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1.
万时杰  夏凊 《流体机械》2004,32(4):60-62
建立了冰球式蓄冷罐的数学模型,并在TRNSIS仿真平台上编制了蓄冷罐的仿真模型;通过仿真计算数据与已有试验数据的比较,验证了该模型的合理性和准确性。  相似文献   

2.
曹红奋 《流体机械》2001,29(5):46-49,31
通过Yong分析与能分析的比较,说明了对冰蓄冷空调系统进行Yong分析的必要性,建立了冰蓄冷系统的Yong分析模型,并通过对一个具体工程的冰球式蓄冷系统进行Yong损失分析计算,揭示了系统中真正的能量损失所在,指出了系统节能的有效途径。  相似文献   

3.
采用有限元分析方法对冰和某型高温相变材料蓄冷球进行了蓄释冷过程模拟仿真,探讨了两种材料蓄冷球在蓄冷和释冷过程中蓄冷量和蓄释冷时间的变化规律,并对两种材料的蓄释冷性能进行了分析比较.研究表明:高温相变材料蓄冷周期短、蓄冷量大,制冷机组节能效果好,能较好地满足潜艇蓄冷空调要求,有利于提高潜艇的隐蔽性和水下续航力.  相似文献   

4.
分析了平板蓄冷器的蓄冷过程,绘制了蓄冷剂、栽冷剂在蓄冷过程中温度随时间变化的曲线,从而总结了蓄冷规律。并对其在中央空调中的应用作了探讨,这在中央空调节能、稳定运行工况、减少用电高峰期电网压力方面有重要意义。  相似文献   

5.
壳管式蓄冰槽蓄冷特性的试验研究   总被引:4,自引:0,他引:4  
对壳管式蓄冰槽蓄冷特性进行了试验研究。研究表明,载冷剂温度、流量及其冰槽内水体初始温度直接影响着蓄冰槽的蓄冷特性,其中载冷剂温度更为明显;蓄冷过程包括显冷蓄存和潜冷蓄存两个阶段,在显冷蓄存阶段蓄冷速率较大,而潜冷蓄存阶段蓄冷速率近似常量,且冰槽内具有-2~-1℃的过冷度,这些特征表明,壳管式蓄冰槽与常规外融式蓄冰槽的蓄冷特性具有相同的变化规律。  相似文献   

6.
三元近共沸混合工质MP52和MP39的水合物蓄冷研究   总被引:1,自引:0,他引:1  
肖立全  王世平 《流体机械》2000,28(10):47-50,16
在间接接触式水合物蓄冷实验台上,对三元非共沸工质MP52和MP39的水合物蓄、放冷过程中的传热特性进行了试验研究,详细分析了非离子型表面活性剂TWEEN80和SPAN20对蓄、放冷过程的影响。  相似文献   

7.
曹红奋 《流体机械》2001,29(5):46-49
通过火用分析与能分析的比较 ,说明了对冰蓄冷空调系统进行火用分析的必要性 ,建立了冰蓄冷系统的火用分析模型 ,并通过对一个具体工程应用的冰球式蓄冷系统进行火用损失分析计算 ,揭示了系统中真正的能量损失所在 ,指出了系统节能的有效途径  相似文献   

8.
气体水合物蓄冷技术的应用前景   总被引:2,自引:0,他引:2  
在以R134a为蓄冷工质的实验基础上,阐明气体水合物作为蓄冷工质的蓄冷技术可行性。通过大量实验得以进行气体水合物蓄冷技术中工质选择,规划蓄冷槽的设计原则,揭示添加表面活性剂的作用机理,蓄冷、放冷过程中传热传质规律及最佳运行工况,达到实用空调系统中低温送风空气调节的目的。  相似文献   

9.
为量化充冷管道外添加肋片对采用相变蓄冷技术的城市冷链配送小型冷藏车用蓄冷板充/补冷过程的影响,以相变材料(PCM)RT5 HC作为蓄冷介质,对PCM凝固过程进行计算,分析充冷管道上肋片数量、肋片形状、肋片厚度及相邻管道上肋片布置方式对充冷时间及蓄冷效率的影响。结果表明,充冷管道上设置肋片,蓄冷板充冷过程中液态和部分凝固的PCM被分隔为多个小区域,小区域内自然对流得到强化,同时相界面延长,传热面增大,冷量传递加快;与充冷管道上无肋片的蓄冷板相比,设置肋片使充冷时间大大降低,蓄冷效率ε得到极大的提升,而蓄冷量略有降低;当肋片数量由4条依次增加至6,8条时,对应的ε及肋片效率εf增长速率升高,而由8条增加至10条时,ε及εf增长速率下降;对比肋片截面形状,矩形肋片效率最高,为3.19;肋片厚度t增大对蓄冷效率的提升作用较小;相邻充冷管道上不同肋片布置方式对充冷过程影响较小。研究结果为蓄冷板内充冷管道设计提供参考。  相似文献   

