共查询到19条相似文献,搜索用时 218 毫秒
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采用流动型比热容测量法,在相同温度、不同压力和相同压力、不同温度条件下,开展航空喷气燃料RP-3的比热容特性试验,研究航空喷气燃料比热容参数随温度和压力的变化规律。结果表明,在相同压力、不同温度条件下,比热容随温度的升高逐渐增加;在相同温度、不同压力条件下,比热容随压力的升高逐渐降低。 相似文献
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针对机械搅拌反应器内非牛顿流体混合效率问题,对机械搅拌反应器内非牛顿流体流场特性进行了研究。采用非接触式流场测试PIV技术,对试验规模四斜叶桨搅拌反应器内非牛顿流体流场进行了测量,讨论和分析了不同溶液浓度和不同搅拌速度对机械搅拌反应器内流场分布的影响。研究结果表明:搅拌速度不仅可以影响流体间对流强度,而且会改变流体流场结构;溶液浓度对流场结构影响不大,但影响桨叶下部高流速区域大小和流体的最大速度。 相似文献
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盐浴氯化钡、氯化钠混合盐的快速测定 总被引:1,自引:0,他引:1
利用置换滴定法原理,在pH=10的氨性缓冲溶液中,加入适量MgY,以络黑T为指示剂,用EDTA滴定Ba2 ,测定试样中氯化钡的含量.在中性溶液中,加入少量淀粉,以二氯荧光素为指示剂,用硝酸银标准溶液滴定溶液中的Cl-,并在计算氯化钠含量时扣除氯化钡中Cl-的影响,从而求得试样中氯化钠的含量.该方法用于中温盐浴氯化钡、氯化钠混合盐中氯化钡、氯化钠的测定,结果满意. 相似文献
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机械搅拌槽内非牛顿流体内流特性研究 总被引:1,自引:0,他引:1
在工业生产中获得广泛应用的机械搅拌混合,其流体大都是非牛顿流体,具有与牛顿流体不同的流变性质(弹性效应,剪切稀化以及剪切变稠),所以急需对非牛顿流体情况下搅拌槽内的内流特性开展研究。基于Lin-A315桨型的粒子图像测速技术(Particle Image velocimetry,PIV)试验结果对搅拌槽内非牛顿流体的流场特性进行定常/非定常数值模拟,研究不同质量分数的黄原胶溶液在不同搅拌速度下的轴面流速分布、湍动能分布、径向截线的流速剖面、所需要的搅拌混合时间以及搅拌能耗。结果表明,数值模拟可以很好地模拟分析机械搅拌槽内非牛顿流体的流场特性;提高搅拌速度可以增加槽内主循环流的范围和强度,搅拌槽内涡的分布和湍动能分布范围也相应变大,与100 r/min相比,300 r/min和500 r/min工况下的轴向速度最大值增加3.6倍和5.9倍,所需要的混合时间缩短0.46倍和0.36倍;增加黄原胶溶液的浓度会减小流场的主循环流范围,增加速度梯度,降低槽底区域循环速度,所以与非牛顿流体溶液浓度的变化相比,所需要混合时间对转速变化更为敏感;另外提高搅拌速度会增加搅拌能耗,因此对低浓度非牛顿流体宜选择中等转速、高浓度非牛顿流体宜选择高转速以有利于溶液混合和能源节约。 相似文献
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采用磁性Fe_3O_4纳米颗粒为磁核,用反相悬浮聚合法制备了磁性壳聚糖复合微球,用激光粒度仪和透射电镜对磁性壳聚糖微球的尺寸和形貌进行分析,考察了壳聚糖浓度、乳化剂用量、交联剂浓度、搅拌速度等参数对壳聚糖成球的影响。结果表明:使用4 mL质量浓度为4 g·L~(-1)壳聚糖溶液、0.1 mL司本-80和0.1 mg磁性Fe_3O_4纳米颗粒,经超声分散1 h后,加入0.5 mL4%的戊二醛,在转速350 r·min~(-1)搅拌条件下,室温下反应2 h,可得到形貌光滑、粒径为0.5~2 μm的磁性壳聚糖复合微球,该壳聚糖复合微球具有较好的磁响应性能。 相似文献
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屠宗礼 《机械工人(热加工)》1956,(12)
在喷漆中,香蕉水是作为溶剂用的,它并能使喷漆面光泽。但它的价格相当高,每箱要76元。我厂装配车间漆工组线长赵阿福同志,提出用樟脑酒精溶液来代替香蕉水的建议,经过几次试验,证明可以收到节约的效果(酒精每箱只29.76元)。试验的情况如下。用3%樟脑酒精溶液(每3克樟脑丸溶解于100克工业用酒精内)来全部代替香蕉水,结果喷漆表面的光泽较差。另外用樟脑酒精溶液代替一半香蕉水(即用一半香蕉水,一半樟脑酒精溶液),结果喷漆表面光 相似文献
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A differential, membrane-based nanocalorimeter for general specific heat studies of very small samples, ranging from 0.5 mg to sub-μg in mass, is described. The calorimeter operates over the temperature range from above room temperature down to 0.5 K. It consists of a pair of cells, each of which is a stack of heaters and thermometer in the center of a silicon nitride membrane, in total giving a background heat capacity less than 100 nJ/K at 300 K, decreasing to 10 pJ/K at 1 K. The device has several distinctive features: (i) The resistive thermometer, made of a Ge(1 - x)Au(x) alloy, displays a high dimensionless sensitivity ∣dlnR∕dlnT∣ ? 1 over the entire temperature range. (ii) The sample is placed in direct contact with the thermometer, which is allowed to self-heat. The thermometer can thus be operated at high dc current to increase the resolution. (iii) Data are acquired with a set of eight synchronized lock-in amplifiers measuring dc, 1st and 2nd harmonic signals of heaters and thermometer. This gives high resolution and allows continuous output adjustments without additional noise. (iv) Absolute accuracy is achieved via a variable-frequency-fixed-phase technique in which the measurement frequency is automatically adjusted during the measurements to account for the temperature variation of the sample heat capacity and the device thermal conductance. The performance of the calorimeter is illustrated by studying the heat capacity of a small Au sample and the specific heat of a 2.6?μg piece of superconducting Pb in various magnetic fields. 相似文献
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Junsheng Wang Yongxin Song Sun Jinyang Xudong Wu Yeqing Sun Xinxiang Pan Dongqing Li 《Measurement》2013
