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《制冷与空调(北京)》2016,(5)
通过对带排气冷却器的R290/CO_2复叠式制冷系统的性能分析,以及与不带排气冷却器的R290/CO_2复叠式制冷系统的性能进行比较,得出在相同的运行工况下,当排气冷却器的热负荷为1.4 kW,低温循环的冷凝温度为-20℃,制冷量为10kW时,排气冷却器在降低冷凝蒸发器CO_2的入口温度方面起到显著作用,高温循环制冷剂R290的质量流量减少11.4%,相应的高温循环压缩机的功耗和冷凝器的热负荷均降低11.4%,R290/CO_2复叠式制冷系统的COP提高8.8%。 相似文献
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空气源热泵热水器比燃气或电热水器更为节能。本文提出了一种外绕微通道冷凝器,可以减少制冷剂充灌量、提高换热效率、降低成本、提高安全性。建立了热泵热水器的准稳态系统模型,制冷剂侧采用稳态模型,水箱和水侧采用动态模型。通过实验证明了该系统模型可以准确地预测时变的系统功耗、水温,以及系统时均COP。通过仿真分析,发现水箱隔热层可以缩短水的加热时间、并提高系统COP约9.2%。增大冷凝器也可提升系统COP,但几乎不改变水的加热时间。最后提出了微通道冷凝器的三流程优化设计方法。 相似文献
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本文分析了R290直接接触冷凝(DCC)制冷循环的性能,并与R290常规单级压缩制冷循环的热力性能进行对比,得出:在最佳主循环冷凝温度下,R290直接接触冷凝制冷循环可获得最大性能系数和最低冷凝器热负荷。主循环过冷液体的过冷度增大,最优性能系数降低、最低冷凝器热负荷增加、蒸发器的制冷剂质量流量减少,同时,获得最优性能系数和最低冷凝器热负荷的最佳主循环冷凝温度升高。当蒸发温度为-15~-6℃,R290直接接触冷凝制冷循环相比R290单级压缩制冷循环的性能系数提高了7.5%~14.9%,冷间供冷设备蒸发器的制冷剂质量流量减少了26.5%~36.7%,冷凝器热负荷减少了1.5%~3.7%。结果表明R290直接接触冷凝制冷循环具有很好的发展前景。 相似文献
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热泵空调系统在满足电动汽车冬季供暖需求方面发挥了重要作用。本文采用新型低GWP值的R1234yf为制冷剂?对电动汽车热泵空调系统在-20~7 ℃环境下的低温制热性能进行了测试?对电动汽车冬季热负荷进行标定,并且与制冷剂R134a进行了对比,研究了系统制冷剂充注量、制热量、COP和排气温度的变化,同时对系统各部件火用损失进行了分析计算并根据结果
确定系统优化方向。结果表明:该系统最佳制冷剂充注量为1406g,制热量与COP在大部分工况下达到2kW与18以上,能够满足低温制热需求;R1234yf 直接替代R134a时,系统制热量与COP比R134a系统低71%与66%,系统的排气温度比R134a平均低53 ℃,系统工作更稳定可靠;热泵空调系统内冷凝器与压缩机的火用损失占系统总火用损的80%以上,是重点优化方向;增大内部冷凝器换热面积、增大风量、提高压缩机转速可显著提升R1234yf系统制热性能,使之与R134a系统的制热性能相比大约相等或者更高。 相似文献
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自复叠制冷系统广泛应用于小型制冷装置,制取-40℃~-150℃之间的低温环境。套管式冷凝器在自复叠制冷系统中常用作冷凝设备,其特性与结构深刻地影响着制冷装置系统。自动复叠制冷系统用套管式冷凝器为研究对象,研究其冷凝过程特性和结构尺寸;在冷凝压力2.0 MPa,当R600a和R23混合工质的质量分数为7∶3时,计算其冷凝负荷为1610 W;根据混合工质和冷却水的换热系数,确定套管式冷凝器长度为4.842 m。最后对不同冷凝水流量的吸气温度、排气温度、蒸发温度,以及冷却水进出口温度进行了对比分析。 相似文献
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针对采用微通道冷凝器的商用空调,对制冷剂在系统中的分布和迁移进行试验研究。并与采用铜管翅片冷凝器的商用空调制冷剂迁移现象进行对比。结果表明,在相同条件下,与采用铜管翅片冷凝器的商用空调相比,采用微通道冷凝器的商用空调在停机时制冷剂液体更容易从排气管回流到压缩机。 相似文献
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研究了电子膨胀阀在低温系统中的应用特性,并对热力膨胀阀和电子膨胀阀在相近工况下进行降温特性的对比性试验。根据实验结果进行分析,可以看出电子膨胀阀在低温条件下的控温曲线也是非常平稳的,并可调节电子膨胀阀的不同开度,使低温箱体达到不同的降温速率及终温。另外通过改变电子膨胀阀开度以及在箱体内加入不同的热负荷,研究了在变负荷条件下,对制冷系统循环参数的影响,尤其是对蒸发器、压缩机、冷凝器进出口温度的影响。 相似文献
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A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils. 相似文献
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The end of over unit products of more than Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits beer wine yellow wine fruit syrup wine others cover over % of the national top-branded liquor products.…… 《中国标准化(英文版)》2008,25(1):30
The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.…… 相似文献
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Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster. 相似文献
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N.A. Odintsova N.V. Ageenko K.V. Kiselev N.M. Sanina E.Y. Kostetsky 《International Journal of Refrigeration》2006,29(3):387
We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes. 相似文献
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David R. Smith F. R. Fickett 《Journal of research of the National Institute of Standards and Technology》1995,100(2):119-171
Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability. 相似文献
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Fco. Javier Franco Pérez Marc Gener Moret 《Materials and Manufacturing Processes》2017,32(7-8):876-884
ABSTRACTThe production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials. 相似文献
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As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion. 相似文献
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Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting. 相似文献
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TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure. 相似文献
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R. Owsiński S. Kamiński M. Szymaniec A. Niesłony T. Łagoda 《Materialwissenschaft und Werkstofftechnik》2015,46(10):1059-1067
The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase. 相似文献