Papers by Keyword: Temperature Variation

Abstract: The thermal model of a permanent magnet motor (PMM) is investigated in this study using the lumped parameter thermal approach to calculate temperature variation at steady-state and transient conditions. The temperature variation of the motor components over time under various loads is investigated. The proposed thermal model was constructed with the MATLAB code. The thermal characteristics of the motor are examined using the simulation results. The optimization and sensitivity analysis are done using the response surface method (RSM) by design expert software. It can be seen that increasing the load and time increases the temperature of all parts in the machine. Also, point multiplication with 0.998 desirability is presented, which has the best efficiency with the lowest temperature.

Abstract: By considering the momentum source term of surface tension and the source term of heat transfer in gas-liquid two phase flow, a computational model based on the VOF was established to discuss the rules of the temperature outside tube in the evaporative air cooler.The result shows that under a wind velocity and spray density, the temperature of water near the wall dropped sharply at first, with wall distance increasing, finally to environmental temperature, and with annular angle increase, the temperature of water film increases. And the higher the wind speed, the higher the water film temperature, but the changes of wind speed has little influence on the temperature within less than 60 º angle. The smaller the spray density, the higher water film temperature.

Abstract: This paper by taking the hypersonic speed wing surface as the research object, according to the basic theory of thermal mode analysis, calculates and analyzes the influence of temperature variation on model vibration characteristics. According to the analysis, the structural natural vibration characteristics can be influenced by different temperature loads obviously. As for the 7075 root fixed wing surface model under the temperature range of 150K~500K, the basic linearity of frequencies of different order modals decreases with the rise of temperature; The structural frequency decreases sharply with the rise of temperature when the temperature is higher than 500K.

Abstract: During temperature was decreased first before it was increased again in low-temperature environment of 3°C~15°C, the variation law on characteristics of activated sludge in urban sewage treatment by activated sludge process were investigated. The results showed that settling property and dewatering performance of activated sludge became worse due to the influences from low temperature, and it tended to take longer to recover its property in temperature-rise period; the temperature change had a large effect on microbial activity in activated sludge.

Abstract: Large structures are usually made by joining different elements. Fusion welding is one of the most fundamental technique, which is used to make large metallic joints. During fusion welding a large amount of heat is generated which melts the joint surroundings and a joint is created after solidification. Joint configuration is mostly affected by the material parameters and process type. In this paper, a thermo-mechanical simulation of fusion welding of submerged arc welding is performed using ANSYS. A moving heat source model based on Double-Ellipsoidal heat flux distribution is modelled. The transient temperature distributions and temperature variations of the welded plates are calculated during welding process. Effect of welding speed, welding current on temperature profile and angular distortion of plates is further investigated.

Abstract: Greenhouse temperature of the three different types was measured under sunny winter weather conditions. The variation regularity of greenhouses temperature with outdoor temperature was studied according to the monitoring data of experimental greenhouse, which was different roof and floor structure. The results showed that the greenhouse temperature of the herringbone roof construction higher than the greenhouse of the serration roof construction; the greenhouse temperature of the serration roof construction is higher than the greenhouse of arch roof construction. Through analysis of temperature variation on the different type greenhouse, it will provide theoretical basis to construct greenhouse in different areas.

Abstract: The loads on the arch dam and the materials physical properties of the dam and the bedrock are uncertain, and can be described with random variable. Due to the huge volume, the complex structure of the dam and excessive random variable, the reliability analysis of the dam is difficult. The dam is a higher order statically indeterminate structure, and the variation of the temperature obviously affects the stress and displacement of the structure, therefore, it is very important to consider the randomness of the temperature change load in the reliability analysis of arch dam. Based on the analysis of the stable temperature field, temperature rise and temperature drop field of the dam, the calculation method of temperature change field is further studied and applied in the reliability analysis of the arch dam. Considering random variables such as temperature change, water pressure, elastic modulus and strength of the materials, the stress and displacement of the arch dam and bedrock are calculated with a three dimensional finite element method, the limit state equations are established by RSM. Then the tension and compression reliability of the arch dam are analyzed using gradient optimization method. The results indicate that the temperature change field significantly influences the tension and compression reliability of the dam, and should be seriously considered in the reliability analysis of arch dams.

Abstract: The polishing is one of the important methods in manufacturing of silicon wafer and in thinning of completed device wafer. Generally, getting a flat surface such as a mirror is the purpose of the process. The wafer surface roughness is affected by many variables such as the characteristics of the carrier head unit, operation, speed, the pad and slurry temperature. Optimum process conditions for experimental temperature, down-force, slurry ratio are investigated, time is used as a fixed factor. This study will report the evaluation on surface of wafer by dependent of varying platen, chuck rpm, temperature variation, and oscillation which affect it has on the surface roughness. In this experiment, it is determined the optimum condition for polishing silicon wafers. By using optimum condition, it helps to achieve an ultra precision mirror like surface.

Abstract: An analytical model based on multilayer structure with thermal expansion mismatch caused by temperature gradients was established to predict the residual stress in the system. The solution obtained from the model is independent of the number of layers. Three simplified models: bi-layer structure, coating system and film system with great compatibility are developed considering different engineering application. And the bilayer structure is verified by Stoney’s equation under the same conditions. Tri-layer coating system ZrO₂/ Al₂O₃/1Cr₁₈Ni₉Ti is established in order to research the effect of temperature variations on the residual stress between different layers. The results suggested the stress has obvious mutation in coating interface with different temperature variation. And the residual stress with different temperature variation in different layers is larger than that with identical temperature variation. Key words: multilayer structures; residual stress; analytical model; thermal expansion mismatch; temperature variation