Results 1 - 10 of 105
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[en] The process of laser metal deposition was easy to be affected by fluctuations of environment and process parameters, leading to the deviation of melt pool temperature or deposition morphology and so on. Accumulation of small deviation would result in the instability of deposition process and lead to the failure of forming. Therefore, the on-line monitoring of laser metal deposition process was studied, involving thermal history of forming parts, temperature and size of melt pool, deposition morphology and forming defects, and so on. In this paper, the on-line monitoring technologies, such as thermocouple temperature measurement, infrared thermal imaging, high-speed camera and other monitoring methods, were introduced, and the open-loop monitoring, closed-loop feedback control and closed-loop feedforward control technologies were illustrated in detail. According to the research situation, the future development of on-line monitoring in laser metal deposition was prospected. (paper)
[en] Press hardening of steels for the production of car body components is very common. The reason for this is that the process allows the use of blanks with low wall thickness and the production of ultra-high strength components with complex geometries. The Hot Metal Gas Forming (HMGF) process for closed profiles combines the advantages of hydroforming, such as increased rigidity, functional integration or elimination of joining operations, with those of press hardening. In this paper results of continuous tests with actively cooled tools are presented in combination with temperature and displacement measurement. Furthermore, test results for HMGF with tool integrated conductive heating are demonstrated. Tests were done with tube material PHS1800 by SSAB, part temperatures over the Point of austenitisation and maximum internal pressure of 70 MPa. Thermocouples recorded the heat distribution in the tools. Other measured and recorded variables were the displacement of the component wall while forming under increasing internal pressure by a tactile displacement sensor and simultaneous temperature of its surface with a thermal sensor head. For the first time, information on pressure, the corresponding deformation stage and temperature profile could be documented during an entire forming step. A close to series production geometry DP4 was used to investigate the tool-integrated conductive heating of components. (paper)
[en] Extensive convective heat transfer measurements have been collected in the Supercritical University of Ottawa Loop (SCUOL) with carbon dioxide at supercritical pressures flowing vertically upwards in tubular test sections having inner diameters equal to 22.0, 8.0, and 4.6 mm. Outer wall temperature was measured by a large number of thermocouples, from which the inner wall temperature and the local heat transfer coefficient were estimated. The measurements extend over wide ranges of conditions, which cover both the normal and deteriorated heat transfer modes. Experiments were conducted using all three test sections with the purpose of determining the tube diameter effects on the local heat transfer coefficient h for normal heat transfer. Measurements were collected for 15 different flow and heating conditions, all at P/Pcritical ≈ 1.13. The results showed that, in most cases, the corresponding h was higher for smaller diameter tubes. Nevertheless, for flows at low mass fluxes (G ≤ 400 kg/m2s), the h values from the 8 and 22 mm test sections were comparable, especially at high specific bulk enthalpies (Hb > 300 kJ/kg); for G = 300 kg/m2s, the h values from all three test sections in the high enthalpy range actually nearly coincided. At higher mass fluxes, however, the h values remained distinct for each test section over the full range of Hb values examined, with higher h values for smaller test section diameters.
