# 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 ?
It was our view that although the critical temperature and critical pressure tests are indeed performed differently and using different test protocols, they are still both measures of the inherent RCP performance of the pipe.
The minimum pressure of mining has to be equal to or greater than the critical pressure causing damage.
For example, the critical pressure and temperature for the oil sample from well 1 in field E are deviating away from the rest of the samples.
Observe that if the pressure is above the critical pressure in a vessel, the temperature will decrease somewhat causing the density to decrease in turn decreasing the flow rate.
2]: There is no significant difference in the ranking of critical pressure points before and after the recent global financial crisis.
The most frequently described methods of evaluating upper airway collapsibility are the critical pressure measurement (Pcrit) and the negative expiratory pressure (NEP) technique.
It is seen clearly that the expansion process began from the supercritical region, and the pressure decreased quickly before it reached the critical pressure.
As can be seen in Table 5, the MMP predictions from tuned EOS of critical temperature, critical pressure, acentric factor, binary interaction coefficient, and [[OMEGA].
The 5-Gpa critical pressure where potassium is fluidized is approximately the pressure at the base of continental crust.
Although this arrangement is dearly only a temporary expedient for African studies at Columbia, it has the merits of both being transparent about the limitations of the program now and creating the critical pressure to rectify the situation that our previous practice of recruiting temporary institute directors, however dedicated, did not," Anderson wrote in a June letter to students, faculty and alumni.
Addressing functionality, the Engineered Solutions Team identified valve hysteresis as the key to improved response time and, consequently, critical pressure maintenance.
The modular control system will use AlarmPager[TM] to call out to cell phones and pagers whenever a critical pressure or temperature is exceeded, and will call until it gets a response from one of the people being paged.

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