混合工质R407C泄漏对制冷系统性能影响的探讨

本文主要探讨混合工质 R4 0 7C泄漏对制冷系统性能影响及其相关性能参数变化趋势。     

HFC125/HCs二元混合工质理论制冷循环性能分析

利用NIST REFPROP数据库计算HFC125/HCs(包括丙烷、丁烷、异丁烷)三类二元混合工质的热力学性质,并对其理论制冷循环性能进行分析计算,筛选出最佳配比.结果显示其理论循环性能比HCFC22高16.9%,并且压缩机排气温度也有所降低.     

混合工质应用于制冷系统中泄漏的理论分析

本文对制冷系统中混合工质发生泄漏后其成分的变化和由此引起的循环性能变化进行了理论分析。计算结果表明：在工业实际应用中,制冷系统发生泄漏后再充灌,其成分的变化引起循环性能变化很小。作者认为：工业上混合工质的充灌和泄漏后再充灌其成分发生变化不成为其推广应用的障碍。     

制冷空调系统应用混合工质的性能和泄漏研究

尽管非共沸混合制冷剂的优点很多,但其工业应用至今仍是很有限的。主要原因是制冷装置内混合工质的泄漏以及由此引起的浓度变化。另一个缺点是,尚缺乏一种有效简便的方法以确定循环系统内工质的浓度。本文介绍了作者的研究结果。研究的非共沸混合物具有大的沸点差。其目的是评估上述问题的严重性。研究内容为: 1.进行泄漏试验和计算机摸拟,以确定泄漏引起的浓度变化; 2.简单地确定循环系统内混合物的浓度。为了与沸点差极大的最恶劣情况比较,作者对沸点差较小的实际情况进行了研究。在此实际情况中,用一种新开发的三元混合物代替超级市场的制冷系统中使用的R502。     

非共沸混合工质泄漏拓展模型的理论分析

非共沸混合工质泄漏拓展模型的理论分析顾惠军高志明马一太（天津大学热能系,天津３０００７２）ＮｅｗＴｈｅｏｒｅｔｉｃａｌＭｏｄｅｌｏｎｔｈｅＬｅａｋａｇｅｏｆＲｅｆｒｉｇｅｒａｎｔＭｉｘｔｕｒｅｓｉｎａＴａｎｋＡｂｓｔｒａｃｔＴｈｅｒｅａｓｏｎｗｈｙＲ...     

HCs替代HCFC22的理论空调循环分析

关联了4种二元碳氢化合物系基于PT状态方程及其混合规则的交互作用参数,对16种HCs纯质和混合物系进行了理论空调循环分析。结果表明HC1270、HC290、HC1270／HC290、HC1270／HC600a、HC290／HC600a等具有在空调系统中替代HCFC22的潜力。     

汽车空调应用混合工质泄漏性能的研究

本文对混合工质用于汽车空调替代Ｒ１２的重要问题─—泄漏问题进行了理论分析计算及试验研究。证明混合工质Ｒ２２／Ｒ１５２ａ／Ｒ１４２ｂ在汽车空调系统中正常泄漏对系统性能影响不大。并且参过试验证明系统中工质泄漏后,充灌相同浓度的混合工质可保持系统性能稳定。     

活塞式制冷压缩机活塞环结构的泄漏分析

分析活塞环结构泄漏的原因和特性,讨论影响泄漏量的因素。介绍无润滑油时泄漏量的理论计算方法处理方法。     

不凝气体对跨临界CO2制冷系统性能影响的分析

本文选择不凝气体氮气作为添加剂加入到CO2跨临界制冷循环系统中,通过理论分析和计算仿真研究氮气对系统制冷性能的影响。首先分析CO2工质和氮气的基本物性参数,N2的加入会改变CO2工质物性参数,本文通过计算得出添加剂使CO2工质的饱和压力和液体比热提高,粘度系数、表面张力、液/汽密度比和导热系数降低。同时分析N2在蒸发器内可作为汽化核心,实现非均匀核化过程,从而降低成核温度,提高换热系数。同时N2的加入会降低压缩机排气温度,减小压缩机功率,从而提高系统制冷性能,并随浓度的增加而增加。本文为跨临界CO2制冷循环系统高效应用研究提供理论依据。     

HCs冷柜系统最佳充注量的实验研究与理论分析

本文对一台使用R290/R600a(1/1)制冷剂的冷柜系统进行了选择最佳充注量的实验研究,讨论了充注量的多少对蒸发压力、冷凝压力、蒸发器温度分布、压缩机开停机时间等方面的影响,得到了耗电量最少的充注量,并对此条件下的循环特点进行了理论分析.     

