Water cooler temperature control scheme

If the total amount of a certain fluid cannot be easily changed, installing a bypass is a necessary measure in such cases. Setting up a bypass reduces the efficiency of the heat exchanger. 1. The process gas bypass reduces the efficiency of the heat exchanger ； 2. The circulating cooling water bypass reduces the dynamic efficiency of the circulating water ； 3. Adopt bypass control to ensure that the heat exchange capacity of the heat exchanger has sufficient margin ； a. When using a process gas bypass, it is required that the temperature of the stream passing through the heat exchanger be higher than the process design temperature, so that the temperature after mixing with the cold process gas from the bypass meets the specified requirements ； b. When a circulating water bypass is used, the cooling water flowing through the branch connected to the heat exchanger (which is obviously less than the total cooling water flow rate) can meet the cooling requirements of the process equipment, thus providing room for adjustment. If the flow rate of the cooling water (main pipe) can be adjusted, it is appropriate to install control valves at the inlet of the circulating water; that is, by measuring the temperature at the outlet of the process gas, the control valve at the inlet of the circulating water is adjusted. Adopting a process gas (main pipe) inlet flow rate scheme will cause fluctuations in the process load, affecting the upstream and downstream process units. In summary, it is most reasonable to control the outlet temperature of the process gas by adjusting the inlet flow rate of the circulating water. If the total flow rate remains constant, a process gas bypass flow control is employed to maintain a reasonable process gas outlet temperature. Secondly, adopting a circulating cooling water flow control scheme to regulate the process gas outlet temperature is also an option.

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Actually, the second floor overlooks an important issue: the return temperature of the circulating water in the circulating water cooling area is generally not allowed to exceed 60°C. If the temperature of the circulating water becomes too high, scaling will occur. In my opinion, if one has to choose among the three options suggested by the original poster, the first approach – setting up a bypass for the process gas – is the best; in fact, most installations are designed this way. Options two and three both involve reducing the flow rate of the circulating water, which inevitably leads to an excessively high outlet temperature of the circulating water.

Currently, the heat exchanger has a large margin of tolerance; if the flow rate of the circulating water is controlled, the temperature at the outlet of this water will indeed be relatively high, reaching around 90°C. Another issue is that, due to the low pressure of the process gas and the large diameter of the pipes, the bypass control valves for the process gas need to be much larger than those used in the circulating water pipeline, which increases costs significantly. Moreover, the space required by the three-valve assembly for these control valves is also much greater.