Heat transfer enhancement in superheated hydrocarbon fluids due to traces of water

For the specific mode of pulse heating of a wire probe immersed in a test liquid (saturated hydrocarbon), the effect of enhancement of the heat transfer through the probe surface has been revealed. The characteristic heating time is from 10 to 20 ms. The objects of research are n-hexane, n-decane, and n-hexadecane. It is shown that the addition of 0.003% water increases the heat transfer to 10% in the course of approaching the boiling-up temperature of liquid. Simulation of the experimental conditions shows the possibility of microconvection in the most heated boundary layer of a liquid about 10 μm thick.

Calibration and data reduction for X-hotwires using cross validation

A strategy for calibration of X-wire probes and data inversion is described in this article. The approach used has elements of full velocity vs yaw-angle calibration with robust curve fitting. The responses of an X-wire probe placed in a calibration jet are recorded for a set of velocity and yaw inputs followed by fitting cross-validated splines. These spline functions trained from calibration data are evaluated for the probe responses during measurement. X-wire probes are calibrated for low to moderate velocities (0.65 m/s to 32 m/s) and yaw angles in the range −40° to 40° and comparisons with conventional interpolation schemes are made. The proposed algorithm can be extended to calibration of other multiple wire probes and for higher velocities. Some measurements in a single round turbulent jet flow at high Reynolds number using the proposed inversion algorithm are also presented. The present scheme is found to perform better particularly at low flow magnitudes and/or extreme flow angles than the schemes used previously.

Repositioning of the Severe Prolapsed Silicone Tubes after Bicanalicular Nasal Intubation: A Novel Technique

Background. Bicanalicular nasal intubation is widely used in lacrimal drainage system surgery. Its common complication is lateral displacement or spontaneous prolapse. When the distal part of the silicone tubes cannot be seen in the nose endoscopically, either repositioning or removal could be a challenge. We developed a simple technique to reposition the severe prolapsed silicone tubes. Method. This retrospective study included 6 patients with severe prolapsed silicone tubes who had undergone bicanalicular nasal intubation between January 2017 and December 2019. We used a memory wire probe to pull a nylon suture through the lacrimal passage retrograde. Then, the nylon suture was cut into two lines. One line was coiled to the prolapsed tube and tied to another line. This nylon turned into a “lasso” to capture the silicone tube and then lock its knot. By pulling the nylon suture, the severe prolapsed silicone tube was repositioned to the nasal cavity. Results. Using this technique, we successfully repositioned severe prolapsed silicone tubes without any complication in 6 cases. Conclusions. Silicone tube reposition guiding by using a memory wire probe is an optional technique in the treatment of prolapse of silicone tubes, particularly if the distal part of the silicon tube was embedded in the lacrimal sac and cannot be seen in the nose by endoscopy. It is a feasible, minimally invasive, safe, and effective method, avoiding premature tube removal.

Numerical and Experimental Study of Topographic Speed-Up Effects in Complex Terrain

Our research group is developing computational fluid dynamics (CFD)-based software for wind resource and energy production assessments in complex terrain called RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University (RIAM)-Computational Prediction of Airflow over Complex Terrain), based on large eddy simulation (LES). In order to verify the prediction accuracy of RIAM-COMPACT, we conduct a wind tunnel experiment that uses a two-dimensional steep ridge model with a smooth surface. In the wind tunnel experiments, airflow measurements are performed using an I-type hot-wire probe and a split film probe that can detect forward and reverse flows. The results of the numerical simulation by LES are in better agreement with the wind tunnel experiment using the split film probe than the results of the wind tunnel experiment using the I-type hot wire probe. Furthermore, we calculate that the two-dimensional ridge model by changing the length in the spanwise direction, and discussed the instantaneous flow field and the time-averaged flow field for the three-dimensional structure of the flow behind the model. It was shown that the eddies in the downwind flow-separated region formed behind the two-dimensional ridge model were almost the same size in all cases, regardless of the difference in the length in the spanwise direction. In this study, we also perform a calculation with a varying inflow shear at the inflow boundary. It was clear that the size in the vortex region behind the model was almost the same in all the calculation results, regardless of the difference in the inflow shear. Next, we conduct wind tunnel experiments on complex terrain. In the wind tunnel experiments using a 1/2800 scale model, the effect of artificial irregularities on the terrain surface did not significantly appear on the airflow at the hub height of the wind turbine. On the other hand, in order to investigate the three-dimensional structure of the airflow in the swept area in detail, it was clearly shown that LES using a high-resolution computational grid is very effective.

