The greater the pressure difference, the greater the flow rate and the greater the resistance; conversely, the smaller the pressure difference, the lower the flow rate
Thread Content
A large pressure difference and high flow velocity result in an increased flow rate； But the greater the resistance, the greater the pressure difference as well; with higher resistance, doesn’t the flow rate decrease? How should these two meanings be expressed to be clear? Another option is a control valve and a shut-off ball valve of the same diameter; the pressure difference across the control valve is definitely higher than that across the ball valve, but the ball valve has a lower pressure difference while allowing a higher flow rate. (This contradicts the fact that the greater the pressure difference, the greater the flow rate.)
Don’t create contradictions for yourself. Just like the three situations encountered when discussing math problems, namely the situation when it is 10. First, determine what the pressure and flow rate are when the flow volume is constant, or what they are when the pressure and flow rate are constant. For reference.
They must have the same initial conditions in order to be compared with each other
The original poster doesn’t quite understand the relationship between pressure difference and flow rate. Simply put, for a fluid to flow, there needs to be a pressure difference; pressure difference = initial pressure – pressure loss. The greater the pressure difference, the higher the flow velocity and the greater the flow rate. However, different valves represent different pressure losses; the higher the pressure loss of the valve chosen, the smaller the pressure difference will be, and consequently the flow rate will be lower.
For gaseous states, the pressure difference is high, resulting in a low flow rate. Although the flow rate increases, the pressure decreases, which is similar to the effect of expansion
The first question has been explained very clearly earlier. Second question: First, it should be clear that ball valves can also be a type of control valve; not all ball valves use O-ring seals – V-ring seals are also used. Both questions are based on common sense; take your time and don’t get stuck on them.
Agreed. For control valves and cut-off ball valves of the same diameter, the pressure difference is related to the valve’s opening degree; different opening degrees result in different diameters.
Increased flow rate in the same pipeline → higher flow velocity → greater pressure difference； The smaller the opening of the same valve → the higher the flow rate → the greater the pressure difference ； When the flow velocity is the same for different valves, the larger the resistance coefficient, the greater the pressure difference. Resistance = (coefficient of resistance * density * velocity^2) / 2
Prerequisite: For the same pipeline, the greater the flow rate, the greater the pressure difference, that is, the greater the resistance； It was clearly explained upstairs----Resistance=(coefficient of resistance*density*velocity^2)/2