太阳能喷射制冷系统临界冷凝特性实验研究

为了了解太阳能喷射制冷系统的系统性能随冷凝温度的变化规律,进而提出合理的系统运行控制策略,文中设计并搭建了太阳能喷射制冷实验研究平台,以HFC134a为制冷剂,对太阳能喷射制冷系统的临界冷凝特性进行了实验研究.研究表明:太阳能喷射制冷系统工作时,系统性能系数(COP)、制冷量和能效比(EER)等参数随着冷凝温度的升高呈...     

带回热器的R1234yf热泵系统能量分析和分析

蒸汽压缩式系统引入回热器,可有效提高系统性能。与R134a相比,制冷剂R1234yf具有较低温室效应潜值,其环保效应更加明显。针对R1234yf热泵系统建立能量平衡方程和平衡方程,分析了蒸发温度、冷凝温度和过热度对系统性能系数COP、制热量、排气温度和系统效率的影响,并与R134a系统对比。结果表明:R134a系统COP和制热量比R1234yf系统分别高1.39%—4.06%和0.53%—4.08%,系统效率比R1234yf热泵系统高2.03%—3.27%。随过热度的提高,两系统COP和效率的差值不断减小。     

低GWP工质空调冷凝器性能模拟计算

建立了翅片管式冷凝器的稳态分布参数数学模型,考虑了冷凝器内部的实际流动状态,包括压降和流动型态,用Visual Basic计算机语言编写了翅片管式冷凝器模拟计算程序,并利用R22的计算结果与文献中的实验结果进行了对比验证,得到了较好的一致性。基于此模型模拟了低全球变暖潜能（global warming potential,GWP）工质R290、HFO1234yf和HFO1234ze在冷凝器内的流动换热特性,分析了改变迎面风速、制冷剂质量流量以及管内径尺寸时换热量和压降的变化情况,并与现在广泛使用的R410A进行了性能的对比分析。结果表明,稳定风速时R290换热量最大,HFO1234yf最小;相同情况下HFO1234yf和HFO1234ze最容易达到过冷状态;压降相同时,R410A的质量流量最大,R290的最小;换热量相同时,HFO1234yf的质量流量最大,R290的质量流量最小。为低GWP工质翅片管式冷凝器的优化设计和系统匹配以及制冷剂的替代提供理论基础。     

美国批准使用新型汽车制冷剂

美国环保署2011年2月28日批准一款车用空调制冷剂的替代品氢氟烯烃-1234yf(HFO1234yf),其全球变暖潜值只有4。HFO 1234yf将由霍尼韦尔和杜邦的合资公司生产。目前在汽车空调上广泛应用的HFC-134a,虽然不会破坏臭氧层,但其全球变暖潜值高达1430。     

喷射器几何结构对压缩/喷射制冷循环性能的影响研究

以R134a为工质,采用包含混合室内摩擦损失的等面积混合模型,研究了两相喷射器几何结构和工况参数对压缩/喷射制冷循环性能系数(COP)、单位容积制冷量(qv)、压缩比和排气温度的影响,并与传统压缩制冷循环的性能进行对比。结果表明:喷射器存在一个最优面积比使压缩/喷射制冷循环COP和单位容积制冷量qv最大,且最优面积比值随工质的不同和工况参数的变化而变化;在相同工况参数下,以R134a为工质的喷射器最优面积比大于以R1234yf为工质的喷射器最优面积比;在相同工质和工况参数下,等面积混合模型计算的最优面积比小于等压混合模型的计算值,即在相同工质和工况参数下,按照等面积混合模型设计的喷射器外型尺寸较小;给出的以R134a和R1234yf为工质的喷射器最优面积比与冷凝温度、蒸发温度、过冷度和过热度之间的关联式,可供工程设计参考;在所进行的研究工况范围内,压缩/喷射制冷循环较传统压缩制冷循环COP最大可提高20%,单位容积制冷量qv最大可提高28%,此时冷凝温度为55℃,蒸发温度为-10℃,过冷度和过热度都为0℃,对应的喷射器最优面积比为4.5。     

