Solidification :
For simulated the solidification process, a time of 7200 seconds was
considered for the investigation of the three models, which are to be
compared. The results obtained are as follows:”:
Figure (8) presents the liquid fraction contour during the
solidification process for the three models. It depicts the growth of
the solid PCM layer on the fin surfaces over time and the separation of
fully melted PCM to the top of the heat exchanger. The time lapse of the
liquid fraction contour reveals distinct stages. In the first stage, the
melted PCM adjusts to the fin surfaces, and the cooled melted PCM
settles down. The next stage involves the generation of fully solid PCM
at the fin surfaces. During this stage, fully melted PCM floats in the
upper quarter, while the remainder of the PCM is partially melted. In
the later stages of solidification, the width of the fully solid layer
increases, and the upper fully melted PCM disappears as the process
reaches full solidification. It’s noteworthy that the upper fully melted
quarter in the A-1 model disappears sooner than in the A-2 model, and
the upper melted PCM in A-2 also vanishes earlier than in the A-3 model.
This variation is explained by the top fin’s length (1), which provides
superior conductivity than the shorter fins.
Figure (9) shows the liquid fraction with time, indicating three
separate zones. The first region is distinguished by a short, constant
liquid fraction, which is followed by a second region in which the
liquid fraction rapidly drops over time. These two regions correspond to
the first stage of the liquid fraction contour. The third region begins
at approximately 1000 seconds, displaying a slow, gradual decrease in
liquid fraction over time.
When examining the liquid fraction graph, it’s evident that Model A-1
consistently maintains a lower liquid fraction at each time point, while
Model A-3 exhibits slightly higher liquid fractions. Model A-2, on the
other hand, displays the highest liquid fraction. Model A-1 and A-3 are
roughly equal, or there are only minor differences between them,
primarily due to the same top fin length, which facilitates cooling in
the upper, hotter half.