Pressure drop and heat transfer enhancement factors for heat exchangers using single-phase nanofluids

R.F.P. Tiecher, J.A.R. Parise
Pontifícia Universidade católica do Rio de Janeiro, BR

Keywords: nanofluids, heat exchangers, enhancement factor

Summary:

For their enhanced thermophysical properties and heat transfer characteristics, considerable attention has been recently given to nanofluids. Most studies of the heat transfer performance of nanofluids have been carried out so far with focus on the enhancements on their thermophysical properties, like thermal conductivity and viscosity, and on the heat transfer coefficient enhancements. However, one of the main applications of nanofluids as heat transfer fluids would be in heat exchangers, where thermal resistances from the other fluid, as well as increased friction, would attenuate the advantages from their high thermal conductivity and eventually high Nusselt number. The present study provides a general model for the analysis of heat exchangers in which a single-phase nanofluid exchanges heat with another fluid. A comparative analysis of the heat transfer rate and pumping power is carried out for typical nanofluids. Non-dimensional enhancement factors, for pressure drop and heat exchange rate, related to pumping power and thermal capacity of the heat exchanger, respectively, were defined. Results show that properties enhancement factors are greater than the heat capacity gain factor of the heat exchanger. It depends on the other thermal resistances of the heat exchanger. The model is applied to experimental data from the literature.