الفهرس 
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Abstract
One of the goals engineers pursue in the energy production and recovery field is
to design a heat exchanger that can store a large amount of thermal energy in a
shorter time. Thermal energy storage systems can be incorporated in the solar
applications to conserve the solar heat energy and to store the waste heat from
industrial processes such as oil, cement, ceramic, steel, and glass industries,
which are considered major waste heat sources.
The present work practically tests the performance attributes of a latent heat
thermal energy storage system in a vertical shell-and-tube heat exchanger
configuration, seven different arrangements of the heat exchanger are studied
over various operating conditions. Water (heat transfer fluid) flows in the straight
tubes that are arranged as circular layers at certain radii in the shell, which is
occupied by organic paraffin phase change material (RT60).
The experiments consider the effects of the tubes area ratio, layer radius ratio,
number of layers, and distribution of the tubes (inline/staggered), besides
incorporating semi-circular tubes instead of complete circular ones. These
experiments are conducted by employing heating water (65C to 75C)
corresponds to Stefan number range (0.096 to 0.233) during the charging process
and cooling water (25C) corresponds to Stefan number of 0.452 during the
discharging process, in addition the water volume flow rate of 15 LPM in the
opposite direction of gravity.
Effects of the different heat exchanger arrangements besides the operating
conditions on the PCM total melting/solidification time, time at which the
melting/solidification begins, melted/solidified mass fraction, stored/recovered
heat energy and charging/discharging effectiveness are studied.The key findings from this work are that increasing the radius ratio from 1/3 to
2/3, employing semicircular tubes instead of complete ones, increasing the area
ratio from 2.4% to 4.3%, and distributing the same number of tubes in two layers
rather than one layer provide reductions in the charging time of 7.2%, 7.3%,
17.6%, and 11%, respectively. The corresponding augmentations in the
charging/discharging effectiveness are 8.1%/2.6%, 7.4%/3.3%, 19.7%/5.7%, and
8%/4.5%, respectively.
Moreover, by applying a staggered distribution of the tubes instead of an inline
one, the charging effectiveness is amplified by 5.3%. Furthermore, increasing the
inlet HTF charging temperature from 65C to 75C decreases the charging time
and boosts the charging effectiveness by 4.3% and 5.4%, respectively.
Finally, a set of experimental correlations is developed to predict the charging
effectiveness of the LHTES system as a function of the investigated parameters.