The Applications of Nanofluids in Solar Energy

Reporter: Qin Lianwei

solid–liquid composite materials consisting of nanometer sized

solid particles suspended in different base fluids

Nanofluids:Suspensions of nanoparticles in base fluids

Properties of Nanofluids

Advanced flow and heat transfer fluids• Enhancing functions and properties by combining and

controlling interactions• Combining different nanoparticles in different base-

fluids with additives• Controlling interactions using different “mixing”

methods and thermal-, flow-, catalyst-, and other field-conditions

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.

Preparation of nanofluids

Criteria Conventional Nanofluids

Stability Settle Stable

Surface/volume ratio Low High

Thermal Conductivity Low High

Clogging High Low

Pumping Power Large Small

Conventional solid-liquid suspensions compared to nanofluids

Four Characteristic Features of Nanofluids

Nanofluids have 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)

Thermal Conductivity

Particle material Particle Size Base fluid material

Temperature Particle volume concentration

pH

Factors influencing thermal conductivity of nanofluids:

TEM Characteristics of Copper Nanofluids

• By the single-step method

• very small copper particles (about 10 nm)

• Very little agglomeration and sedimentation

Bright-field TEM micrograph of Cu nanoparticles produced by direct evaporation into ethylene glycol

Applications of Nanofluids in Solar Energy

Schematic of nanofluid-based concentrated parabolic solar collector

Schematic of the nanofluid-based direct absorption solar collector

Nanofluids provide 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.

Conclusions

Thanks for Your attention!