ABSTRACT
A numerical and experimental study was carried out to investigate the transient
response of a modified latent heat storage system. The proposed system was
composed of phase change material (PCM) packed in the spaces between
externally finned flow channels. Preliminary modeling for a system containing
PCM with simple geometry and flow configuration was carried out either
considering the natural convection or the effective thermal conductivity. The
natural convection model was based on the solution of the vorticity and energy
equations of both the PCM and the working fluid via a finite difference technique
with Alternating Direction Implicit method (ADI). The conduction model was
adopted based on an effective thermal conductivity (Keff) of the melted zone of the
PCM. The results of the natural convection model were utilized in a parametric
study to estimate Keff and new correlation was obtained. This correlation was
permitted to a modified conduction model to predict the performance of enhanced
storage systems enclosed externally finned flow channels with different
configurations.
An experimental apparatus was designed and constructed to verify the numerical
results. The influences of the working fluid mass flow rate, inlet fluid
temperature, initial temperature of the PCM, flow channel pitch and fin
configurations on the storage characteristics were investigated. It was found that
the storage performance of the plain -channel systems is independent on Reynold s
number beyond a value of 300. Also the enhancement in the storage
characteristics of the finned channel systems is strongly dependent on the fin pitch
and the fin length while it does not depend on the fin thickness. New correlations
were obtained for the melted volume ratio and the amount of the heat stored for
the finned channel systems as functions of the different operating parameters. |
