光谱分频水基ZnO纳米流体制备及其热电性能调控

Study on preparation and thermoelectric regulation performance of water-ZnO nanofluids for spectral-beam splitting

制备低成本水基ZnO纳米流体作为分频介质以降低分频式光伏光热(SBS-PV/T)集热器的推广应用成本;优化了其高稳定性制备工艺,实验测试了质量分数、粒径及光程对其光谱透过率的影响,并模拟分析了上述变量对集热器热电性能的调控特性,评估了不同变量对不同评价指标的敏感性。结果表明,六偏磷酸钠作为分散剂,分散比为1∶5,超声处理1.5 h可最大程度增强水基ZnO纳米流体的稳定性;集热器热效率、热电比、综合效率及优值因子均随ZnO纳米颗粒粒径、质量分数及光程的增大而增大,电效率则相反。SBS-PV/T集热器的热电比最易受纳米流体参数变化的影响,平均敏感性系数为0.45;集热器综合性能对纳米流体光程变化最敏感,其对热电效率、热电比及优值因子的敏感性系数分别为0.53、-0.27、0.76及0.09。

To reduce the popularization and application cost of the photovoltaic/thermal(PV/T)collector,using nanofluids as the spectral-beam splitter(SBS),low-cost water-ZnO nanofluid is prepared by the two-step method as the SBS,and its preparation parameters are optimized to enhance its stability,including the dispersant type,dispersion ratio,and ultrasonic duration.On this basis,the effects of mass fraction,nanoparticle size,and optical path on the spectral transmittance of water-ZnO nanofluid are first tested experimentally;secondly,the effects of the above parameters on the regulation performance of heat-to-electricity of the SBS-PV/T collector are simulated and analyzed;finally,the sensitivity of the above parameters to four evaluation indexes is evaluated.The results show that adding sodium hexametaphosphate as a dispersant with the dispersion ratio of 1∶5 and ultrasonic treatment for 1.5 hours can maximize the stability of water-based ZnO nanofluid.Secondly,the mass fraction,particle size,and optical path have a linear influence on the thermal and electric performances of the SBS-PV/T collector;concretely,the photothermal efficiency,heat-to-electric ratio,overall efficiency,and merit function of the SBS-PV/T collector increase with the mass fraction,particle size,and optical path;while the photovoltaic efficiency is the opposite.Of which,the heat-to-electric ratio is most sensitive to the change of nanofluid parameters,with an average sensitivity coefficient of 0.45;on the other hand,the performance of the SBS-PV/T collector is most sensitive to the optical path,and its sensitivity coefficients to photothermal efficiency,photovoltaic efficiency,heatto-electric ratio,and merit function of the collector are 0.53,-0.27,0.76,and 0.09,respectively.