Heat Transfer-Vibration Study Expanded at SwRI Acoustical vibrations boost heat transfer from condensing steam, remove scale from transfer surfaces Southwest Research Institute is extend ing its studies on acoustical vibration (C&EN, May 30, page 92) to many uses where heat and mass transfer rates are limiting. The major effort, however, is still saline water distilla tion, says Dr. W. E. Thompson, di rector of chemistry and chemieal engi neering at SwRI. Acoustical vibration significantly im proves heat transfer from condensing steam and reduces scaling problems, SwRI says. In same tests, vibration improved heat transfer from condens ing steam by more than 50%. Under scaling conditions, vibration knocks off enough scale to keep heat transfer significantly better than without vi bration, but more study is needed to better define the exact improvement that results from knocking off scale. Applied to saline water stills, vibra tion could increase a given plant's capacity by a conservative 30%, ac cording to Irwin Raben, SwRI's man ager of chemical engineering. Other possible uses for acoustical vibration vary from improving poly merization of viscous materials to im proving mass and heat transfer at the interface in liquid-liquid extraction processes. However, much of this SwRI work remains confidential.
Transverse Vibration.
and on seawater at SwRI. Initial ex periments, with and without vibration, show that scale deposits increase with operating time and rate of heat trans fer decreases, as might be expected. In no case does vibration keep the pipe free of scale. But vibration does cause the scale to come off in pieces roughly l/A to 1 / 2 in. square. Under scaling conditions with vi bration, heat transfer changes with time about like this. Initially, the over-all boiling coefficient is about 900 B.t.u./hr./ft. 2 /°F., Mr. Raben says. If scaling is appreciable, as with seawater, the coefficient drops to 600 to 700 in about two hours. By then, scale reaches a thickness heavy enough to come off. Scaling still grows worse; the coefficient drops gradually to 400 to 500 after eight hours and levels off there. Without vibration, the heat transfer coefficient initially is about 600. It drops to about 300 in roughly eight hours and then continues to drop slowly as the scale builds up.
BRIEFS General Electric will have a general compiler available for its 225 computer by next spring. The general compiler will take instructions in many of the computer languages used today, both business and scientific, GE says. For instance, both COBOL (common busi ness oriented language) and ALGOL ( algorithmic language ) instructions can be fed to the general compiler, and it will accept combinations of the two. For one thing, this will answer the need for fast handling of the complex mathematics of many modern business problems, GE be lieves. Also, a computer customer with programs already prepared in one of the major computer languages will not have to reprogram them for the 225, GE says.
A patent on the insecticide DDVP ( Ο,Ο-dimethyl 0-2,2-dichlorovinyl phosphate) has been issued to Shell Oil (U.S. 2,956,073). The insecti cide, marketed by Shell under the name Vapona, is for the control of both agricultural and household pests, Shell says. A recent label acceptance by the Department of Agriculture al lows test control operators to spray a 1 / 2 % solution of Vapona in house holds, restaurants, theaters, food proc essing plants, industrial plants, and warehouses, Shell adds.
SwRI uses
about the same approach in all its studies of the effects of acoustic vibra tion on heat transfer. The experi mental unit is a vertically mounted, double pipe heat exchanger with a glass outer pipe. The inner metal pipe vibrates in a transverse direction. In the heat transfer studies with steam, the steam condenses on the outside of a water cooled pipe. In scaling ex periments, the scaling liquor flows through the annular space, with steam condensing inside the metal pipe. This apparatus allows the scientists to watch the effects of vibration on drops of condensed water. Vibration appears to keep the drops small and throws the condensate off the pipe to ward the glass tube's inner wall. As yet SwRI has not studied the effect of steam velocity plus vibration in remov ing condensate drops. Scale Off. Scaling studies have been made on solutions of calcium sulfate
SCALE OFF. Close-up of SwRI's double pipe heat exchanger shows sloughed scale passing through annulus. Bright area near center is where scale has re cently come off
The Snap Experimental Reactor, pro totype for an outer space power re actor, has completed operational ground tests, according to Lt. Col. G. M. Anderson of the Atomic Energy Commission. The reactor is about the size of a 5 gal. can, fueled with en riched uranium, weighs 250 lb., and produces 50 kw. at a coolant tem perature of 1200° F. The experi mental reactor has verified significant performance characteristics necessary for design of the final flight reactor, Col, Anderson told a conference of the Atomic Industrial Forum in San Francisco. The Snap Experimental Reactor is prototype for Snap 2, 8, and 10, expected to produce power continuously for one year. Snap 2 and 8 will generate electricity through miniature turbine generators; Snap 10 will use a thermoelectric converter. Flight tests of Snap 10 are expected in 1962 or 1963, Col. Anderson said. DEC.
2 6, 1960
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