Abstract:
A system and method for storage and delivery of a cryogenic mixed gas is disclosed, the storage apparatus including a compact and lightweight dewar for containing cryogenic temperature mixed gas at supercritical pressure. Different heat exchangers associated with the dewar provide for heat input to the dewar to maintain gas therein in a single phase and provide continued expulsion energy. A backpack receives the dewar and includes means for quick connect of the dewar with an end use outlet, intermediate heat exchangers in the backpack conditioning the mixed gas for end use. No electrical input for fluid circulation is required.

Description:
RELATED APPLICATION 
     This Application is a continuation of U.S. patent application Ser. No. 09/008,393 filed Jan. 16, 1998 titled “Self Contained, Cryogenic Mixed Gas Single Phase Storage and Delivery”, now U.S. Pat. No. 6,089,226 which was a continuation of U.S. Pat. No. 5,709,203 issued Jan. 20, 1998 (Ser. No. 08/755,249 filed Nov. 22, 1996) entitled “Self Contained, Cryogenic Mixed Gas Single Phase Storage and Delivery System and Method for Body Cooling, Gas Conditioning and Utilization” by Harold L. Gier, which is a continuation of U.S. patent application Ser. No. 08/328,743 filed Oct. 24, 1994 entitled “Heat Exchange in a Mixed Gas Delivery System for Body Cooling and Gas Conditioning” by Harold L. Gier (now abandoned) and a continuation-in-part of U.S. patent application Ser. No. 08/480,555 entitled “Loading, Storage and Delivery Apparatus and Method for Fluid at Cryogenic Temperature” filed Jun. 7, 1995 by Harold L. Gier and Richard L. Jetley (now abandoned), which Applications are a continuation-in-part and a continuation, respectively, of now abandoned U.S. patent application Ser. No. 07/879,581 filed May 7, 1992 and entitled “Loading, Storage and Delivery Apparatus And Method For Fluid At Cryogenic Temperature” by Harold L. Gier and Richard L. Jetley. 
    