Revisiting hot-wire anemometer measurement of Tollmien–Schlichting waves on a flat plate

The amplification of Tollmien–Schlichting (T-S) wave plays an important role in the process of boundary-layer transition. This paper investigates the measurement of T-S wave using hot-wire anemometer (HWA) in a wind tunnel. To precisely acquire T-S wave, the vibration of hot-wire probe and the influence of electromagnetic interference (EMI) are considered. By introducing different amplitudes and frequencies of vibration ribbon, the development of T-S waves is obtained. Lift-up of low-speed fluid and downward of high-speed fluid are observed during the transition.

Experimental Investigation of the Vortex Flow around an Axisymmetric Body with the Five-Hole Probe and Hot Wire Probe

Anaxisymmetric body experiences the vertical flow around itself at incidence angle. If the adverse pressure gradient is significant, the boundary layers separated and a vortex is formed. The flow over a submarine at AOA (angle of attack) has specified separation of boundary layer and large vortex structures around the body. This flow influences body drag, acoustic and maneuverability. A propermethod to decrease and control the impacts of this separated flowis to use vortex generator. The mainobjective of the present study is to investigate the flow field around a Suboff model with applying the vortex generator by using the hot wire and five-hole probe in 0° ≤ α ≤ 20° angles of attack. The novelty of present study is application of two experimental method, (hot wire probe and five-hole probe) which can help to precisely study the structure of three-dimensional vortical flow field, the boundary layer velocity profiles and probability of the separation on the model with and without existence of vortex generator. The results indicate that vortex generators significantly decrease cross-flow separation, the size of vortices and the vortical flow.

Electrical characterization of CIGS thin-film solar cells by two- and four-wire probe technique

A precise characterization of thin-film solar cells is of huge importance for obtaining high open-circuit voltage and low recombination rates from the interfaces or within the bulk of the main materials. Among many electrical characterization techniques, the two- and four-wire probe using the Cascade instrument is of interest since the resistance of the wires and the electrical contacts can be excluded by the additional two wires in four-wire probe configuration. In this paper, both two- and four-point probes configuration are employed to characterize the CIGS chalcogenide thin-film solar cells. The two-wire probe has been used to measure the current–voltage characteristics of the cell which results in a huge internal resistance. Therefore, the four-wire connection is also used to eliminate the load resistance to enhance the characterization’s accuracy. The load resistance in the two-wire probe diminishes the photogenerated current density at smaller voltage ranges. In contrast, the proposed four-wire probe collects more current at higher voltages due to enhanced carrier collection efficiency from contact electrodes. The current conduction mechanism is also identified at every voltage region represented by the value of the ideality factor of that voltage region. It is observed that a longer time given to the charge collection results in increased current density at a higher voltage. According to the results and device characteristics, a novel double-diode model is suggested to extract the saturation current density, shunt and series resistances and ideality factor of the cells. These cells are shown to be efficient in terms of low recombination at the interfaces and with lower series resistance as the quality of the materials is in its most possible conductive form. The measured internal resistance and saturation current density and ideality factor of the two measurement configurations are measured and compared.

Electrical Characterization of CIGS Thin Film Solar Cells by Two and Four-Wires Probe Technique

The characterization of thin-film solar cells is of huge importance for obtaining high open-circuit voltage and low recombination rates from the interfaces or within the bulk of the main materials. Among the many electrical characterization techniques, the two- and four-wire probe using the Cascade instrument is of interest since the resistance of the wires, and the electrical contacts can be excluded by the additional two wires in 4-wire probe configuration. In this paper, both two and four-point probes configuration are employed to characterize the CIGS chalcogenide thin-film solar cells. The two-wire probe has been used to measure the current-voltage characteristics of the cell which results in a huge internal resistance. Therefore, the four-wire connection is also used to eliminate the lead resistance to enhance the characterization’s accuracy. The load resistance in the two-wire probe diminishes the photogenerated current density at smaller voltage ranges. In contrast, the proposed four-wire probe collects more current at higher voltages due to enhanced carrier collection efficiency from contact electrodes. The current conduction mechanism is also identified at every voltage region represented by the value of the ideality factor of that voltage region. It is observed that a long time given to the charge collection results in increased current density at a higher voltage. According to the results and device characteristics, a novel double-diode model is suggested to extract the saturation current density, shunt and series resistances and the ideality factor of the cells. These cells are shown to be efficient in terms of low recombination at the interfaces and with lower series resistance as the quality of the materials is in its most possible conductive form. The measured internal resistance and saturation current density and ideality factor of the two measurement configuration is measured and compared.