Convective heat transfer to non-newtonian fluids
Shojaeian, Mostafa (2015) Convective heat transfer to non-newtonian fluids. [Thesis]
In this thesis, the perturbation method was implemented to analytically solve the governing equations relevant to both hydrodynamically and thermally fully developed power-law fluid and plug flows through parallel-plates and circular microchannels under constant isoflux thermal and slip boundary condition. The temperature-dependent properties, being viscosity and thermal conductivity, were considered along with nonlinear slip condition in the analysis in addition to viscous dissipation. The velocity, temperature and constant property Nusselt number closed form expressions were derived and then the Nusselt number corresponding to temperature-dependent thermophysical properties was numerically obtained due to their complexity nature. Numerical simulations were also performed for verifying the analytical results. The results indicated that the property variations and slip condition significantly affected thermo-fluid characteristics. The second law analysis was further performed for both constant and variable properties. Furthermore, an experimental study was performed on nucleate pool boiling of polymeric solutions (aqueous Xanthan gum solutions) by the dissolution of Xanthan gum powder in different amounts into deionized water. Their advantage over new generation fluids such as nanofluids is that they have no side effects such as agglomeration and sedimentation of particles, which is common for nanofluids. The results revealed that heat transfer coefficients of prepared polymeric solutions were lower than those of pure water, while concentration played a significant role in the performance of the heat transfer. In visualization studies, different pool boiling patterns were recorded particularly for high concentrations, which bolsters the heat transfer results.
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