10.
导热塑料盘管蓄冰槽外融冰取冷动态特性实验   总被引:1,自引:0,他引:1  
朱煜  陈国邦 《流体机械》2006,34(10):58-61
在名义蓄冷量为63.3kW的导热塑料盘管蓄冰槽实验台上研究了外融冰取冷的动态过程,在给定取冷强度下,分别考察了取冷进出口模式、鼓气扰动、初始蓄冰量、取冷水流量变化等因素对蓄冰槽融冰性能的影响,为设计同时具有高蓄冰率和低出水温度的蓄冰槽提供厂参考。  相似文献   

11.
Cryo-electron microscopy of vitrified specimens makes it possible to observe fully hydrated biological samples unimpaired by chemical fixation, staining and dehydration. High-pressure freezing represents important progress since it allows a 10-fold increase in the vitrification depth. High-pressure freezing can also induce the formation of undesirable high-pressure forms of ice. We show that ice III or IX is amorphized under the electron beam at a dose of about 2400 electronsnm−2 and that the resulting amorphous ice is similar to the vitreous water obtained by high-pressure freezing.  相似文献   

12.
The effects on water of two cooling methods, immersion in a liquid cryogen and high-pressure freezing, were studied by X-ray cryodiffraction on different sucrose solutions. The nature of the ice formed by each method depends on both the sucrose concentration and the specimen thickness. In order to compare the two methods, we mainly studied specimens having a thickness of 0.2 mm. Under these conditions, freezing by immersion gives rise to hexagonal (IH), cubic (IC) and amorphous (IV) ices when the sucrose concentration (weight/weight) has a value within the range 0–30%, 30–60%, 60% and higher, respectively. The temperature of the phase transitions IV–IC, IC–IH depends on the sucrose concentration. High-pressure freezing gives rise to two specific forms of ice: an amorphous and a crystalline ice (ice III). Ice III is observed when pure water samples are high-pressure frozen provided that the sample temperature does not rise above −150 °C. Above this temperature, ice III transforms into hexagonal ice. Amorphous ice is formed when the sucrose concentration is higher than 20%. The amorphous ice formed under high pressure has a similar, but not identical, X-ray diffraction pattern to that of amorphous ice formed at atmospheric pressure. While the X-ray diffraction pattern of amorphous ice formed at atmospheric pressure (IV) shows a broad ring at a position corresponding to 0.37 nm, that of high-pressure amorphous ice (IVHP) shows a broader ring, located at 0.35 nm. IVHP presents a phase transition (IVHP–IV) at temperatures that depend on the sucrose concentration. We also observed that some precautions have to be taken in order to minimize the alcohol contamination of high-pressure frozen samples. The ice-phase diagram presented in this paper should be taken into account in all methods dedicated to the structural study of frozen biological specimens.  相似文献   

13.
干冰升华式天然气水合物孔底冷冻取样器的研制   总被引:2,自引:0,他引:2  
针对天然气水合物的赋存特点,研制天然气水合物孔底冷冻取样器。取样器是以干冰为冷冻剂,酒精为助冷催化剂和载冷剂的冷冻方式来实现孔底冷冻岩样。介绍了取样器的技术参数、冷冻方式原理、工作原理和结构特点。  相似文献   

14.
针对2台小型制冰机开展试验研究,获得了制冰周期的典型功耗曲线,发现制冰阶段能耗平稳、脱冰阶段能耗急剧增大;分析了不同环境温度和水温对制冰效果的影响,并开展整体取冰和分次取冰的对比试验以验证样机的保温性能,结果表明:与水温相比,环境温度对制冰效果的影响更为明显,且整体取冰得到的总冰量比分次取冰少16%左右。  相似文献   

15.
A freezing-stage has been developed for use on a standard light-microscope, which can provide reproducible, precisely linear cooling and warming rates in the range from 0·1 to 10,000 K/min. Biological cells in aqueous solutions can be observed during the freeze-thaw cycle; the volume loss due to osmotic efflux of water and the intracellular crystallization of water are detected by video-monitoring. The temperature field generated in the observed samples is comparable to extended cylindrical probes and allows the transfer of cryomicroscopic data to technically used vial geometries. Lymphocytes and granulocytes were observed during freezing using the system described. They were separated and washed, and then frozen on the cold stage of the cryomicroscope at cooling rates ranging from 2 to 500 K/min. Shrinkage of the cells was observed up to 100 K/min and intracellular ice formation could be detected starting at 10 K/min. The results show that human leucocytes show excessive shrinkage up to 36% of their initial volume; the probability of intracellular ice formation exhibits a sharp increase from 10 to 100 K/min where nearly all cells contain ice.  相似文献   

