系统性能;在流经被测试电子膨胀阀的工质质量流量为0.02~0.18 kg/s工况下,该系统冷凝热负荷较实际制冷方法减小了71.6%,较液环法降低了37.9%,耗功总和则比实际制冷方法下降了63.7%~38.6%,但比液环法约增加了7.5%。该系统可为新能源汽车空调行业电子膨胀阀性能测试提供可行且节能的测试方法。

双逆流式露点间接蒸发冷却器的性能试验研究

为了将蒸发冷却器应用于住宅建筑中,实现更大的降温温差和露点芯体尺寸的减小,提出了一种双逆流式露点间接蒸发冷却器,该冷却器采用双逆流式结构和高效湿通道材料。在双焓差试验室内,以干球温度35℃、湿球温度25.8℃工况为例,分析了该冷却器的冷却效率及制冷量等。结果表明,在中等湿度地区,二/一次风量比为0.9,采用喷15 s停60 s的喷淋方式时,冷却器湿球效率达到104%,露点效率达到79%,制冷量达到1.76 kW,COP最高为7.5,能够满足应用于住宅建筑中室内送风温度26~28℃及能耗降低等指标要求。该研究可为住宅建筑用露点空调器的设计提供参考。

长区间隧道冻结法施工冷却水二次降温系统设计

为解决冻结法施工采用常规冷却水降温方式时冷却水温度高的难题,设计一种长区间隧道冻结法施工冷却水二次降温系统。该系统主要由冷却水二次降温冷冻机、中温清水泵、高温清水泵组成,利用中温清水泵将一次冷却水送入冷却水二次降温冷冻机蒸发器后变成二次冷却水,在冷却水二次冷却过程中,高压液态制冷剂受到再冷却。由于高压液态制冷剂的再冷却,在制冷过程中,制冷剂熵值与单位质量制冷量均得到增加,而压缩功不变。工程实际应用结果表明,与常规冷却水降温方式相比,该系统具有以下降温效果:1)盐水降温速率较快,可有效缩短冻结壁交圈时间;2)盐水温度低,冻结帷幕强度高;3)不仅可获得更低的盐水温度进而能更早地达到设计冻结制冷效果,而且制出同等冷量的综合能耗更少。

湿度测量的综述

大气湿度是水汽含量的重要衡量指标,在地面和高空气象观测中都占有关键地位。当前,测量湿度的技术包括称重测湿法、光腔衰荡光谱(CRDS)、热力学法、可调谐半导体激光吸收光谱技术(TDLAS)和露点法。称重测湿法操作繁琐,耗时较长,主要应用于国家级计量标准,不适用于日常测量。CRDS技术结合高反射镜可延长光程,灵敏度较高,但对光路的稳定性要求较高,在恶劣环境下进行现场测量时,容易造成较大的误差。TDLAS利用扫描气体分子吸收的光谱,通过计算获得气体的浓度、温度等信息。露点法是一种简便而准确的湿度测量方法,适用范围广泛,备受学术界瞩目。

基于冷凝法的油气回收工艺分析

油气作为高沸点VOCs,排放后会产生高浓度的有机挥发物,不仅污染环境、损害人体健康,还造成了大量的能源浪费。基于冷凝法的油气回收工艺,能够一步实现油气的资源化回用,因此该工艺的多级冷凝、深度冷凝技术,是近年来的重点研究方向。根据制冷原理的不同,冷凝法主要分为机械制冷和液氮制冷,本文对这2种冷凝工艺进行了对比分析,并以汽油的油气回收装置为例,对冷凝法工艺进行了研究分析。结果表明,采用机械制冷时,油气温度从30℃冷凝至-75℃时,能耗低于液氮制冷,但未能达到排放标准,需要增加末端处理设施。采用液氮制冷,可将油气温度一步深度冷凝至-120℃,油气的排放浓度达到排放标准。采用先机械制冷再液氮制冷的组合冷凝工艺,不仅回收效率高,能达标排放,而且相比液氮制冷,经济效益增加了10%以上。