θ ¼ sin
À1 2rh
r 2 þ h
2
ð10:1Þ
where r and h are obtained by using an image processing software (ImageJ).
10.2.3 Effect of Irradiations on Surface Wettability
Figure 10.4a–c shows the wettability change from ultraviolet, γ-ray, and proton-beam
irradiation, respectively. The horizontal axis denotes an integrated irradiation dose or
irradiation time and the vertical axis denotes the measured contact angle. As shown in
these figures, the contact angle decreases with the irradiation dose. In these experiments, the ambient effect is also studied during the irradiations, which are performed
in air or water. As shown in Fig. 10.4a, the ambient effect on the contact angle change
is not obvious in the ultraviolet irradiation. However, the ambient effect is very distinct
both in the γ-ray and the proton-beam irradiations. It is suggested that the wettability
enhancement by the radiations may be attributed to the radiolysis of water.
10.3 Effect of Boiling Heat Transfer on Surface Wettability
10.3.1 Experimental Setup and Procedure
A schematic view of the experimental apparatus for pool boiling experiments with
small heat transfer area is shown in Fig. 10.5. The apparatus consists of a copper
block, a furnace, a rectangular container, and a heat exchanger. The copper block
has a cylindrical part (10 mm in diameter, 15 mm in height). Several cartridge
Fig. 10.2 Contact angle
measurement system
Fig. 10.3 Estimation
of contact angle
98
D. Ito et al.
À1 2rh
r 2 þ h
2
ð10:1Þ
where r and h are obtained by using an image processing software (ImageJ).
10.2.3 Effect of Irradiations on Surface Wettability
Figure 10.4a–c shows the wettability change from ultraviolet, γ-ray, and proton-beam
irradiation, respectively. The horizontal axis denotes an integrated irradiation dose or
irradiation time and the vertical axis denotes the measured contact angle. As shown in
these figures, the contact angle decreases with the irradiation dose. In these experiments, the ambient effect is also studied during the irradiations, which are performed
in air or water. As shown in Fig. 10.4a, the ambient effect on the contact angle change
is not obvious in the ultraviolet irradiation. However, the ambient effect is very distinct
both in the γ-ray and the proton-beam irradiations. It is suggested that the wettability
enhancement by the radiations may be attributed to the radiolysis of water.
10.3 Effect of Boiling Heat Transfer on Surface Wettability
10.3.1 Experimental Setup and Procedure
A schematic view of the experimental apparatus for pool boiling experiments with
small heat transfer area is shown in Fig. 10.5. The apparatus consists of a copper
block, a furnace, a rectangular container, and a heat exchanger. The copper block
has a cylindrical part (10 mm in diameter, 15 mm in height). Several cartridge
Fig. 10.2 Contact angle
measurement system
Fig. 10.3 Estimation
of contact angle
98
D. Ito et al.