SLURRY VISCOSITY STUDY AND ITS INFLUENCE ON HEAT TRANSFER ENHANCEMENT EFFECT OF PCM SLURRY FLOW IN MICRO/MINI CHANNELS

摘要

A recent numerical study [1] involving micro-size Phase-Change-Materials (PCM) particles in micro-channels revealed significant heat transfer enhancement, provided that an optimal balance among the Reynolds number, particle size, tube length and heat flux is achieved. The numerical simulation is based on a model developed in [1] for non-thermal equilibrium, two-phase (solid-fluid) flow using the continuum theory, in which each phase is treated separately in thermal, mass and momentum transports, yet they are related through interaction terms. A particle viscosity μ_P is introduced in this model and it's not available for the system of liquid-solid two phase flow. Therefore, this paper focuses on the study of the particle viscosity and its relation to the bulk viscosity to clarify its influence to the heat transfer enhancement effect of the PCM slurry flow. A review and comparative analysis of the available literature concerning particulate flow viscosity are presented. Different correlations to calculate the bulk viscosities are analyzed and their application range and limitations are discussed. Then, by using these different viscosity correlations to the numerical simulations, their influence to the heat transfer enhancement effect of the PCM slurry flow is discussed and a more realistic particle viscosity correlation for the PCM slurry flow is suggested through comparison with our experimental results.