Heat exchange orientation problem
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The vacuum pump system in our unit is scheduled for renovation, and I’m quite puzzled by this issue that has arisen now. When measuring the water output of the five vacuum pumps, all five of them drained water into the return water tank at the same time; it was found that the return water tank collected approximately 3.5 m3 of water per hour. According to the manual for the vacuum pumps, each pump (SK-12) consumes 50 L of water per minute; therefore, the water consumption per pump is 3 m3/h. The total water consumption for five pumps should be 15 m3/h. There is a big difference between the water tank’s discharge volume as measured on-site and the actual value; why is that? ? ? ? ? A heat exchanger needs to be installed on the vacuum pump pipeline (the return water temperature is very high, at 70 degrees). How should the flow rate be determined? Should it be based on the drainage volume of 3.5 m3/h measured at the site, or should it be the total water consumption of the five units, which is 15 m3/h? ? ? ? This post was last edited by lhxo524 on 2008-3-5 17:51]
Everyone, please share some suggestions; it might help broaden our thinking as well
In my opinion, no cooler is needed in the return vacuum pipeline of SK series water ring vacuum pumps. The high temperature of the return water, at 70 degrees, may be due to the excessive temperature of the return vacuum pipeline and too low circulation flow rate of the circulating water inside the vacuum pump. It is recommended to increase the diameter of the pipes for the incoming and outgoing circulating water in order to lower the temperature of the water entering the pump. When arranging the pipes, care should be taken to ensure that the water flow rate at the inlets of all five pumps is evenly distributed.
In fact, the current operating condition is just right; if too much circulating water is fed into the vacuum pump, it will trip. Moreover, one of the reasons for the high return water temperature is that the vacuum pump draws in some hot steam from the workshop. What will happen if the water flow entering the inlet of the pump is not evenly distributed? ? ? There is also a heat exchanger; how should the flow rate be determined? Is it appropriate to use some intermediate value? ? ?
In the operation of a vacuum pump, water should be recycled. The so-called water consumption refers to the amount of water used in the circulation within the vacuum pump, which is 3 m3/h. However, it’s not necessary to use exactly 3 m3 of water to achieve this circulation volume ? It’s just my personal opinion; there might be a misunderstanding!
Previously, the water supply for the SK12 water ring pump was connected to the main cooling water pipeline; five thin pipes were connected to this main pipeline to serve as the water supply source. The return water from the vacuum pump went into the return water tank, from where it was pumped by a pipeline pump into the cooling tower and integrated into the factory’s overall cooling water system. Now, it is planned to change the piping connection, so that the vacuum pump operates in its own closed system and is not connected to the entire water system. So the plan is as follows: The water returned by the vacuum pump goes into the water tank, and from there, the water is pumped through a pipeline to the heat exchanger before being sent back to the vacuum pump to complete the cycle. First, it is necessary to calculate the heat exchange area, which requires knowing the flow rate of the vacuum return water. Second, it is needed to determine the capacity of the pipeline pump as well as the flow rate. Do anyone have any suggestions? ? ? ?
Waiting for everyone to reply. This is a very typical question – did no one notice it before? ? ? ?
Actually, this will work fine: the working capacity can be set at 6 m3/h, but it can be increased to 15 m3/h
It is sufficient to calculate based on a total design flow rate of 15 m3/h. The heat exchange area is not large anyway; a plate heat exchanger with an area of 40–60 m2 has a very small volume. The pipeline pump should be designed for a flow rate of 15 m3/h, with a head of 20 m; its power requirement is estimated to be only 2 kW. The flow rate can be adjusted using an outlet valve. My advice is this: for projects of this kind with limited investment, there’s not much money to save anyway; it’s better to allocate a larger amount to ensure everything goes smoothly. Otherwise, if the results are not satisfactory, it will be a huge embarrassment.
How is the head of a pipeline pump determined? ? ? Is there one on site with a flow rate of 24 and a head of 34 that can be used???
The head of a pipeline pump should be determined in the same way as that of a conventional centrifugal pump; the specific head depends on the pressure required to be achieved by the fluid and the resistance in the pipes. If a pump is available, its performance curve should be checked to see whether it is suitable for the intended operating conditions. If both the flow rate and head exceed the actual requirements by too much, this leads to power waste, difficulties in adjustment, and pressure buildup within the pump. One solution is to modify the impeller, which can reduce the flow rate and head. Each case needs to be analyzed on its own; there are things that cannot be understood without being on the spot, so you need to put in more effort.
Thank you so much for the reminder from above; sometimes it feels like I’m back in college, and it’s been of great help to me.