    
     GOVERNMENT SUPPORT 
     This invention was made with Government support under-contracts awarded by the National Aeronautics and Space Administration and the U.S. Air Force. The Government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to mixed gas storage and delivery apparatus and methods, and, more particularly, relates to integrated systems for storage, delivery and conditioning of mixed gas initially contained at cryogenic temperature. 
     BACKGROUND OF THE INVENTION 
     High pressure, ambient temperature gas storage and delivery devices have been heretofore suggested for providing attitude independent supply of mixed gasses such as breathable air to a user thereof. Such devices, while in use, have limited gas delivery time, are bulky, and must be operated at extremely high pressures. 
     Liquid air storage and delivery devices have also been suggested (see U.S. Pat. Nos. 1,448,590, 3,318,307, 3,570,481, 3,572,048, 4,181,126, 3,699,775, 1,459,158, and 3,227,208), but suffer from limited stand-by time due to oxygen enrichment inherent in such storage, some being unduly complex in an effort to confront this problem, are not attitude independent, and are often quite heavy. 
     Dispensers for cryogenic temperature elemental and compound gasses (below −175° F.) such as oxygen held for use at supercritical pressure (above 730 psia) have been heretofore suggested (see U.S. Pat. Nos. 3,062,017 and 3,827,246) In such dispensers a heat transfer mechanism (i.e., an electrical heating element or a heat exchanger) is utilized to pressurize the storage vessel having liquid oxygen loaded therein at atmospheric pressure (thus making the dispenser less than desirable as an air supply, where oxygen enrichment could occur while liquid air is in standby storage) for expelling the oxygen. 
     Pressure sensing is thereafter used to sense the heat transfer needs in the vessel to maintain pressure therein above critical pressure by activating the heating element periodically. Heat exchange is accomplished utilizing at least in part active means separate from the dewar thus encumbering these heretofore known dispensers with complex sensing and activating mechanisms to assure proper heat input. Improvement in such dispensers could thus still be utilized. 
     While the integrated system above described may be effective in some applications, such system fails to provided a compact unit (capable of being carried on one&#39;s body) such as might be required by fire fighters or other mobile personnel needing such a system. Such systems require electrical input (undesirable in gaseous environments), rely on manual activation to control flow rates and thus cooling, and make no use of heat exchange to control system operational parameters other than temperature of the breathable air. Moreover, the oxygen converting systems used therein suffer many of the same drawbacks as heretofore discussed. Further improvement could thus be utilized. 
     SUMMARY OF THE INVENTION 
     This invention provides a body mountable mixed gas storage and delivery system and method which maintains conditioning of a mixed gas for end use. The system is lightweight and includes a containment apparatus (or vessel) for storing mixed gas received at cryogenic temperature and supercritical pressure and delivering the mixed gas at a non-cryogenic temperature to a utilization fixture, such as a breathing mask in the case of air or a torch or engine in the-case of other mixed gasses. The system requires no electrical input, requires no manual manipulation to control cooling fluid flow rates, and makes use of passive heat exchange for control of system operational parameters including temperature of the usable gas and maintenance of remaining stored gas in a single phase and at,proper expulsion pressure. 
     The containment vessel has an outlet for selective expulsion of the mixed gas from the containment vessel to the utilization fixture and a passive heat exchanger thereat for receiving mixed gas expelled through the outlet and routing the mixed gas at the containment vessel to introduce sufficient heat into the containment vessel so that the mixed gas remaining in the containment vessel is in a single phase. Heat exchange is calculated and configured for introducing heat into the containment vessel at a rate determined by the rate of expulsion of the mixed gas from the containment vessel through the outlet to thereby maintain sufficient energy to expel the mixed gas remaining in the containment vessel and so that the mixed gas remaining is in the single phase. 
     A body mountable unit is provided and includes a pack structure configured for releasably receiving the containment vessel. The unit includes conditioning means integrally maintained in the pack structure and connectable with the passive heat exchanger when the containment vessel is mounted in the pack structure, the conditioning means for raising the temperature of the mixed gas to a usable temperature. 
     The containment vessel preferably includes a pressure vessel having an inlet and outlet and an outer shell having the pressure vessel therein. Surface area increasing means, such as fins, are connected with the outer shell for effectively increasing surface area of the outer shell, the mass flow heat exchanger connected adjacent to the outer shell and with the outlet of the pressure vessel for receiving the mixed gas from the pressure vessel through the outlet and conducting it to a connection. 
     The body mountable unit preferably includes a quick disconnect connected with the conditioning means and readily connectable/disconnectable with the connection of the heat exchanger when the containment vessel is mounted in the pack structure. 
