Abstract:
A personal air conditioning device cools and moistens environmentally hot and dry blower-forced air using water vaporization occurring on external surface of a hollow fiber micro-porous membrane while water or other liquid coolant is taken from a container by means of internal capillaries of hollow fiber tubes. The device is able to deliver the pre-cooled air flow over any desired body fragment, particularly under a protective vest.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a personal air conditioning device, and more particularly to an evaporative personal cooler utilizing a membrane arranged in a bundle of hollow tubes and permeable to a vaporized liquid. 
     BACKGROUND OF THE INVENTION 
     People subjected to extremely hot and dry environments for long periods are exposed to risks of body overheating and dehydration that can cause severe disorders or even death. There are several areas in which personnel must be equipped to endure such environmental conditions, for example, soldiers and guards deployed in desert climates, firefighters and steel production workers. Such individuals are supposed to wear heavy protective gear, accelerating body water loss unless the space underneath the gear, such as a vest is properly vented and cooled. 
     Presently, a prominent way to prevent heat buildup and resulting heavy body precipitation under a vest is the use of pre-cooled gel bags placed in special vest pockets. Such cooling technique depends on external refrigerator, can transfer body heat at uncontrolled rates and requires time for vest loading. 
     Some other cooling methods use water vaporization supplied into an air stream followed by heat withdrawal due to the latent energy absorption. Water mist devices can deliver water directly into an air flow created with a blower or fan. A water mist can be applied periodically to a skin or clothing making them wet. These methods can be limited to short-term relief and present water accumulation. To avoid direct water distribution in some cooling devices, it is disclosed in U.S. Pat. No. 6,189,327, for example, that blower-forced air is introduced to a body portion covered with a heat dissipating member having a liquid-retainable surface only on a side external relative to the body. However, a device operating in accordance with this principle provides the cooling effect only to body fragments, such as a neck or forehead, that is covered with the protective member. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a personal wearable air conditioning system capable of delivering blower-forced air, pre-cooled by means of the vaporization of a liquid, over any desired body fragment, particularly under a protecting vest. 
     Another object of the invention is to provide a personal air conditioning system that can utilize replaceable moisture exchange cartridges which can use various cooling liquids. 
     Still another object of the invention is to provide a personal air conditioning system that can be arranged in a compact housing for carrying by the wearer in a pouch or pocket of such garments as belted waist packed, back packs or vests. 
     A personal air conditioning system in accordance with aspects of the present invention comprises, at least, a moisture exchange cartridge, a blower, and a reservoir to contain a liquid intended for cooling vaporization, such water, alcohols or their mixture. The moisture exchange cartridge has a bundle of capillary tubes extending from a first bundle end to a second bundle end. The bundle is arranged to provide interstitial space between and among outside surfaces of the tubes. The capillary tubes are constructed of a polymer permeable to a liquid coolant. A cartridge housing surrounds the bundle and provides an inlet for receiving air flow to the interstitial space and an outlet for exhausting the air flow. A sealant, such as epoxy, is preferably used to closing the interstitial space portion of the first end of the bundle while interiors of the tubes remain open at the first end for receiving a liquid coolant. At the second, opposite end, the tube interiors are closed, again by a sealant, such as epoxy, and the interstitial space surrounding the plugs tube ends can be left open and unsealed to provide an exhaust path for the air flow passing through the space between and among the capillary tubes. 
     The system further provides a liquid coolant reservoir operatively connected to the bundle first end for presenting a liquid coolant to the tube interiors at the first end and an air blower for supplying an air flow to the cartridge housing inlet. With this system, relatively dry and warm air flow forced by the blower through the interstitial space can be cooled and moistened by evaporation of a liquid coolant at the outside surfaces of the tubes and exhausted from the cartridge as a relatively cool and moist air flow for distribution to selected areas of the user&#39;s body, for example, under a vest in a torso region, or to a helmet or cooling collar. 
