Recirculating Cooling-Water Network with an Intermediate Cooling-Water Main

Recirculating cooling-water systems are, by far, the most common method used for the rejection of waste heat to the environment. To reduce the recirculating cooling-water flow rate to improve the performance of the cooling tower, and, at the same time, to make the recirculating cooling-water network simpler and more flexible, so that it is easier to operate and control, a new recirculating cooling-water network configuration with an intermediate cooling-water main is proposed in this paper. In the network, an intermediate cooling-water main is positioned between the cooling-water supply main and the cooling-water return main, with the temperature usually at the pinch. The intermediate main receives used recirculating cooling water from some coolers at temperatures less than or equal to its temperature and provides cooling water to some other coolers, which can use cooling water at temperatures higher than or equal to its temperature. In this way, the recirculating cooling water into or out of each cooler will be coming from or going into one of the three mains. Compared to the traditional parallel network, the new configuration can obviously reduce the recirculating cooling-water flow rate and increase the return temperature to the cooling tower, so that the effectiveness of the cooling tower is increased. In addition, compared to the series arrangements that have been proposed recently, the new configuration has a simpler network, which will be easier to operate and control. A methodology has been developed for the design of cooling networks with an intermediate cooling-water main.