     The method for storing and delivering mixed gas of this invention includes the steps of loading cryogenic temperature mixed gas into a container so that the mixed gas at time of use is in a single phase, with the container configured to be mountable in a pack that can be carried on the body of a user. Mixed gas is selectively expelled from the container and routed to deliver sufficient heat to the container so that mixed gas remaining in the container remains in the single phase. The expelled mixed gas is received, conditioned for end use, and delivered at structure integrally associated with the pack. 
     It is therefore an object of this invention to provide an improved self contained cryogenic mixed gas single phase storage and delivery system and method. 
     It is another object of this invention to provide an improved integrated body mountable mixed gas storage, conditioning and delivery system and method. 
     It is still another object of this invention to provide a lightweight apparatus for storing mixed gas received at cryogenic temperature and supercritical pressure and delivering the mixed gas at a non-cryogenic temperature to a utilization fixture, such as a breathing mask in the case of air or a torch or engine in the case of other mixed gasses. 
     It is still another object of this invention to provide a cryogenic mixed gas storage and delivery apparatus which makes use of heat exchange for control of apparatus operational parameters including temperature of the usable gas and maintenance of remaining stored gas in a single phase and-at proper expulsion pressure. 
     It is another object of this invention to provide a body mountable system for mixed gas storage and delivery comprising containment means for receiving mixed gas at cryogenic temperature and in an amount so that the mixed gas is initially at a pressure sufficient to maintain the mixed gas in a single phase, outlet means connected with the containment means for selective expulsion of the mixed gas from the containment means therethrough, passive heat exchange means connected with the outlet means for receiving the expelled mixed gas at the outlet means and conducting the expelled mixed gas to a connection, the heat exchange means being routed for introducing heat into the containment means at a rate determined by a rate of expulsion of the mixed gas from the containment means through the outlet means to thereby maintain sufficient energy to expel the mixed gas remaining in the containment means from the containment means and so that the mixed gas remaining in the containment means remains in the single phase. 
     Is is another object to provide a body mountable unit including a pack structure configured for releasably receiving a cryogenic fluid container and passive heat exchange means therein, the unit including conditioning means integrally maintained in the pack structure and connectable with the connection of the passive heat exchange means when the containment means. 
     It is another object of this invention to provide an air storage and delivery system comprising an air storage and maintenance unit including a pressure vessel for containing air at cryogenic temperature and at a pressure so that air in the vessel is in a single phase, the vessel having an inlet and an outlet, an outer shell having the pressure vessel therein, and mass flow heat exchange means connected adjacent to the outer shell and with the outlet of the pressure vessel for receiving the air from the pressure vessel through the outlet and conducting the air to a connection, the heat exchange means being routed for introducing heat by free convection into the air being conducted to the connection and into the pressure vessel from the air thus routed to thereby maintain sufficient energy in the pressure vessel to expel the air therefrom. 
     It is still another object of this invention to provide a method for storing and delivering mixed gas comprising the steps of loading cryogenic temperature mixed gas from a source at or above supercritical pressure into a container so that substantially immediately after time of loading the mixed gas is at or above supercritical pressure in the container and at time of use is in a single phase, selectively expelling the mixed gas from the container, and routing the expelled mixed gas to introduce heat into the container during conduct or the mixed gas toga destination for use, heat introduction sufficient to maintain the mixed gas remaining in the container in a single phase and with sufficient continued expulsion energy based subastantially solely on rate of expulsion of the mixed gas from the container. 
     With these and other objects in view, which will become apparent to one skilled in the art as the description proceeds, this invention resides in the novel construction, combination, arrangement of parts and method substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that changes in the precise embodiment of the herein disclosed invention are meant to be included as come within the scope of the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate a complete embodiment of the invention according to the best mode so far devised for the practical application of the principles thereof, and in which: 
     FIG. 1 is a perspective view of the fluid storage and delivery apparatus used in this invention; 
     FIG. 2 is a schematic diagram of the apparatus of FIG. 1; 
     FIG. 3 is a diagrammatic illustration of heat exchange in the apparatus of FIG. 1; 
     FIG. 4 is a diagrammatic sectional illustration of the storage and delivery apparatus of FIG. 1; 
     FIG. 5 is a side view of the outer routed portion of the heat exchanger of the storage and delivery apparatus of FIG. 1; 
     FIG. 6 is a sectional view illustrating part of the inner routed portion of the heat exchanger of the storage and delivery apparatus of FIG. 1; 
     FIG. 7 is a sectional view taken through section line  7 — 7  of FIG. 6; 