     The coolant fluid can be stored in a reservoir housed together with the cartridge or it can be held in a separate container, such as a water bottle, and fluidly connected to the cartridge enclosure through a tube. Similarly, the air blower and a replaceable power supply, such as a battery pack, can be housed with the cartridge or located apart and connected by an air tube. Preferably, the moisture exchange cartridge, the coolant reservoir, the air blower and the power supply are housed together in a compact device enclosure that is sized to fit conveniently in a pouch or pocket on the wearer, such as in a fanny pack, a back pack or on a vest. 
     The device enclosure is preferably equipped with a closeable opening for refilling the coolant reservoir, a closeable door for accessing the replaceable power supply and a removable cap for accessing the moisture exchange cartridge. To provide quick access to the features, particularly without removing from a storage pouch, the opening, the door and the cap are each accessible from a top of the device enclosure. 
     The cartridge can be replaceable and removably installed in a enclosure shell. The shell can provide an air intake opening for permitting the passage of air flow from the air blower to the cartridge inlet and an air outlet opening for permitting the release of air flow from the cartridge outlet to outside the device enclosure. The shell can also provide a coolant interface opening for permitting coolant access to the tube interiors at cartridge first end. This cartridge shell can be closed by a removable cap with the shell air outlet located on the cap. The air outlet can provide a rim or other interface for attaching a distribution tube or hose. 
     In addition to supplying forced air to the moisture exchange cartridge, a conduit provided within the device enclosure for routing air flow from the air blower to the cartridge shell intake can also provide a reservoir duct for routing airflow from the air blower to the coolant reservoir to pressurize the coolant reservoir. 
     The moisture exchange cartridge is preferably shaped as a cylindrical housing surrounding a cylindrically arranged tube bundle. The cartridge housing inlet can be formed as a series of two or more openings around the periphery of cartridge housing adjacent the first end. The cartridge housing outlet can be formed as an open top at the second end of the housing. 
     At the interface between the liquid coolant from the reservoir and the open ends of the capillary tubes, it is preferred to have a liquid coolant transport media, for example, a sponge material, contacting said bundle first end for absorbing liquid coolant from the coolant reservoir and presenting the liquid coolant to the bundle first end. The liquid coolant transport media has a lower capillarity than the capillary tubes to ensure the uptake of the liquid from the media material to the tube interiors. In this way, liquid coolant can be consistently supplied to the bundle first end even when liquid coolant levels in the coolant reservoir are low or fluctuate with movement. 
     The system according to aspects of the invention can be used in conjunction with a vest having a ventilation channel and holes facing the wearer&#39;s body and a distribution tube for routing air flow from the device enclosure to ventilation channel. 
     In operation, a liquid coolant is driven from the reservoir into the internal capillaries of the hollow tubes and further to the external surface of the hollow tubes across the membrane itself. A relatively hot and dry air flow is introduced by the blower under the housing of the cartridge through the air inlet and forced to move over the membrane through the interstitial spaces between the bundled tubes. The adsorption of latent heat required for the vaporization of the liquid occurring on the external surfaces of the hollow tube cools and humidifies the passing air which is discharged at the air outlet of the device. The mechanism for the transport a liquid through the membrane, particularly across the walls of the hollow tubes, depends on the nature of membrane material. Membranes made of a sulphonated fluoroethylene (PTFE) and well-known as a proton exchange membrane (PEM) are able to transfer only water due to highly hydrophilic properties of sulphonic acid groups. A membrane produced from synthetic micro-porous materials (for example, polysulfone) is permeable also for alcohol-based liquid (ethanol, isopropanol, and their aqueous solutions) to provide a cooling effect at a damp ambient condition when water is not useful. A synthetic membrane having an asymmetric structure with pores widening as they extend to the external surface of the hollow tubes can be more preferable for evaporation. 
