Helium storage vessels

Figure 2 is a similar curve for liquid-helium storage vessels. Here, however, the tankage is assumed to operate bottled up, and performance is therefore shown in terms of pressure rise. Accordingly, the curve is based on 100-psi pressure rise over a storage period of 14 days. As a matter of interest, this rate of heat addition is equivalent to a vented loss rate of approximately 1.7 per day. Ullage was taken at 10 as with liquid hydrogen. 

Most of the cryogenic fluids are now available commercially in many parts of the world. These are shipped and stored in special insulated containers from which they are either used directly or are transferred to portable dewars and used as required. However, liquid helium and some of the reactive fluids are ordinarily produced in laboratory liquefiers as they are needed. For simplicity, laboratory experiments may be conducted with these fluids directly in the liquefier storage vessel, although provisions are usually made for the withdrawal of the liquid through an evacuated transfer tube. 

To measure adsorption a certain amount of gas of mass (m ) is prepared in the storage vessel and the adsorption chamber is evacuated. Upon opening the expansion valve, the gas expands to the adsorption chamber where it is partly adsorbed on the (external and internal) surface of the sorbent material. This process may last milliseconds, minutes, hours or even several days - as in case of helium on activated carbon (Norit Rl) [2.8]. After thermod)mainic equilibrium, i. e. constancy of pressure (p) and temperature (T) inside the vessels has been realized, these data can be taken as a basis to calculate the mass of the gas adsorbed on the sorbent (m ). That is, volumetric adsorption experiments mainly result in pressure measurements. Hence the name Manometry for this method should be used [2.2]. 

This method was used in the early days of adsorption sciences by Langmuir, Dubinin, and others. It basically comprises a gas expansion process Ifom a storage vessel (the reference cell) to an adsorption chamber including adsorbent (the adsorption cell) through a controlling valve C, as schematically shown in Fig. 3. The reference cell with volume is kept at a constant temperature ref> which is usually as close to room temperature as possible. The value of includes the volume of the tube between the reference cell and valve C. The adsorption cell, where adsorbent might be confined, is kept at the specified equilibrium temperature T. The volume of the connecting tube between the adsorption cell and valve C is divided into two parts one part with volume L, exposures in room and, therefore, of the same temperature as the reference cell. Another part is buried in an atmosphere of temperature ad and, hence, its volume is added to the volume of adsorption cell, which is determined by helium at ref-... 

SI-4 insulation (A-7) on liquid-hydrogen and -helium storage tanks. Some loss rates reported are 2.5-3 per day loss on 150-liter vessels, per day loss on 1000-liter vessels, and 0.5 per day loss on 7800-gal trailers. They further show that the capacity of a 26,000-gal rail tank car insulated with 15 in. of perlite could be increased to 35,000 gal by using lin. of SI-4 insulation, while maintaining the same loss rate of 0.5 per day. Most of these super insulations involve the use of closely packed layers of aluminum foil radiation shielding and fiber glass paper spacers. 

These three basic differences in liquid-helium and liquid-hydrogen storage make it difficult to speak of storage of both fluids as though they were similar. A liquid-helium transport vessel design which provides for the three differences outlined above will differ from a similar liquid-hydrogen vessel in the following respects ... 

Since the flash evaporation of liquid helium is independent of the source of warm liquid, a refrigeration stage of this type can be associated either with a storage vessel maintained at atmospheric pressure or with a closed-cycle, continuously operating liquefier. The former appears to have usefulness in the laboratory and will be discussed later. 

For removing liquid hydrogen or helium by gas pressurization froni a dewar, a more detailed analysis is required. In this analysis consider the ullage space of the storage vessel to be the system as shown in Fig. 7.27. If an energy balance is written around the system, the heat transferred to the system minus the work done by the system equals the increase in internal energy of the system plus the heat transferred to the liquid minus the heat transferred from the inlet gas. In equation form this can be represented by... 

In the vertical and horizontal storage configurations, an internal canister stores the spent fuel assemblies in a safe subcritical configuration. The internal canister is a welded stainless steel pressure vessel that provides for criticality control, an inert helium environment, structural support of the fuel assemblies, and confinement of the highly radioactive... 

In calculating the adsorbed masses of nitrogen, the thermal expansion of the storage and of the adsorption vessel at higher temperatures must be taken into account. Also slight changes in the so-called helium-volume of the zeolite depending also on temperature should be considered. 

Until very recently liquid hydrogen has been in limited supply and its use has been restricted to small quantities at any one time. The transfer of small quantities of liquid from storage dewars to the use points has been effected by pressurization of the dewar with hydrogen or helium gas or by the use of specially designed centrifugal pumps. As the use of liquid hydrogen for missiles and for other activities increases, the quantity of gas required to pressurize and transfer the liquid from a dewar becomes large audits cost and that of the pressure vessel required become important considerations in the selection of the type of transfer system to be used. 

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