     FIG. 8 is a Mollier chart showing performance of the apparatus of FIG. 1 under a variety of loading densities; 
     FIG. 9 is a perspective view of a loading apparatus for loading fluid into the storage apparatus; 
     FIG. 10 is a schematic sectional view of the loading apparatus of FIG. 9; 
     FIG. 11 is a diagram illustrating operation of the loading apparatus of FIG. 9; 
     FIG. 12 is a rear view of a carriage and conditioning unit used with the apparatus of FIG. 1; 
     FIG. 13 is a side view of the unit of FIG. 12; 
     FIG. 14 is a schematic illustration of the body cooling system of this invention used in association with a modified apparatus of FIG. 2; 
     FIG. 15 is a schematic illustration of a fluid circulation network incorporated into a garment for use in the system of FIG. 14; and 
     FIG. 16 is a second embodiment of the body cooling system of this invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     Storage and delivery apparatus  21  (incorporated into, or used in association with, this invention) is shown in FIG. 1 for containing supercritical pressure cryogenic air as a breathing supply to thus obviate the problems of oxygen enrichment and attitude dependence of a liquid air breathing bottle. The use of a supercritical cryogenic fluid state for the air provides a gas which is in a single phase, high density condition and which can be withdrawn from any location in the apparatus which may itself be in any attitude. Supercritical pressure is required so that the. air at cryogenic temperature will exhibit no two phase characteristics. 
     While an air delivery apparatus will be described and referred to herein, it should be understood that the apparatus could as well be used for any fluid delivery to a utilization fixture, for example elemental and/or compound gasses, or, most particularly, mixed gasses such as air (nitrogen-oxygen), helium-oxygen, argon-oxygen, helium-argon, methane-hydrogen, or the like where prevention of separation of the components due to gravitational effects and/or due to frictional separation from boiling of a liquid is desired. 
     The critical pressure for air is 37.25 atm. (547.37 psia) and the critical temperature is 132.5 K (238.54° R). The colder the initial temperature of the air (preferably down to 140° R) and to a much lesser extent the higher the pressure (preferably in a range between 750 psia and 2,000 psia), the greater will be the storage density and thus the ability to provide significant rated use times while utilizing smaller, lighter storage units. 
     The use of supercritical fluid also provides a standby storage advantage over liquid in that energy required to expel a pound of fluid in the single phase storage condition is greater than that required to boil-off a pound of liquid and expel the vapor (161.68 Btu/Lbm at 750 psia versus 86.67 Btu/Lbm at one atmosphere, respectively). Supercritical air may thus be stored for longer times before reservicing than liquid air. 
     As shown in FIGS.  1  and/or  2 , apparatus  21  includes outer shell, or vacuum jacket,  23 , protective head  25  (for example, a one-piece cast aluminum head) sealed to shell  23  and pressure vessel  27  within shell  23  for containing the air. Fill line  29  passes through shell  23  and vessel  27  at inlet  31  for filling and/or refilling as hereinafter set forth (all connections and passages with, to and from vessel  27  and shell  23  set forth herein being formed by means known to those skilled in the pertinent art). Passive heat exchange and fluid transport system  33  is connected to vessel  27  at outlet  35  for conducting air expelled from vessel  27  to a use destination (for example to the carriage and conditioning unit hereinafter described). 
     Insulation  37  fills, and is vacuum jacketed within, space  39  between vessel  27  and shell  23  and can be, for example, formed of ten layers of multi-layered insulation consisting of double aluminized MYLAR spaced with tissue glass (a borosilicate fiber paper) or polyester netting. Fins  41  (in one embodiment being about four inches wide by 0.083 inch thick aluminum fins) are welded to, or formed integrally with (though they could also be remote from the shell), shell  23  for effectively increasing the surface area of the shell exposed to ambient temperature air to enhance heat exchange as discussed in more detail hereinbelow. 
     Vent line  43  is connected with vessel  27  for relief venting through relief valve  45  and to maintain pressure during standby and during filling. Relief valve  45  should include a TEFLON seal and be rated for cryogenic temperatures, and as illustrated is preferably biased at atmospheric pressure for relieving top pressure and thus reducing pressure through transport system  33  without waste of fluid. Relief valve  47  is employed as a final high reliability safety device, and should be sized to relieve at approximately 10% (approximately 200 psi) above relief pressure of valve  45 . 
     Flow control valves  49 ,  51  and  53  are manual valves for control of filling, draining and use of apparatus  21 , and may be bellows type valves of all welded construction designed for temperature cycling applications, and/or may be combined into one or more operational units. Quick disconnects  55 ,  57 , and  59  are provided for making required connections to a loading apparatus (for example, as hereinafter described) or carriage and conditioning unit. 
     Pressure gauge  61 , for example a small bourdon tube pressure gauge, is used for checking tank pressure, and quantity sensor  63  having readout  65  monitors fluid quantity in vessel  27  (for example, using a capacitance probe to measure the dielectric constant which varies from approximately 1.4 in the full condition to 1.0 in the empty condition). An audible alarm can be provided to alert a user when the fluid quantity reaches a selected low level, all electronics being powered, for example, by a 9 volt battery. 
