Using surface plasmon resonance imaging (SPRi), we have recently shown for the first time the existence of a monolayer water film between droplets during dropwise condensation. This study examines the effect of adsorbed volatile organic compounds (VOCs) on the ultrathin film measurement using SPRi. Further, the work presents the proper surface-treatment process that enables measurements of the ultrathin water layer during high-speed imaging of dropwise condensation at 3000 frame per second. In this study, two methods were applied for cleaning the surface (gold-coated glass)—(1) standard cleaning procedure (SCP) using acetone, isopropyl alcohol, and deionized water and (2) SCP followed by air plasma cleaning. This work discusses the effect of the cleaning procedures on surface roughness, contact angle, and surface chemistry using atomic force microscopy, optical microscopy, and an X-ray photoelectron spectroscope meter. The results showed that SCP before the SPRi is a proper surface-treatment method. The effect of adsorbed VOCs during dropwise condensation on a surface treated with SCP was measured to be 0.0025 (reflectivity unit), which was 70% smaller than the reflectance associated with a monolayer water film. The results of this work confirm a monolayer water film observation during the dropwise condensation, which has been reported before.

This study investigates the transient behavior of an electro-thermal drilling probe (ETDP) during a close-contact melting process within a glacier. In particular, the present work analyzes the effect of the tip temperature on the formation of molten thin liquid films and the subsequent rate of penetration (ROP) through numerical simulation. We used the commercial code of ANSYS Fluent (v.17.2) to solve the Reynolds-averaged Navier–Stokes equation, together with an energy equation considering the solidification and melting model. The ROP of the drilling probe is determined based on the energy balance between the heating power and melting rate of ice. As the results, the ETDP penetrates the ice through a close-contact melting process. The molten liquid layer with less than 1 mm of thickness forms near the heated probe tip. In addition, the ROP increases with the heated temperature of the probe tip.

This study numerically investigates the propagation characteristics of hazardous noxious substances (HNSs) spilled from transport ships and suggests the metal model for predicting the HNS propagation velocity varied with the current velocity and HNS density. The commercial computational fluid dynamics (CFD) code ANSYS FLUENT (V. 17.2) was used for two-dimensional simulation based on the Reynolds-averaged Navier–Stokes (RANS) equation together with the standard k–ε model. The scalar transport equation was also solved to estimate the spatial and transient behaviors of HNS. The main parameters to analyze the near-field propagation characteristics of HNSs spilled from the ship were layer thickness, HNS concentration, and propagation velocity. It was found that advection becomes more dominant in propagating an HNS layer that becomes thinner as the current velocity increases. When the current velocity increased beyond a certain level (~0.75 m/s), the mixing effect made the HNS layer less dense but thicker. Consequently, lower-density HNS causes increased HNS concentrations at sea level. As the current velocity increased, the concentration distribution became homogeneous regardless of HNS density. In particular, the second-order response surface model provided for three variables on the basis of the numerical results for 15 cases with the use of the general least-squares regression method, showing a good fit. This model would be useful in estimating the propagation velocity of HNS spilled from a ship.

The present study aims to measure the solid–liquid interface temperature of an evaporating droplet on a heated surface using a thermoresponsive polymer. Poly(N-isopropylacrylamide) (pNIPAM) was used owing to its sensitive optical and mechanical properties to the temperature. We also measured the refractive index variation of the pNIPAM solution by using the surface plasmon resonance imaging (SPRi). In particular, the present study proposed a new method to measure the solid–liquid interface temperature using the correlation among reflectance, refractive index, and temperature. It was found that the reflectance of a pNIPAM solution decreased after the droplet deposition. The solid–liquid interface temperature, estimated from the reflectance, showed a lower value at the center of the droplet, and it gradually increased along the radial direction. The lowest temperature at the contact line region is present because of the maximum evaporative cooling. Moreover, the solid–liquid interface temperature deviation increased with the surface temperature, which means solid–liquid interface temperature should be considered at high temperature to predict the evaporation flux of the droplet accurately.

This study aims to numerically analyze the near-field propagation behavior of hazardous and noxious substances (HNSs) and to develop a new metamodel for HNS propagation. Extensive computational fluid dynamics (CFD) simulations were conducted using the ANSYS FLUENT (V. 17.2) code for various HNS spill scenarios. We newly introduced several key parameters, including the streamwise propagation velocity, transverse propagation velocity, and averaged HNS mass fraction. From the results, the advection effect is more dominant with an increase in the current velocity and streamwise propagation velocity, and with a decrease in the transverse propagation velocity. Also, the HNS mass fraction decreases as the current velocity increases with the change of concentration and propagation area. Particularly, a new metamodel of HNS propagation based on the current CFD results was validated by the hidden point test, showing very good fit. We believe this model would make useful predictions under various scenarios without CFD simulations.

This study investigates numerically gaseous CO₂ leakage characteristics inside the containers of a transport ship and examines thermal effects on the structural damage that might happen in the containers. First, with consideration of the phase change, the ejected mass flow rate was estimated using the commercial code of DNV PHAST. Based on this estimated mass flow rate, we introduced an effective area model for accounting for the fast evaporation of liquefied CO₂ occurring in the vicinity of a crack hole. Using this leakage modeling, along with a concept of the effective area, the computational fluid dynamics (CFD) simulations for analyzing transient three-dimensional characteristics of gas propagation in a confined space with nine containers, as well as the thermal effect on the walls on which the leaking gas impinges, were conducted. The commercial code, ANSYS FLUENT V. 17.0, was used for all CFD simulations. It was found that there are substantial changes in the pressure and temperature of the gas mixture for different crack sizes. The CO₂ concentration at human nasal height, a measure of clear height for safety, was also estimated to be higher than the safety threshold of 10% within 200 s. Moreover, very cold gas created by the evaporation of liquefied CO₂ can cool the cargo walls rapidly, which might cause thermal damage.