自复叠制冷系统混合工质配比研究

分析了混合工质组分选择时必须考虑的几个选配原则。针对一种五级自动复叠制冷循环混合工质的配比,分析了相关制冷工质的性能及非共沸混合工质的特性。根据所要达到的温度,选择了R22、R23、R 4、R740和R728五种制冷工质作为系统循环工质,应用制冷工质性能商业计算软件Refprop,对混合工质的配比进行了模拟计算,得到了可以接受的一种混合工质配比。     

一种新型自复叠制冷循环特性研究

提出一种新型自复叠制冷循环,通过设置喷射器,利用高压高沸点液态制冷剂引射低压低沸点气态制冷剂,充分回收高沸点组分的节流损失,提高压缩机吸气口处低沸点组分的吸气压力并获取更低制冷温度。建立了组成系统部件热力学数学模型,分析了冷凝温度、混合工质配比和压缩比等参数对传统自复叠制冷循环和新型自复叠制冷循环的工作特性影响。研究表明,新型自复叠制冷循环制冷效率与传统自复叠制冷循环相当,但前者所获得制冷温度比后者所获得制冷温度可降低约10～20℃     

一种四级自动复叠制冷循环的试验研究

提出了一种四级自动复叠制冷循环,搭建相应的试验装置,选取合理的混合工质及配比并成功制取了-140℃的低温。测量系统各级节流后的温度特性,并进行分析,指出混合工质配比对蒸发温度的影响。     

自复叠制冷循环中混合工质泄漏性能的研究

尽管自复叠制冷循环越来越广泛的用于深冷及普冷领域,对于循环中工质泄漏特性的研究却较少。以非共沸混合工质两相区的等温泄漏为基础,分析了在自复叠循环装置中各部件的泄漏对工质组成的影响,其中发生在冷凝器出口处、气液分离器和蒸发器出口处的泄漏对工质组成影响较大。以采用非共沸混合工质R600 a/CO2的自复叠低温冷冻箱为例,研究了不同泄漏点不同泄漏率的泄漏特性。结果说明当工质泄漏时混合工质组成和循环性能发生变化,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成发生较大变化时,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。     

喷射增效自复叠制冷循环工质选择

为选择适合喷射增效自复叠制冷循环的工质,选取R32/R1234ze、R23/R134a、R170/R290和R23/R227ea四组混合工质,计算分析在给定工况下不同工质对喷射增效自复叠制冷循环性能的影响,并与传统自复叠制冷循环进行对比。结果表明,在喷射增效自复叠制冷循环中,R170/R290制冷量最大,R23/R227e压缩机压比最小,R23/R227e具有最佳性能,其性能系数较传统自复叠制冷循环提高了13.8%—28.4%;各组混合工质均存在最优组分配比使循环COP最大。     

复叠系统低温级制冷剂的循环性能对比实验

通过实验测试,比较了不同冷凝温度和蒸发温度下复叠系统低温级常用制冷工质R13、R23、R503和RS08B的COP、压比及制冷量等循环性能,又结合各制冷工质的环境性能、热工性能,分析了现有常用复叠系统低温级制冷工质各自的优缺点,为新工质的开发及进一步的制冷性能对比实验工作提供了有益的帮助.     

CO_2/二甲醚混合制冷剂跨临界制冷循环性能分析

本文通过理论计算对CO_2/DME混合制冷剂替代CO_2的跨临界制冷循环特性进行了分析,结果表明:CO_2/DME混合制冷剂的质量配比范围为90/10～100/0时,可实现混合制冷剂的直接充灌.在相同的工况下,CO_2/DME跨临界制冷循环的最优高压侧压力降低了3 MPa,制冷系数提高4.3%;过热度对循环性能的影响,纯质CO_2要大于混合工质CO_2/DME.     

