Nanofluids are a potential alternative to significantly improving the performance of heat transfer applications. In this work, a numerical analysis to examine the eff ect of dispersing copper(Cu), copper oxide(CuO), a...Nanofluids are a potential alternative to significantly improving the performance of heat transfer applications. In this work, a numerical analysis to examine the eff ect of dispersing copper(Cu), copper oxide(CuO), and aluminum(Al2O3) nanoparticles in pure water on the performance of a flat plate solar collector(FPSC) and a numerical model was proposed. The influence of the nanofluid type on the thermal efficiency was critically investigated and discussed. The eff ect of the mass flow rate on the performance was also analyzed and discussed. Based on correlations of the thermophysical properties of nanofluids, a sensitivity analysis was used to analyze the impact of the nanoparticles on the base fluid. The results indicate that the performance of the FPSC with Cu/water nanofluid was better than that of FPSCs using CuO/water or Al2O3/water nanofluids. When the mass flow rate of the nanofluids was 8.0 L/min, the efficiency of the FPSC was much greater than those at the flow rates of 5.0 L/min and 2.0 L/min. Mean enhancements in thermal efficiency of 4.44%, 4.27%, and 4.21% were observed when 2.0 L/min was applied using Cu/water, Cu O/water, and Al2O3/water nanofluids, respectively. Improvements in thermal efficiency of 2.76%, 2.53%, and 2.47% occurred when 8.0 L/min was applied.展开更多
Application of CuO-water nanofluid with size of the nanoparticles of 20 nm and volume concentrations up 2% is numerically investigated in a radiator of Chevrolet Suburban diesel engine under turbulent flow conditions....Application of CuO-water nanofluid with size of the nanoparticles of 20 nm and volume concentrations up 2% is numerically investigated in a radiator of Chevrolet Suburban diesel engine under turbulent flow conditions. The heat transfer relations between airflow and nanofluid coolant have been obtained to evaluate local convective and overall heat transfer coefficients and also pumping power for nanofluid flowing in the radiator with a given heat exchange capacity. In the present study, the effects of the automotive speed and Reynolds number of the nanofluid in the different volume concentrations on the radiator performance are also investigated. The results show that for CuO-water nanofluid at 2% volume concentration circulating through the flat tubes with Renf = 6000 while the automotive speed is 70 km/hr, the overall heat transfer coefficient and pumping power are approximately 10% and 23.8% more than that of base fluid for given conditions, respectively.展开更多
选用改进后的"两步法"制备Cu O/导热油纳米流体,并通过实验得到最佳分散剂为油酸、最佳油酸量为1m L/0.3 g Cu O、最佳超声振动时间为1.5 h。对于该纳米流体在中温(80~150℃)下的热稳定性进行试验探究,结果表明温度的升高、...选用改进后的"两步法"制备Cu O/导热油纳米流体,并通过实验得到最佳分散剂为油酸、最佳油酸量为1m L/0.3 g Cu O、最佳超声振动时间为1.5 h。对于该纳米流体在中温(80~150℃)下的热稳定性进行试验探究,结果表明温度的升高、加热次数和时间的增加都会加剧纳米流体的团聚。随后提出了四点改进措施,并设计了正交试验验证,得到了各因素的影响程度主次以及提高纳米流体热稳定性的最佳措施。展开更多
With ball-bearing and tribofilm lubrication effects,CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties.In this study,CuO nanofluids were synthesized by a one-step e...With ball-bearing and tribofilm lubrication effects,CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties.In this study,CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid,respectively.Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings.Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts.The results of pin-on-disk tests revealed that adding nanofluids containing 0.5%and 1%(mass fraction)CuO nanoparticles to the base fluid reduced the wear rate by 66.7%and 71.2%,respectively,compared with pure lubricant.The lubricating action of 1%(mass fraction)CuO nanofluid reduced the ground surface roughness by up to 30%compared with grinding using lubricant without nano-additives.These effects were attributed to the formation of a lubrication film between the contact pairs,providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces.The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations.展开更多
文摘Nanofluids are a potential alternative to significantly improving the performance of heat transfer applications. In this work, a numerical analysis to examine the eff ect of dispersing copper(Cu), copper oxide(CuO), and aluminum(Al2O3) nanoparticles in pure water on the performance of a flat plate solar collector(FPSC) and a numerical model was proposed. The influence of the nanofluid type on the thermal efficiency was critically investigated and discussed. The eff ect of the mass flow rate on the performance was also analyzed and discussed. Based on correlations of the thermophysical properties of nanofluids, a sensitivity analysis was used to analyze the impact of the nanoparticles on the base fluid. The results indicate that the performance of the FPSC with Cu/water nanofluid was better than that of FPSCs using CuO/water or Al2O3/water nanofluids. When the mass flow rate of the nanofluids was 8.0 L/min, the efficiency of the FPSC was much greater than those at the flow rates of 5.0 L/min and 2.0 L/min. Mean enhancements in thermal efficiency of 4.44%, 4.27%, and 4.21% were observed when 2.0 L/min was applied using Cu/water, Cu O/water, and Al2O3/water nanofluids, respectively. Improvements in thermal efficiency of 2.76%, 2.53%, and 2.47% occurred when 8.0 L/min was applied.
文摘Application of CuO-water nanofluid with size of the nanoparticles of 20 nm and volume concentrations up 2% is numerically investigated in a radiator of Chevrolet Suburban diesel engine under turbulent flow conditions. The heat transfer relations between airflow and nanofluid coolant have been obtained to evaluate local convective and overall heat transfer coefficients and also pumping power for nanofluid flowing in the radiator with a given heat exchange capacity. In the present study, the effects of the automotive speed and Reynolds number of the nanofluid in the different volume concentrations on the radiator performance are also investigated. The results show that for CuO-water nanofluid at 2% volume concentration circulating through the flat tubes with Renf = 6000 while the automotive speed is 70 km/hr, the overall heat transfer coefficient and pumping power are approximately 10% and 23.8% more than that of base fluid for given conditions, respectively.
文摘选用改进后的"两步法"制备Cu O/导热油纳米流体,并通过实验得到最佳分散剂为油酸、最佳油酸量为1m L/0.3 g Cu O、最佳超声振动时间为1.5 h。对于该纳米流体在中温(80~150℃)下的热稳定性进行试验探究,结果表明温度的升高、加热次数和时间的增加都会加剧纳米流体的团聚。随后提出了四点改进措施,并设计了正交试验验证,得到了各因素的影响程度主次以及提高纳米流体热稳定性的最佳措施。
基金The technical support of the Central laboratory of Tabriz University,Nano Technology Laboratory of Khazar University,and Material Science Laboratory of ATÜare also highly appreciated.
文摘With ball-bearing and tribofilm lubrication effects,CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties.In this study,CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid,respectively.Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings.Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts.The results of pin-on-disk tests revealed that adding nanofluids containing 0.5%and 1%(mass fraction)CuO nanoparticles to the base fluid reduced the wear rate by 66.7%and 71.2%,respectively,compared with pure lubricant.The lubricating action of 1%(mass fraction)CuO nanofluid reduced the ground surface roughness by up to 30%compared with grinding using lubricant without nano-additives.These effects were attributed to the formation of a lubrication film between the contact pairs,providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces.The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations.
