Fluid handling – Processes – Affecting flow by the addition of material or energy
Patent
1997-09-03
1999-11-09
Hruskoci, Peter A.
Fluid handling
Processes
Affecting flow by the addition of material or energy
210698, 422 16, 507 90, 508555, F17D 117
Patent
active
059794798
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP96/00155, filed Jan. 9, 1996.
The present invention relates to the use of an alkoxylated alkanolamide together with an alkoxylated alcohol in a water-base system for reducing the flow resistance between a solid surface and the water-base liquid system.
Surfactants with the ability to form extremely long, cylindrical micelles have, in recent years, attracted a great interest as friction-reducing additives to systems with circulating water, especially those destined for heat or cold distribution.
An important reason for this interest is that, although one desires to maintain a laminar flow in the conduits, one wishes at the same time to have turbulence in the heat exchangers to achieve therein a high heat transfer per unit area.
As may easily be understood, fibres or chain polymers are unable to provide this double function which, however, can be achieved with rod-shaped micelles, since the flow rate (the Reynold's number) usually is much higher in the heat exchangers than in the conduit.
The rod-shaped micelles are distinguished by operating in a fairly disorderly fashion at low Reynold's numbers (below 10.sup.4), having no or only a very slight effect on the flow resistance.
At higher Reynold's numbers (above 10.sup.4), the micelles are paralleled and result in a friction reduction very close to that which is theoretically possible.
At even higher Reynold's numbers (e.g. above (10.sup.5), the shear forces in the liquid become so high that the micelles start to get torn and the friction-reducing effect rapidly decreases as the Reynold's number increases above this value.
The range of Reynold's numbers within which the surface-active agents have a maximum friction-reducing effect is heavily dependent on the concentration, the range increasing with the concentration.
By choosing the right concentration of surface-active agents and suitable flow rates in tubings and heat exchangers, it is thus possible to establish a laminar flow in the tubes and turbulence in the heat exchangers. Thus, the dimensions of both the tubes and the exchangers can be kept at a low level, or the number of pump stations, and consequently the pump work, can alternatively be reduced while retaining the same tubular dimensions.
The surface active agents most commonly used as friction-reducing additives to circulating water systems for heat or cold distribution are of the type represented by alkyltrimethyl ammonium salicylate wherein the alkyl group is a long alkyl chain which has 12-22 carbon atoms and which may either be saturated or contain one or more double bonds.
This type of surface-active agent functions satisfactorily already at a concentration of 0.5-2 kg/m.sup.3, but is degraded very slowly, both aerobically and anaerobically, and further is highly toxic to marine organisms.
Since heat-distribution systems for small houses usually suffer from important leaks (it is estimated that in one year 60-100 per cent of the water leaks out), it follows that the added chemicals end up in the ground water and in various fresh-water recipients. This combination of low bio-degradability and high toxicity is a fundamental criterion for a product injurious to the environment.
Thus there is a general demand for surface-active agents which are less harmful to the environment but which have the same excellent ability as the quaternary ammonium compounds described above to reduce the flow resistance in circulating water systems.
In the U.S. Pat. No. 5,339,855 it is described that alkoxylated alkanolamides with the general formula ##STR1## wherein R is a hydrocarbon group having 9-23 carbon atoms, A is an alkyleneoxy group having 2-4 carbon atoms and n is 3-12, are capable of forming long cylindrical micelles in water and thus reduce the friction in water-based system.
These products are easily degradable and function excellently in deionized water especially at low temperatures. However, the friction-reducing effects are hampered in hard water and by the presence of high amounts of electrolytes. Further the tempe
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patent: 3961639 (1976-06-01), Chang et al.
patent: 4427562 (1984-01-01), Horodysky et al.
patent: 5339855 (1994-08-01), Hellsten et al.
patent: 5454984 (1995-10-01), Graubart et al.
PCT International Search Report, Jun. 7, 1996.
Derwent Abstract 91-007873, Aug. 1990.
Derwent Abstract 91-007872, Aug. 1990.
Harwigsson Ian
Hellsten Martin
Akzo Nobel nv
Hruskoci Peter A.
Mancini Ralph J.
McGillycuddy Joan M.
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