How to calculate the relationship between pressure and flow rate?

The pressure difference between the two pipes = a* l * p * u * The unit of u/2d is pa and a is the friction coefficient of the pipeline, which is related to the age and material of the pipeline. l is the distance between the two points you took, the unit is meters p is the density of the fluid kg/m3 u is the flow rate of the fluid in the pipe, the unit is meters/second d is the diameter of the pipe, the unit is meters

Knowing the pressure difference means knowing the resistance drop. For a certain pipe diameter, pipe length, pipe fittings, valves, etc., the flow rate can be calculated, and the flow rate can be calculated

Let’s talk about a=64w/dup in detail. W represents the viscosity of the fluid dup. The same concept as above. Here you need to know the viscosity of the fluid, which can be measured in a general laboratory.

If it is just an ordinary steel pipe, just take a as 0.1.

The calculation formula can be found in the Fluid Flow section of Chemical Engineering Principles or in commonly used chemical engineering design manuals. The key is that the physical property parameters need to be accurate.

The main thing is this. The resistance is not known. A 40mm pipe goes into the water cooling device, and another 40mm pipe comes out of the water cooling device. Now I want to see how big a water pump is needed to achieve a flow rate of 2m/s!

For a 40 pipe with a flow rate of 2m/s, it can be calculated that q=2* 0.04 * 0.04 * pi * 3600/4=9.05m3/h, you need at least 9.05m3/h water pump

You should be talking about what flow rate and lift to use. The brother on the 8th floor has taught you how to calculate the lift. You can still use the formula I provided you to calculate the resistance. In fact, if you want to choose a pump, you must calculate the total resistance from the pump outlet to the final discharge port. That is the minimum lift required by your pump.

Very good. I’ll ask you for advice on any pump issues I don’t understand in the future.

It seems that it is necessary to learn the principles of chemical engineering well

It’s better to read engineering books, you can find the answer in them!

We often encounter this situation in engineering. When the diameter, pressure and flow rate of the water pipe are determined, the flow rate or flow rate of the pipe is determined.: Knowing the flow rate, pressure and velocity of the pipe, find the diameter of the pipe. Other: The medium is water and saturated steam. In general engineering calculations, the pressure of water pipelines is usually 0.1--0.6MPa, and the flow rate of water in water pipes is 1--3 m/s, usually 1.5 m/s. Flow rate = pipe cross-sectional area: square. Pipe diameter unit: mm pipe diameter=sqrt(353.68X flow/flow rate) sqrt: The formula for the square root of saturated steam is the same as that for water, except that the flow rate is generally 20-40 meters/second. If you need an accurate calculation, you must first assume the flow rate, and then calculate the Reynolds number based on the viscosity, density and pipe diameter of the water. Then use the Reynolds number to calculate the resistance coefficient along the way, and look up all the pipe fittings in the pipeline (such as tees, elbows, valves, reducers, etc.) in the table. Equivalent pipe length, and finally the total pipeline pressure loss is calculated based on the resistance coefficient along the way and the total pipeline length (including equivalent pipe length), and the actual flow rate is calculated based on Bernoulli, and the actual flow rate is used again to calculate according to the above process until the two are close (iterative trial algorithm). Therefore, in practice, few friends calculate this way. Basically, they choose different flow rates based on the pressure difference.

It’s really good to learn chemical engineering well