The Applications of Nanofluids in Solar Energy

1. The Applications of Nanofluidsin Solar Energy Reporter: Qin Lianwei

2. Nanofluids: Suspensions of nanoparticles in base fluids solid–liquid composite materials consisting of nanometer sized solid particles suspended in different base fluids

3. Properties of Nanofluids Advanced flow and heat transfer fluids • Enhancing functions and properties by combining and controlling interactions • Combiningdifferent nanoparticles in different base-fluids with additives • Controlling interactions using different “mixing” methods and thermal-, flow-, catalyst-, and other field-conditions

4. Preparation of nanofluids The single-step method The single step simultaneously makes and disperses the nanoparticles directly into a base fluid. Nanoparticles agglomeration is minimized. Only suitable for low vapor pressure fluid. The two-step method (widely used) Nanoparticles was first produced and dispersed into the base fluids. Good for oxides nanoparticles. Not suitable for metallic nanoparticles.

5. Conventional solid-liquid suspensions compared to nanofluids

6. Four Characteristic Features of Nanofluids • Nanofluidshave an unprecedented combination of four characteristic features desired in energy systems: • Increased thermal conductivity (TC)at low nanoparticle concentrations • Strong temperature-dependent TC • Non-linear increase in TC with nanoparticle concentration • Increase in boiling critical heat flux (CHF)

7. Factors influencing thermal conductivity of nanofluids: Particle material Particle Size Base fluid material Thermal Conductivity Temperature pH Particle volume concentration

8. TEM Characteristics of Copper Nanofluids • By the single-step method • very small copperparticles (about10 nm) • Very little agglomeration and sedimentation Bright-field TEM micrograph of Cu nanoparticles produced by direct evaporation into ethylene glycol

9. Applications of Nanofluidsin Solar Energy Schematic of the nanofluid-based direct absorption solar collector Schematic of nanofluid-based concentrated parabolic solar collector

10. Conclusions Nanofluidsprovide a promising technical selection for enhancing heat transfer. Pioneering nanofluids research has inspired physicists, chemists, and engineers around the world. These characteristic features of nanofluids make them suitable for the next generation of flow and heat-transfer fluids.

11. Thanks for Your attention!