Heat transfer in pipes conveying slurries of microencapsulated phase-change materials in water

Complementary computational and experimental investigations of steady, laminar, mixed convection in a heated vertical pipe, with slurries of a microencapsulated phase-change material (MCPCM) suspended in distilled water as the working fluid, are presented in this thesis.The MCPCM consists of particles composed of a core of phase-change material (PCM) surrounded by a solid shell: The effective diameter of the particles is 2.5 mum; the melting and freezing temperatures of the PCM in the particles are in the ranges 27°C to 31°C (mean value 29.94°C) and 12°C to 16°C (mean value of 14.64°C), respectively; the latent heat of fusion during melting is 131.8 kJ/kg. Experimental apparatus and procedures for measurements of the effective density, the effective viscosity, the effective thermal conductivity, and the effective specific heat of the MCPCM slurries are presented along with results and correlations that apply to temperatures in the range 5ºC to 60ºC.In the presentation of the computational investigation, a homogenous mathematical model is shown to be applicable and proposed; procedures for incorporation of correlations for the effective properties of the MCPCM slurries are discussed; difficulties with the standard definition of bulk temperature when the specific heat of the fluid changes significantly with temperature are elaborated; a modified bulk temperature that overcomes these difficulties is proposed; a finite volume method is described; and its validation and use in the computer simulations are discussed.An apparatus that was designed, constructed, benchmarked, and used in the mixed-convection experiments is described. Details of this experimental investigation, conducted with slurries of mass concentration 0% (pure distilled water), 5%, 10%, 15%, and 20%, temperatures in the range 20°C to 60°C, and volume flow rates in the range 1.78 mL/s to 2.69 mL/s, are presented.The experimental and numerical results are presented, compared, and discussed. They show that the proposed homogenous model, with input of correlations that give the variation of the effective properties of the MCPCM slurries with temperature, provides a cost-effective and accurate foundation for computer simulations of the problems of interest