     Pressure regulator  67  is a back-pressure regulator used, in conjunction with valve  51 , to maintain pressure during standby and filling operations. As shown in FIG. 2, line  43  may be couplable through valve  45  with conditioning unit  69  at carriage and conditioning unit  71  using quick disconnect  73  so that air expelled therethrough may be. used in the system. 
     Conditioning unit  69  includes heat exchanger  75  for heating expelled air, to a breathable temperature, pressure regulator  77 , optional flowmeter  79  and quick disconnect  81  for connection with a utilization-device such as a mask. 
     Configuration of the various components varies with operation. During storage, valves  49  and  53  and quick disconnects  55 ,  57  and  81  are all closed. During loading operations valves  49  and  51 , quick disconnects  55  and  59  and pressure regulator  67  are operational. During standby, valve  51 , quick disconnect  59  and pressure regulator  67  remain open, while in operation valve  51 , quick disconnect  59  and pressure regulator  67  are closed, and valve  53  is opened. 
     Vessel  27 , in one particularly useful embodiment, has a volume of less than 4.2 liters (preferably about 4 liters), the apparatus having an overall diameter of about five inches, length of about 22 inches, operating pressure of 1,600 psia, and weight empty of about 10.7 pounds (filled weight of about 19 pounds) for a rated delivery time of about one hour (“rated delivery” herein refers to NIOSH rating of 40 SLM (standard liters per minute) for breathing apparatus, equating to about 6.7 lbs. of air per hour of delivery). In such case, vessel  27  is made of titanium, though other materials could be used. 
     By way of further example, for a rated time of two hours at the same operating pressure, the apparatus having a titanium vessel  27  weighs under 30 pounds filled, has a vessel volume of about 7.2 liters, a diameter of 6.5 inches and a length of about 25 inches. 
     Apparatus weight depends on vessel  27  volume, operating pressure and materials. Pressure vessel and outer shell materials could include composites such as FIBERGLASS, KEVLAR or graphite. Metals that could be used include stainless steel, aluminum, INCONEL or titanium. Aluminum or composite pressure vessels would require bimetal joints, with a composite vessel  27  possibly including an aluminum liner and neck plug  83  (shown in FIG. 4 for housing inlet and outlet plumbing and for, in part, positioning vessel  27  in shell  23 ) overlaid with an S-glass/epoxy composite (a composite fabric heretofore used in aerospace applications). The advantage in weight of such construction is significant, with a 4 liter apparatus (rated use exceeding 60 minutes) having a diameter of 4.5 inches and a vessel weight of less than four pounds. Overall, weights for a 4 liter apparatus range from about 10.7 to 16.4 pounds at an operating pressure of 1,600 psig, the lightest having a titanium, INCONEL 718 or aluminum (6061-T6 welded and heat treated with a burst pressure in excess of 6,000 psig) vessel  27  with an aluminum shell  23 . 
     Referring now to FIGS. 2 and 3, passive heat exchange system  33  is a double loop heat exchange system (a single loop system could be used in a system as hereinafter set forth) including inner exchange loop portions  85  and  87  connected either to the outer part of vessel  27  or passing into vessel  27  in direct contact with fluid therein. Outer exchange loop portions  89  and  91  are connected with shell  23  or fins  41  or could be made integral to fins  41  as shown in FIG.  7 . The heat exchange loop portions are preferably constructed of ⅛″ diameter aluminum tubing, though other materials could be utilized. 
     Sufficient heat must be efficiently transported from outer shell  23  to pressure vessel  27  to maintain the gas in the vessel in the single phase and to provide expulsion energy for delivery of the gas from the vessel. A design to provide adequate heat transfer for expulsion must recognize that the process is a transient one. Fluid conditions and properties constantly change throughout the entire expulsion process. 
     For example, the expulsion energy for supercritical air ranges from approximately 35 BTU/Lbm to 160 BTU/Lbm in the pressure and temperature range of interest, with the integrated average expulsion energy being approximately 65 BTU/Lbm. Since heat leak through plumbing and other fixtures alone is insignificant compared to that required to expel the air needed (only about 9.0 BTU/Hr for a shell temperature of 530° R and a vessel temperature of 180° R) for use by an individual user at maximum exertion (estimated to be about 16.0 lbm/hr), mass flow heat exchange system  33  must be calculated to deliver sufficient heat for operation of the apparatus. 
     An example demonstrating heat transfer requirement for a single point in the expulsion process follows. As illustrated by FIG. 3, expelled tank fluid passes through heat exchangers  89 / 91  increasing its temperature to nearly that of the surface of outer shell  23  (preferably by free convection to the ambient-air though various means of forced convection of ambient air to shell  23  could be utilized to provide more energy exchange). The fluid then flows to heat exchangers  85 / 87 , respectively, cooling the fluid and dumping heat for fluid expulsion and single phase maintenance into fluid remaining in pressure vessel  27 . The maximum amount of heat (Q) that can be transported from shell  23  to vessel  27  depends on the mass flow rate of outflowing fluid (m  supply ), the specific heat of the cryogenic air (C p ), and the temperature difference between shell  23  and vessel  27  as in the following equation: 
     
