An investigation was conducted to determine the feasibility of computing liquid impact loads as evacuated systems are filled with liquid. The computations were performed using the FLOW-NET program, a general two-phase compressible flow circuit analysis program. Test data were generated at the NASA White Sands Test Facility as part of a Space Station propulsion module design. Analysis results were compared to test data for a number of configurations, composed of straight pipes, tees, and bends. Comparisons were made of the magnitude of the initial impact, subsequent impacts, and the time duration between impacts, or impact frequency. (Author)

Venting of cryogenic and non-cryogenic fluids to a vacuum or a very low pressure will take place in many space-based systems that are currently being designed. This may cause liquid freezing either internally within the flow circuit or on external spacecraft surfaces. Typical ammonia flow circuits were investigated to determine the effect of the geometric configuration and initial temperature, pressure, and void fraction on the freezing characteristics of the system. The analysis was conducted also to investigate the ranges of applicability of the FLOW-NET program. It was shown that a typical system can be vented to very low liquid fractions before freezing occurs. However, very small restrictions in the flow circuit can hasten the inception of freezing. The FLOW-NET program provided solutions over broad ranges of system conditions, such as venting of an ammonia tank, initially completely filled with liquid, through a series of contracting and expanding line cross sections to near-vacuum conditions.

SOLA-LOOP is designed for the solution of transient two-phase flow in networks composed of one-dimensional components. The fluid dynamics is described by a nonequilibrium, drift-flux formulation of the fluid conservation laws. Although developed for nuclear reactor safety analysis, SOLA-LOOP may be used as the basis for other types of special-purpose network codes. The program can accommodate almost any set of constitutive relations, property tables, or other special features required for different applications.

The coupled fluid-structure dynamics of a pressurized water reactor core support barrel can be calculated with the K-FIX(3D, FLX) code for blowdown and seismic induced transients. The K-FIX solution method has been used to perform pre- and post-test analyses of a full scale blowdown test at the HDR facility in Frankfurt, Germany. The results verified the accuracy of the fully three-dimensional method, which solves the nonequilibrium, two-fluid equations for the fluid dynamics and the Timoshenko elastic shell equations for the core barrel motion.

In certain pressurized water reactor (PWR) designs, emergency core coolant (ECC) is injected through the hot legs into the upper plenum. The condensation of steam on this subcooled liquid stream reduces the pressure in the hot legs and upper plenum and thereby affects flow conditions throughout the reactor. In the present study, we examine countercurrent steam-water flow in the hot leg to determine the deceleration of the ECC flow that results from an adverse pressure gradient and from momentum exchange from the steam by interfacial drag and condensation. For the parameters examined in the study, water flow reversal is observed for a pressure drop of 22 to 32 mBar over the 1.5 m hot leg. We have also performed a three-dimensional study of subcooled water injection into air and steam environments of the upper plenum. The ECC water is deflected by an array of cylindrical guide tubes in its passage through the upper plenum. Comparisons of the air-water results with data obtained in a full scale experiment shows reasonable agreement, but indicates that there may be too much resistance to horizontal flow about the columns because of the use of a stair-step representation of the cylindrical guide tube cross section.more » Calculations of flow past single columns of stair-step, square and circular cross section do indicate excessive water deeentrainment by the noncircular column. This has prompted the use of an arbitrary mesh computational procedure to more accuratey represent the circular cross-section guide tubes. 15 figures.« less

A new model is described for nonequilibrium vapor production (flashing) in critical two-phase flow. The model is based on a description of turbulence enhanced thermal diffusivity in the liquid and a Weber number criterion for bubble size. In a quiescent environment, the model reduces to the well-known conduction controlled rate. Results of calculations are compared with flow rate and pressure data from blowdown experiments with various nozzle geometries. The nozzle throat diameters range from 1.8 to 51.0 cm and nozzle inlet conditions vary from water subcooled 30°C to saturated water at 98% vapor volume fraction. The calculations are made with the two-fluid code K-FIX and show very good agreement throughout the entire blowdown.

The coupled fluid-structure dynamics of a light water reactor core support barrel can be calculated by the K-FIX(3D,FLX) and SOLA-FLX codes. The fluid dynamics is described by the three-dimensional, two-fluid code K-FIX(3D) or the two-dimensional, drift-flux code SOLA-DF. The structural dynamics is described by the three-dimensional, elastic shell code FLX. FLX, which uses an explicit finite-difference solution algorithm to solve the shell equations, is explicitly coupled to the fluid-dynamics codes. Motion may be induced by blowdown, prescribed displacement, or seismic action. A sample calculation is provided for verification.

"Reply to “Comment on the Drift-Flux Approximation in Transient Two-Phase Flows”." Nuclear Science and Engineering, 71(1), p. 79

This package consists of two programs K-FIX(3D) and K-FIX(3D,FLX) which extend the transient, two-dimensional, two-fluid program K-FIX to perform three-dimensional calculations. The transient dynamics of three-dimensional, two-phase flow with interfacial exchange are calculated at all flow speeds. Each phase is described in terms of its own density, velocity, and temperature. The application is to flow in the annulus between two cylinders where the inner cylinder moves periodically perpendicular to its axis. K-FIX(3D) is easily adaptable to a variety of two phase flow problems while K-FIX(3D,FLX) combines KFIX(3D), the three-dimensional version of the KFIX code, with the three-dimensional, elastic shell code FLX for application to a very specific class of problems. KFIX(3D,FLX) was developed specifically to calculate the coupled fluid-structure dynamics of a light water reactor core support barrel under accident conditions. Motion may be induced by blowdown, prescribed displacement, or seismic action.