SiO_2纳米流体在太阳能集热管中的传热特性  

Heat transfer characteristics of SiO_2 nanofluid flow inside solar-collector vacuum tubes

作　　者：赵聪颖[1] 闫素英[1,2] 田瑞[1,2] 史志国[1] 仲伟浩[1] 

机构地区：[1]内蒙古工业大学能源与动力工程学院,呼和浩特010051 [2]风能太阳能利用技术省部共建教育部重点实验室,呼和浩特010051

出　　处：《农业工程学报》2014年第20期236-243,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：内蒙古自然科学基金项目(2011BS0702);风能太阳能利用技术省部共建教育部重点实验室开放基金(201405)

摘　　要：为研究SiO2-水纳米流体在太阳能集热管中的传热特性，该文采用数值模拟与试验结合的方法进行分析。通过高压微射流制备了稳定的SiO2纳米流体，并利用粒度分析表征了其悬浮稳定性，同时试验测试了质量分数为1%～5%的SiO2-水纳米流体的导热系数和透射率。针对纳米流体集热管换热特性，模拟计算了蒸馏水和不同质量分数的纳米流体的温度场和速度场分布，同时，对以SiO2纳米流体和蒸馏水为工质的集热管进行了闷晒试验研究，结果表明，纳米流体具有比蒸馏水高的换热特性且随着其质量分数的增加而增大。在此基础上，该文分析了放置时间对纳米流体换热特性的影响，结果表明，放置时间越长，纳米流体团聚越明显，导致其光热特性降低。该研究为纳米流体在太阳能光热及光伏冷却应用方面提供参考。Nanofluid is an innovative heat transfer fluid with superior potential for developing the heat transfer performance of fluids. Recent developments in nanotechnology showed that the nanofluid was an efficient working fluid and coolant in the solar thermal application. In this paper, the heat transfer characteristics of SiO2-water nanofluids were investigated both numerically and experimentally. Stable SiO2-water nanofluids were produced by the M-110P Microfluidizer Processor using two-step method in the experiment. The suspension stability was characterized through particle size analysis; Meanwhile, the thermal conductivity was measured by the Hot Disk Thermal Constant Analyzer, the results showed that the thermal conductivity was increased with the increase of mass fraction and temperature. The thermal conductivity of nanofluid with mass fraction 5% placed for 20 d was the least compared with other fresh nanofluids （mass fraction 5%, 3%, 1%） at the same temperatures. What＆#39;s more, the transmittance of SiO2-water nanofluids with the mass fraction from 1% to 5% were tested and analyzed by the spectrophotometer. The results indicated that the transmittance of SiO2-water nanofluids was increase as the mass fraction decrease. Also, the results showed that the transmittance of SiO2-water nanofluid changed with the retention time. The transmittance of 5% nanofluid was 0.76, which is 0.09 higher than that of the nanofluid （5%） placed for 20 days at the same wavelength. Mainly for the heat transfer characteristics of SiO2-water nanofluid flowing inside the collector tube, the temperature field and velocity field distribution of distilled water and nanofluid were simulated by the finite element software ANSYS. The velocity of 5%, 3% and 1% nanofluids were 1.25, 1.14 and 1.02 mm/s after heated for 60 min, respectively. The velocity of 5% nanofluid was 1.61 mm/s after heated for 142 min, which was 0.86 mm/s faster than that of distilled water at the same position. For the experimental study, the distilled water

关 键 词：太阳能集热管 热转换 速度 导热系数 SiO2纳米流体 

分 类 号：TK515[动力工程及工程热物理—热能工程]