       
           Q=m   supply   C   p ( T   s   −T   v ) 
       
     
     Since the C p  of cryogenic air varies with temperature, a more accurate representation of the heat transported is: 
     
       
           Q=m   supply ( h   s−h   v ) 
       
     
     where h s  is the enthalpy of air at the outer shell temperature and fluid pressure and h v  is the enthalpy of air at the pressure vessel temperature and fluid pressure. 
     A realistic number for heat exchanger efficiency is considered to be 0.90, so that the Q calculated above would be multiplied by this efficiency twice (for external and internal heat exchangers) to obtain a heat flux for the heat exchanger described. Assuming a nominal fluid pressure of 800 psia, an ambient temperature of 530° R (h s =122 BTU/Lbm) and pressure vessel fluid temperature of 150° R (h v =−48 BTU/Lbm), the total Q transferred to the pressure vessel fluid is 
     
       
           Q =(0.9)(0.9)16.0 Lbm/Hr(122−(−48)BTU/Lbm 
       
     
     Q=2200 BTU/Hr 
     Taking these numbers into consideration as well as the required increase in temperature of vessel  27 , a double loop exchange system as shown would be required to achieve approximately 2480 Btu/hr that will drive 16 lbm/hr out of vessel  27  while remaining single phase. 
     In order to predict the amount of heat transfer between the outer shell and ambient air, a free convection correlation for a long horizontal cylinder geometry is utilized so that heat transfer by free convection, q conv , from ambient air to shell  23  is given by: 
     
       
           q   conv   =hπDL ( T   S   −T   ∞ ) 
       
     
     where h equals the average free convection film coefficient, D equals cylinder diameter, L equals cylinder length, T S  equals cylinder temperature, and T ∞ equals ambient air temperature. The free convection film coefficient may be obtained from the dimensionless Rayleigh number, Ra, by: 
     
