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Fluids Glossary

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Bingham plastic A fluid that behaves in a Newtonian fashion but with a requirement that some stress to set it in motion .
Best Efficiency Point (B.E.P.) The point on a pump's performance curve that corresponds to the highest efficiency.
Casing The body of the pump which encloses the impeller, syn volute .
Cavitation The sudden collapse of gas bubbles due to the sudden pressure increase.
Centrifugal force A force associated with a rotating body. In the case of a pump, the rotating impeller pushes fluid on the back of the impeller blade, imparting circular and radial motion. A body that moves in a circular path will has a centrifugal force associated with it.
Control volume The limits imposed for the theoretical study of a system. The limits are usually set to intersect the system at locations where conditions are known (syn system boundary).
Datum plane A reference plane. A conveniently accessible known surface from which all vertical measurements are taken or referred to.
Delta (D ) A Greek symbol used to express a difference between two terms. For example, D H means that the variable H is the difference of two other terms such as H1 and H2.
Dilatant The property of a fluid whose viscosity increases with strain or displacement.
Discharge Static Head The difference in elevation between the liquid level of the discharge tank and the centerline of the pump. This head also includes any additional pressure head that may be present at the discharge tank fluid surface.
e.g Exemplar gracia, for example in latin.
Enthalpy A thermodynamic property of a fluid. The enthalpy of a fluid consists of the energy associated with the fluid at a microscopic level (related to the temperature of the fluid) plus the energy present in the form of pressure at the inlet and outlet of the system.
Equipment Refers to any device in the system other than pipes, pipe fittings and isolation valves.
Equipment pressure head difference The difference in pressure head between the outlet and inlet of an equipment.
Friction The force produced as reaction to movement. All fluids produce friction when they are in motion. The higher the fluid viscosity, the higher the friction force for the same flow rate. Friction is produced internally as one layer of fluid moves with respect to another and also at the fluid wall interface.
Friction head difference The difference in head required to move a mass of fluid from one position to another at a certain flow rate within a piping system. It is also the specific energy required to overcome friction in the system.
Head Specific energy or energy per unit weight of fluid, the unit of head is a distance in feet or meters.
Heat loss The heat lost by a system or the heat lost due to friction.
Heat transfer The heat lost or gain by a system.
i.e. Id est, "that is" in latin.
Impeller The rotating element of a pump which imparts movement and pressure to a fluid.
Internal energy A thermodynamic property. The energy associated with a substance at a molecular level.
Iteration A method of solving an equation by trial and error. An iteration technique is used to solve equations where the unknown variable cannot be explicitly isolated. A frequently used technique is the Newton-Raphson method.
Kinetic energy A thermodynamic property. The energy associated with the mass and velocity of a body.
Laminar A distinct flow regime that occurs at low Reynolds number (Re <2000). It is characterized by particles in successive layers moving past one another without mixing.
Mercury (Hg) A metal which remains liquid at room temperature. This property makes it useful when used in a thin vertical glass tube since small changes in pressure can be measured as changes in the mercury column height. The inch of mercury is often used as a unit for negative pressure.
Moody diagram A graphical representation of the laminar and turbulent (Colebrook) flow equations.
Negative pressure Pressure that is less than the pressure in the local environment, syn vacuum.
Net Positive Suction Head (N.P.S.H.) The head in fluid column height absolute as measured or calculated at the pump suction flange, less the vapor pressure (converted to fluid column absolute) of the fluid.
Newtonian A fluid whose viscosity is independent of the rate of shear. In addition, a linear relationship between the rate of shear and the tangential stress between layers characterize it.
Operating point The point which intersects the system curve and the performance curve and corresponds to the flow and head required for the process.
Performance curve A curve of Total Head vs. flow for a specific pump model and impeller diameter (syn characteristic curve, water performance curve).
Pipe roughness A measurement of the average height of peaks producing roughness on the internal surface of pipes. Roughness is measured in many locations and then averaged. It is usually defined in micro-inches RMS (root mean square).
Potential energy A thermodynamic property. The energy associated with the mass and height of a body above a reference plane.
Pressure The application of external or internal forces to a body producing tension or compression within the body. In a fluid only compression (no tension) is possible.
Pressure head The specific energy of pressure (equal to p/g ).
Pseudoplastic The property of a fluid whose viscosity decreases with rate of shear.
Rheopectic The property of a fluid whose viscosity increases with time.
Shut-off head The Total Head corresponding to zero flow on the pump performance curve.
Specific gravity The ratio of the density of a fluid to that of water at standard conditions.
Strain The ratio between the absolute displacement of a reference point within a body to a characteristic length of the body.
Stress In this case refers to tangential stress or the force between the layers of fluid divided by the surface area between them.
Suction Static Head The difference in elevation between the liquid level of the fluid source and the centerline of the pump. This head also includes any additional pressure head that may be present at the suction tank fluid surface.
Suction Static Lift The same definition as the Suction Static head. This term is only used when the pump centerline is above the suction tank fluid surface.
Siphon A system of piping or tubing where the exit point is lower than the entry point and where some part of the piping is above the free surface of the fluid source.
System The system as referred to in this book includes all the piping with or without a pump, starting at the inlet point (often the fluid surface of the suction tank) and ending at the outlet point (often the fluid surface of the discharge tank).
System Curve A plot of Total Head vs. flow that satisfies the system requirements.
System equation The equation for Total Head vs. flow for a specific system (syn system curve).
System requirements The parameters that determine Total Head, that is: friction and the system inlet and outlet conditions (i.e. velocity, elevation and pressure).
Thixotropic The property of a fluid whose viscosity decreases with time (see Appendix A).
Total Dynamic Head Identical to Total Head. This term is no longer used and has been replaced by the shorter Total Head.
Total Head The difference between the head at the discharge and suction flange of the pump (syn Total Dynamic Head. pump head, system head).
Total Static Head The difference between the discharge and suction static head including the difference between the surface pressure of the discharge and suction tanks. It is also the specific potential energy of the system if we do not consider the pressure head in the discharge or suction tank.
Turbulent A type of flow regime characterized by the rapid movement of fluid particles in many direction as welt as the general direction of the overall fluid flow.
Vacuum Syn negative pressure.
Vapor pressure The pressure at which a liquid boils at a specified temperature.
Velocity Head difference The difference in velocity head between the outlet and inlet of the system.
Viscosity A property from which a fluid's resistance to movement can be evaluated. The resistance is caused by friction between the fluid and the boundary wall and internally by the fluid layers moving at different velocities.
Volute syn casing.
Work The energy required to drive the fluid through the system.
Yield Dilatant (see Appendix A).


For free calculations go to the Calculator page.  The calculators should be used with caution.  Many of these calculators are not verified and are only intended to provide a starting point in performing a design calculations.  All final design calculations should  be performed using verified and validated programs or calculators that have documented evidence of the verification and validation.

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Company Profile

EDA, Incorporated provides quality-engineering services on time, on schedule and within budget.  EDA, Inc. is able to do this by performing the work correctly the first time. We accept the most challenging problems and look forward to working with the client as a team member.  EDA believes that the client should be an active participant in the work process to ensure that the product is commensurate with client expectations and is delivered within schedule and budget constraints.

EDA, Inc. belongs to the American Society of Mechanical Engineers (ASME), the National Society of Professional Engineers (NSPE), the Society of Instrument Control Engineers, Society of Professional Engineers (ISA) and the American Nuclear Society (ANS).

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