热-电驱动喷射压缩复合制冷循环特性研究

自复叠制冷循环具有获得制冷温度低优点,但其完全消耗的是高品位电能或机械能;喷射制冷具有利用低品位低温热源(60~100℃)制取冷量、且制冷温度较高时制冷效率高等优点,但难以获得较低制冷温度。因此,为了实现低品位热在低温冷冻领域高效利用并节省高品位电能,本文提出一种由低品位低温热源与电能联合驱动的混合工质喷射/压缩复合制冷循环。建立组成新循环各部件热力学数学模型,分析喷射器压缩比和压缩机压缩比对复合式制冷循环的热性能系数和机械性能系数影响,并与传统的自复叠制冷循环特性进行比较分析。研究表明,低品位热源与电能联合驱动喷射/压缩复合制冷循环较传统I刍复叠制冷循环可显著提高制冷效率并获得更低制冷温度。     

混合工质内复叠节流制冷机的分析及初步实验研究

本文对采用多元非共沸混合物工质的内复叠节流制冷循环进行了热力分析.采用分析的方法对制冷循环各部件进行了分析,同时比较了混合工质一次节流循环和内复叠循环热力性能.同时文章报道了混合工质内复叠节流制冷机的初步整机性能测试实验结果.     

单级自动复叠混合工质制冷循环的实验研究

由于压缩机压比的局限,制约着单一制冷剂的压缩回热循环发展,本系统采用单一压缩机和混合工质的自复叠制冷循环系统取得了较好的制冷效果。文中对单级自动复叠制冷系统进行了理论模拟,并设计和搭建了实验台进行分析。通过理论和实验数据的分析得出混合工质组合R600a/R23,并初步得到最优配比。     

燃气轮机中间回热循环性能分析

本文质疑文献[1提出的中间回热循环技术,通过基本分析,揭示其特殊规律。且通过与常规回热比较,从透平初温、最佳循环压比、回热器参数等方面分析了关键参数对循环性能的影响。结果表明:与文献[1]不同,相对于简单循环和中间回热,常规回热具有更高的效率、更低的最佳压比。本文并指出文献[1]得出不合适分析结果之故。此外由计算结果得知,高、低压缸透平压比分配的优化可有效地提高中间回热循环性能。     

Enhancing transmission efficiency of bending waveguide based on graded sonic crystals using antireflection structures

The conventional antireflection coating (ARC) structure for sonic crystal devices is to place the cylinders at the interface between a sonic crystal device and a background medium. The radius of ARC cylinders and the distance between the ARC and the sonic crystal device are adjusted to obtain an optimal antireflection effect. We propose that ARC structures are directly designed by using the conventional ARC theory instead of scanning the geometric and spatial parameters of the conventional ARC structures. According to the concept of the effective refractive index of sonic crystals, the exact ARC structures can be implemented by sonic crystals. The transmission efficiency of a bending waveguide designed by graded sonic crystals can be enhanced by introducing the ARC structures based on sonic crystals. The performances of different ARC structure designs are compared and discussed.     

全息光刻中的驻波效应研究

对光刻胶内光强分布进行了计算与模拟, 结果表明, 来自基底的反射光与入射光干涉, 光强在垂直基底的方向上呈现强弱周期性变化, 即驻波效应. 进一步的分析与实验结果表明, 随着基底反射率的增加, 驻波效应变得严重, 进而影响光栅掩模的槽形、占宽比并限制线条高度. 为减弱驻波效应的影响, 尝试了使用减反射膜降低基底反射光强度, 实验结果表明, 在基底与光刻胶之间增加一层减反射膜吸收来自基底的反射光强度, 减弱驻波效应的效果显著. 关键词： 全息光刻 驻波 减反射膜     

Fourth- and sixth-order polarization aberrations of antireflection-coated optical surfaces

For single-layer antireflection-coated (ARC) optical surfaces, the first five derivatives of reflectance with respect to angle of incidence phi for the p and s polarizations are zero at normal incidence, whereas the first three derivatives of differential transmission phase shift D(t)(= D(tp)-D(ts)) with respect to phi are also zero at phi=0 . Consequently, ARC optical systems with numerical apertures of <0.7(phi<45 degrees ) exhibit fourth- and sixth-order polarization aberrations owing to retardance and diattenuation, respectively. Results for ARC Ge and ZnS surfaces are presented to illustrate these effects.     

基于感兴趣区域的幅型比变换新方法

基于人类视觉系统对运动目标比较敏感的特性,提出了一种新的幅型比变换方法.综合时空信息提取视频序列中的运动目标,利用图像修复技术对被提取运动目标后的视频图像进行背景修补.采用插值算法以不同的方式分别缩放运动目标和修复后的背景,并将变换后的运动目标与背景相叠加合成相应幅型比的视频图像.实验结果表明：此方法避免了已有幅型比变换方法的缺陷,保证了变换后运动目标的无失真性,与人类的视觉感知有较好的一致性.     

