Pressurized cryogen transfer

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... 

Liquid cryogen transfer lines should be designed so that liquid cannot be trapped in any nonvented part of the system. Experiments in supercritical fluids include high pressure and should be carried out with appropriate protective systems. 

AN ANALYTICAL METHOD FOR ESTIMATING GAS REQUIREMENTS IN THE PRESSURIZATION AND TRANSFER OF CRYOGENIC FLUIDS... 

Equation (18) shows that in a constant volume, constant pressure ullage in which the gas cools only by contact with the walls, the average wall temperature varies as the reciprocal of the average gas temperature. This functional relation between and as given by (17) and (18) has been checked with data taken in several cryogenic transfer systems operatedat ADL [1,2,3], Excellent agreement was obtained. 

TESTS OF EQUIVALENT MASS MODEL. For all reported tests, reliable data were obtained on gas consuriiptions during the pressurization and transfer of cryogenic fluids. These data were compared with calculated results using the equivalent mass method. 

Arthur D. Little, Inc.. Technical Report No. 2, "Gas Requirements in the Pressurization and Transfer of Cryogenic Fluids," Cambridge. Massachusetts (March, 1960). 

J. Burke, W. Byrnes, A. Post, and F. E. Ruccia, "Pressurized Cool-down of Cryogenic Transfer Line," Advances in Cryogenic Engineering, Vol. 4, K. D. Timmerhaus, (ed.). Plenum Press, Inc., New York (1960). 

A Liquid Air Device for Cooling the Wearer of a Totally Enclosed Liquid Rocket Propellant Handler s Suit (4) 196 Pressurized Cooldown of Cryogenic Transfer Lines (4) 378... 

FIGURE 8.1 Sources of Heat Leak into a Cryogenic PropeiiantTank. Shown in the pressurant gas transfer lines are high pressure Composite Overwrapped Pressure Vessei, Pressure Control Assembly (PCA), and HEX. 

The first unit is a medium pressure liquid oxygen transfer pump designed for 35 gpm and a 600 foot head rise at 8400 RPM. This unit was designed and manufactured by Turbocraft for the Cambridge Corporation, The other unit is one of the Turbocraft Company s line of close-coupled cryogenic transfer pumps. This unit was supplied as a transfer pump on a Corps of Engineers, 9-ton LOX trailer. Its operating point is 150 gpm with a 125 foot head rise at 3500 RPM,... 

Estimation of gas requirements to pressurize and transfer cryogenic fluids is best made with the saturation rule. This rule is on the average 10 to 15 per cent conservative if only pressurization and transfer are considered. It will still predict gas consumption quite well if a hold period up to 1 hour after transfer is included. 

A method for calculating the pressurized cooldown time of cryogenic transfer lines has been developed. This method has been found to be in good agreement with test data obtained over a fairly wide range of operating conditions in a small-scale pressurized transfer system. The analysis presented should prove to be useful for estimation of the time required for the pressurized cooldown of conventional cryogenic transfer lines. 

Answer by author Our experience has shown that the fastest cooldown is obtained by suddenly admitting the pressurized cryogenic liquid to the transfer line. Of course, in some applications this approach may be impractical due to the necessity for keeping the receiver tank pressure below some acceptable value. 

D. C. Bowersock, R. W. Gardner, and R. C. Reid, "Pressurized cooldown of cryogenic transfer lines," 1958 Cryogenic Engineering Conference Proceedings. 

Unfortunately, however, the problem of analytically predicting two-phase flow behavior is complicated by the mass transition, usually from the liquid to the vapor, that results from the heat influx into the pipe and from pressure changes. Moreover, the liquid and vapor are quite frequently not in equilibrium, and this introduces additional variables into the prediction. In attempting to describe two-phase flow in a cryogenic transfer line, one must first realize that the flow in the vapor phase may be laminar or turbulent, and the flow in the liquid phase may be similar to or different from the gas. Further, this flow pattern may be altered by the incline of the pipe and by the heat influx or pressure drop. 

Using the saturation rule, determine the pressurization mass requirement for a nominal 117.77 m liquid oxygen storage vessel with a 10% ullage volume. The pressurization is to be maintained at 405 kPa for a 30-min transfer period at a rate of 0.025 m s. Assume that the vessel initially contains 106 m of liquid oxygen at a pressure of 101.3 kPa before it is suddenly pressurized to initiate the cryogen transfer. 

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