Advanced Study: Numerical Assessment on Fin Design Parameters Employed for Augmentation of Natural Convection and Fluid Flow in a Horizontal Latent Heat Thermal Energy Storage Unit

The present work focus on the thermal performance of a horizontal concentric heat exchanger, which
is numerically investigated to evaluate the heat transfer enhancement process by adding fins with
different configurations. As a part of this investigation, the melting process is simulated from the onset
of phase change to the offset involving physics of natural convection in PCM fluid pool. The
investigation is carried out by ANSYS Fluent code, which is an efficient numerical analysis tool for
investigating fluid flow and convective heat transfer phenomena during PCM melting process. The
attention is mainly focused on the extension of contact area between the PCM body and cylindrical
capsule to enhance heat transfer rates to PCM bodies during the melting process by employing
longitudinal fins in the enclosed capsule. Precise evaluation of heat transfer from extended heat
transfer area of complex structure to PCM due to convection and conduction is a complicated issue
but crucial for the design optimization of thermal storage system. Two commercial PCMs: RT50 and
C58, are introduced in a 2D cylindrical pipe with their thermo-physical properties as input for
modelling. The selected modelling approach is validated against experimental result with respect to
the total enthalpy changes that qualify our model to run in the proceeding calculation. It is ensured
that an isothermal boundary condition (373 K) is applied to the inner pipe throughout the series of
simulation cases and the corresponding Rayleigh number (Ra) ranges from 104 - 105 and Prandtl
number (Pr) 0.05 - 0.07. Finally, parametric study is carried out to evaluate the effect of length,
thickness and number of longitudinal fins on the thermal performance of PCM-LHTES (Latent Heat
Thermal Energy Storage) system associated with the physics of natural convection process during
PCM melting. Future CFD analysis can be conducted with other CFD code like CFX, OPENFOAM,
STAR CCM+ or CFD++ and compared with the current code ANSYS Fluent to justify their applicability
in the area of study.