Thermal performance of microencapsulated phase change material slurry in turbulent flow under constant heat flux

Current cooling and heating distribution systems that use water as secondary fluid exhibit limited thermal capacity which can only be overcome by high flow rates and large (volume) capacity. A successful way to enhance the thermal capacity of secondary fluid systems is by incorporating microencapsulated phase change material (MPCM) slurry. However, a full understanding of the physical properties and heat transfer characteristics of MPCM slurry in the 2-8 degrees C range (35.5-46.5 degrees F) still is lacking. In the paper, latent heat of fusion, melting and freezing points, and temperature- and concentration-dependent viscosity data, are presented. Results indicate that selection of nucleating agent type and concentration is required to prevent the supercooling phenomenon. Pressure drop and convective heat transfer data were measured using a heat transfer loop operated at different flow rates and heat flux values. Results indicate that the phase change process and slurry mass fraction affect the heat transfer process. The paper also examines the impact of using enhanced surface tubing in combination with MPCM slurry under constant heat flux and turbulent conditions. (c) 2006 Elsevier Ltd. All rights reserved.