Effects of Surface Conditions on Nucleate Pool Boiling of Sodium

Commercial grade sodium was boiled from a horizontal disk at pressures of 65 mm, 200 mm, and 400 mm Hg absolute, with sodium temperatures ranging from 1200 F to 1500 deg F. Heat fluxes as high as 236,000 Btu/hr sqft were attained. Boiler surface finishes ranged from highly polished mirror finishes to coarse, porous coatings. By following a prescribed cleaning and filling procedure, nucleate-boiling results were generally reproducible for a given-type surface. The effect of roughness as well as any aging and hysteresis effects were experimentally determined. Incipient nucleate boiling results are discussed as well as the effect of pressure and pool depth on the nucleateboiling curve.This work was supported jointly by the National Science Foundation, National Aeronautics and Space Administration, and the U. S. Atomic Energy Commission

Mixing experiments in an alternating wire wrapped assembly

The salt injection experiment was performed in an alternating wire-wrapped, triangular-array bundle to study the coolant mixing behavior pertaining to alternating wrapped wires. Results show that the coolant mixing is much enhanced in the subchannels for this type of bundle compared to the in-phase wire-wrapped bundle currently used in the LMFBR design. A strong interaction between the coolants in the edge and the interior subchannels at four assembly faces (where the alternating wires give 180/sup 0/ out-of-phase configuration) has also been observed. After calibrating the input parameters for the sweeping flow of the COBRA-IIIC/MIT code against this experimental data, the code is employed to predict the coolant temperatures for a skew-powered alternating wire-wrapped blanket assembly. Comparing the code results with the SUPERENERGY code predicted coolant temperature data for an in-phase wrapped assembly under identical operating conditions, it is observed that the hot spot temperature for the alternating wire-wrapped assembly is less than that for the in-phase wire-wrapped bundle by 5 percent (normalized to the hot spot axial temperature rise)

Improvement of the environmental and economic characteristics of cooling towers. Part II. Periodic cooling towers

Non

Turbulent sweeping flow mixing model for wire wrapped LMFBR assemblies

A physical model is proposed to derive the sweeping flow for LMFBR triangular array wire-wrapped assemblies under the turbulent flow condition. Two correlations are suggested for the sweeping flow through two different types of gaps between subchannels, the gap between the interior subchannels and the gap between the wall subchannels. These two sweeping flow correlations are evolved by calibrating the constants in the proposed model against the available experimental data. Agreement between the correlations and all the experimental data of +- 35% is obtained over the assembly design range of 1.315 > P/D > 1.067 and 52 > H/D > 4. Based on these correlations, flow sweeping input parameters for two popular computer codes, i.e., COBRA and SUPERENERGY, are recommended

Pressure drop measurements in LMFBR wire wrapped blanket assemblies

In this experiment, measurements of subchannel static pressure for an interior and edge subchannel were taken at two elevations in two wire-wrapped 61-pin bundles. One of the bundles has geometric characteristics of P/D = 1.067 and H/D = 8.0 (4 inch lead length and 0.501 inch rod diameter) and the other bundle has geometric characteristics of P/D = 1.067 and H/D = 4.0 (2 inch lead length and 0.501 inch rod diameter). The bundle average friction factors as well as the local subchannel friction factors for both interior and edge subchannels were determined from the experimental static pressure data. The average subchannel flow rates for both edge and interior subchannels were determined in a separate experiment. Results show that two correlations suggested by Rehme and Novendstern for the bundle average friction factor cannot predict the data within the range of experimental error. The bundle average friction factors for both bundles under test were underestimated by Rehme's correlation and overestimated by Novendstern's correlation. The results of the local subchannel friction factors indicate the effect of the wire lead length is more pronounced in the interior subchannel friction factor than in the edge subchannel friction factor. As the wire wrap lead length decreases, both interior and edge subchannel friction factors increase