Cryogenic liquids transfer

PRESSURIZED COOL-DOWN OF A CRYOGENIC LIQUID TRANSFER SYSTEM CONTAINING VERTICAL SECTIONS... 

Drawings and specifications for standard transfer connections for cryogenic liquids are contained in CGA V-6, Standard Cryogenic Liquid Transfer Connections [11]. Drawings and specifications for carbon dioxide liquid and vapor transfer connections are contained in CGA V-6.1, Standard Carbon Dioxide Transfer Connections [12]. 

V-6 Standard Cryogenic Liquid Transfer Connections. Offers cryogenic liquid connections which provide mechanical protection for product integrity. Engineering specifications and cutaway drawings are provided (19 pages). 

CGA V-6, Standard Cryogenic Liquid Transfer Connections, Compressed Gas Association, Inc., 1235 Jefferson Davis Highway, Arlington, VA 22202. 

All of these systems share to some degree several typical design problems associated with cryogenic liquid transfer. One class of difficulties results from cooling the system down from ambient to cryogenic temperature. Evidence of cooldown is in the form of two-phase flow, thermal contraction, and line bowing. Thermal contraction of a transfer line must not result in contact between the inner and outer lines, a condition most frequently encountered at changes in direction of the transfer lines. Expansion joints, bellows, and U-bends have been employed to solve the problem of thermal contraction. 

The various types of insulation used in the storage and transfer of cryogenic liquids can be divided into five categories (1) vacuum, (2) multilayer, (3) powder and fibrous, (4) foam, and (5) special. The boundaries between these... 

Intermolecular energy transfer from a vibrationally excited molecule such as benzene to CCI4 could occur by two mechanisms termed direct and indirect, as diagrammed in Fig. 18. In a liquid mixture, the phonons are collective excitations of the mixture. But the coupling between intramolecular vibrations on adjacent molecules is ordinarily quite weak. Direct intermolecular transfer is important primarily in the long-lived vibrations of cryogenic liquids (7,84). In polyatomic liquid mixtures, VER... 

Film boiling is not usually desired in commercial equipment because the heat-transfer rate is low for such a large temperature drop. Heat-transfer apparatus should be so designed and operated that the temperature drop in the film of boiling liquid is smaller than the critical temperature drop, although with cryogenic liquids this is not always feasible. 

T quations of state have been traditionally developed to describe the pressure-molar volume-temperature-composition (PVTx) behavior for fluid mixtures. If an equation of state can describe the V(P, T, x) surface for a cryogenic liquid mixture to an accuracy approaching 0.1%, then it is satisfactory for all current industrial needs, including custody transfer calculations. Analytical equations of this accuracy have been developed for certain pure cryogens. It is nearly impossible to generalize these complicated equations of state to mixtures, other than by corresponding-states techniques. Accuracy approaching the required level has... 

Cargo tanks are large-capacity cryogenic storage tanks either mounted on a truck body or forming a semitrailer body. The maximum capacity of these units is 11,300 U.S. gal although the most common size used to ship liquefied industrial gas products over the road is 7000 U.S. gal [2]. The truck has a high pressure liquid transfer pump on board which can fill a... 

FFTEM samples can also be prepared [29] by a double-replica freeze-fracture technique, in which a drop of sample is deposited on a metal disk. A second disk is then placed on top, and the two disks are centered. A further drop is placed in the central bore of the specimen sandwich, any excess sample being removed with filter paper. The sample is plunged into liquid cryogen and transferred to the cleavage unit of the microscope, also maintained under cold conditions. The sample is subsequently cleaved, etched, coated, and imaged. 

A violent vapor explosion can result when a cold volatile liquid is suddenly brought into contact with a hot liquid. The explosion is due to the rapid vaporization of the cold liquid from heat transfer from the hot liquid. Such explosions are referred to as vapor, steam, physical, or thermal explosions rapid-phase-transitions (RPTs) (typically when referring to explosions involving cryogenic liquids) and molten fuel-coolant interactions (FCIs) when applied to nuclear reactor accidents. Accidental vapor explosions are frequent occurrences in the metallurgical, pulp and paper, and cryogenic industries. General reviews of the various aspects of vapor explosions can be found in Reid [1] and Corradini et al. [2]. 

FIGURE S.3.9.3 Phase Separator. This device allows a cryogenic liquid to be transferred with minimal splashing. (Courtesy of Office of Environmental Health and Radiation Safety, University of Pennsylvania, Philadelphia, PA.)... 

Answer by author In laboratory operations the phenomena you refer to, associated with addition and withdrawal of liquid, are quite likely more important than diffusion. However, in large-scale storage of cryogenic liquids, we believe that this is not the case, and that liquid transfer as such is certainly not a predictable source of contamination. 

In order to maintain adequate lubrication, the wear rate of the lubricant must be controlled when it is introduced as a solid at the interface, where its properties and those of the cryogenic liquid will be influenced by the much higher temperature and vapor phase conditions which exist at this point. The over-all heat transfer, and therefore the interface temperature, depends on a considerable number of factors, with thermal conduction paramount. Since a solid lubricant with poor thermal conductivity is desirable for tensile property reasons, arrangements must be made elsewhere in the lubricant housing and the mating components favorable to good therm.al conductivity. 

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