ZEMCH 2019 International Conference Proceedings April.2020 | Page 119
of PCM so that the temperature increment from S1 and RT is similar. However, it is clear that the
temperatures from S1 and S2 are clearly higher than one from 1m in Ref. Figure 3 presents the obtained
thermal images, suggesting thermal energy storage of the PCM‐LCA plate. In the case of A_2000,
overall surface temperature is slowly increased and different thermal distribution is observed, which
is not shown from Ref.
Figure 4 presents results of contactless ultrasonic system. This obtained signal data are visualized,
where B‐scan image represents time increment of ultrasonic waves in X‐axis, operating time of
experiment in Y‐axis, and signal amplitude in Z‐axis (color). Therefore, B‐scan represents the arrival of
ultrasonic waves during the temperature controlled experiment. It is noted that the acoustic waves
propagated in air are arrived around 670 μs, which is much slower than leaky portion of Rayleigh
waves. The faster arrivals of acoustics are recorded as increasing temperature. Ref shows constant
arrivals (slightly faster) of Rayleigh waves while increasing temperature. This represents that
mechanical properties have minimal change over the experiment. On the other hand, A_2000 presents
delayed arrivals of Rayleigh waves. This is because PCM‐LWA is melted and the mechanical properties
of the plate is significantly different from the original. The arrival time is decreased up to 7 μs, which
represents maximum 56% decrease of elastic modulus.
S1
S2
1 m
40
RT
35 35
30 30
40
25
20
15
5
60
90
0
12
0
15
0
18
0
0
21
Operating time (min)
RT
15
5
30
1 m
20
10
0
S2
25
10
0
S1
0
30
60
90
0
15
0
12
Operating time (min)
(a)
0
18
(b)
Figure 2. Thermal room temperatures; (a) A_2000 and (b) Ref
None
24 ℃
30 ℃
36 ℃
42 ℃
48 ℃
(a)
(b)
Figure 3. Thermal images; (a) A_2000 and (b) Ref
Evaluation of PCM-LWA Mixed Plates Using Contactless Ultrasonic Method
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