纳米颗粒粒径对太阳能热水系统热性能的影响研究

Study on influence of nanoparticle size on the thermal performanceof solar water heating systems

为研究纳米颗粒粒径对太阳能热水系统热性能的影响,利用TRNSYS软件对海口地区纳米流体太阳能热水系统热性能进行了动态模拟研究。采用Cu-水、Al_(2)O_(3)-水、TiO_(2)-水和SiO_(2)-水4种不同的纳米流体作为系统的换热介质,选取全年和典型天进行仿真模拟,分析了纳米颗粒粒径对太阳能保证率、系统效率、集热器出口温度和系统有效得热量得影响。研究结果表明,随着纳米颗粒粒径的增大,太阳能保证率、系统效率、集热器出口温度和系统有效得热量逐渐降低。当纳米颗粒粒径大小为25 nm时,相比于水,太阳能保证率、系统效率、集热器出口温度和系统有效得热量分别提高了7.18%、7.43%、8.68%和3.84%。而粒径大小为50 nm是一个很明显的分界点,当粒径大于50 nm时,有效得热量的下降速率变的平缓。因此,减小纳米颗粒粒径可以提升热水系统热性能,在设计纳米流体太阳能热水系统时,粒径大小应小于50 nm。

To study the effect of nanoparticle size on the thermal performance of solar water heating systems,a dynamic simulation study was conducted using TRNSYS software on the thermal performance of nanofluid solar water heating systems in Haikou area.Four different nanofluids,Cu water,Al_(2)O_(3) water,TiO_(2) water,and SiO_(2) water,were used as the heat transfer media for the system.Simulation was conducted throughout the year and typical days to analyze the effects of nanoparticle size on solar fraction,system efficiency,collector outlet temperature,and useful energy.The research results indicate that as the particle size of nanoparticles increases,the solar fraction,system efficiency,collector outlet temperature,and useful energy of the system gradually decrease.When the particle size of the nanoparticles is 25 nm,compared to water,the solar fraction,system efficiency,collector outlet temperature,and system useful energy are increased by 7.18%,7.43%,8.68%,and 3.84%,respectively.A particle size of 50 nm is a clear boundary point,and when the particle size is greater than 50 nm,the rate of decrease in useful energy becomes smoother.Therefore,reducing the particle size of nanoparticles can improve the thermal performance of hot water systems.When designing nanofluid solar hot water systems,the particle size should be less than 50 nm.