液相添加剂对纳米溴化锂溶液表面张力和沸腾温度的影响

通过在纳米溴化锂溶液中添加液相添加剂降低溶液沸腾温度,从而有助于大幅度应用工业余热、废热等低品味热源。溶液沸腾温度主要反映了溶液汽泡成核所需的临界活化能(过热度)。尽管影响沸腾温度的因素较多,但是溶液的表面张力是一个重要的因素。此外纳米流体中的分散剂能造成纳米颗粒在加热面上如淤泥般的沉积,湮没了汽化核心,导致沸腾温度升高。     

高温液相添加剂对纳米LiBr溶液表面张力和沸腾温度的影响

通过在纳米溴化锂(LiBr)溶液中添加表面活性剂降低溶液沸腾温度,从而有助于大幅度应用工业余热、废热等低品味热源。尽管影响沸腾温度的因素较多,但是溶液的表面张力是一个重要的因素,首先对异辛醇(C8H18O)、壬醇(C9H20O)和癸醇(C10H22O)3种高沸点液相添加剂对纳米LiBr溶液的表面张力的影响做了深入研究,并进一步研究了相对应的沸腾温度。并且通过实验发现随着烷醇中烷基数增加,表面张力更低,使得沸腾温度也进一步降低。     

分散剂对纳米LiBr溶液稳定性的影响

文章在论述分散剂增强纳米流体分散稳定性的基础上,通过添加E414和C6H5O7（NH4）,验证分散剂增强纳米LiBr溶液的分散稳定性,通过测量分别添加异辛醇（C8H18O）、壬醇（C9H20O）和癸醇（C10H220）基液的表面张力,发现分散剂也能增强纳米LiBr溶液表面张力的稳定性,主要因为表面张力和汽化成核临界功之间存在相关性,因此,分散剂同样能增强纳米LiBr溶液沸腾温度的稳定性。     

添加纳米微粒的溴化锂溶液稳定性及烧结特性研究

通过在58%浓度工业用溴化锂水溶液中添加纳米微粒及其相应的分散剂,对纳米溴化锂溶液的稳定性及其在高温温度下的烧结特性进行研究。研究结果表明,在纳米溴化锂溶液中分散剂浓度从0.3%变化到0.6%,具有最佳组分值,即:最佳稳定性能值。纳米溶液在160℃温度下,分散剂组分由0.1%增至1.0%,加热过程的24h中,烧结物粒径增长率较大,48h后,所有组分的粒径增长趋于缓慢;在纳米溶液分散剂组分不改变,加热温度由50℃增加到160℃期间,12h过程中,粒径增长速率较快,48h后纳米粒径增长趋势平稳。烧结粒径微观分析可知,分散剂组分从0.1%增加至1.0%,烧结体粒径变小,这说明分散剂组分越浓,烧结体粒径越小,烧结层越密实。因此,需要在改变纳米溴化锂溶液的稳定性和烧结现象之间进行优化组合,并选择耐高温的分散剂。     

添加纳米颗粒和分散剂的相变流体性能测试研究

结合太阳能低温集热蓄热,基于前期选定的烃类相变流体,通过热物性和稳定性测试对比,选取了适合的纳米颗粒(TiO_2)和分散剂(SDBS),分析了纳米颗粒质量分数、粒径以及分散剂质量分数对相变流体的热物性及稳定性的影响。结果表明,纳米颗粒质量分数越大,颗粒粒径越大,相变流体的热物性及动态稳定性越差,而分散剂质量分数对相变流体的动态稳定性影响不大。烃类相变流体中分别添加质量分数为0.1%的20 nm TiO_2纳米颗粒和质量分数为0.1%的SDBS分散剂,其热物性及稳定性最佳。     

基于太阳能低温集热蓄热的相变流体制备及性能研究

基于前期对相变流体的实验研究,选定了以质量分数为20%的烃类相变流体作为基液,制备了多组以TiO_2纳米颗粒为添加剂,SDBS为分散剂的添加纳米颗粒的相变流体。通过改变纳米颗粒质量分数、粒径以及分散剂质量分数,分析不同相变流体随温度变化的热物性及稳定性,最终得出烃类相变流体中分别添加质量分数为0.1%的20 nm TiO_2纳米颗粒及质量分数为0.1%的SDBS分散剂,其热物性及稳定性最佳。为添加纳米颗粒的相变流体的制备及其在太阳能低温集热蓄热领域的应用提供了参考。     

纳米CuO微粒对冷冻机油性能的影响

研究纳米氧化铜微粒对冷冻机油性能的影响。由于纳米微粒作为油品添加剂具有降磨减磨的作用,但是纳米流体的稳定性较差使得纳米微粒作为油品添加剂的应用受到了很大的限制。从稳定性、黏度及表面张力3个方面对纳米CuO微粒对冷冻机油性能的影响进行试验研究。结果表明,在选用分散剂为MH-95,超声波振荡及纳米CuO微粒添加量为1％时的纳米流体性能最优。     

超声空化对溴化锂溶液气泡运动的影响

根据溴化锂溶液的物性参数方程,利用试验数据和超声作用于均相液体中空化气泡运动的动力学模型,推导出溴化锂溶液超声空化气泡运动方程。利用MATLAB对溴化锂溶液超声空化气泡的运动特性进行数值模拟,对过冷沸腾和饱和沸腾条件下溴化锂溶液沸腾气泡的运动变化特性进行研究,得到超声空化效应对气泡运动特性变化影响的模拟结果。为溴化锂溶液传热性能和吸收式制冷机组制冷效率的提高提供一定的理论依据。     

