Is it true that the lower the temperature of the circulating water in chemical plants, the better?
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The temperature of the circulating water is generally low in winter. Some companies shut down some fans in order to meet the design requirements and prevent the temperature of the circulating water from dropping too low. However, from a process perspective, lower temperatures result in lower consumption. Is it true that the lower the temperature of the circulating water, the better – of course, as long as it does not affect the safe operation of the equipment? Let’s all discuss this together.
Not really; factors such as flow rate, residence time, and heat exchange area also need to be taken into consideration
It definitely won’t work. The lower the water temperature, the less water is needed for the heat exchange equipment; the circulating water stays in the equipment for a shorter time, and the water pressure is low. If the water quality is poor, it can easily cause blockages in the equipment.
Heat exchangers have requirements regarding temperature differences, and if the flow rate is insufficient, scaling occurs severely in the heat exchanger.
This needs to be determined based on the process design principles. Generally speaking, the lower, the better. But it can’t be generalized!
In actual factory production, the temperature range of the circulating water used for cooling is usually between 20°C and 32°C, which is essentially at room temperature. In my opinion, the main reasons for this are as follows: First, the temperature control of materials cooled by circulating water is often set at a relatively high level, so there is no need for lower temperature controls； II. Regarding energy consumption, from the user’s perspective, lower temperatures may result in better energy efficiency, but the energy consumption of the circulating water system will increase, leading to an overall rise in energy consumption ； III. Material cost of heat exchangers: A large temperature difference between the hot and cold fluids necessitates the use of higher-grade materials, which increases costs.
The analysis upstairs makes a lot of sense; the temperature of the circulating water and the flow rate are all related to the design of the heat exchanger.
We are simply discussing the balance of each within this 4 to 5 range. What do you think are the main factors behind rising costs, and what impacts does this have on users’ energy savings?
We are discussing a factory that has already been built; with the heat exchangers remaining unchanged, we adjust the temperature of the circulating water appropriately to examine its impact on the users.
Circulating water users generally prefer water at a lower temperature, as this reduces the amount of circulating water required to maintain the same temperature of the process materials, which in turn results in lower energy consumption – what is commonly referred to as energy savings； However, the circulating water system will minimize the number of fans in operation as much as possible, provided that the temperature of the circulating water meets the required standards, with the aim of saving energy ； From an overall perspective (users + utility circulating water systems), fans convert electrical energy into mechanical energy; this mechanical energy is used to act on the circulating water, resulting in a decrease in its temperature. However, the conversion efficiency of energy cannot be 100% – losses are inevitable. As a result, when more fans are used, the overall energy consumption necessarily increases.
According to you, then we currently have a total of 7 fans. To keep the circulating water within a certain range, usually only about 5 fans are operated in winter; if one more fan is turned on as appropriate, it might yield even better results in terms of balancing the energy consumption of the entire system.