Experimental Investigation on the Performance of Heat Pump Operating with Copper and Alumina Nanofluids

In the present study,an attempt ismade to enhance the performance of heat pump by utilizing two types of nanofluids namely,copper and alumina nanofluids.These nanofluids were employed around the evaporator coil of the heat pump.The nanofluids were used to enhance the heat input to the system by means of providing an external jacket around the evaporator coil.Both the nanofluids were prepared in three volume fractions 1%,2%and 5%.Water was chosen as the base fluid.The performance of the heat pump was assessed by calculating the coefficient of performance of the system when it was operated with and without nanofluid jacket.A significant enhancement in the coefficient of performance was noticed when copper and alumina nanofluids were employed in the system.Also,the coefficient of performance was found to have a direct relationship with the tested volume fractions.For the highest volume fraction of 5%,the performance of the heat pump was found to enhance by 23%with alumina nanofluid,while for copper nanofluid,a very significant enhancement in performance by 72%was observed.Thus,utilizing of nanofluids in heat pumps can be very beneficial towards performance enhancement and the idea can also be extended to other thermal systems such as steam power plant,automobile radiator,industrial heat exchangers and refrigeration systems.

Unsteady MHD Casson Nanofluid Flow Past an Exponentially Accelerated Vertical Plate:An Analytical Strategy

In this study,the characteristics of heat transfer on an unsteady magnetohydrodynamic(MHD)Casson nanofluid over an exponentially accelerated vertical porous plate with rotating effects were investigated.The flow was driven by the combined effects of the magnetic field,heat radiation,heat source/sink and chemical reaction.Copper oxide(CuO)and titanium oxide(TiO2)are acknowledged as nanoparticle materials.The nondimensional governing equations were subjected to the Laplace transformation technique to derive closed-form solutions.Graphical representations are provided to analyze how changes in physical parameters,such as the magnetic field,heat radiation,heat source/sink and chemical reaction,affect the velocity,temperature and concentration profiles.The computed values of skin friction,heat and mass transfer rates at the surface were tabulated for various sets of input parameters.It is perceived that there is a drop in temperature due to the rise in the heat source/sink and the Prandtl number.It should be noted that a boost in the thermal radiation parameter prompts an increase in temperature.An increase in the Prandtl number,heat source/sink parameter,time and a decrease in the thermal radiation parameter result in an increase in theNusselt number.The computed values of the skin friction,heat andmass transfer rates at the surface were tabulated for various values of the flow parameters.The present results were compared with those of previously published studies andwere found to be in excellent agreement.This research has practical applications in areas such as drug delivery,thermal medicine and cancer treatment.

Heat transfer of copper/water nanofluid flow through converging-diverging channel

The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.

The Interesting of Antifungal Effects of Novel In Vitro Fabrics of Stabilized ZnO Nanofluids

According to the extent of fungal infections, to be chronic these such diseases and recently the emerging issue of increased antibiotic resistance in fungal infections, most of scientists are going to find a proper way to replace antibacterial agent by significant semiconductor ZnO nanoparticles (NPs). They are well known to be one of the most important and special metal oxide nanoparticles in pharmaceutical against the most common fungi. ZnO nanoparticles were synthesized using sol-gel, hydrothermal and functionalized surface methods and formulated in water solutions as nanofluids. XRD, FTIR and SEM techniques and UV-Vis absorbance spectroscopy characterized their ZnO modified nanostructures. Also antimycotic potential according to generally tests such as: (MIC) minimum inhibitory concentration, (MFC) minimum fungicidal concentration and normally well diffusion method with standard strains fungi were performed. Among five common fungi strains using in this research, new various ZnO nanofluids showed noticeable results for dermatophyte fungi like Trichophyton mentagrophytes, Microsporum gypseum, Microsporum canis, Candida albicans and Candid tropicalis which had un growth zones in order 70, 40, 35, 30 and 30 mm in comparing with Clotrimazole reference reagent: 30, 25, 25, 18 and 20 mm by well method. The performance of MIC for ZnO nanofluids on fungi was determined to be equal to 0.35, 3.12, 6.25, 6.25 and 6.25 μgr/ml and MFC of nanoproducts showed the 1.5, 12.5, 25, 25 and 25 μgr/ml. Therefore, the designed ZnO nanofluids could reveal the most effect on fungi which cause dermal (ringworm), mucosal (thrush) and vaginal infections, so we are able to apply these surface high energetic ZnO water-based nanofluid formulations as in vitro nanomedicine and nanohygiene for the first time.

