Determination of the maximum flow rate for DN50 pipes (e.g., water at normal temperature and pressure)

Since you have mentioned that vaporization is not possible, the first step in solving this problem should be to determine the length of the pipe. Can it be calculated as follows: the temperature at the inlet of the pipe is at room temperature, while the temperature at the outlet reaches the boiling point; by using an average value for the heat capacity, it is possible to calculate the heat generated due to friction in the fluid (under the assumption of adiabatic conditions). This heat generation is measured in joules per meter. There should be an expression relating frictional heat to the flow velocity, for example, q = f(u); by using this equation, it is possible to determine the flow velocity u. Given the flow rate, and since the power of the pump is essentially converted into frictional heat (kinetic energy can be ignored in this case), it is then possible to determine the pump’s required head pressure

Can a DN50 pipe have a flow rate of 4 m/s? If that’s possible, then 3 m/s isn’t the maximum flow rate; it’s just a commonly used economic flow velocity

This post was last edited by Chemical Engineering, hehe, machinery on 2017-7-11 13:24

First of all, thanks to the expert for the advice; it is indeed a valid method. My idea is as follows: Suppose the pump has been selected (e.g., 100 m3/h, head of 50 m, outlet diameter of DN80). If I try to connect it to a pipe with a DN50 diameter using an adapter, it will cause pressure buildup in the pump (and if I use a DN6 pipe, the pressure buildup will be even greater). So, what will be the flow rate under these conditions? I suddenly thought of this question, so I brought it up for discussion

Your idea is only theoretically valid; you can refer to the method mentioned on floor 3 for calculations. Moreover, if you install a cooling device on your pipeline, wouldn’t it be possible to increase the speed indefinitely? So it’s pointless to calculate this; in practice, it’s sufficient to use the recommended flow rate. An excessively high flow rate causes greater wear on the pipes as well as a higher pressure drop.

This is possible; we can assume that the tube is absolutely smooth and ignore any resistance.

Excessively high flow rates cause significant wear on the pipes as well as a large pressure drop; this is inevitable. What if I use a DN50 pipe and must achieve a certain flow rate (that is, a certain velocity of flow)? This is how I handled it: I determined the flow rate based on the required flow volume, and then calculated the head loss across the entire pipeline. If the head loss was acceptable and did not result in too many bubbles (i.e., the level of turbulence was acceptable), then the setup could be used; otherwise, the piping layout had to be adjusted. I calculated using the recommended flow rate of 3 m/s; to achieve a flow rate of 80 m3/h, a pipe diameter of DN100 is required, which isn’t what I want. The goal is to have a small pipe diameter while still achieving a high flow rate

Based on the premise of \"infinite pressure-bearing capacity, allowing the pump to achieve arbitrarily high flow rates and head values\", along with assumptions such as heat generated by friction being dissipated through heat exchange, the flow velocity of water inside the pipe can reach the speed of light, namely 3*10^8 m/s. Using this flow velocity, the flow rate would be 5.88*10^5 m3/s

Is the original poster here to get stuck in a dead end?