Discussion on the problem of simultaneous feeding and discharging of two storage tanks
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The existing tank C flows into tank A and tank B through gravity. The elevations of tanks A and B are equal. The length of the pipe from C->A is shorter than the length of the pipe from C->B, so the amount of liquid entering tank A is greater than the amount of liquid entering tank B.； The bottoms of tanks A and B are connected to the discharge pump at the same time (the backflow of the pump is connected to tank B). Because the pipeline from B to the discharge pump is shorter, the discharge volume of tank B is greater than the discharge volume of tank A. To sum up, analyze the situation that will occur during actual operation.: (1) Assuming that the feed volume of tanks A and B is the same, because the discharge volume of B is greater than A, the liquid level of tank A will be higher than that of tank B during operation. The liquid level difference = the pipeline resistance loss from tank A to the pump - the pipeline resistance loss from tank B to the pump. ； (2) Actually, due to the different feed amounts (A>B), the liquid level of tank A fluctuates during operation. Please let me know, experts, is this my understanding correct?
Supplement that tanks A and B are connected to each other, that is, the pressures in the two tanks are equal.
If I understand your question according to the process, it seems that there is no need to go around like this, right? There is a valve on it, you just know how to control it. Maybe I don’t understand your intention, should you consider including valves in it, for reference.
Controlling the valve openings of C->A and C->B can solve the problem and it doesn't need to be so complicated.
If there is no control valve but a manual valve, will the liquid level of A be higher than the liquid level of B in actual operation?
The gas phase is balanced, the liquid phase is connected, and the pipe diameter is slightly larger.
The bottoms of the two tanks are connected through the pump inlet pipe, forming a connector. If the top of the storage tank is connected to the atmosphere, the pressure at the top will be equal, and theoretically the liquid levels in the two tanks will always remain balanced.； The pressure drop between the inlet and outlet pipes of the two tanks is negligible. ； If the liquid level of a tank fluctuates, it means that the inlet or outlet flow is biased. You only need to adjust the opening of the inlet valve and the outlet valve appropriately. Without adjustment, the liquid level fluctuation is acceptable.
When the pump is running and pumping out, it is indeed as the author understands. The liquid level of B drops, which is a dynamic balance at this time. But when the pump ends, I believe the tank discharge valve will close in time, so the connecting tube effect will not have time to show up. As someone said above, it is a hand valve anyway. Adjusting the valve opening can solve the problem.
The pump is continuously running, so the pipeline connecting the AB tank and the pump cannot function as a connecting pipe. The liquid level can only be balanced when the pump stops. During actual operation, the pipeline resistance loss cannot be ignored. It is precisely because of the difference in resistance loss between the inlet and outlet pipelines of the storage tank that the liquid level of A is higher than that of B when the pump is running. ； If each AB tank feed pipe is equipped with a control valve linked to its respective liquid level to control the feed amount. Is it possible to achieve the same liquid level in both storage tanks? What I understand is that it can be achieved, but the feed and discharge volume of tank A will be smaller than that of tank B. Is my understanding correct? Thanks~
The first half of the sentence is correct, but adding the control valve and liquid level switch is a bit cumbersome. My job is to make the pipeline resistance of the two equal, and the hand valve control is enough. In the second half of the sentence, to achieve the equal liquid levels of both of them, the final means is that the feed volume of tank AB is equal and the discharge volume is also equal.
First of all, thank you for your reply, it helps me a lot. If the feeding amount and the discharging amount are equal, then the feeding valve of A needs to be closed small, and the discharging valve of B also needs to be closed small to achieve this.