纳米流体太阳集热器的光热性能研究

采用直流碳弧法制备了平均粒径为25nm的碳包铜纳米颗粒,包覆的碳层有效避免了周围环境对铜纳米粒子的影响。采用超声波振荡和添加分散剂的方法,将碳包铜纳米颗粒均匀稳定的分散在体积比为1:1的乙二醇水溶液中,获得了用于直接吸收式太阳集热器的循环工质—碳包铜纳米流体。通过闷晒实验,研究了碳包铜纳米流体的光热转换性能;通过对集热器热效率的测试,研究了碳包铜纳米流体太阳集热器的热性能,结果表明:添加纳米颗粒后,碳包铜纳米流体的光热转换性能明显优于基液和涂有黑漆的铜管表面。直接吸收式的碳包铜纳米流体太阳集热器显著提高了集热器的集热效率,实验中的最高集热效率可达74.688%,比传统平板型集热器的集热效率提高了近10%。

液相还原-步法制备超细铜纳米流体的研究

采用硼氢化钾液相一步法还原硫酸铜水溶液,加入了络合剂EDTA-2Na和阳离子型分散剂CTAB(C19H42NBr),获得了铜纳米流体。由动态光散射粒度分析仪测得加入0.05mol/LCTAB的纳米流体的平均粒度仅为1.02nm,经X射线衍射分析离心分离所得粉末绝大部分为纯净的纳米铜粉,还存在极少量的Cu2O,这受到络合剂EDTA-2Na化学反应的影响。

纳米铜粉在太阳能集热器循环工质中的分散

以阿拉伯树胶和六偏磷酸钠为分散剂,以乙二醇水溶液为分散介质,采用球磨分散法制备用作太阳能集热器循环工质的铜纳米流体。通过分光光度法和沉降法研究分散剂含量和球磨时间等因素对铜纳米流体稳定性的影响。结果表明,阿拉伯树胶和六偏磷酸钠均能有效的分散铜纳米颗粒,得到均匀、稳定的铜纳米流体。当用阿拉伯树胶作分散剂时,质量分数为0.25%、球磨时间为6h时,分散效果最佳。用六偏磷酸钠作分散剂,质量分数为0.1%、球磨时间为2h时,分散效果最佳。阿拉伯树胶对铜纳米颗粒的稳定分散作用主要是通过空间位阻机制来实现的,而六偏磷酸钠对铜纳米颗粒的稳定分散作用则主要是通过静电稳定机制来实现的。

TiO_2—蒸馏水纳米流体在内螺纹铜管内表面传热试验研究

为研究TiO2—蒸馏水纳米流体在内螺纹管内的表面传热特性,自行设计并建立一套纳米流体表面传热试验系统和数据采集系统,试验系统核心部分分别采用铜光管和内螺纹铜管,将基液和TiO2—蒸馏水纳米流体分别应用于铜光管和内螺纹铜管内Re为3 000～8 000范围内进行表面传热试验研究,结果表明,在内螺纹铜管内,TiO2—蒸馏水纳米流体表面传热系数都是随着流速的增加而不断提高,随着纳米颗粒质量分数的不断增加,TiO2—蒸馏水纳米流体表面传热效果越来越差,而且弱于基液的表面传热效果,纳米颗粒质量分数不变的情况下,纳米流体表面传热效果随着流体平均温度的提高而加强。通过对纳米流体在不同圆管内试验结果进行对比,发现TiO2—蒸馏水纳米流体在内螺纹管内表面传热效果相对于光管内表面传热效果的强化程度低于基液的强化程度,TiO2—蒸馏水纳米流体不适用于内螺纹强化换热管。

化学处理法制备碳包铜导热纳米流体及其性能表征

氩电弧等离子体法制备碳包铜纳米粒子,采用双氧水化学处理和添加十二烷基苯磺酸钠两种方法制备碳包铜-水纳米流体,探讨了不同分散方法对碳包铜纳米流体导热性能的影响。结果表明,双氧水化学处理碳包铜纳米粒子制备水介质分散体系具有比添加分散剂制备分散体系更高的导热性能。采用化学处理法,添加质量分数为2.0%的碳包铜-水纳米流体导热率可提高60%。

纳米铜对蓖麻油酸流体热导率提升机制的分子动力学模拟

为了研究铜纳米粒子对蓖麻油酸基础流体热导率提升的作用机制,基于分子动力学模拟(MD)方法,以铜纳米粒子直径、添加量、形状、布朗运动及系统温度为变量,对纳米流体热导率的影响机制进行研究。结果表明:纳米粒子的布朗运动会提高纳米流体的热导率;纳米铜(Cu)的加入改变了蓖麻油酸基流体的部分区域密度,产生的液体吸附层对基础流体导热性有阻碍作用;纳米流体的热导率随纳米粒子直径、添加量、系统温度的增加而增加;当纳米粒子体积相同时,表面积大的形状会提高热导率。

