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Cavitation occurs when the pressure on a liquid drops below the vapor pressure for the liquid or when gas is otherwise introduced to a pump such that it disrupts the flow of the liquid through the pump.
Positive displacement pumps trap a quantity of liquid (or gas) and then increase the pressure by pushing (displacing) it into the discharge pipe. External pressure pushes the liquid into the pump chamber which then is made smaller before the pump chamber discharges its contents. If any gas enters the pump chamber along with a liquid it is simply compressed along with the liquid. Positive displacement pumps work just fine with both gases and liquids - although when gases are being compressed it is usually necessary to cool the pump chamber which heats up quite a bit during the almost adiabatic compression step of the pump. Cavitation does not occur in part because the pressure in the pump chamber is almost completely uniform. If the compression chamber drops below the vapor pressure of a liquid being pushed into it, the external pressure will continue to push the liquid in, then when the pump begins to decrease the volume, the valve allowing the liquid to enter will close and the volume of the contents is decreased until the pressure rises back above the vapor pressure of the liquid and it condenses in the pump chamber.
A centrifugal pump uses a rotating impeller to increase the pressure and flow rate of a fluid. In centrifugal pumps, pressure is added by increasing the kinetic energy of the liquid and then, in essence, "throwing" the liquid into the discharge pipe where the higher kinetic energy liquid pushes on the liquid ahead of it to increase pressure. As the impeller moves through the liquid being pumped, it pushes on the liquid ahead of it, imparting additional kinetic energy to it. The liquid behind the impeller, however, actually experiences a little bit of a drop in pressure as the impeller tries to move away from it. Because liquids are fairly incompressible, this usually does not create any problem and the internal pressure of the liquid is sufficient to keep it in contact with the backside of the impeller. If the drop in pressure is low enough that the pressure drops below the vapor pressure of the liquid at the temperature present in the pump, the liquid will begin to vaporize. Once gas is present in the pump, it begins to cavitate - the liquid separates from the back of the impeller - especially near the tips. For this reason, introducing air or other gas into the liquid can cause cavitation, even if the pressure never drops below the vapor pressure of the liquid being pumped. This is also why centrifugal pumps are usually "primed" prior to being started up - to get all, or at least most, of the gas out of the line so that the pump won't cavitate.
What else can I help you with?
Can reciprocating compressor surge?
Compressor surge only occur in centrifugal compressors. reciprocating compressor don't as they increase pressure by volume reduction, unlike centrifugal compressors where they increase pressure by converting kinetic energy to potential energy (pressure).
What is the use of recirculation line in boiler feed pump?
A recirculation line in a boiler feed pump is used to return part of the pumped water back to the inlet of the pump. This helps to prevent cavitation and maintain a steady flow of water through the pump. Cavitation is a phenomenon that can occur in pumps when the pressure of the water being pumped drops below the vapor pressure of the water. When this happens, bubbles of vapor can form in the pump, which can cause damage to the pump and reduce its efficiency. The recirculation line helps to prevent cavitation by returning part of the water that has been pumped back to the inlet of the pump. This increases the pressure of the water at the inlet, which helps to prevent the formation of vapor bubbles. As a result, the pump can operate more efficiently and reliably. Overall, the use of a recirculation line in a boiler feed pump helps to prevent cavitation and maintain a steady flow of water through the pump. This can improve the performance and reliability of the pump.
In a damped free excitation system when does maximum amplitude occur?
it will occur just before the resonance.
Where do stresses occur in a loaded beam?
Stress occur everywhere in the beam. Maximum occur at mid span and at support of simply supported beams and cantilever beams respectively - M. Velsamy, Mobile 9884585625
Where does the maximum bending moment occur in a simply supported beam?
It depends on the loading conditions of the beam, it will generally occur close to the middle of the span.
How cavitation can be eleminated in a pump?
cavitation is caused when vapour pressure in the fluid in higher equal to the surrronding presure. in the case of centrifugal pump, when the hydraulic pressure (due to height) in the fluid falls below the vapour pressure of the fluid itself, cavitation wil occur.
What causes cavitation in a pump?
cavitation is caused when vapour pressure in the fluid in higher equal to the surrronding presure. in the case of centrifugal pump, when the hydraulic pressure (due to height) in the fluid falls below the vapour pressure of the fluid itself, cavitation wil occur.
What is caviation?
Cavitation is the formation of vapour cavities in a liquid, caused by rapid changes in pressure. These cavities collapse with great force, leading to damage in equipment and machinery operating in the liquid. Cavitation can occur in pumps, propellers, and other hydraulic systems.
How does goal displacement occur?
In soccer
What must be produced for a double displacement reaction to occur?
A precipitate, water, or a gas must be produced for a double displacement reaction to occur.
What happens when both chemicals are alkaline?
Displacement may occur, or if both are made up in water, displacement reactions may occur between the ions of water and each chemical may occur
Does hydrodynamic cavitation micro bubbles contain dissolved O2?
Yes, It contains all the gasses that occur in the liquid. the amount of dissolved gases effects the formation of cavitation bubbles along with viscosity, temperature and presence of a nucleation surface. A typical cavitation bubble is about 1 million water molecules in size prior to collapsing, very small.
Where an interaction potentially can and cannot occur?
Character displacement in Galapagos (Darwin's) Finches Character displacement in Minks
When will a double displacement reaction not occur?
A double displacement reaction will not occur if the products formed are insoluble in the solvent, if no reaction occurs between the two compounds, or if the reaction conditions are not suitable for the reaction to proceed.
Do displacement reactions only occur between halogens?
Also other elements can be involved.
What must be produced for a double-displacement reaction to occur?
In a double-displacement reaction, two compounds switch ions to form two new compounds. This generally requires the presence of two ionic compounds in a solution. When the cations and anions in the two compounds switch partners, a double-displacement reaction occurs.
Can reciprocating compressor surge?
Compressor surge only occur in centrifugal compressors. reciprocating compressor don't as they increase pressure by volume reduction, unlike centrifugal compressors where they increase pressure by converting kinetic energy to potential energy (pressure).