       
           Ra=g β( T   S   −T   ∞ ) L   3   /αv   
       
     
     where g equals acceleration of gravity, β equals the volume coefficient of expansion, α equals thermal diffusivity, and v equals dynamic viscosity. 
     In the case at hand, solution for Ra yields 1.4×10 9 . An appropriate correlation for the Nusselt number, Nu, is: 
     
       
           NU   D =0.10( Ra ) ⅓   
       
     
     which for this example-is equal to approximately 110.0. The film coefficient is related to the Nusselt number by: 
     
       
           h =( Nu k )/ L   
       
     
     where the thermal conductivity, k, for air at the average air temperature is 0.013 BTU/Hr-Ft-° F. This results in an average film coefficient, h, of 0.95 BTU/Hr-Ft 2 -° F. 
     Thus, for an outer shell area of approximately 2.5 ft 2 , an ambient temperature of 530° R and average shell temperature of 300° R, the total amount of heat available from free convection will be 550 BTU/Hr. Therefore, a higher product of film coefficient and outer shell  23  surface area is required in order to transfer adequate heat to vessel  27  to maintain desired pressure. Since the free convection heat transfer coefficient is fixed due to geometry and fluid conditions, the only method to increase this product in the embodiment of apparatus  21  shown in FIG. 1 is to effectively increase the surface area of shell  23  as is done utilizing fins  41 . 
     FIGS. 4 through 7 show routing of the heat exchange loop portions as suggested hereinabove. For a 3 liter tank design, 63-64 feet total of tubing is utilized for heat exchange system  33 . FIG. 8 is a Mollier chart having plotted thereon results of various tests illustrating an adequate degree of separation of the transient fluid condition from the two-phase region utilizing the apparatus of this invention. 
     While not illustrated herein, vessel  27  is preferably supported in shell  23  on neck tube support  83  attached to both vessel  27  and shell  23 . Bumpers, or pads, would be desirable adjacent to the lower, unsupported, end of vessel  27  to thwart movement of vessel  27  in excess of maximum allowable stress to neck  83  or its connections to vessel  27  and shell  23 . 
     FIGS. 9 through 11 illustrate a loading apparatus  99  usable with this invention, advantageous in that loading at supercritical pressure is made possible (it being understood that any loading method for placing the cryogenic gas in vessel  27  could be utilized with the body cooling system of this invention as hereinafter set forth). Apparatus  99  has coolant (such as LN 2 . i.e., liquid nitrogen) supply  101  connected thereto by supply conduit  103  (an LN 2  refrigerator or other means could be utilized). Air supply  107  is connected to apparatus  99  by conduit  109  (a compressor being illustrated, though a high pressure compressed air bottle could also be utilized). An alternative fill apparatus could be provided which utilizes a source of cryogenic temperature air itself maintained at supercritical pressure, in which case, loading would be simplified even if possibly more expensive and unwieldy. 
     Apparatus  99  includes housing  111 , vacuum chamber  113  having LN 2  bath chamber  115  and precooling chamber  117  therein, and storage apparatus insertion chamber  119  for receipt thereinto of a storage apparatus to be serviced (preferably having a self aligning load, securing and quick disconnect mechanism for ease of use by an operator). Precooling chamber  117  includes heat exchange chamber  121  connected with boil-off line  123  and chamber  125  connected with fill vent quick disconnect  59  from apparatus  21  to provide preliminary cooling (from about 20° C. to about −60° C.) of air received through inlet  127  from supply  107 . 
     Exchange coils  129  and  131  are positioned in chambers  125  and  121 , respectively, air flowing in the coils then being passed through LN 2  bath in coil  133  of conduit  135  (it should be recognized that mechanical refrigeration could also be utilized) to lower temperature of the air to about −195° C. The air is then received in apparatus  21  through quick disconnect  55 . Since the air from supply  107  is received at loading apparatus  99  at or above the critical pressure (about 800 psi), the fluid is received at apparatus  21  in the single phase condition, thus rendering apparatus  21  usable substantially immediately after filling. 
     Where supply compressor unit  107  is utilized rather than a high pressure gas bottle containing high purity air, filter/dryer/CO 2  scrubber  137  and pressure regulator  139  are provided. Compressor supply unit  107  may include for example, an oil-free 1,000 psi compressor. Various gauges, readouts, program controls and the like could be utilized to enhance ease of operation and safety of the apparatus. 
     FIGS. 12 and 13 illustrate carriage and conditioning unit  71  utilizable with this invention. Unit  71  includes pack structure  147  made, for example, of high strength, light weight molded plastic. Structure  147  has a plurality of openings  149  therein to assure proper flow of ambient air around apparatus  21  and the various heat exchangers mounted therein (for example heat exchanger  75 , though the openings will serve the same function for other exchangers as hereinafter set forth). Air conditioning heat exchangers  75  and pressure regulator  77  are mounted on structure  147  by any convenient means, and adjustable harness  151  and waist belt  153  are mounted in selected sets of receiving slots at the back of the pack structure. Remote fluid quantity readout  65  may be attached to harness  151  for ease of observation. Apparatus  21  is snugly maintained in structure  147  by molded head  157  and hinged door  159  connected at hinge  161 . 
     Turning now to FIGS. 14 and 15 illustrating a first embodiment of body cooling system  165  of this invention, many of the features of apparatus  21  as shown in FIG. 2 remain substantially the same for use with the system, including outer shell  23  having an insulated pressure vessel  27  therein, various outlets  31  and  35 , lines  29 ,  33  and  43 , quick disconnects  55 ,  57 ,  59  and  73 , relief valve  45 , pressure regulators  67  and  77 , and pressure and quantity gauges and readout  61 ,  63  and  65 . However, only one internal heat exchange loop  85  is required for maintaining cryogenic gas in vessel  27  in a single phase and providing sufficient expulsion pressure since heat input is no longer provided by exchange with the ambient atmosphere (formerly at exchange loops  89  and  91  at fins  41  and shell  23  in FIG.  2 ), but by heat exchange with fluid heated by the body of a wearer of garment  167 . 
     Quick disconnect  59  is now connected at carriage unit  71  to valve  169  through passive heat exchanger  171  for recycling of gas expelled thereat into the system when valve  169  is on. Valve  169  is off when the unit is not connected at carriage unit  71  and in a standby condition. Relief valve  173  is provided to maintain desired pressure (for relief at about 1,000 psi). Heat exchanger  171  is situated to pre-warm gas before passage through valve  169  to prevent valve damage and thus leaking. 
     Quick disconnects  179  and  181  are provided for interconnection of vessel  27  at carriage unit  71  with system  165 . Mixed gas expelled at outlet  35  through line  33  first reaches control valve  182  where the gas is directed either to pre-warming heat exchanger  183  or directly to body cooling heat exchanger  185 , depending on valve setting. Pre-warming heat exchanger  183  includes gas conduit  187  in heat exchange relationship with fluid conduit  189 . Fluid conduit  189  is connected by disconnects  191  and  193  into a discrete fluid (water or water and antifreeze) circulation loop  195  including heat exchanger  197  located in an outer protective garment  199  worn over garment  167  for heat exchange with the ambient atmosphere. Gas at conduit  187  is thus warmed (for air, from approximately −160° C. to about −30° to 15° C.) before it reaches heat exchanger  185 , pre-warming being necessary in some circumstances to prevent over cooling of the user&#39;s body. 
