SURFACE WETTABILITY OF WATER DROPLETS IN HIGH-TEMPERATURE,　HIGH-PRESSURE ENVIRONMENT

Objective In the case of a high-temperature condition, wall surface wettability and heat transfer with the phase change are definitely expected to be different from those in a low-temperature condition. Therefore, wall surface wettability in high-temperature conditions becomes an important evaluation point in practical system design of nuclear plants. However, very limited experimental data can be obtained about the wall surface wettability in high-temperature condition, or in the range from 250 to 300℃. From this point of view, we conducted an experimental study of surface wettability in a high-temperature, high-pressure environment.

Conducting experimental study of surface wettability under various ambient pressures (7.7, 14 and 15MPa), atmospheric gases (nitrogen and argon), and test plate materials (aluminum, stainless 304, Zircaloy). Measured contact angles ・Decreased with temperature below 250oC ・Clustered around a straight line for temperatures below 120oC ・Clustered around another line over the range from 120 to 250oC. At temperatures above 250oC ・Contact angles remained constant independent of temperature ・Contrary to the existing theoretical results, no highly hydrophilic condition or null contact angle condition was achieved.