Abstract
This article mainly concerns theoretical research on entropy generation influences due to heat transfer and flow in nanofluid suspensions. A conventional nanofluid of alumina-water (Al2O3-H2O) was considered as the fluid model. Due to the sensitivity of entropy to duct diameter, mini- and microchannels with diameters of 3 mm and 0.05 mm were considered, and a laminar flow regime was assumed. The conductivity and viscosity of two different nanofluid models were examined with the help of theoretical and experimentally determined parameter values. It was shown that order of the magnitude analysis can be used for estimating entropy generation characteristics of nanofluids in mini- and microchannels. It was found that using highly viscous alumina-water nanofluid under laminar flow regime in microchannels was not desirable. Thus, there is a need for the development of low viscosity alumina-water (Al2O3-H2O) nanofluids for use in microchannels under laminar flow condition. On the other hand, Al2O3-H2O nanofluid was a superior coolant under laminar flow regime in minichannels. The presented results also indicate that flow friction and thermal irreversibility are, respectively, more significant at lower and higher tube diameters.
Highlights
In the past few decades, along with the continuous growth of industries and developments in nanotechnology, a need has arisen for more effective methods of cooling and for enhanced heat transfer characteristics
The performance of micro-electromechanical systems (MEMS) in heat transfer devices and engines is improved with the increasing ability of a fluid medium to transfer large amounts of heat through a small temperature difference, which enhances the efficiency of converting energy in these devices [1]
Because solid particles have higher thermal conductivity compared to the conventional base fluid, it is expected that the addition of solid nanoparticles would increase the effective thermal conductivity of the nanofluids [5,6]
Summary
In the past few decades, along with the continuous growth of industries and developments in nanotechnology, a need has arisen for more effective methods of cooling and for enhanced heat transfer characteristics. The performance of micro-electromechanical systems (MEMS) in heat transfer devices and engines is improved with the increasing ability of a fluid medium to transfer large amounts of heat through a small temperature difference, which enhances the efficiency of converting energy in these devices [1]. This circumstance has led to the appearance of a new group of coolants using nanofluids. Because solid particles have higher thermal conductivity compared to the conventional base fluid, it is expected that the addition of solid nanoparticles would increase the effective thermal conductivity of the nanofluids [5,6]. The thermal conductivity of Cu (copper) is 700 and 3,000 times the heat conductivity of water and engine oil, respectively [7]
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