Real-time mass detection of trace water vapor frosting on a cryogenic surface based on quartz crystal Microbalance (QCM) sensor

Abstract

Trace water vapor remaining in a large-scale cryogenic wind tunnel may form an extremely thin frost layer on the scaled model, significantly affecting the aerodynamic characteristics and degrading the data quality. Developing a high-precision detection method for trace water vapor frosting can be very helpful in revealing the underlying mechanisms. In this work, utilizing the relationship between deposited mass and frequency variation of Quartz Crystal Microbalance (QCM), an ultra-sensitive (nanogram level) mass sensor for cryogenic and flow conditions was developed. Furthermore, after investigating the effects of different parameters (flow velocity, pressure, temperature and mass) on frequency, the real-time mass detection of trace water vapor frosting under cryogenic and flow conditions was achieved for the first time. The results show that the effect of flow velocity or pressure on frequency is almost negligible compared to that of temperature or mass. Although temperature (from 290 K to 140 K) has a significant effect on frequency, by using the relationship between the measurement surface and the reference surface, the separate effect of mass on frequency can be obtained and the real-time mass detection is achieved. The calculated total deposited mass by trace water vapor frosting is about 4.64 μg/cm2 when the water vapor content, lowest surface temperature, pressure, velocity and frosting time are 186.5 ppb, 140 K, 0.1 MPa(G), 1.0 m/s, 160 min, respectively. This self-designed device and the analysis results of this work can be used as a reference for the quantitative measurement of trace water frosting as well as the phase change process of other trace substances in cryogenic and flow environments.