What is critical cavitation number?
What is critical cavitation number?
Typically a critical cavitation number, σa, is defined at which the head loss is 2, 3 or 5%. Further reduction in the cavitation number will lead to major deterioration in the performance; the cavitation number at which this occurs is termed the breakdown cavitation number, and is denoted by σb.
At what cavitation number does cavitation occur?
Pvap: vapor pressure of the liquid, Pa; ρ: density of the liquid, kg/m3; v: flow velocity through the restriction, m/s. A cavitation number of less than 1.5 indicates that cavitations may occur.
How do you determine if cavitation will occur?
Cavitation will only occur if the local pressure declines to some point below the saturated vapor pressure of the liquid and subsequent recovery above the vapor pressure. If the recovery pressure is not above the vapor pressure then flashing is said to have occurred.
What is cavitation factor?
Cavitation is the formation and collapsing of cavities or bubbles in a liquid mostly developed in the areas which have relatively low pressure around the pump impeller. It occurs in the absence of the net positive suction head the pump. It occurs when the vapor pressure goes beyond the static pressure of the liquid.
How do you calculate cavitation coefficient?
The cavitation coefficient Kc is the ratio between the valve pressure drop at which cavitation starts and the difference between the inlet and the vapor pressure of the application. The allowable maximum ∆p before cavitation begins is ∆p = Kc (p1 – pv).
What is valve cavitation?
Cavitation is the sudden vaporization and violent condensation of a liquid downstream of the valve due to localized low pressure zones. When flow passes through a throttled valve, a localized low pressure zone forms immediately downstream of the valve. The sound of cavitation in a pipeline is unmistakable.
What conditions cause cavitation?
Discharge cavitation occurs when pressure at the discharge end of the pump is too high. High discharge pressure limits the volume of fluid flowing out of the pump, causing high-velocity fluid to recirculate between pump impeller and housing, causing cavitation.
Which is the best description of the cavitation parameter?
Cavitation Number. The Cavitation Number or Cavitation Parameter is a “special edition” of the dimensionless Euler Number. The Euler Number – an introduction to and a definition of the Euler Number The Cavitation Number is useful when analyzing fluid flow dynamics problems where cavitation may occur. The Cavitation Number can be expressed as σ…
When to use the cavitation number in fluid mechanics?
The Cavitation Number is useful when analyzing fluid flow dynamics problems where cavitation may occur. small amounts of air supplied to the suction system may reduce the amount of cavitation damage keep available NPSH well above required NPSH. Fluid Mechanics – The study of fluids – liquids and gases.
Where does cavitation occur in the recovery zone?
Downstream of the Vena Contracta in the recovery zone, the fluid decelerates converting excess kinetic energy into pressure energy as it slows. Therefore the intermediate pressure in the Vena Contracta is lower than the final system pressure and thus the highest chance of experiencing cavitation as demonstrated in the figures below.
When does cavitation occur in a pressure reduction system?
Cavitation may occur in a pressure reduction system even if the final system pressure is the above vapour pressure of the liquid. This is because the intermediate pressures may fall below the final pressure.