非晶炭包裹铜纳米粒子在导热流体中的应用

采用氩电弧等离子体法制备不同粒径的炭包铜纳米粒子,研究其抗氧化性能、在水介质中的分散性能和导热性能。结果表明:炭层的保护作用赋予铜晶体更高的抗氧化性能;非晶炭层的特殊结构可通过双氧水化学处理使其表面产生羧基和羟基,提高其在水介质中的分散性能;炭包铜粒径越小,纳米流体导热性能越好。

水基纳米流体大容积沸腾换热特性分析

以提高换热设备工质换热效率为背景,通过在系统压力0.1MPa下对去离子水、水基氧化铝、水基氧化铜纳米流体进行池沸腾换热实验,从过热度、沸腾换热系数、强化率等方面综合分析不同热流密度的纯水及浓度分别为0.001%、0.01%、0.1%、1%、2%的两种纳米流体的沸腾换热效果,并从活性气泡临界直径、汽化核心、工件内外表面面积比值等方面进行机制分析。结果表明,水基氧化铝纳米流体的换热特性要好于水基氧化铜纳米流体。当纳米颗粒浓度小于1%时,导热系数提高,从而使热流密度增加;表面张力降低,从而使活性气泡临界直径减小;沸腾换热效率将随着颗粒浓度的上升而提高。同时,颗粒浓度过大,由于颗粒沉积降低了汽化核心的分布密度,纳米颗粒对沸腾换热的改善作用将会被弱化。

用于太阳能集热介质的纳米铜制备技术与铜纳米流体性能综述

纳米流体技术的不断发展为直接吸收式太阳能集热介质的研究提供了强有力的支持。铜价格低廉、储量丰富且导热性能良好,将纳米尺度的铜粒子稳定分散于传统集热介质中制得的纳米流体悬浮液对可见光波段表现出强吸收性能。本文首先对纳米流体中常见的球形、立方体、棒状和线状铜纳米粒子添加物的水热还原制备方法进行了综述,重点讨论了表面活性剂在产物形貌控制中的作用及其对纳米粒子在基液中分散稳定性的影响。进而分别对铜纳米流体的导热系数、粘度、比热及光能辐射特性的研究现状进行了归纳总结,给出了铜纳米流体在直接吸收式太阳能集热系统中的应用现状。最后,提出了铜纳米流体应用于太阳集热器循环工质尚需解决的问题及进一步的研究方向。

不同形貌纳米氧化铜的合成成及导热应用

纳米氧化铜(CuO)在传感器、催化及强化传热领域有优异的性能。以微生物法浸取的Cu^(2+)为铜源,通过改变溶液的pH制备不同形貌的纳米CuO,并对产物进行表征与分析。制备了以硅油为基体的含纳米CuO的纳米流体,并测试了其热导率。结果表明,纳米流体的热导率与添加CuO的体积分数基本呈线性关系。当添加相的体积分数为5%时,片状、梭子状和蒲公英状的CuO纳米流体热导率分别提高了12.3%、12.9%和29.0%。这说明CuO的形貌对复合体系的热导率有显著的影响,其中蒲公英状的纳米材料效果最佳。

颗粒团聚对水基铜纳米流体导热系数影响机理研究

研究表明纳米颗粒团聚影响纳米流体的导热系数,但颗粒团聚对导热系数的影响机理尚不清晰.文中构建水基铜纳米流体模拟体系,采用平衡分子动力学方法分析颗粒团聚行为对纳米流体导热系数的影响规律与机理.结果表明,铜颗粒发生团聚导致纳米流体的导热系数升高.纳米流体体系中铜颗粒表面存在致密水分子吸附层,不同颗粒水吸附层间强吸引作用是颗粒相向运动与发生团聚的驱动力.通过分析影响纳米流体导热系数的动能、势能及应力贡献项发现,颗粒发生团聚后颗粒势能绝对值增加,是引起纳米流体导热系数升高的主要原因.

