Investigation of Rayleigh-Taylor Instability Wavelength under Pressure Effect using High Speed Video and Particle Image Velocimetry

In the present study, the observation of RT instability wavelength with one-dimensional horizontal wire surface is studied in the pressurized wire pool boiling facility to show the relation between RT instability wavelength and CHF or MHF. The pressure effect is considered instead of using different working fluids. The observation of RT instability wavelength at different system pressure with bare Ni-Cr wire (0.5 mm dia) was studied. The CHF using R-123 refrigerant was enhanced according with higher system pressure. There was a tendency that RT instability wavelength was decreased when CHF and MHF is increased. The measurement value of wavelength in the experiment is less than the predicted wavelength equation. Different wire radius and system pressures should be conducted with bare wire surface to establish the fundamental data for the experiment of nano-coated wire. The analysis of minimum heat flux based on unstable wavelength (RT instability wavelength) has been studied to quantify the available experimental data. The experiments were studied using different inorganic fluids. To quantify the data, the dimensionless terms such as radius and minimum heat flux were considered. Nowadays, nanofluids and depositions of nano-particle on heater surface have been used to enhance of thermal margin in terms of critical heat flux (CHF) and boiling heat transfer. The enhancement of thermal margin is described as surface wettability, thermal activity (effusivity), and the change Rayleigh-Taylor (RT) instability wavelength due to deposition of nanoparticles which could make the surface as porous structure. In our research group, the change of RT instability wavelength using a simple condensation method was studied because the graphene-oxide deposition layer did not show the surface wettability improvement. Based on the enhancement of CHF studies, Lee et al. proposed the change of Rayleigh-Taylor instability wavelength could explain all the methods of CHF enhancement on pool boiling experiment. Therefore, the analysis of RT instability wavelength is needed to explain the effect of wavelength to the CHF enhancement