     Body cooling heat exchange and heat exchange for heat input to vessel  27  at heat exchange loop  85  is accomplished at exchanger  185  including gas conduit  201  in heat exchange relationship with fluid conduit  203 . Fluid conduit  203  is connected by disconnects  205  and  207  into a discrete fluid circulation loop. 209  including heat exchange network (a fluid circulation network in garment  167  as also shown in FIG.  15 ). 
     Where pre-warming is not required under the circumstances, valve  182  directs the mixed gas to heat exchanger  185 .(in the case of air, at a temperature of about −160° C.) for heat exchange with fluid in loop  209 , preferably lowering fluid temperature to no lower than about 10° C., for example, in the case of water or water and antifreeze, and raising the temperature of the gas, for example to about 20° C. in the case of air where fluid circulating in loop  209  is raised in temperature by the user&#39;s body at exchange network  211  to about 30° C. Where the gas has been pre-warmed, since gas entering exchanger  185  is of a higher temperature, the overall body cooling effect is controlled (i.e., fluid temperature at network  211  is controlled). The warmed gas is then directed to heat exchange loop  85  through disconnect  181 , providing energy as heretofore discussed at vessel  27 . 
     Gas exiting exchange loop  85 , again cooled to about −160° C. in the case of air, is presented through quick disconnect  57  at control valve  213  where the gas is directed either to pre-warming heat exchanger  215  or directly to body cooling heat exchanger  217 , depending on valve setting. Pre-warming heat exchanger  215  serves the same purpose for exchanger  217  as heretofore described for exchangers  183  and  185 , and is similarly arranged for heat exchange, utilizing quick disconnects  219  and  221  to provide fluid circulation loop  223  having external heat exchanger  225 . 
     Body cooling heat exchange and heat exchange to condition gas for use (formerly provided at heat exchanger  75  in FIG.  2 ), for example to raise the temperature of cryogenic air to a breathable temperature, are accomplished at heat exchanger  217  including gas conduit  227  in heat exchange relationship with fluid conduit  229 . Fluid conduit  229  is connected by disconnects  231  and  233  into a discrete fluid circulation loop  235  including heat exchange network  237 , a fluid circulation network in garment  167 . 
     Where pre-warming is not required under the circumstances, valve  213  directs the mixed gas to heat exchanger  217  (in the case of air at a temperature of about −160° C.) for heat exchange with fluid in loop  235 , preferably lowering fluid temperature to no lower than about 10° C., for example, in the case of water or water and antifreeze, and raising the temperature of the gas, for example to about 20° C. in the-case of air where fluid circulating in loop  235  is raised in temperature by the user&#39;s body at exchange network  237  to about 30° C. Where the gas has been pre-warmed, since gas entering exchanger  227  is of a higher temperature, the overall body cooling effect is controlled (i.e., fluid temperature at network  237  is controlled). The warmed gas is then directed through valve  77  to a utilization fixture (such as a face mask for breathable air). 
     While fluid circulation at loops  195 ,  209 ,  223  and  235  may be accomplished by any means adequate to the task, non-electrical pumping is preferred. Pumps  240 ,  242 ,  244  and  246  are preferably, particularly where the fluid is liquid such as water or water and antifreeze, pneumatic pumps connected into gas outflow lines  248 ,  250 ,  252  and  254  from heat exchangers  183 ,  185 ,  215  and  217 , and into fluid circulation loops  195 ,  209 ,  223  and  235 . The pneumatic pumps utilize the pressure drop of gas moving thereacross to circulate the fluid in their respective loops. 
     While again not required, the pumps are preferably variable rate pumps capable of increasing fluid flow rates in the fluid circulating loops responsive to the rate of use of gas through the system and thus moving through the pumps. For example, in the case of air, increased respiratory rate of a user (indicative of work exerted by the user&#39;s body) will increase fluid flow rate through networks  211  and  237  and exchangers  185  and  217  thus increasing the rate of cooling of the body precisely at the time that the user demands increased cooling due to an increased work rate. 
     The pumps are preferably centrifugal or turbine pneumatic pumps capable of operation at gas pressures up to about 1250 psi and providing variable liquid flow rates between about 0.05 and 1 cubic feet per hour at pressures up to about 20 psi. Materials used in construction may be mostly aluminum and nylon, and, though designed to withstand normally cold ambient temperatures, because of placement at the outflow lines form the heat exchangers need not be designed for cryogenic temperatures. 
     Valves  182  and  213  are preferably automatically controlled by a processor for switching responsive to sensed body temperature and/or air temperature inputs to the processor. Garment  167  as illustrated in FIG. 15 may be either a one or two piece garment of types heretofore known. Heat exchangers  183 ,  185 ,  215  and  217 , when used with a liquid secondary loop, are designed to provide heat exchange without freezing the liquid in the presence of low flow rates (of the cold gas between about 0.05 and 0.25 cubic feet per hour, and of the liquid between about 0.2 to 1.0 cubic feet per hour). 
     A second embodiment  260  of the body cooling system of this invention is illustrated in FIG.  16 . The system illustrated is the same in most regards to that heretofore shown (like elements being indicated by like numbers). However, heat exchanger  262  now combines all heat exchange functions of exchangers  171 ,  185  and  217  shown in FIG. 14 into a single heat exchange unit. A single fluid circulation loop  264  in circulation with fluid heat exchange conduit  265  of exchanger  262 , and including a unified circulation network  266  at garment  167 , is provided with fluid supply reservoir  268  at carriage unit  71 . Pre-warming heat exchanger  270  (performing the control function of heat exchangers  183  and  215  as shown in FIG. 14) is also located at the carriage structure and is integral with fluid circulation loop  264 . Automatic control valve  272  (processor controlled as heretofore discussed with regard to valves  182  and  213 ) is located in loop  264  for control of fluid flow within the loop. Additional backup heat exchanger  274  is provided to insure adequate conditioning of the mixed gas before use as may be necessary, for example, as a safety feature in a breathing system. 
     Exchanger  262  includes gas conduits  276 ,  278  and  280 , conduits  276  and  278  connected in flow paths and for the functions as heretofore described for conduits  201  and  227  of exchangers  185  and  217  in FIG.  14 . Gas conduit  280  is connected in a flow path and for the function as hereto described for exchanger  171  in FIG.  14 . 
     As may be appreciated from the foregoing, an improved integrated system and method for body cooling and mixed gas conditioning are provided for use with cryogenic fluid containment and delivery apparatus.