Local Fluid Flow Research Articles

On the relationship between continuum mixture theory and integral averaged equations for immiscible fluids

The local fluid flow equations governing the flow of two immiscible fluids are averaged to obtain the two-component flow equations. A one-to-one correspondence is shown to exist between the averaged two-component flow equations and the continuum theory of mixtures when a proper identification of the mixture free energies has been made in terms of the constituent properties of the fluids comprising the mixture.

Simulator for adjusting optical meters of local fluid flow velocities

Simulator for adjusting optical meters of local fluid flow velocities

Numerical Simulation of Turbulent Fluid Flow and Heat Transfer in a Ribbed Rotating Two-Pass Square Duct

The local turbulent fluid flow and heat transfer in a rotating two-pass square duct with 19 pairs of in-line90∘ribs have been investigated computationally. A Reynolds-averaged Navier-Stokes equation (RANS) with a two-layerk−εturbulence model was solved. The in-line90∘ribs were arranged on the leading and trailing walls with rib height-to-hydraulic diameter ratio and pitch-to-height ratio of0.136and 10, respectively. The Reynolds number, based on duct hydraulic diameter and bulk mean velocity, was fixed at1.0×104whereas the rotational number varied from 0 to0.2. Results are validated with previous measured velocity field and heat transfer coefficient distributions. The validation shows that the effect of rotation on the passage-averaged Nusselt number ratio can be predicted reasonably well; nevertheless, the transverse mean velocity and, in turn, the distribution of regional-averaged Nusselt number ratio are markedly underpredicted in the regions toward which the Coriolis force is directed. Further CFD studies are needed.

Forced-convection boiling burnout for water in uniformly heated tubular test sections

To thoroughly study the effects of the major variables in forced-convective burnout, 402 high-pressure critical heat flux determinations were made with seven uniformly heated, internally-cooled, tubular test sections using water, subcooled at the inlet, as the coolant. Data were collected over the following range of variables: Critical heat flux0.44 to 2.57 × 106 Btu/hr-ft2Mass velocity0.5 to 13.7 × 106 lb/hr-ft2Exit coolant conditions116.6°F subcooled to 59.2% qualityPressure500 to 1500 psiaHeated length24 to 7758 in.Inside diameter0.245 to 1.475 in. The 1.475 in. tube represents the largest tube ever tested. The results indicate the existence of three burnout regimes: nucleate boiling, annular flow, and the still not fully explored “transition” region. An analytical study of annular flow burnout based on observations and dimensional analysis yielded a correlation which relates the critical heat flux to the significant local fluid properties and flow parameters. This equation was used to correlate and study the critical heat flux data obtained in the present work together with a selection of additional data points from the major available sources, including data for freon-12. The equation contains four dimensionless groups and constants determined by regression analysis with a limited portion of the data. Critical heat fluxes calculated by the correlation are in good agreement with the measured values. Observations of the effects of the parameters in subcooled nucleate boiling burnout enabled the formulation of an empirical equation for this regime. The equation relates the critical heat flux only to the mass flow rate and subcooling. In testing the equation with available data it was found that the correlation holds throughout the 60 to 2000 psia pressure range equally well, thus implying that there is no pressure effect on subcooled burnout over this entire range. The complete form of this study, including tabulated data, correlating procedures, literature survey, etc., is available as ref. [1] of the bibliography.

Forced-convection boiling burnout for water in uniformly heated tubular test sections

To thoroughly study the effects of the major variables in forced-convective burnout, 402 high-pressure critical heat flux determinations were made with seven uniformly heated, internally-cooled, tubular test sections using water, subcooled at the inlet, as the coolant. Data were collected over the following range of variables: Critical heat flux 0.44 to 2.57 × 10 6 Btu/hr-ft 2 Mass velocity 0.5 to 13.7 × 10 6 lb/hr-ft 2 Exit coolant conditions 116.6°F subcooled to 59.2% quality Pressure 500 to 1500 psia Heated length 24 to 77 5 8 in. Inside diameter 0.245 to 1.475 in. The 1.475 in. tube represents the largest tube ever tested. The results indicate the existence of three burnout regimes: nucleate boiling, annular flow, and the still not fully explored “transition” region. An analytical study of annular flow burnout based on observations and dimensional analysis yielded a correlation which relates the critical heat flux to the significant local fluid properties and flow parameters. This equation was used to correlate and study the critical heat flux data obtained in the present work together with a selection of additional data points from the major available sources, including data for freon-12. The equation contains four dimensionless groups and constants determined by regression analysis with a limited portion of the data. Critical heat fluxes calculated by the correlation are in good agreement with the measured values. Observations of the effects of the parameters in subcooled nucleate boiling burnout enabled the formulation of an empirical equation for this regime. The equation relates the critical heat flux only to the mass flow rate and subcooling. In testing the equation with available data it was found that the correlation holds throughout the 60 to 2000 psia pressure range equally well, thus implying that there is no pressure effect on subcooled burnout over this entire range. The complete form of this study, including tabulated data, correlating procedures, literature survey, etc., is available as ref. [1] of the bibliography.