任何一项工程的设计与规划都希望能可靠地达到预定的工程目的,同时所花的工程费用又最省。但是,由于设计对象及设计依据本身的复杂性,使设计具有许多困难。尤其是给排水工程的规划与设计,涉及面比较宽,困难也就更大了。例如一个化工企业的冷却水系统,通过水冷却冷凝化工产品,冷却水水温及水量严重地影响着工厂的产率,如选择不合理会造成很大的经济损失。选择冷却水温较高,产率较小,但冷却水系统的 The design and planning of any project is expected to reliably achieve the intended project objectives, and at the same time, the engineering costs spent are the least. However, due to the complexity of the design object and the design basis itself, the design has many difficulties. In particular, the planning and design of water supply and drainage works involve a relatively wide area and the difficulty is even greater. For example, a chemical company’s cooling water system condenses chemical products through water cooling. The cooling water temperature and water quantity seriously affect the productivity of the factory. If the selection is unreasonable, it will cause great economic losses. Select higher cooling water temperature, lower yield, but the cooling water system