Liangliang Zhu

An Investigation of the Forced Convection and Heat Transfer with a Cylindrical Agitator Subjected to Non-Newtonian Nanofluids

Abstract The present research performed a numerical simulation of laminar forced convection nanofluid-based non-Newtonian flow in a channel connecting a tank with heating regions. To achieve a rapid diffusion of heat, a cylindrical agitator is inserted into the tank. Power-law modelling is employed to describe the effect of non-Newtonian behaviour. The velocity and temperature fields and heat transfer coefficient ratio are studied systematically, taking into account the impact of various parameters, such as the generalised Reynolds number Re, generalised Prandtl number Pr, angular velocity of a cylinder ω, nanoparticle volume fraction ϕ, mixer size and location. Our research reveals that, to improve the heat transfer in practice, several applicable strategies are available, including the addition of more nanoparticles into the base fluid, which proved to be the most efficient method to enhance the heat transfer of a nanofluid.

On heat transfer of weakly compressible power-law flows

This paper completes a numerical research on steady momentum and heat n transfer in power-law fluids in a channel. Weakly compressible laminar fluids n are studied with no slip at the walls and uniform wall temperatures. The full n governing equations are solved by continuous finite element method. Three n thermal conductivity models are adopted in this paper, that is, constant n thermal conductivity model, thermal conductivity varying as a function of n temperature gradient, and a modified temperature-gradient-dependent thermal n conductivity model. The results are compared with each other and the physical n characteristics for values of parameters are also discussed in details. It is n shown that the velocity curve from the solution becomes straight at higher n power-law index. The effects of Reynolds numbers on the dilatant fluid and n the pseudo-plastic look similar to each other and their trends can be easily n predicted. Furthermore, for different models, the temperature curves also n present pseudo-plastic and dilatant properties.

Forced convection heat transfer of power law non-Newtonian fluids between two semi-infinite plates with variable thermal conductivity

This paper presents an investigation of forced convection heat transfer in power-law non-Newtonian fluids between two semi-infinite plates with variable thermal conductivity. Three cases of different thermal conductivity models are considered: (i) thermal conductivity is a constant, (ii) thermal conductivity is a linear function of temperature, (iii) thermal conductivity is a power-law function of temperature gradient (Zhengs model). Governing equations are solved using the finite element method with the ghost time introduced to the control equations, which does not affect the results because the velocity and temperature will remain unchanged when the steady state is reached. Results for the solutions of different variable models are presented as well as the analysis of the associated heat transfer characteristics. It is shown that the heat transfer behaviours are strongly dependent on the power-law index (n) in all models. For example, when n 1.