[en] Bio oil from seeds of Kemiri Sunan (reutealis trisperma (Blanco) airy shaw) plant is particularly attractive to be studied since its high potential as alternative of biodiesel. This paper describes the results of a fundamental study of the combustion characteristics of a single droplet of blended fuel of Kemiri Sunan (reutealis trisperma (Blanco) airy shaw) biodiesel and ethanol in various levels of ambient pressure. The ambient pressures of the burning chamber were varied at 1, 3, and 5 bars. The fuels were prepared by mixing the biodiesel with the ethanol at concentrations of 0%, 10%, 20%, and 30% vol/vol. The single droplets of blended fuels were suspended using micro-syringe on a tip of the thermocouple. It was ignited and combusted using an electrical heater. The ignition and combustion processes of the single droplets were recorded using a high-speed camera. It was found that the ignition delay of the droplet decrease with the increase of ambient pressure and the concentration of ethanol in blended fuels. Also, the burning rate of blended droplets increased with increasing biodiesel concentration and pressure. The maximum droplet temperature slightly increased during the combustion with the increasing ethanol concentration, but not with increasing ambient pressure. (paper)
[en] Using skin temperature to predict thermal comfort typically results in higher accuracy of thermal comfort prediction compared to other methods, however, such nonintrusive thermo-graphic cameras with high resolution/accuracy are more expensive compared to the thermistors with single point. Thus, a low-cost (and low resolution) thermal camera MLX90640 was studied in this study to predict individual thermal comfort, and compared with the prediction results from high accuracy thermocouple at single point of somewhere of localized body skin. Results show that the low-cost (low resolution) infrared camera (MLX90640) with accuracy of ± 2 °C and resolution of 32 × 24 pixels is able to be used to predict thermal sensation with a performance better than skin temperature measure system including thermocouples at different points of skin with an accuracy of ±0.15 °C. And the performance of infrared camera (MLX90640) is as good as the performance of environmental air temperature sensor with accuracy of ±0.10 °C. Thus, the usage of low-cost (and low resolution) thermal camera to predict individual thermal comfort worth to be further studied. (paper)
[en] In data acquisition, it is necessary to improve the performance of the instrumentation system by developing a LabVIEW based data acquisition system, one of which is by ensuring that the data obtained is correct and reliable. The data must go through a calibration process. In this experiment, the calibration was done by comparing the results of the temperature measurements from the recorded thermocouples in the form of NI cDAQ 91 data acquisition with measurements of the standard Fluke digital thermometer that functions as a calibrator. The NI cDAQ 91 module used is channel 1 and channel 2. Each channel has two parts of data taken, namely for low temperatures with smaller ranges and higher temperatures with a greater range. The results of the calibration data will be processed and the results of the uncertainty will be searched. After going through the calibration process it turns out the data results are not much different because it does not reach a temperature of 1 °C means that the calibration data results can be trusted with errors less than 1 °C. (author)
[en] A heater tank was designed and fabricated to simulate behavior of nuclear core by using electrical heating rods. This paper reports the experimental results for six heat rods. These rods were tested at 40 degree Celsius in air at room temperature. Setup parameters were verified. The results suggest that its temperature profile follows the trend for a heat distribution profile in nuclear fuel element. (author)
[en] In this paper fault detection of brushed DC motor is described. Recently, Thermal Signature Analysis (TSA) has become a common tool for fault analysis of AC induction motors. Currently, very little research has been performed using thermal signature analysis on brushed DC motors. This paper is a present fault detection of DC motors using thermal signature analysis. In order to organize the detection, the thermal behaviour of DC motor was analysed using the K-type thermocouple with data logger. The thermocouples were mounted on 4 part of the DC motor, casing, permanent magnet, brush and bearing. The initial measurements of thermal behaviour were realized by using healthy DC motor as a sample of a thermal behaviour. Furthermore, the measurements of thermal behaviour for the same type of motor with thick carbon impurities on commutator has been implemented to compare with the thermal behaviour of healthy DC motor. The significant observation on steady state temperature of thermal behaviour between healthy DC motors and faulty DC motor will be analysed. From the analysis of thermal behaviour between healthy DC motor and commutator fault DC motor, that can clearly recognize the commutator fault by through the different of characteristic temperature profile of DC motor. (paper)
[en] Semisolid processing of Al–4.3%Cu (A206) alloy was carried out using gas-induced semisolid (GISS) process in different conditions. The flow rate of inert gas, 1, 2, and 4 L min−1, starting temperature for gas purging (the temperature of superheated melt), 670, 660, and 650 °C, and the duration of gas purging, 10, 20, and 30 s, were three key process variables which were changed during this investigation. Thermal analysis was successfully implemented through CA-CCTA technique for GISS samples as well as conventionally cast sample. The two-thermocouple thermal analysis technique was utilized to determine the dendrite coherency point of GISS sample and conventionally cast sample. The results showed that gas purging into the melt led to temperature drop of the melt to its liquidus temperature. In fact, copious nucleation is induced by cooling effect of inert gas bubbles. GISS process delays the dendrite coherency point from 644.2 to 637.3 °C which leads to increase the solid percentage from 9 to 21% at this point and therefore enhance the casting characteristics. It is found that inert gas purging into the molten metal, regardless of the process parameters, leads to the microstructural modification from fully dendritic to globular structure. Microstructural evaluation showed that the best sample which included fine grains of 76 μm in average size and with high level of globularity of 0.86 was achieved from a semisolid sample in which the gas purging started at 670 °C and its duration time was 20 s with the gas flow rate of 4 L min−1.
[en] The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method