一步化学法制备铜纳米流体的研究进展

介绍了一步化学法制备铜纳米流体的研究状况,阐述了通过调整铜盐浓度、还原剂浓度、温度、分散剂种类及加入量等制备参数可以获得具有优良导热性能的、分散稳定的铜纳米流体。

Synthesis and Characterization of Various Protein <i>α</i>-Lactalbumin Nanotubes Structures by Chemical Hydrolysis Method

New water-based nanofluids including unparalleled milk protein α-lactalbumin hollow nano-bio-tubes using low cost, available and advanced partial chemical hydrolysis strategy in bottom-up nano-assembly have been employed in this work. The aqueous sol-gel chemistry in nanotechnology which we selected for this goal offers new fabrication as interesting smart protein nanotubes. The kinds of nanometer sized tubular structures such as waved, helically coiled, bent, bamboo-shaped, bead-like and branched single-walled protein nanotubes (SWPNTs) with a range of 3 - 8 nm in outer diameters were produced by this method. Complete characterization for natural produced nanotubes including SEM, TEM images, G bond and D bond in Raman spectroscopy, XRD patterns, DLS (Dynamic Light Scattering) and FTIR analysis were evaluated which they are most significant experiments in synthesized protein nanotubes soluble in clear water nanofluids and stabilization of transparent nanofluids was proved within more than one year after preparation. Various necessary ligand ion salts such as Mn2+, Zn2+ and Ca2+ or mixtures as bridge makers and producing biological self-assembly hollow SWPNTs were performed and we focused on new chemical technology under specific acidic hydrolysis method not conventional enzymatic proteolysis and applying surfactants, pH reagent, Tris-HCl buffer, polar solvent which could be produced by β-sheet stacked hydrolysed protein α-lactalbumin mechanism under appropriate conditions to achieving high efficiency new protein nanotubes skeleton. They can be promising materials applied in food science, diet nutrition, nanomedicine, nano-biotechnology and surgery.

氧化铜/石墨烯纳米流体的制备及光吸收-光热性能

采用湿化学方法制备得到氧化铜纳米颗粒,进而制备氧化铜纳米流体并与石墨烯纳米流体复合得到CuO/G纳米流体。利用X-射线衍射、透射电镜、紫外-可见分光光谱仪等测试方法对样品进行表征。CuO/G纳米流体在太阳光波段显示出比氧化铜纳米流体和石墨烯纳米流体更加优异的光吸收性能,随着石墨烯含量的增加,CuO/G纳米流体的辐照度逐渐与太阳辐照度契合。在模拟太阳光照射下对不同质量分数的CuO/G纳米流体进行光热转换性能测试,发现随着质量分数的增加CuO/G纳米流体光热转换效率显著提高,0.10%的CuO/G纳米流体光热转换效率可以达到92%,体现出优异的光热转换性能。

Hydromagnetic peristaltic transport of copper-water nanofluid with temperature-dependent effective viscosity

The unique chemical mechanical, and thermodynamic properties of nanofluids make them a subject of great interest for scientists from all domains. Such fluids are of particular significance in biomedical engineering owing to their vast and novel applications in modern drug delivery systems; for example, mixed convective peristaltic flow of water-based nanofluids under the influence of an externally applied magnetic field is of particular significance. Hence, a lot of research has focused on peristalsis in the presence of velocity and thermal slip effects. An empirical relation for the effective viscosity of the nanofluid is proposed here for the first time. The viscosity of the nanofluid varies with temperature and nanoparticle volume fraction. Numerical simulation of the resulting nonlinear system of equations is presented for different quantities of interest. The results indicate that the maximum velocity and temperature of the copper-water nanofluid increase for larger variable viscosity parameter. The pressure gradient in the wider part of the channel is also found to increase as a function of the variable viscosity parameter. The variable viscosity parameter also influences the size of the trapped bolus. An increase in the nanoparticle volume fraction reduces the reflux phenomenon in a peristaltic flow.

微通道中原位分散技术可控制备氧化铜纳米流体及复合薄膜前体

疏水纳米颗粒分散于有机体系中形成的纳米分散体,具有独特的理化性质和重要的应用价值。其中,纳米颗粒的单分散性、均匀性和稳定性是决定纳米分散体性能的关键。以Cu O纳米分散体作为纳米流体和复合薄膜前体这一典型体系为研究对象,通过设计平板型微通道实现了Cu O纳米分散体制备过程中的液滴聚并和改性Cu O纳米颗粒的原位分散。制备了颗粒体积分数达2%、平均粒径约30 nm的Cu O-基础油纳米流体,该纳米流体具有良好的稳定性和达到0.184 W·m^(–1)·K^(–1)的较高热导率;制备的Cu O-PDMS(聚二甲基硅氧烷)复合薄膜具有较强的抗菌性能和颗粒复合层稳定性。通过系统性实验研究,证明了原位分散方法在强化改性颗粒高效分散中的重要作用,确定了颗粒性能及分散行为对分散体性能的影响规律。