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The housing of totally enclosed fan-cooled electrical machines is usually finned to maximize the heat dissipation over its surface. Complex models involving heat and fluid flow simultaneously are necessary to evaluate a single design. An optimization over a wide parameter range is, therefore, not possible. In this paper, a novel approach on how to model this particular conjugate heat transfer problem in 2-D without the help of lumped circuits is presented. The proposed method is applied to an optimization process controlled by an evolutionary algorithm. Comparative, more detailed simulations in computational fluid dynamic (CFD) verify the tendencies obtained in the optimization. In another case, the method is used to evaluate the allowable degree of engineering tolerance for a given design. Although the method does not provide results as accurate as CFD, it is very helpful to study a large parameter set and determine the CFD candidates. [ABSTRACT FROM PUBLISHER]

This paper studies the effects of blades' forward-swept amount in the rotation direction and forward-inclined amount in the intake direction on the flow around the fan blades of a large open-type motor. The authors have previously clarified this flow separation on the blade surface under high ventilation resistance from flow analysis and visualization experiments. To prevent flow separation, they proposed forward-swept and inclined blades, together with reduction of the air path's ventilation resistance. In this study, numerical fluid analyses were performed on the flow around forward-swept and inclined blades of axial fans for large open-type motors. Several combinations of forward-swept and inclined amounts were studied. The relationship between forward-swept and inclined amounts and flow was evaluated quantitatively, and an ideal combination was obtained. The study revealed that an axial fan with this combination showed much higher flow rate than a conventional fan without forward-swept and inclined blades. Furthermore, it significantly decreased fluid noise and axis power. [ABSTRACT FROM AUTHOR]

Due to ever increasing consumer demand, today's marketplace is full of portable computing devices such as notebook computers, gaming machines, personal digital assistants, and smart phones. In each of these technologies, processing power and functionality levels are continuing to increase, resulting in increased thermal management issues. The former of these technologies already use an active cooling solution with a profile of 10-15mm while the latter two are quickly approaching the limits of passive cooling. Since a common characteristic in each of these technologies is the desire to reduce profile height, there exists a need to develop low profile cooling solutions that are capable of supporting this growing market. However, a prerequisite to developing such solutions is an accurate understanding of how the noise level characteristics of the driving fans scale with height. This paper experimentally addresses the acoustic scaling of low profile fans. The rotor heights range from 0.5mm to 15mm with diameters from 15mm to 32mm, giving an aspect ratio of height relative to diameter of 0.03-0.6. The results can be used as a foundation for the development of active cooling in mobile devices where both correlations for noise levels and basic design criteria are identified. [ABSTRACT FROM AUTHOR]

The noise produced by cooling air passing through electronics packages arises from two sources. One source is the noise of the air-moving fan of either an axial or centrifugal type. This noise may have both tonal and random components and is strongly dependent on the way that the fan is placed in the unit and on where its operation is on the fan's operating curve. Often, fans are the dominant noise sources. The flow of air produces random noise due to the turbulence generated throughout the unit. Because the turbulent airflow is also responsible for heat transfer between the components and the air stream, we can regard this part of the noise as the irreducible noise due to cooling. If fan noise were eliminated, this part of the noise would remain. There is a relation, therefore, between the irreducible noise and the cooling of the unit. But the fan noise must also be considered. The relation between total airflow related noise and cooling requirements is developed in this paper for the irreducible noise. [ABSTRACT FROM AUTHOR]

This paper studies the cooling performance by axial fans with forward-swept and inclined blades and a structure with low ventilation resistance for large-capacity open-type motors. The ventilation resistance of axial fans for motors is much greater than that of common fans for creating draughts. Flow separates remarkably on the blades' surfaces and fluid noise is large. We reduced the ventilation resistance inside an electric motor and adopted axial fans with forward-swept and inclined blades. We confirmed by wind tunnel experiment that the flow rate with this combination increases remarkably compared with the conventional ventilation structure and axial fans. Numerical fluid analysis was performed on the flow around the blade at this flow rate. It was confirmed that no flow separation appeared for the air flow along the blade surfaces. This was also observed in a flow visualization experiment. Furthermore, an actual motor with both the low-ventilation-resistance structure and axial fans with forward- swept and inclined blades showed that the flow rate of cooling air increased by 80% compared with that of conventional machines, and the average temperature rise of stator windings decreased by 30%. Thus, the cooling performance was greatly improved. [ABSTRACT FROM AUTHOR]