Forced convection heat transfer with phase-change-material slurries: Turbulent flow in a circular tube

Abstract

The present study investigates the increase in the convective heat transfer coefficient as well as the increase in the thermal capacity of a working fluid by using the latent heat from a solid-liquid phase change of particles. A long heating test section (627 diameters) with a uniform heat flux boundary condition is constructed in order to study the effects of the phase-change phenomenon produced by a phase-change-material (PCM)—water slurry on the convective heat transfer coefficient in a turbulent flow. The study introduces a method to generate very fine PCM particles inside a flow loop using an emulsifier. With such fine PCM particles, the flow loop did not clog. Local pressure drops and local heat transfer coefficients are measured along the test section. The pressure drop significantly decreased at the point where the PCM particles in the slurry melted. The local convective heat transfer coefficient was found to vary significantly when the particles melted. This made it difficult to apply the LMTD method to the analysis of the PCM slurry flow heat transfer. The study proposes a new three-region melting model, and provides an explanation of the physical mechanism of the convective heat transfer enhancement due to the PCM particles.