critical pressure

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critical pressure

[′krid·ə·kəl ′presh·ər]
(fluid mechanics)
For a nozzle whose cross section at each point is such that a fluid in isentropic flow just fills it, the pressure at the section of minimum area of the nozzle; if the nozzle is cut off at this point with no diverging section, decrease in the discharge pressure below the critical pressure (at constant admission pressure) does not result in increased flow.
(thermodynamics)
The pressure of the liquid-vapor critical point.

Critical Pressure

 

the pressure of a substance or mixture of substances in the critical state. At pressures less than the critical pressure, the system may dissociate into two equilibrium phases, a liquid and a gas. At the critical pressure the physical distinction between the liquid and gas is lost, and the substance undergoes transition to a single-phase state. Thus, the critical pressure may also be defined as the limiting (highest) saturated vapor pressure under conditions of existence of the liquid and vapor phases.

The critical pressure is a physicochemical constant of the substance. (For values of the critical pressure pc of a number of substances, see Table 1 in CRITICAL POINT.) The critical state of mixtures differs in the dependence of the critical pressure on the composition and thus exists not at a single critical point but on a curve on which all points are characterized by critical values of pressure, temperature, and concentration.

critical pressure

The highest pressure of the fuel-air mixture inside the cylinder of a reciprocating engine that allows a mixture to burn evenly, rather than detonate or explode.
References in periodicals archive ?
DNV GL strongly advises the operators of PE gas pipe distribution systems to determine whether pipe materials used within their systems have been My tested to determine the RCP critical pressure level.
The Irwin--Corten model (18) predicts RCP critical pressure by applying linear elastic fracture mechanics (LEFM) analysis to a pipe geometry.
Davis (24) proposed, "the critical pressure must therefore counteract this closing moment before providing a sufficiently high crack driving force for propagation.
The crack front will be dragged back on the bore surface increasing the fracture resistance and thus increasing the critical pressure.
Also, as temperature increases, plane stress fracture resistance increases and more work is required to separate the ligament at the bore surface, which increases the critical pressure further.
It was shown in this work that both the FS and S4 Pc results for pipe of equal diameter and different wall thickness can exhibit lower critical pressures with decreasing pipe wall thickness.
As such, S4 critical pressure (Pc) results must be converted into equivalent FS Pc prior for design and specification purposes.
S4 critical pressure tests at 0[degrees]C were performed by Chevron Phillips Chemical Company LP at their Research Center in Bartlesville, OK, in accordance with the ISO 13477 standard (2).
Relative to the S4 test, the FS tests yields higher values of critical pressure for pipes tested at the same temperatures.
Using the formulas discussed in that section, we could calculate the total critical pressure drop from the observed apparent critical shear rate.
The combination of this result with the slight decrease in the capillary pressure drop, leads to a decrease in the total critical pressure drop (or possibly a minimum at [Alpha] [approximately equal to] 30 [degrees]), as seen in Fig.