Physically Consistent Implementation of the Mixture Model for Modelling Nanofluid Conjugate Heat Transfer in Minichannel Heat Sinks

Abstract

As much as two-phase mixture models resolve more physics than single-phase homogeneous models, their inconsistent heat transfer predictions have limited their use in modelling nanofluid cooled minichannel heat sinks. This work investigates, addresses, and solves this key shortcoming, enabling reliable physically sound predictions of minichannel nanoflows, using the two-phase mixture model. It does so by applying the single-phase and the two-phase mixture model to a nine-passages rectangular minichannel, 3 mm deep and 1 mm wide, cooled by a 1% by volume suspension of Al2O3 nanoparticles in water, over the Reynolds number range 92 to 455. By varying the volume fraction of the second phase between 2% and 50%, under a constant heat flux of 16.67 W/cm2 and 30 Celsius coolant inflow, it is shown that the two-phase mixture model predicts heat transfer coefficient, pressure loss, friction factor, exergy destruction rate, exergy expenditure rate, and second law efficiency values converging to the single-phase model ones at increasing . A two-phase mixture model defined with 1% second phase volume fraction and 100% nanoparticles volume fraction in the second phase breaks the Newtonian fluid assumption within the model and produces outlier predictions. By avoiding this unphysical regime, the two-phase mixture model matched experimental measurements of average heat transfer coefficient to within 1.76%. This has opened the way for using the two-phase mixture model with confidence to assess and resolve uneven nanoparticle dispersion effects and increase the thermal and mass transport performance of minichannels.

Analysis of natural convection and the generation of entropy within an enclosure filled with nanofluid-packed structured pebble beds subjected to an external magnetic field and thermal radiation

“…Similar to single-phase model, the magnetic field and S2S radiation model are applied to calculations. The governing equations, taking into account the assumptions mentioned above, take the following general form [30,34]:…”

Aqueous Theta-Phase Aluminum Oxide Nanofluid for Energy Applications: Experimental Study on Thermal Conductivity

“…Its use in the field of renewable and sustainable energy technologies allows for creating high-efficient and more economic systems. In this regard, many research studies [1][2][3][4][5][6][7][8] have evaluated, theoretically and experimentally, the increase in performance in heat transfer applications and solar thermal systems associated with the use of alumina-water as working fluid.…”

Numerical Investigation of Various Twisted Tapes Enhancing a Circular Microchannel Heat Sink Performance

“…The flow and heat transport through microchannel passages depends on the coolant type. The performance of various coolants has been studied, including that of water, methanol (Peng et al, 1994), other refrigerants (Zhuan and Wang, 2013), and of nanofluids Ali et al, 2022). Gaseous coolants, including air (Kleiner et al, 1995), argon, helium, nitrogen (Harley et al, 1995), and ammonia (Adham et al, 2012), were also used.…”