Computational Investigation of Laminar Mixed Convection in a Vertical Pipe With Slurries of a Microencapsulated Phase-Change Material in Distilled Water

A computational investigation of steady, laminar, mixed convection in a vertical pipe, with essentially uniform heat flux imposed on its outer surface and slurries of a microencapsulated phase-change material (MCPCM) particles suspended in distilled water as the working fluid flowing upwards, is presented. The MCPCM particles considered here have a core of solid-liquid PCM contained in a thin solid shell. The mean effective diameter of these particles is 2.5μm; the melting of the core PCM takes place primarily in the temperature range 26°C to 30°C; and the latent heat of fusion of this PCM is 129.5kJ/kg. The total length of the pipe is 2.2479m; and its inside and outside diameters are 0.01257m and 0.01588m, respectively. The main contributions of this paper are the following: i) a homogenous mathematical model is shown to be applicable to the aforementioned mixed convection phenomena; ii) correlations for the effective properties of the MCPCM slurries and procedures for their implementation are presented; iii) difficulties with the standard definition of bulk temperature when the specific heat of the fluid changes significantly with temperature are elaborated; iv) a modified bulk temperature that overcomes these difficulties is proposed; v) a finite volume method (FVM) for the solution of the proposed mathematical model is described briefly; and vi) the numerical results are presented, compared to complementary experimental data, and discussed. These comparisons show that proposed model and FVM allow cost-effective computer simulations of the problems of interest.