The Influence of Pantograph Carbon–Metal Composite Slider Thermal Properties on the Railroad Wire Temperature

This article presents the methodology, description, and results of experimental studies aimed at determining the impact of the copper concentration in a carbon–metal composite contact strip on the maximum temperature of the copper contact wire during a contact event when used for operation in the railway industry in Europe. Based on these tests, we determined the minimum percentage of copper that is required for the composite to meet the normative requirements for current loads. In addition to experimental research, a 3D FEM numerical model was also developed in which the contact strip and contact wire geometry were mapped, along with imposed loads resulting from the test for current loads mentioned above. Fifteen simulation variants were carried out for the established model, where the value of the thermal conductivity coefficient and the specific heat coefficient were varied. On this basis, we analyzed the sensitivity of thermal coefficients to the contact wire temperature and determined the minimum conductivity coefficient value, which allowed the maximum copper contact wire temperature of 120 °C to be obtained during the verification tests.

Development of a CFD-based simulation model and optimization of thermal diffusion column: application on noble gas separation

In this study, numerical simulations were carried out to investigate the separation of the helium-argon gas mixture by thermal diffusion column. This research determined the significant parameters and their effects on the process performance. Effects of feed flow rate, cut ratio, and hot wire temperature in a 950 mm height column with an inner tube of 9.5 mm radius were examined through the simulation of the thermal diffusion column. For minimizing the number of simulations and obtaining the optimum operating conditions, response surface methodology (RSM) was used. Analysis of separative work unit (SWU) values as a target function for helium-argon separation clearly showed that the maximum amount of SWU in thermal diffusion column was achieved, when hot wire temperature increased as large as technically possible, and the feed rate and cut ratio were equal to 55 Standard Cubic Centimeters per Minute (SCCM) and 0.44, respectively. Finally, the SWU value in optimum conditions was compared with the experimental data. Results illustrated that the experimental data were in good agreement with simulation data with an accuracy of about 90%.

Mathematical model of a remote monitoring module by wire temperature of an overhead power line

In continuation of the previously published research results (Energy Safety and Energy Economy, iss. 2, 2021), we have developed wire temperature-based mathematical models for overhead power line monitoring. Mathematical models simulate allowable amperage load considering the temperature and an allowable wire sag considering the temperature and amperage. The proposed mathematical models became a base for overhead power line remote control tools being currently tested at power utility companies.

Device for contactless ice buildup monitoring of overhead power line wires

Ice buildup monitoring is essential to prevent wire breakage on overhead power lines. Conventional telemetry systems which are based on load cell sensors have some drawbacks as reflected in this paper. We suggest an innovative device for contactless ice buildup monitoring of overhead power line wires video recording the power line clearance. A specific algorithm for detecting the lowest point of wire sag has been provided. Also, we analyze a possibility of indirect contact sensor-free measurements of a wire temperature when the wire is being covered by icy deposits. A specific buildup type can be determined comparing a dew point and desublimation point as shown in this paper.

Simplified Calibration Method for Constant-Temperature Hot-Wire Anemometry

This study proposes a unique approach to convert a voltage signal obtained from a hot-wire anemometry to flow velocity data by making a slight modification to existing temperature-correction methods. The approach was a simplified calibration method for the constant-temperature mode of hot-wire anemometry without knowing exact wire temperature. The necessary data are the freestream temperature and a set of known velocity data which gives reference velocities in addition to the hot-wire signal. The proposed method was applied to various boundary layer velocity profiles with large temperature variations while the wire temperature was unknown. The target flow velocity was ranged between 20 and 80 m/s. By using a best-fit approach between the velocities in the boundary layer obtained by hot-wire anemometry and by the pitot-tube measurement, which provides reference data, the unknown wire temperature was sought. Results showed that the proposed simplified calibration approach was applicable to a velocity range between 20 and 80 m/s and with temperature variations up to 15 °C with an uncertainty level of 2.6% at most for the current datasets.

A Method of Crack Monitoring for Electrically Activated SMA Wires Using Thermography

Predicting the remaining lifetime of an operating shape memory actuator is a great goal to achieve to increase its reliability. The shape memory wires used in these actuators are mostly activated using Joule Heating. Therefore the electrical resistance during activation can easily be measured. Studies show an increase in electrical resistance with an increasing number of activations due to fatigue. Therefore monitoring the electrical resistance leads to a prediction regarding the remaining lifetime of the actuator. The electrical resistance depends on the ambient temperature and the load case (yielded stress, activation frequency, voltage, and current) resulting in different maximum activation temperatures of the wire. The increase in electrical resistance should lead to a higher wire temperature. Before the wire fails due to fracture cumulating cracks should appear. These cracks decrease the diameter of the wire that leads to locally increased electrical resistance and therefore a local higher temperature. This work investigates if those hotspots can be monitored using thermal imaging. Binary Ni50Ti50 wires with a diameter of 0.28 mm were investigated. Measuring the exact temperature of the wires is difficult since the specimens are round and the emission coefficient is unknown. Therefore only qualitative measurement of the temperature is performed. 10 experiments at different stresses and voltages were performed. The results show some indications, that the position and the moment of the fracture can be determined using this setup. Several models are matching the wire temperature after activation to its fracture strength and fatigue behavior. Further investigations must be performed combining the presented models to the results of this work.