Sweat test based on chloride ion selective electrode is the common method for the diagnosis of Cystic Fibrosis (CF). In our previous study, the possibility of using chloride ion sensitive fluorescent dye to determine the chloride ion concentration with a small volume of sample has been explored. However, we found the conventional Stern–Volmer Equation is applicable only for large systems such as a fluorescent microscope with a large volume of sample and dye solution; and it is not valid for portable devices using a small photo detector and a small volume of sample and dye solution. Therefore, in this paper, extensive experiments were performed by using a miniature fluorescent detection system; the effects of the parameters including the concentration and the volume of fluorescent dye solution, the coefficient of Stern–Volmer plot, and the volume ratio of the fluorescent dye solution and the chloride solution were studied; and a modified Stern–Volmer Equation was obtained. Using the modified Stern–Volmer correlation, the miniature fluorescent detection device can detect the chloride ion concentration correctly and rapidly. 相似文献
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《流体机械》2016,(2):71-76
我国的低温热源资源非常丰富,但由于部分低温热源的温度较低,利用率不高,造成了一定的浪费。毛细管自然对流散热器是一种新型的低温供暖末端设备,以毛细管网为换热芯,以自然对流为主要散热方式,可使用不低于30℃的热水采暖,从而对其他类型供暖末端设备难以利用的低品位热源加以循环利用。本文利用数值模拟的方法,分析了毛细管自然对流散热器的散热规律,得出了设备高度、厚度、进风口和送风口尺寸等几个结构因素与设备散热强度的制约关系,并根据关系曲线和数据总结出了最优结构因素的计算公式,为毛细管自然对流散热器的进一步研究和应用提供了依据。为保证结果的可信性,本文还通过相应样机的散热量试验结果和温度场实测数据对模拟结果进行验证,结果表明模拟计算结果正确。 相似文献
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Fuzhu Han Gang Cheng Zhijing Feng Isago Soichiro 《The International Journal of Advanced Manufacturing Technology》2009,41(9-10):871-879
Wire temperature is an important parameter in the wire electro-discharge machining (WEDM) process because overheating of the wire can cause the wire to break. It is difficult, however, to measure the wire temperature directly under the condition that the wire is emerged in water and surrounded by the workpiece. Only mathematical analyses by now have been reported to determine such temperature but limited by the assumption of convective heat transfer coefficient and the percentage of energy distribution. Based on the relationship between the wire temperature and the value of its resistance, this paper proposes a measuring system that has been developed to experimentally track and record the average temperature increment of the wire electrode for the WEDM process. With this system, the average temperature increment of the wire under discharges can be as high as 130°C. The average temperature increment of the wire under normal discharges has also been measured for low discharging energy. A typical application of this system is finally discussed in this paper. By measuring the average temperature increment of the wire electrode heated by Joule heating energy, the convective heat transfer coefficient in WEDM is experimentally determined. 相似文献
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Attentions has been given to ionic liquids as an alternative physical solvent for carbon dioxide (CO2) absorption because of their potential for gas selectivity, absorption capacity and low desorption energy by tailoring the molecules. Ionic liquid normally have a high viscosity, which influences the performance of absorption processes, and therefore, efficiency. This study investigates the hydrodynamics of ionic liquids in a two-phase gas–liquid flow by determination of the bubble formation, distribution of gas and bubble velocity profiles. A dual plane electrical resistance tomography (ERT) system and an optical imaging device were applied to a bubble column reactor of 50 mm internal diameter for the study. The model ionic liquids were aqueous solutions of sodium chloride (NaCl) with conductivity adjusted by altering the concentration of NaCl. Gas holdup has been estimated by analyses of conductivity data obtained from ERT by application of Maxwell's relationship which reveals significant increase in gas holdup as ionic concentration increases and is in good agreement with other studies. 相似文献
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介绍一种以氯化钙/活性炭复合吸附剂和氨作为吸附工质对的多功能热管型吸附式制冰机组,该机组利用低品位余热作为驱动热源进行制冰。为了强化机组换热及防止余热腐蚀现象,采用热管技术完成吸附床的加热解吸、冷却吸附及回热过程,吸附床加热解吸时,形成以余热发生装置为热管蒸发段、以吸附床为热管冷凝段的热管型加热回路;两吸附床间回热时形成以高温解吸床为热管蒸发段、以低温吸附床为热管冷凝段的热管型回热回路;吸附床冷却吸附时,形成以吸附床为热管蒸发段、以冷却器为热管冷凝段的热管型冷却回路。在此基础上采用新回质回热循环方式对机组性能进行了研究。试验结果表明:新回质回热方式与传统回质回热方式相比,可大幅度增加机组制冷量,单位质量吸附剂制冷功率,(Specific cooling power,SCP)和性能系数(Coefficient of performance,COP)增大幅度均在17 %以上;相对基本循环,传统回质回热方式可使机组COP提高43.8 %,新回质回热方式可使机组COP提高幅度高达68.7 %。可见采用新回质回热方式更有利于提高吸附制冰机组的工作性能。 相似文献