16.
The freezing of biological cell suspensions can be understood in terms of ice formation in the external suspension medium and the cellular reactions to the changing environment. Cryomicroscopy allows a quantitative analysis of both categories of phenomena. Besides freezing stages of appropriate thermal design, the components used for that purpose include a microcomputer (PSI 80) based control system, an image analysis system (Intellect 100) and a spectrophotometer (MPV compact). The investigation of extracellular ice formation is focused on the following effects: The redistribution of solutes in the residual liquid and the resulting concentration profiles are determined photometrically or densitometrically. The transitions between various morphologies of the ice–liquid phase boundary (planar–cellular–dendritic) can be related to interface instability theories. With respect to solute segregation, the studies also involve the formation of bubbles from supersaturated gaseous solutes and freezing potentials resulting from the differential incorporation of cations and anions into the solid phase. The interaction between particles or cells and the advancing ice front is determined from critical interface velocities marking the transition between repulsion and entrapment. The effects of freezing on biological cells are studied mainly with blood cells, especially lymphocytes. The water efflux due to osmotical gradients across the membrane yields volume shrinkage curves which are recorded and analysed from video images for various cooling rates. Beyond a certain threshold cooling rate, intracellular ice starts to form, and different crystallization morphologies can be detected. The intracellular crystallization temperatures depend on cooling and warming rates as well as on the presence of penetrating cryoadditives. A fluorescence viability is used to determine the percentage of damaged cells immediately after thawing.  相似文献   

17.
The performance of a commercial double-propane-jet freezer (Balzers QFD 101) has been assessed, for rapid freezing of fresh tissues in freeze-etch work. Samples of diaphragm muscle and intestinal villi were frozen between copper sheets, with a spacer to give 20–30μm thickness of tissue. Fracture cuts were made with the Balzers BAF 400 freeze-etch microtome within 5–10μm of a freezing face (i.e. a tissue face in contact with the copper sheets of the frozen sandwich). After some modifications to the QFD 101, replicas showing no evidence of ice were obtained of muscle cells, although for intestinal epithelial cells some evidence of ice formation was found. Infiltration with 5% glycerol or dimethylsulphoxide improves the depth of good freezing. Results and problems arising from such infiltration are briefly discussed.  相似文献   

18.
非闭合电极电容层析成像传感器在冻土测试中的应用   总被引:1,自引:1,他引:0  
为了实现电容层析成像技术对冻土冻结冰峰面的在线、非侵入测试,研制出了满足冻土测试要求的非闭合电极电容层析成像传感器,并对该种传感器的电容分布特性进行了实测;确定出了适合冻土测试的的高、低介电常数的标定物质;搭建了冻土一维冻结实验系统.对含水量8%的湿土样冻结过程的冰峰面迁移进行了电容层析成像测试,并利用IMNSNOF图像重建算法重建出了冻结过程各时刻的冻结截面物质分布图像,由图像可确定出冻土中已冻土、未冻区以及冰峰面的位置.电容层析成像测试结果与温度测试结果相吻合.  相似文献   

19.
《流体机械》2013,(10):65-68
对刮片式冰浆生成器进行试验研究,探讨不同浓度下的氯化钠溶液结晶的试验过程与现象。试验结果表明:对浓度为3%5%的氯化钠溶液制取冰浆,能效系数最高达到1.9。纯净水和氯化钠溶液在试验过程中,存在一定的过冷度下才开始结晶,并且随着浓度的增加冰点温度呈线性减小,与理论相比,由于氯化钠溶液在低温下容易发生析晶,试验得到的溶液结晶点温度比理论的温度要高一些。  相似文献   

20.
We have investigated the freezing of specimens in a confined volume for preparation of vitreous samples for cryosectioning. With 15% dextran as a cryoprotectant, a sample sealed in a copper tube begins to freeze into crystalline ice when plunged into liquid ethane. Crystallization rapidly causes an increase in the pressure to the point that much of the sample freezes in a vitreous state. We used synchrotron X‐ray diffraction of samples frozen with various amounts of dextran to characterize the ice phases and crystal orientation, providing insights on the freezing process. We have characterized cryosections obtained from these samples to explore the optimum amount of cryoprotectant. Images of cryosectioned bacteria frozen with various levels of cryoprotectant illustrate effects of cryoprotectant concentration.  相似文献   

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