Can a disc valve change pressure while also changing flow rate?
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If a butterfly valve is installed in a piping system, with the pipe diameters on both sides being identical, and the pressure and flow rate at the inlet being fixed! Since the pipe diameter remains unchanged, the flow velocity stays the same, and so does the head ； Meanwhile, according to the principle of conservation of kinetic energy, the change in head is set to 0; therefore, the pressure difference across the valve body equals the local resistance loss of the valve body? :(I wonder if my understanding is correct?) Beginners, please give some advice! ! Thank you! !
This question is interesting. If the position of the butterfly valve’s disc remains unchanged, the pressure difference on both sides of the valve body should be approximately equal to the local resistance loss of the valve body. Since butterfly valves are generally used to regulate flow, under normal circumstances, only the pressure before the valve can remain constant, while the flow rate changes. The control capability of a butterfly valve lies in adjusting the flow rate by changing the resistance in the pipeline. Therefore, a butterfly valve can simultaneously change both the flow rate and the pressure at its outlet (provided that the pressure before the valve remains constant). If the pressure before the valve changes, even if the position of the butterfly valve’s disc remains unchanged, the flow rate and pressure at the outlet of the butterfly valve will still change.
Thank you very much for your answer! In the scenario I have set up, does the pressure reducing valve function in the same way as a butterfly valve? Is it just that the range of adjustment is different? What is the difference between a pressure reducing valve and a butterfly valve? It seems that both work by increasing local resistance to change the pressure in the piping system. I am designing the air pipeline system for a heat treatment furnace, and I want to adjust the pressure in the piping system so that the blower can operate under optimal conditions. I’m not sure which type of valve would be better for this purpose; previous drawings showed the use of butterfly valves. I think a pressure reducing valve should also work for this purpose, but I’m not sure what the differences are. Thank you again!!
When the opening of the disc valve in the same pipeline changes, the flow rate changes, and the pressure also changes simultaneously. A gas line pressure regulator only changes the pressure in the pipeline downstream of the valve, but it also involves the issue of pressure-induced expansion.
The pressure difference before and after a pressure reducing valve is relatively large, while for butterfly valves, the pressure difference before and after is generally not that significant. The choice of valve depends on the required pressures and flow rates. In my opinion, a butterfly valve is a better option, as the air volume is high but the pressure is not very high. Using a pressure reducing valve requires significant investment, and it is also more difficult to design and install. Butterfly valves are more convenient, require less investment, and allow for better control of pressure and flow rates.
Thank you all for your advice! I’ve learned so much from it!!