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We studied a jet impingement heat sink for cooling modular power semiconductor devices. The purpose of the study was to investigate the influences on cooling performance of simplified structures of the heat sinks that suppresses the jet velocity to avoid pitting corrosion or erosion of the impingement wall. The influence on the cooling performance of partition plates used to prevent mutual interference between jets from circular nozzles was verified. We confirmed the influence on the cooling performance of the wall shape of the header and the influence of the distance from the nozzle to the wall (jet height) in the case of small ratio of the jet height to the nozzle diameter. We verified the influence on the cooling performance of the relation between the directions of the array of multiple jets and the direction of the exhaust flow. Flow visualization was performed using a mock-up model of a jet impingement heat sink. From the visualization, we found the reason on the influence of the relation between those directions. As a result, we found that the structure of the heat sink was able to be simplified maintaining the cooling performance of the conventional heat sink. [ABSTRACT FROM PUBLISHER]

We studied reactor size reduction by applying a slot jet cooling method. In power electronics products such as large power conversion equipments for industry applications (conversion equipments), reactors take up a large proportion of the volume and weight, and miniaturization of reactors is an important issue in reducing the size of conversion equipments. Reactors cooled by forced air convection are generally almost the same size as those cooled by natural air convection. We applied a slot jet cooling method to make cooling air flowing out from two or more slots impinge on the reactor surface at high speed. There have been many reports concerning jets from single slots or two or more slots distributed in parallel. However, many of the details of mutual interference and the exhaust flow along the direction of the slot after jet impingement on a surface remain unknown. Therefore, these basic findings were experimentally verified, and an optimum slot jet giving the greatest improvement in cooling performance, while taking account of exhaust flow, was found. By applying this slot jet cooling, the mass was reduced by about half compared with a conventional reactor. [ABSTRACT FROM AUTHOR]

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]

In this paper, the cooling airflow in a unidirectional ventilated open-type motor for electric vehicles (EV) was studied. Numerical fluid analysis was performed on the airflow in the motor through a ventilation path outside the stator iron core inside the frame. It is confirmed that there was a flow separation where air did not flow along the path surfaces. This was observed in a flow visualization experiment using water instead of air. We propose a new structure to prevent air separation and confirm its effectiveness by a visualization experiment. It is also shown that another structure with paths both inside and outside the stator iron core in the frame improves the motor's cooling performance. These structures are effective for EV motor downsizing. [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]