Modified-DBR-based semi-omnidirectional multilayer anti-reflection coating for tandem solar cells

In this paper, multilayer antireflection coatings are designed by modifying the thickness of two and three paired layer distributed Bragg reflector （DBR） structure. Our proposed DBR-based structures show antireflection behaviors, in spite of the reflection treatment in traditional DBR structures. Firstly, the proposed structures are designed to be equivalent to the theoretical ideal triple-layer （TL） antireflection coating （ARC）. Therefore, the problem of finding a suitable material for the middle layer of triple structure is solved. Simulation results show the significant equivalency for the reflectance of proposed structures to the ideal TL ARC at the same wavelengths and incident angles. Also, the design of the structure is changed in order to present the constant reflectance coefficient over a wide range of wavelengths. This structure enhances the omni-directionality of the multilayer ARC.     

An effective reflectance method for designing broadband antireflection films coupled with solar cells

The solar spectrum covers a broad wavelength range, which requires that antireflection coating (ARC) is effective over a relatively wide wavelength range for more incident light coming into the cell. In this paper, we present two methods to measure the composite reflection of SiO₂/ZnS double-layer ARC in the wavelength ranges of 300-870 nm (dual-junction) and 300-1850 nm (triple-junction), under the solar spectrum AM0. In order to give sufficient consideration to the ARC coupled with the window layer and the dispersion effect of the refractive index of each layer, we use multi-dimensional matrix data for reliable simulation. A comparison between the results obtained from the weighted-average reflectance (WAR) method commonly used and that from the effective-average reflectance (EAR) method introduced here shows that the optimized ARC through minimizing the effective-average reflectance is convenient and available.     

Improved performance of a crystalline silicon solar cell based on ZnO/PS anti-reflection coating layers

A porous silicon (PS) layer was prepared by photoelectrochemical etching (PECE), and a zinc oxide (ZnO) film was deposited on a PS layer using a radio frequency (RF) sputtering system. The surface morphology of the PS and ZnO/PS layers was characterised using scanning electron microscopy (SEM). Nano-pores were produced in the PS layer with an average diameter of 5.7 nm, which increased the porosity to 91%. X-ray diffraction (XRD) of the ZnO/PS layers shows that the ZnO film is highly oriented along the c-axis perpendicular to the PS layer. The average crystallite size of the PS and ZnO/PS layers are 17.06 and 17.94 nm, respectively. The photoluminescence (PL) emission spectra of the ZnO/PS layers present three emission peaks, two peaks located at 387.5 and 605 nm due to the ZnO nanocrystalline film and a third located at 637.5 nm due to nanocrystalline PS. Raman measurements of the ZnO/PS layers were performed at room temperature (RT) and indicate that a high-quality ZnO nanocrystalline film was formed. Optical reflectance for all the layers was obtained using an optical reflectometer. The lowest effective reflectance was obtained for the ZnO/PS layers. The fabrication of crystalline silicon (c-Si) solar cells based on the ZnO/PS anti-reflection coating (ARC) layers was performed. The I–V characteristics of the solar cells were studied under 100 mW/cm² illumination conditions. The ZnO/PS layers were found to be an excellent ARC and to exhibit exceptional light-trapping at wavelengths ranging from 400 to 1000 nm, which led to a high efficiency of the c-Si solar cell of 18.15%. The ZnO/PS ARC layers enhance and increase the efficiency of the c-Si solar cell. In this paper, the fabrication processes of the c-Si solar cell with ZnO/PS ARC layers are an attractive and promising technique to produce high-efficiency and low-cost of c-Si solar cells.     

An effective reflectance method for designing broadband antireflection films coupled with solar cells

The solar spectrum covers a broad wavelength range,which requires that antireflection coating(ARC) is effective over a relatively wide wavelength range for more incident light coming into the cell.In this paper,we present two methods to measure the composite reflection of SiO2/ZnS double-layer ARC in the wavelength ranges of 300-870 nm(dualjunction) and 300-1850 nm(triple-junction),under the solar spectrum AM0.In order to give sufficient consideration to the ARC coupled with the window layer and the dispersion effect of the refractive index of each layer,we use multidimensional matrix data for reliable simulation.A comparison between the results obtained from the weighted-average reflectance(WAR) method commonly used and that from the effective-average reflectance(EAR) method introduced here shows that the optimized ARC through minimizing the effective-average reflectance is convenient and available.