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A procedure has been developed and tested for evaluating the capillary pressure and wetting properties of rock/fluid systems from unsteady-state displacement data such as that used for calculating two-phase relative permeability characteristics. Currently, the common practice is to conduct most coreflooding experiments so that the capillary pressure gradient in the direction of flow is small compared with the imposed pressure gradient. The proposed method, on the other hand, is based on performing low rate displacements during which capillary forces and, hence, end effects can influence the saturation distribution and pressure response of the core sample. Besides providing a means for monitoring capillary forces and wettability during the dynamic displacement test, the proposed method has the advantage of permitting the displacement tests to be conducted at rates more typical of those in the reservoir. Thus, it is possible to avoid potential problems such as fines migration and emulsion formation, and the method permits a realistic representation of transient interfacial effects that can be important with reservoir fluid systems and chemical flooding agents. Specifically, the method involves performing low rate displacements between the irreducible-water and residual-oil endpoint saturations. Except for the added provision of stopping, restarting, and sometimes reversing the flow after the endpoints have been reached, these are routine unsteady-state displacements in which the standard pressure drop is measured external to the core between the inlet and outlet fluid streams. The dynamically measured capillary pressure properties—besides indicating strong, weak, intermediate, or mixed wettability—then can be used to derive relative permeabilities from the displacement data. Examples of the technique for determining wettability are given for pure-fluids/Berea-sandstone andreservoir-fluids/preserved-reservoir-rock systems. Introduction It long has been recognized that capillary forces can influence the results of relative permeability and oil recovery measurements on core samples.1–5 A scaling criterion for linear displacement tests has been proposed to remove the dependence of oil recovery on displacement rate and system length.5 The objective is to avoid appreciable influence of capillary forces on the flooding behavior that causes a spreading of the displacement front and the well-known end effect or buildup of the wetting phase at the ends of the core. The suggested scaling causes the capillary pressure gradient in the direction of flow to be small compared with the imposed pressure gradient and is expressed asEquation 1 where L is system length (in centimeters), µ is displacing phase viscosity (in centipoise or millipascal-seconds), and q/A is flow rate per unit cross-sectional area (in centimeters per minute). Bentsen6 refined the criterion for neglecting capillary forces to include consideration of the mobility ratio. In related work, Peters and Flock7 recently proposed a dimensionless number and its critical value for predicting the onset of instabilities resulting from viscous fingering at unfavorable mobility ratios. In apparent contrast to the scaling coefficient suggested in Eq. 1, displacements were shown to decline at high flow rates for a given core system and wettability condition.

An experimental investigation of the initial heating rate of 50 nm ferromagnetic nanoparticles (Fe3O4) suspended in water and incorporated in an agar gel was conducted to study the thermal heating effects resulting from Brownian motion and hysteresis losses. Particles were placed in an alternating current magnetic field with intensities of 28.6, 35.8, 38.9, and 43.0 kA m−1, at frequencies ranging from 161 to 284 kHz. The specific absorption rate based on the heating rate was calculated and the contributions from the Brownian motion and hysteresis losses are compared and analyzed.

Increased nonspecific bronchial responsiveness (NSBR) may be a risk factor for the development of chronic airflow obstruction. We evaluated this hypothesis in a cohort of 378 underground coal miners and working nonminers. Methacholine testing was performed at the beginning and end of a 5-yr study period. Spirometry was repeated at 6-mo intervals and individual 5-yr FEV1 slopes were calculated by linear regression. Relationships between FEV1 slopes and NSBR were examined using multiple linear regression models, controlling for FEV1 level, smoking, and mining. Increasing NSBR at the initial survey was associated with a somewhat greater rate of subsequent FEV1 decline. Methacholine responders at the final survey had a considerably increased rate of decline during the previous years. Responsiveness status changed over the 5 yr in 22% of the subjects. Both the development and persistence of increased NSBR were strongly associated with higher rates of FEV1 decline. In contrast, FEV1 declines were not accelerated among workers with increased NSBR that reverted to normal. Smoking and mining were both independently associated with FEV1 declines, but did not substantially modify the effect of NSBR. Due to its variability over time, NSBR testing predicts lung function decline only in some individuals, and its value as a prognostic test for chronic airway disorders is limited. Because improvement in bronchial hyperresponsiveness was associated with a reduction in the rate of FEV1 loss, interventions directed at preventing or reducing nonspecific airway hyperresponsiveness should be investigated.

Spherical glass and copper beads have been used to create bead packed porous structures for an investigation of two-phase heat transfer bubble dynamics under geometric constraints. The results demonstrated a variety of bubble dynamics characteristics under a range of heating conditions. The bubble generation, growth, and detachment during the nucleate pool boiling heat transfer have been filmed, the heating surface temperatures and heat flux were recorded, and theoretical models have been employed to study bubble dynamic characteristics. Computer simulation results were combined with experimental observations to clarify the details of the vapor bubble growth process and the liquid water replenishing the inside of the porous structures. This investigation has clearly shown, with both experimental and computer simulation evidence, that the millimeter scale bead packed porous structures could greatly influence pool boiling heat transfer by forcing a single bubble to depart at a smaller size, as compared with that in a plain surface situation at low heat flux situations, and could trigger the earlier occurrence of critical heat flux by trapping the vapor into interstitial space and forming a vapor column net at high heat flux situations. The results also proved data for further development of theoretical models of pool boiling heat transfer in bead packed porous structures.