ABSTRACT

The heat transfer and friction characteristics of thermosyphon solar flat plate collector using Al₂O₃/water nanofluid as working fluid with helical twist insert and its impacts are analysed. Thermal behaviour, heat augmentation and pressure drop characteristics of the modified collector are compared with those of conventional riser tube collector. Alumina nanofluid of 0.1%, 0.3% and 0.5% volume concentrations are used in riser tube of the solar flat plate collector which has helical twist with rod as insert. Correlations for heat augmentation and friction factor in terms of performance parameters like Nusselt number, Prandtl number and fluid concentrations showed acceptable deviations. The convective heat transfer coefficient varies directly with the volume concentration of Al₂O₃ nanoparticles in base fluid, conversely increasing the fluid concentration increase the density of the nanofluid leading to increase in pressure drop and friction. Results favour to modified nanofluid collector in terms of thermal performance, higher heat removal rate from absorber plate in solar flat plate collector.

摘要

_{分析了以Al 2} O ₃ /水纳米流体为工作流体的热虹吸太阳能平板集热器的传热摩擦特性及其影响。将改进的集热器的热行为、增热和压降特性与传统的立管集热器进行了比较。太阳能平板集热器的升管采用体积浓度分别为0.1%、0.3%和0.5%的氧化铝纳米流体，该集热管呈螺旋扭曲，以棒为插入件。在努塞尔数、普朗特数和流体浓度等性能参数方面，热增强和摩擦系数的相关性显示出可接受的偏差。对流传热系数直接随铝的体积浓度而变化_{基础流体中的2} O ₃纳米颗粒，相反地增加流体浓度会增加纳米流体的密度，从而导致压降和摩擦增加。结果表明，在太阳能平板集热器中，改性纳米流体集热器的热性能、吸收板的热量去除率更高。