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 ?
Pc calculated in accordance with ISO 13478 Table 3 - Results of FS and S4 critical pressure (Pc) tests at 0[degrees]C on DRISCOPLEX[R] 6500 MDPE Pipe Nominal Outside Measured Measured Diameter FS [P.sub.c] S4 [P.sub.c] (mm) SDR (bars) (1) (bars) 219 11 8.5 1.10 219 17 8.5 (3) 0.90 168 11 9.5 1.15 168 17 8.5 1.08 Nominal S4-to-FS Measured Outside Converted S4-to-FS Diameter [P.sub.c] (2) Correlation (mm) SDR (bars) Factor 219 11 6.56 4.5 219 17 5.84 5.0 (3) 168 11 6.74 4.9 168 17 6.49 4.6 1.
As the pressure decreases there comes a point at which the pressure of the fluid becomes smaller than the critical pressure of C[O.sub.2].
Figure 2 gives the isobaric plots near the critical point of [P.sub.c]] = 0.0006631 and Figure 3 displays the effects of YM charge and BI parameter on the critical pressures. On T-[r.sub.+] plot of Figure 2, just as the case of [beta] [right arrow] [infinity], P > [P.sub.c] isobar describes the "ideal gas" phase.
Davis (24) proposed, "the critical pressure must therefore counteract this closing moment before providing a sufficiently high crack driving force for propagation." By applying simple beam theory to a semi-circular section of pipe geometry and Castigliano's first theorem.
This indicates that x = [r.sub.c]/[r.sub.+] is fixed; however the critical effective temperature, critical volume, and critical pressure are dependent on the value of [r.sub.c].
Its Small Scale Steady State critical pressure of over 10 bar (145 psig) is equivalent to a full-scale critical pressure of over 650 psi, which is equivalent to the PE 100+ materials used internationally."
If the pressure in the pipe is above the critical pressure [CP] and the temperature is below the CT the crack will propagate to the end of the pipe at a very high speed.
* Added rapid crack propagation (RCP) required value of a full-scale critical pressure greater than 1.5 times the maximum operating pressure for polyethylene (PE) materials.
We call this shear rate and the corresponding pressure drop the critical shear rate and the critical pressure drop.
For example, for modern PE pipe RCP critical pressure limitations, using formulas in the current standards, are underestimated by 1.5 to 2 times.