@article{WOS:000641410200002,
title = {Emergence of rectangular shell shape in thermal energy storage
applications: Fitting melted phase changing material in a fixed space},
author = {Ismail Gurkan Demirkiran and Erdal Cetkin},
doi = {10.1016/j.est.2021.102455},
year = {2021},
date = {2021-05-01},
journal = {JOURNAL OF ENERGY STORAGE},
volume = {37},
abstract = {Here we document the effect of heat transfer fluid (HTF) tube position
and shell shape on the melting time and sensible energy requirement for
melting a phase change material (PCM) in a multitube latent heat thermal
energy storage (LHTES) application. Tube location and shell shape are
essential as the shape of the melted region, i.e. similar to the
boundary layer, affects convective heat transfer performance. HTF tube
total area is fixed in all cases to have the same amount of PCM. In
order to eliminate the effect of heat transfer surface area variation,
results of two- and four-tube configurations were compared within
themselves. Liquid fraction, sensible enthalpy content, and
latent/sensible enthalpy ratio relative to time were documented for two
and four HTF configurations in various shell shape and tube locations.
Results show that eccentric two tubes with rectangular shell decreases
melting time and sensible energy requirement from 67 min to 32 min and
from 161.8 kJ/kg to 136.3 kJ/kg for 72.3% liquid fraction,
respectively, in comparison to the concentric tubes with the circular
shell. When the number of HTF tubes increases to four, then the required
melting time and sensible energy decrease 80% and 3.8%, respectively,
for PCM to melt completely as the concentric tubes and circular shell is
replaced with eccentric tubes and rectangular shell. Results of liquid
fraction variation relative to time show that S-curve of melting becomes
steeper if PCM distribution is such that the intersection of melted
regions is delayed. Therefore, melted PCM regions could be packed into a
shell that minimizes melting time and required sensible energy. Even
rectangular shell shape increases the heat transfer surface (increased
heat loss rate) because melting time has decreased greatly, total energy
lost to the ambient from the surfaces of shell decreases. Eccentricity
slows down the solidification process but due to increased heat loss
rate from the surface, rectangular shell enables faster solidification
than circular shell shape. There is a trade off in between
solidification time and heat loss energy for rectangular channels which
can be optimized by selecting proper insulation thickness. Overall, the
results show that without any thermal conductivity enhancement (TCE)
method, melting performance and latent heat storage capability can be
significantly enhanced as decreasing the sensible heat storage by
fitting the melted PCM regions into a fixed space for the applications
where charging speed is lot faster than discharging.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}