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Flow characteristics in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The flow field was measured using the two-frame cross-correlation technique. Streamline and velocity contour graphs at different cross-sections were obtained in the experiment. The experimental results indicate that flow maldistribution in the conventional header is very serious, while the improved header configuration with punched baffle can effectively improve the uniformity. The flow maldistribution parameter in plate-fin heat exchanger has been reduced from 1.21 to 0.21, and the ratio of the maximum velocity to the minimum is reduced from 23.2 to 1.8 by installing the punched baffle. The results suggest room for the optimum design of plate-fin heat exchanger. 相似文献
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把青椒贮于10℃,7℃,4℃和1℃条件下20-60天,研究青椒转入室温后的呼吸强度的变化。10℃是青椒冷藏的安全温度,低于7℃就会发生冷害,贮藏在7℃以下的青椒,转入室温后呼吸强度大幅度上升,室温放置3天,病烂指数和花萼褐变率急剧增加,7℃以下可见到种子褐变。 相似文献
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