R290/R600a混合工质制冷系统泄漏点对系统性能的影响

混合工质在不同位置的泄漏所引起的系统中工质对组分比例发生变化会对制冷系统的性能产生很大影响。根据混合法则,从理论上研究R290/R600a工质对泄漏率在5%~40%范围内8种泄漏率条件下,系统工质对组分变化的规律。按照理论计算的要求建立制冷系统工质泄漏实验台,对实验台在4种泄漏率条件下的蒸发压力、冷凝压力、制冷量和COP进行研究。计算和实验结果表明,在蒸发器出口和冷凝器入口处的泄漏使低沸点组分R290在工质对中的比例增大,系统制冷量增加且COP下降;在蒸发器入口和冷凝器出口处的泄漏使高沸点组分R600a在工质对中的比例增大,系统制冷量下降且COP上升。     

非共沸混合天然工质泄漏对自复叠循环制冷机性能的影响

以非共沸混合工质两相区的等温泄漏模型为基础,分析自复叠循环装置中各部件的泄漏对工质组分的影响,以天然工质R600a／CO2自复叠低温冷冻箱为例,研究不同泄漏点和不同泄漏率的泄漏特性。结果表明：当工质泄漏时,混合工质组分和循环性能均发生变化,在蒸发器出口处的泄漏对循环性能影响最大;当泄漏引起循环工质组分发生较大变化时,压缩机变容量和变压力比调节能力明显降低,此时系统不能满足设计工况的要求,工作性能变差。     

以R134a为制冷剂的喷射制冷理论分析及其CFD模拟

介绍以R134a为制冷剂的太阳能喷射制冷系统，并对系统核心部件喷射器进行CFD模拟，根据CFD模拟结果确定喷射器的最佳结构尺寸。在此基础上，对该系统进行理论分析。在发生温度90℃、蒸发温度0℃、冷凝温度34℃的条件下，系统COP可以达到0．182。     

An investigation of refrigerant leakage in commercial refrigeration

Given that refrigerant demand is set to rapidly increase, long term solutions for leakage prevention are required to affect change in the industry. This paper presents the results of a project which investigated refrigerant leakage within two of the UK's major supermarket chains. Leakage data from 1464 maintenance records were analyzed. The analysis categorized the type, location of each leak and volume of refrigerant replaced during repair. Over 82% of the recorded leaks were from R404A refrigeration systems, and mainly consisted of pipe or joint failures or a leaking seal/gland/core located in the compressor pack and the high pressure liquid line. It is recommended that the industry focuses on improving design, installation and maintenance of pipework and valves, at the components that most often develop faults to minimize refrigerant leakage.     

R600a制冷剂用新型冷冻机油的研制

利用新疆环烷基原油资源,采用高压加氢组合工艺新技术生产的基础油,通过原料筛选、优化调合比例及添加剂复配后,研制出满足用户要求的适用于R600a制冷剂的全封闭冷冻机油。研究表明,该冷冻机油解决了与R600a制冷剂相溶性及其与制冷剂共存时的热一化学稳定性、抗磨性能等问题。目前已成功通过压缩机台架试验。     

一种节能环保型复叠式制冷系统

为解决自然工质R290／CO2复叠式制冷循环COP较低的问题，提出采用过热、过冷和用膨胀机代替节流阀的方法。通过热力学分析对比得出，用膨胀机代替节流阀同时过冷的方法可以大大提高R290／CO2复叠式制冷循环的COP。自然工质R290／CO2复叠式制冷循环替代常规工质有很好的前景。     

A new structure and theoretical analysis on leakage and performance of an oil-free R290 rolling piston compressor

Lubricating oil improves the reliability of compressors and systems, whereas increases the system complexity. Compared with other types of compressors that have oil-free models, a rolling piston compressor has more leakage paths and bigger leakage loss. Therefore, the leakage is an important problem to be solved in order to develop an oil-free rolling piston compressor. The paper put forward a new structure of rotary compressor adopting a low pressure shell, connecting the cavities within piston and behind vane to the cavity at suction pressure and using radial compliance mechanisms. Then the leakage models were developed to calculate the mass flow rates within both the present rolling piston compressor without any oil as sealant and the new structure of oil free compressor. Results showed that by the new structure, the influences of leakage on the performance of a R290 oil free rolling piston compressor can be largely decreased.     

R290应用于商用大容积陈列柜的性能研究

对比R290与R134a的热力学性质,分析在商用大容积陈列柜中用R290替代R134a的可行性,并对R290应用于商用大容积陈列柜的性能进行测试。试验结果表明：相对于R134a系统,R290系统的冷却速度较快,较低能耗,噪声较小,冷凝器耗材较少。对于R290的安全性,只要控制合适的充注量并采取适当的安全措施就可以达到安全使用的要求。     

A year-round dynamic simulation of a solar-driven ejector refrigeration system with iso-butane as a refrigerant

In this paper, the performance of the solar-driven ejector refrigeration system with iso-butane (R600a) as the refrigerant is studied. The effects that both the operating conditions and the solar collector types have on the system's performance are also examined by dynamic simulation. The TRNSYS and EES simulation tools are used to model and analyze the performance of a solar-driven ejector refrigeration system. The whole system is modelled under the TRNSYS environment, but the model of the ejector refrigeration subsystem is developed in the Engineering Equations Solver (EES) program. A solar fraction of 75% is obtained when using the evacuated tube solar collector. In the very hot environment, the system requires relatively high generator temperature, thus a flat plate solar collector is not economically competitive because the high amount of auxiliary heat needed to boost up the generator temperature. The results from the simulation indicate that an efficient ejector system can only work in a region with decent solar radiation and where a sufficiently low condenser temperature can be kept. The average yearly system thermal ratio (STR) is about 0.22, the COP of the cooling subsystem is about 0.48, and the solar collector efficiency is about 0.47 at T_e 15 °C, T_c 5 °C above the ambient temperature, evacuated collector area 50 m² and hot storage tank volume 2 m³.