Impact of energy-saving renovation of the plant’s circulating water system on plant operation
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The circulating water pump of the facility was upgraded for energy savings; its head was reduced from 55 meters to 45 meters, while the flow rate remained at 1,250 cubic meters. The unit has four floors, each equipped with a water cooler; there is one tubular heat exchanger on each floor, with an area of 108.25 m2 per unit ； One 1270 m2 shell-and-tube heat exchanger on the second floor ； One 3-layer 290 m2 tube heat exchanger ； One 4-layer, 258.3 m2 shell-and-tube heat exchanger. I would like to ask what differences, if any, exist in the water distribution among various heat exchangers after the pump is replaced compared to before? What impact will this have on the operation of the device?
This mainly depends on the pressure changes before the circulating water enters the cooling tower and/or after the pump outlet valve. Specifically, if the pressure before the water enters the circulating water cooling tower was 1.5 bar g before the pump replacement, and after the energy-saving modifications it is planned to adjust this pressure to 0.5 bar g, then the flow rate will remain unchanged. Similarly, if throttling was previously done via the valve after the pump due to too high a pump outlet pressure, then after the modification, increasing the opening degree of that valve can also ensure that the flow rate remains unchanged. In short, by ensuring that the pressure before and after each heat exchanger remains constant, the flow rate can be kept constant, thereby ensuring an effective heat exchange.
Can it be understood that as long as the pressure difference between the pump outlet and the cooling tower inlet remains constant, then the flow rate and velocity in each heat exchanger will not change, and this will have no impact on the heat exchange efficiency of the system. It turns out that choosing a pump with too high a head is a waste.
Other things remaining constant, the cross-sectional flow rate is determined by the pressure difference; ensuring a sufficient pressure difference guarantees the flow rate as well as an effective heat exchange.
The water volume in the fourth layer will decrease, resulting in a poorer heat exchange effect