颗粒亲水性对纳米流体表面张力的影响研究进展

纳米流体作为一种新型换热介质,其表面张力的变化与流体沸腾换热等热物理性质有着密切的联系。纳米流体通常由"两步法"制得,其表面张力受温度、纳米颗粒粒径、纳米颗粒体积分数或质量分数等多方面影响。在前人的研究中,表面张力随流体温度的升高而减小,随纳米颗粒粒径的增加而增大,但表面张力随纳米颗粒体积分数或质量分数的变化情况则不一致。通过总结由不同颗粒与不同基础流体组成的纳米流体表面张力的变化趋势,分析纳米流体表面张力的变化与颗粒亲水性的关系。分析结果表明:亲水型颗粒与疏水型颗粒对纳米流体表面张力的影响恰好相反;亲水型纳米颗粒体积分数或质量分数不同时,其纳米流体表面张力的变化也不相同。     

VB与Matlab混合编程实现溴化锂溶液物性数据的可视化计算

文章采用VB与Matlab的混合编程,应用ActiveX自动化技术,对溴化锂溶液的热物性数据进行了处理.实现了热物性数据的可视化计算.     

纳米SiO_2在水性介质中的分散稳定性研究

纳米SiO2特殊的性能使其在很多领域都得到了广泛的应用,而纳米SiO2能否在水性介质中稳定分散将会影响产品的最终质量。本实验选择了九水合硅酸钠和聚丙烯酰胺作为分散剂,并通过激光粒度分析仪和沉降实验对纳米颗粒的分散稳定性进行评价。发现高速研磨能够使聚丙烯酰胺充分地吸附到纳米颗粒表面,聚丙烯酰胺能使纳米SiO2颗粒在水溶液中保持良好的分散稳定性,但是,聚丙烯酰胺的加入量过饱和反而会引起纳米SiO2颗粒的团聚,九水合硅酸钠和聚丙烯酰胺结合起来使用可以发挥协同效应,从而显著改善纳米SiO2颗粒在水溶液中的分散稳定性。     

Atmospheric and sub-atmospheric boiling of H2O and LiBr/H2O solutionsEbullition à la pression atmosphérique et au-dessous de H2O et de solutions de LiBrH2O

Measurements are presented for the nucleate pool boiling of LiBrH₂O solutions at concentrations typically used in LiBrH₂O air conditioning systems. A commercial grade copper tube was used for all tests as being typical of the testing surface likely to be used in a commercial plant.The object of this work was to correlate nucleate boiling heat transfer for pure water and aqueous solutions using Re, Pr number expressions and thermophysical properties of the boiling liquid and vapour at a clean surface. Such an equation is proposed and tested.     

Thermophysical Properties of Aqueous Solutions Near the Equilibrium Freezing Temperature

Measurements of the surface tension, viscosity, and thermal conductivity of LiBr and LiSCN aqueous binary solutions have been performed to determine the thermophysical properties near the equilibrium freezing temperature. A differential capillary-rise method for surface tension and the transient hot-wire method for thermal conductivity were employed. Furthermore, a rotational viscometer was utilized for the measurement of viscosity. Correlation equations for the data of the aqueous binary test solutions as a function of temperature and concentration are presented.     

Surface tension of aqueous binary solutions

Measurements of surface tension have been performed to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of D-Sorbitol, potassium chloride, and ammonium chloride. A differential capillary-rise method was employed for the measurements. The results showed that the surface tension of test solutions increased as the temperature decreased and that the surface tension of chloride solutions increased with an increase in its concentration, while for D-Sorbitol solution the surface tension decreased with increasing concentration. Correlation equations for the surface tension of three aqueous binary solutions as a function of temperature and concentration were determined.     

界面活性剂的混合添加对溴化锂溶液吸收水蒸气的影响

在静态池吸收实验中将两种有效添加剂混合添加,测试其对溴化锂水溶液吸收水蒸气的影响,从而探寻不同界面活性剂之间的促进或者抑制作用。通过对正辛醇、仲辛醇、异辛醇、正己醇四种物质采用单种添加和两种混合添加的测试实验表明,混合添加后的效果与其中较好的添加剂单独添加的效果接近,例如,正辛醇在四种添加剂中效果最好,其它添加剂与正辛醇混合添加的效果都与正辛醇单独添加时的效果相近。     

Experiments on saturated vapor pressure of aqueous lithium bromide solution at high temperatures

This work mainly focuses on the determination of the saturated vapor pressure of LiBr aqueous solution with mass fraction ranging from 43.14 to 65.26 wt% at high temperature experimentally. First, the measurement of the saturation vapor pressures is conducted in deionized water as well as in LiBr aqueous solution at a lower temperature. The experimental result has a good agreement with the literature value, which verified the reliability and accuracy of the experimental apparatus. Second, measurement of the saturated vapor pressure of LiBr aqueous solution with mass fraction ranging from 43.14 to 65.26 wt% is systematically carried out in the 156.06~257.84 °C temperature range. Based on the saturated vapor pressure data at lower temperature, a correlation for predicting the saturated vapor pressure data of the LiBr aqueous solution is obtained, which is also available for high temperature condition. Therefore, this work will be very helpful for the modeling and design of high temperature LiBr/H₂O absorption heat transformers.     

Surface tension of low-temperature aqueous solutions

Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.