Critical Pressure Distribution Research Articles

Numerical-based non-dimensional analysis of critical flow of R-12, R-22, and R-134a through horizontal capillary tubes

Development of correlations predicting critical mass flow rate and critical pressure distribution through capillary tubes is presented. In order to accomplish such a work, the critical mass flow rate and pressure distribution for nearly 500 operational conditions for R-12, R-22, and R-134a are evaluated. Operational conditions include inlet pressure varying from 800 to 1500 kPa, inlet subcold temperature between 0 and 10 °C, length varying from 1 to 2 m, and inner diameter between 0.5 and 1.5 mm. By performing non-dimensional analysis on numerical data, general correlations are presented to predict the critical mass flow rate through capillary tubes. In addition, by utilizing numerical data for down-stream pressure, non-dimensional analysis is performed to present correlations to predict critical down-stream pressure and pressure distribution through capillary tubes.

Hypoxic vasoconstriction and fluid filtration in pig lungs.

We have studied the effect of hypoxia [inspired partial pressure of O2 (Po2) 50 mmHg] on the relationships among pulmonary blood flow, pulmonary arterial pressure, and fluid filtration rates in isolated blood-perfused pig lungs. Our results indicate that hypoxia constricted the vasculature in a manner that caused a parallel shift of the pressure-flow curve to higher pressures. During normoxia, filtration rate was zero at flows less than 1.5 1/min but increased with increases in blood flow above this level. In both cases the shape of this relationship was similar, but during hypoxia it was shifted to higher filtration rates. These findings can be interpreted using a parallel-channel Starling resistor model of the lung with a distribution of critical pressures. All the effects of hypoxia found in this study could be explained simply by an increase in critical pressure. According to the model, this increase in critical pressure during hypoxia caused a greater filtration rate because of an increase in the mean intravascular filtration pressure and an increase in the mean filtration coefficient.

Provision of linearity in the law of distribution of critical pressures on a foundation bed

Provision of linearity in the law of distribution of critical pressures on a foundation bed