The major reason a partial waterside economizer system is ever considered is to allow the cooling tower to function as economically as possible within certain temperature ranges which, in this case study, range from 37°F to 47° ambient wb. While the cooling tower can produce cold water on its own, to do so at certain cooler temperatures means it must precisely balance its energy among the various types of equipment including the towers, pumps, and chillers. Therefore, the plate-and-frame heat exchanger in concert with the chiller(s) can reduce overall plant energy consumption.
The original plate-and-frame heat exchanger was installed in parallel, which is common, and is often found in chilled water plants in the Midwestern and Northern regions of the United States. As with all plate-and-frame heat exchangers, they operate in conjunction with a cooling tower to produce cold water during winter and shoulder seasons. However, unlike series installed heat exchangers, their piping does not temper (cool off) the water prior to its entering the chiller(s). As a result, the operational sequence for the heat exchanger installed in parallel is much simpler, e.g., the CHWS temperature is reached or the chiller(s) take over. In other words, the tower and heat exchanger fans and pumps cycle if load fluctuates.