flow temperature is reached. Inline water heaters also may be used to bring the water up to temperature.
Open vs. Closed Systems Two basic types of cooling systems are common in
metalcasting: open and closed. In open systems, heated water travels through pipes from the furnace to the cooling tower. Tere it is sprayed through the air and flows down through a porous material. Evaporation, enhanced by the air flow generated by powerful fans, serves to cool the water, normally collected in a sump at the bottom of the tower and pumped back to the furnace. City water must be added to replace the water lost through evaporation and to dilute the buildup of minerals in the water. All open systems use evaporative cooling towers. Open cooling systems are the simplest to build and
operate and can achieve the lowest water temperatures. But they expose the water to dirt, debris and scale that can build up over time and clog the pumps, pipes and furnace coils, restricting water flow and substantially reducing cooling effectiveness. Open water systems, therefore, must include filters and strainers to capture solids and chemical treatments to reduce scale formation. Other treatments are needed to prevent disease-causing organisms, such as Legionella, from developing in the water. Overall, open water systems require more regular maintenance than closed systems and use more water. Te sumps also require protection from freezing in cold climates. In closed cooling systems, heated water also travels
开放式系统与封闭式系统对比
开放式和封闭式这两种基本类型的冷却系统在铸造 厂都很常见。在开放式系统中，被炉体加热后的水通 过管道进入冷却塔。在那里水经过空气形成喷雾并顺 着多孔材料向下流动。风扇产生的气流增强蒸发作用 使水冷却，通常收集冷却水的储水槽在冷却塔底部， 通过水泵使冷却水循环回到炉体中。必须添加自来水 补充被蒸发掉的水并稀释水中聚集的矿物质。所有开 放式的系统都使用蒸发式冷却塔。
开放式冷却系统的建造和运行最简单，并可以获得 最低的水温。但它们使水暴露在灰尘中，随着时间的 推移碎屑和水垢将堵塞水泵，管道和炉体线圈，限制 水流量从而大大降低冷却效果。因此，开放式冷却系 统必须安装过滤器和过滤网来过滤固体物并通过化学 处理减少水垢的生成。还需要防止致病微生物，如水 中产生的军团杆菌。总体而言，开放式冷却系统比封 闭式系统需要更多的定期保养，并消耗更多的水。在 寒冷的气候条件下需要防止储水槽结冰。 在封闭式冷却系统中，热水也是通过管道从炉体 流进冷却塔。但与开放式系统不同，当水到达冷却
September 2014
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