Proposed Criterion for Steady State Parallel Plate Thermal Conductivity Measurement of Liquids and Nanofluids

Steady state parallel plate thermal conductivity apparatus for different liquids and nanofluids has been studied numerically. Single phase model and the mostpopular theoretical formulas employed to develop the nanofluids heat transfer characteristics. The parallel plate thermal conductivity (PPTC) apparatus consists ofa heating element above the test fluid specimen and a closed cooling system below. Because of downward heat transfer (unidirectional heat transfer), convection effects due to gravity can be avoided until the critical Rayleigh number is reached. Correlations derived forcritical Rayleigh numbers in order to avoid free convection. Results show that critical Rayleigh numbers behave linearly with respect to Prandtl number fordifferent concentrations of nanofluids and using further additive reduces the Rayleigh number needing to instable the test fluid specimen. It has been shown thatthe more thermally conductive additive is used, the less the Rayleigh number is needed to instable the suspension.

Keywords:

Thermal conductivity , nanofluids , measurement , parallel plate , numerical solution