R1234yf/R134a混合物在汽车空调中替代R134a的实验研究

在使用微通道换热器的汽车空调系统中,实验研究了新型混合制冷剂R1234yf/R134a（质量比为89∶11）替代R134a的可行性。实验结果表明,R1234yf/R134a和R134a的制冷量相似,R1234yf/R134a的COP比R134a低4%～9%,R1234yf/R134a的平均压缩机排气温度比R134a低10℃。通过添加质量分数11%的R134a,可以使R1234yf/R134a不可燃。此外,R1234yf/R134a没有臭氧消耗潜力,全球变暖潜能值小于150,符合欧洲汽车空调标准的要求。在几乎不改变原汽车空调系统的情况下,R1234yf/R134a可用作R134a的环保替代品。     

R1234yf/R134a混合物在汽车空调中替代R134a的实验研究

在使用微通道换热器的汽车空调系统中,实验研究了新型混合制冷剂R1234yf/R134a(质量比为89∶11)替代R134a的可行性。实验结果表明,R1234yf/R134a和R134a的制冷量相似,R1234yf/R134a的COP比R134a低4%~9%,R1234yf/R134a的平均压缩机排气温度比R134a低10℃。通过添加质量分数11%的R134a,可以使R1234yf/R134a不可燃。此外,R1234yf/R134a没有臭氧消耗潜力,全球变暖潜能值小于150,符合欧洲汽车空调标准的要求。在几乎不改变原汽车空调系统的情况下,R1234yf/R134a可用作R134a的环保替代品。     

水热焙烧装备的改造及其对分子筛性能的影响

对现有回转窑焙烧装备进行了改造,增加了自动增湿装置并替换了原国产喷雾嘴,为焙烧提供了湿度气氛并大大优化了雾化效果。以HFO-1234 yf为典型的含氟烷烃制冷剂,对水热焙烧得到的制冷系统用分子筛颗粒进行性能研究。结果表明,与改造前空气气氛下制备的分子筛颗粒相比,改造后水热焙烧得到的分子筛颗粒与含氟烷烃制冷剂HFO-1234 yf的相容性更好,颗粒的宏观性能更佳,更符合含氟烷烃制冷剂对干燥剂的要求。因此,水热焙烧装备改造后有利于获得性能更好的制冷系统用分子筛干燥剂。     

操作参数对双蒸发压缩/喷射制冷系统性能的影响

实验研究了操作参数（冷凝器进水温度、高温蒸发器进水温度和低温蒸发器进水温度）对双蒸发压缩/喷射制冷系统及两相喷射器性能的影响。结果显示,喷射器引射系数随冷凝器进水温度和高温蒸发器进水温度的升高而减小,随低温蒸发器进水温度的升高而增大;喷射器压升比随冷凝器进水温度和高温蒸发器进水温度的升高而增大,随低温蒸发器进水温度的升高而减小。冷凝器进水温度和高温蒸发器进水温度对制冷系统性能的影响较大,而低温蒸发器进水温度对制冷系统性能的影响较小。其中,冷凝器进水温度每降低5℃,制冷系统COP增加0.44;高温蒸发器进水温度每升高2℃,制冷系统COP增加0.16。结果可供双蒸发压缩/喷射制冷系统的设计和运行参考。     

操作参数对双蒸发压缩/喷射制冷系统性能的影响

实验研究了操作参数(冷凝器进水温度、高温蒸发器进水温度和低温蒸发器进水温度)对双蒸发压缩/喷射制冷系统及两相喷射器性能的影响。结果显示,喷射器引射系数随冷凝器进水温度和高温蒸发器进水温度的升高而减小,随低温蒸发器进水温度的升高而增大;喷射器压升比随冷凝器进水温度和高温蒸发器进水温度的升高而增大,随低温蒸发器进水温度的升高而减小。冷凝器进水温度和高温蒸发器进水温度对制冷系统性能的影响较大,而低温蒸发器进水温度对制冷系统性能的影响较小。其中,冷凝器进水温度每降低5℃,制冷系统COP增加0.44;高温蒸发器进水温度每升高2℃,制冷系统COP增加0.16。结果可供双蒸发压缩/喷射制冷系统的设计和运行参考。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。