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ABSTRACT
Nanofluids are conventional heat transfer fluids with suspended nanoparticles to enhance their thermal conductivity. However, enhancement of thermal conductivity is coupled with increased viscosity. This study investigates the efficiency of nanofluids (ratio of thermal conductivity and viscosity enhancement) with the effects of particle size and temperature using molecular dynamic (MD) simulation. The efficiency of nanofluids is improved by increasing particle size and temperature. The thermal conductivity enhancement increases with increasing particle size, but is independent of temperature; the viscosity enhancement decreases with increasing particle size and temperature. Particle size variation is therefore shown to be more effective than temperature control.
Nomenclature
| C | = | enhancement coefficient |
| E | = | per atom energy for kinetic and potential, J |
| F | = | force, N |
| h | = | average partial enthalpy, J |
| J | = | heat current, J · m/s |
| k | = | thermal conductivity, W/m · K |
| kB | = | Boltzmann constant, 1.38 × 10−23 J/K |
| m | = | mass, kg |
| N | = | total number of particles |
| P | = | stress tensor, N/m2 |
| r | = | displacement between particles, m |
| t | = | time, s |
| T | = | temperature, K |
| v | = | velocity, m/s |
| V | = | volume, m3 |
| Φ | = | Lennard Jones potential, J |
| ϵ | = | interaction strength, J |
| σ | = | interatomic length scale, m |
| η | = | viscosity, Pa · s |
| ø | = | particle concentration, vol% |
| Subscripts | = | |
| ar | = | argon |
| cu | = | copper |
| f | = | base fluid |
| i | = | particle i |
| j | = | particle j |
| k | = | thermal conductivity |
| nf | = | nanofluid |
| p | = | particle |
| x | = | x axis |
| y | = | y axis |
| z | = | z axis |
| α | = | species α |
| η | = | viscosity |
Nomenclature
| C | = | enhancement coefficient |
| E | = | per atom energy for kinetic and potential, J |
| F | = | force, N |
| h | = | average partial enthalpy, J |
| J | = | heat current, J · m/s |
| k | = | thermal conductivity, W/m · K |
| kB | = | Boltzmann constant, 1.38 × 10−23 J/K |
| m | = | mass, kg |
| N | = | total number of particles |
| P | = | stress tensor, N/m2 |
| r | = | displacement between particles, m |
| t | = | time, s |
| T | = | temperature, K |
| v | = | velocity, m/s |
| V | = | volume, m3 |
| Φ | = | Lennard Jones potential, J |
| ϵ | = | interaction strength, J |
| σ | = | interatomic length scale, m |
| η | = | viscosity, Pa · s |
| ø | = | particle concentration, vol% |
| Subscripts | = | |
| ar | = | argon |
| cu | = | copper |
| f | = | base fluid |
| i | = | particle i |
| j | = | particle j |
| k | = | thermal conductivity |
| nf | = | nanofluid |
| p | = | particle |
| x | = | x axis |
| y | = | y axis |
| z | = | z axis |
| α | = | species α |
| η | = | viscosity |