Оценка нестационарной теплоотдачи при пленочной конденсации пара на вертикальной стенке

Получены расчетные зависимости коэффициента теплоотдачи, скорости движения и трансцендентное уравнение для толщины ламинарной пленки конденсата, справедливые для регулярного теплового режима

Thermisch gespritzte Beschichtungen für den Armaturenbau

In dieser Studie wird die Entwicklung verschiedener thermisch gespritzter Beschichtungen für den Einsatz im Armaturenbau diskutiert. Basierend auf etablierten Verschleißschutzschichten der Armaturenindustrie wurden verschiedene Festschmierstoffe in diese Beschichtungen integriert, um das Verschleiß‐ und Reibungsverhalten bei anwendungsnahen Belastungen für Armaturen zu verbessern. Für die Anwendungen wurden Verschleißschutzschichten auf Basis von WC/CoCr und Cr₃C₂/NiCr entwickelt. Als Festschmierstoffe wurden nickelumhülltes Graphit und hexagonales Bornitrid untersucht. Die Verfahrensvarianten Hochgeschwindigkeitsflammspritzen mit Sauerstoff (HVOF) und das neuartige Ultrahochgeschwindigkeitsflammspritzen (UHVOF) wurden untersucht. Die Ergebnisse zeigen, dass durch eine passende Beschichtungszusammensetzung eine Reduktion des Verschleißes von 53 % und der Reibung von 31 % unter anwendungsnahen Belastungen möglich ist

Исследование остаточных углеводородов в ходе деструкции гептана углеводородокисляющими микроорганизмами рода Pseudomonas и Rodococcus

Molding of micro structures by injection molding leads to special requirements for the molds e.g. regarding wear resistance and low release forces of the molded components. At the same time it is not allowed to affect the replication precision. Physical vapor deposition (PVD) is one of the promising technologies for applying coatings with adapted properties like high hardness, low roughness, low Young's modulus and less adhesion to the melt of polymers. Physical vapor deposition technology allows the deposition of thin films on micro structures. Therefore, the influence of these PVD layers on the contour accuracy of the replicated micro structures has to be investigated. For this purpose injection mold inserts were laser structured with micro structures of different sizes and afterwards coated with two different coatings, which were deposited by a magnetron sputter ion plating PVD technology. After deposition, the coatings were analyzed by techniques regarding hardness, Young's modulus and morphology. The geometries of the micro structures were analyzed by scanning electron microscopy before and after coating. Afterwards, the coated mold inserts were used for injection molding experiments. During the injection molding process, a conventional and a variothermal temperature control of the molds were used. The molded parts were analyzed regarding roughness, structure height and structure width by means of laser microscopy

Study of Convective Heat Transfer in Grinding Applied to Tool Carbide

The grinding temperature is of great importance for the quality and integrity of machined cemented carbide tool. Tool edge surfaces may be damaged by softening or being stressed, hardened, burned, or cracked. Former research on grinding temperature prediction often made assumptions to simplify heat convection due to the grinding fluid. However, these simplifying assumptions can sometimes undermine the mathematical relationships between grinding conditions and surface temperature, particularly in low-temperature grinding where fluid convection is most important. This paper is an attempt to provide an improved comprehensive thermal model for the prediction of contact temperatures and for monitoring and control of thermal damage. Based on previous thermal model research, this paper tackles a key element of the thermal model for temperature prediction. It proposes a convective heat transfer model based on the classic theory of turbulent flow passing a plate. Theoretical predictions from the thermal model of turbulent flow developed in this paper are compared with experimental values. Predictions are further compared with values from a previously published laminar flow model. And it is shown that the new model leads to a significant reduction in predicted temperatures. The results suggest that the thermal model for the turbulent flow provides a reasonable estimate of predicted temperature values within the region of the fluid boiling temperature. The estimates appear to be an improvement compared with the laminar flow thermal model. The turbulent flow thermal model is considered to improve estimates of background contact temperatures in grinding cemented carbide

Развитие бизнес-процессов статистического управления качеством на Юргинском машзаводе

Micro-structured and thus functionalized surfaces offer high potentials for new approaches in processing techniques and product design. However, for mass production purposes quite a few challenges regarding the manufacturing of these surfaces have to be overcome. For the fast and economic production of large quantities of structured polymer films the extrusion embossing process is suitable. For embossing microstructures there are special requirements on temperature control because of the double function of the embossing roll. On the one hand the roll is used as an embossing roll with a high surface temperature to improve the embossing accuracy. On the other hand it is used as a cooling roll with a low surface temperature. Only by using variothermal heating systems these contradictory demands on the temperature control can be met. In order to achieve a high quality of the produced micro-structured films an integrative analysis and optimization of the entire process chain is required. This includes the manufacturing of suitable embossing rolls, the development of coating systems and the adaption of the extrusion process. This paper deals with the entire process chain for functionalized, super hydrophobic plastic parts with contact angles up to 165°. Therefore, conelike surface structures, mimicking the structure of lotus leaves, are replicated. Functionalized parts are produced in the injection molding as well as in the extrusion process; however, this paper focuses on the process chain of the extrusion process