the applications of nanofluids in solar energy reporter: qin lianwei
TRANSCRIPT
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
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