Liquid-Metal Heat Transfer

Temperature difference metal surface to boiling liquid (K) Heat transfer coefficient metal surface to boiling liquid (kW/m2 K)... 

Electromagnetic Force When the fluid is an electrical conductor, as is the case with molten metals, it is possible to impress an electromagnetic field around the fluid conduit in such a way that a driving force that will cause flow is created. Such pumps have been developed for the handling of heat-transfer liquids, especially for nuclear reactors. 

The chief industrial uses of fusible alloys are for fusible automatic sprinklers, anchoring bearings and bushings, for heat transfer liquids, for glass to metal seals, etc (Ref 2) Refs 1) Hackh s Diet (1944), 363-L 2) CondChemDict (1961), 522-23 (1971),... 

Conduction drying is usually carried out using hot cylinders, which are rotating metallic cans that are heated using steam or special heat-transfer liquids. When steam is used, the drying system is often referred to as steam cans, which are shown schematically in Figure 34.6. The energy requirements removed are typically around 4700 kJ/kg, which is usually lower than that of other thermal dryers. 

Liquid metal containers, processing and heat transfer Transition metal carbides 600-1400 Vacuum or inert gas and liquid metals Sangioigi (1994)... 

For turbulent flow of a fluid past a solid, it has long been known that, in the immediate neighborhood of the surface, there exists a relatively quiet zone of fluid, commonly called the Him. As one approaches the wall from the body of the flowing fluid, the flow tends to become less turbulent and develops into laminar flow immediately adjacent to the wall. The film consists of that portion of the flow which is essentially in laminar motion (the laminar sublayer) and through which heat is transferred by molecular conduction. The resistance of the laminar layer to heat flow will vaiy according to its thickness and can range from 95 percent of the total resistance for some fluids to about I percent for other fluids (liquid metals). The turbulent core and the buffer layer between the laminar sublayer and turbulent core each offer a resistance to beat transfer which is a function of the turbulence and the thermal properties of the flowing fluid. The relative temperature difference across each of the layers is dependent upon their resistance to heat flow. 

The analogy has been reasonably successful for simple geometries and for fluids of very low Prandtl number (liquid metals). For high-Prandtl-number fluids the empirical analogy of Colburn [Trans. Am. Tn.st. Chem. Ting., 29, 174 (1933)] has been veiy successful. A J factor for momentum transfer is defined asJ =//2, where/is the friction fac tor for the flow. The J factor for heat transfer is assumed to be equal to the J factor for momentum transfer... 

Further information on liquid-metal heat transfer in tube banks is given by Hsu for spheres and elliptical rod bundles [Int. J. Heat Mass Transfer, 8, 303 (1965)] and by Kahsh and Dwyer for oblique flow across tube banks [Int. ]. Heat Ma.ss Transfer, 10, 1533 (1967)]. For additional details of heat transfer with liqmd metals for various systems see Dwyer (1968 ed., Na and Nak supplement to Liquid Metals Handbook) and Stein ( Liquid Metal Heat Transfer, in Advances in Heat Transfer, vol. 3, Academic, New York, 1966). 

Plate and Frame Composed of metal-formed thin plates separated by gaskets. Compact, easy to clean. Viscous fluids, corrosive fluids slurries. High heat transfer. Not well suited for boiling or condensing limit 350-500°F by gaskets. Used for Liquid-Liquid only not gas-gas. 0.8-1.5... 

In this process ethylene, dissolved in a liquid hydrocarbon such as cyclohexane, is polymerised by a supported metal oxide catalyst at about 130-160°C and at about 200-500 Ibf/in (1.4-3.5 MPa) pressure. The solvent serves to dissolve polymer as it is formed and as a heat transfer medium but is otherwise inert. 

Gauges used for measuring the liquid level in vessels may be of semitransparent and even nontransparent materials. Figure 3.2 illustrates a simple level gauge on a steel vessel used for liquid ammonia storage. As shown, a narrow strip of insulation is taken away from the vessel s shell to expose the bare metal. Consequently, the heat transfer coefficient from the... 

If steam condenses on a surface, there is no boundary layer the resistance to heat flow is due to scale, metal thickness, and the condensed liquid layer, resulting in a high heat transfer factor. A thin layer of air or other noncondensing gas forms at the surface through which the steam diffuses. The heat transfer factor diminishes rapidly but is considerably higher than in dry convection. 

Figure 9-6L. Metal Top-Pak low liquid/high gas flow and high heat transfer packing. Used by permission of Vereinigte Fullkorper-Fabriken GmBH Co. Ransbach Baumbach, Germany.

These properties, coupled with the metal s ability to promote bubble-type vapour formation on the surface when heating liquids, and dropwise condensation when condensing vapours, make the metal an ideal constructional material for heat-transfer equipment for use with strong acids. 

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