ZEMCH 2019 International Conference Proceedings April.2020 | Page 118
at wall and floor, respectively. The controlled temperatures inside the PCM‐LWA mortar plate are as
follows; without setting (None), 24, 30, 36, 42, and 48 ℃. The temperature is controlled by a thermal
bath, and the temperature is increased every 30 minutes. To measure temperatures of the plates and
air, additional data logger is used to measure the temperature onto the sample and in air. Several
thermal gauges are attached; two onto the surface of the plates (S1, S2), one placed 1 m above the surface
of the plates (1m), and one inside thermal controlled room as a reference temperature (RT). Two
different thermal controlled experiments are performed; one for constantly increasing temperature, and
one for applying thermal cycles.
2.2. Materials
PCM‐LWA mortar plate (A_2000) is made of cement, sand and water, where the weight ratio is 1 :
3 : 0.5 (cement : sand : water). Cement is Type 1 portland cement is used. PCM‐LWA consists of
exfoliated graphite nanoplatelets (xGnP) and n‐octadecane. The material properties are presented in
Table 1, and more detail of thermal characteristics are presented in ref 14. After mixing mortar, PCM‐
LWA is added immediately. The size of the plate is 500 mm by 500 mm by 50 mm and the amount of
PCM‐LWA is 2000 g. Additionally, reference sample (Ref) is prepared without PCM‐LWA for the
comparison study.
Figure 1. Schematic drawing of the contactless ultrasonic system.
Table 1. Properties of xGnP and n‐octadecane [14].
xGnP
n‐octadecane
Surface area 0.020 m 2 /kg Melting temperature 28 ℃
Bulk density 5.3 – 10 kg/m 3 Latent heat capacity 0.257 J/kg
Specific heat capacity ‐3 0.71∙10 J/kgK Specific heat capacity 0.092 J/kgK
Thermal conductivity 2 – 300 W/mK Thermal conductivity 0.26 W/mK
3. Results and Discussion
3.1. Results from inceasing temeperature
Figure 2 represents the temperature measurements by attached thermal gauges. As temperature is
increased by thermal bath, entire graphs keep increasing their temperature with respect to operating
time. Both temperatures from RT show similar behavior, representing well insulating thermal
controlled room. In case of S2 at A_2000 shown in Fig 2(b), the temperature drastically increases
compared to the others. It is because the gauge is located on top of hot water supply pipe. Because
PCM‐LWA stores thermal energy by changing its phase, the temperature difference between S1 and
1m from each sample shows distinct behavior. A_2000 stores thermal energy over melting temperature
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ZEMCH 2019 International Conference l Seoul, Korea