     The blower of the air conditioning device is electrically powered with an internal replaceable battery unless a user is in possession of portable power supply, for example, a soldier wearable power system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a cross-section view of a personal air conditioning device accommodating a tubular moisture exchange cartridge in accordance with preferred aspects of the invention. 
         FIG. 2A  is a cross-section view of the tubular moisture exchange cartridge. 
         FIG. 2B  is a close up excerpt from  FIG. 2A , showing the sealed intake end with open tubes. 
         FIG. 2C  is a close up excerpt of  FIG. 2B , showing the opening discharge end with closed tubes. 
         FIG. 2D  is a section view along line A-A from  FIG. 2A . 
         FIG. 3  is a perspective view of a wearable personal air conditioning device equipped in a wearable pouch and supplying to a vest, collar and helmet. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts, an exemplary personal air conditioning device is shown in  FIG. 1  and generally designated by the reference numeral  100 . The personal air conditioning device  100  can include a tubular moisture exchange cartridge  110 , a device enclosure  120 , an air blower  130 , a replaceable power supply  140 , a water transferable media  150 , preferably a porous sponge, inside a liquid coolant reservoir  181 . 
     The tubular moisture exchange cartridge  110  as shown in  FIGS. 2A-D , can include a bundle  111  of polymer membrane hollow capillary tubes  112  having micro-porous structure and a cartridge housing  113  accommodating the bundle  111 . The capillary tubes  112  provide an interstitial space  118  between and among the capillary tubes  112 . The cartridge housing  113  is preferably generally cylindrical. The bundle  111  at a first edge facing an intake side  114  of the tubular moisture exchange cartridge  110  can encapsulated with sealant  116   a , preferably with an epoxy resin, but has internal capillaries of the hollow tubes  112  open. The sealant  116   a  can be applied using a centrifuge to control the extent of sealant penetration into the bundle length, preferably only deep enough to provide a closed end to the cartridge at the intake side  114 , with temporarily clogged tubes. The clogged tube tips and adjacent sealant can then be cut away, leaving open tube ends and the remaining portion of the sealant closing the interstitial space portion of the intake end  114  as shown in  FIG. 2B . At the other edge facing a distribution side  115  of the cartridge  110 , the bundle  111  ends with the loose hollow tubes  112  having internal capillaries clogged with sealing media  116   b , preferably with an epoxy resin. The housing  113  has openings  117  in proximity to the intake side  114  of the tubular moisture exchange cartridge  110 . 
     The tubes  112  can form a collective membrane made of a material permeable to a liquid coolant, such as water and alcohol. The material can include sulphonated fluoroethylene (PTFE) well-known as a proton exchange membrane (PEM) able to transfer only water due to highly hydrophilic properties of sulphonic acid groups. A membrane produced from synthetic micro-porous materials (for example, polysulfone) is permeable also for alcohol-based liquid (ethanol, isopropanol, and their aqueous solutions) to provide a cooling effect at a damp ambient condition when water is not useful. A synthetic membrane having an asymmetric structure with pores widening as they extend to the external surface of the hollow tubes can be more preferable for evaporation. Water permeable membranes can also be used in survival applications, in which salt water or even urine may be used as a coolant, subject to more frequent replacement of the moisture exchange cartridges. 
     Referring again, to  FIG. 1 , the device enclosure  120  can have a cap  123  hermetically covering a water refilling opening  124 , a cartridge cover  121  hermetically adjusted to the distribution side  115  of the tubular moisture exchange cartridge  110  by means of an o-ring  160   a  and a thread  125  and a utility cover  122  allowing an assess to a replaceable power supply  140 . Internal configuration of the device enclosure  120  divides its interior into the liquid reservoir  181 , a shell  182  accommodating the tubular moisture exchange cartridge  110  and a compartment  183  housing the air blower  130  and the replaceable power supply  140 . A top of the liquid reservoir  181  is in fluid communication with an outlet of the blower by means of a duct  126  to pressurize the liquid reservoir  181 . A perimeter of the intake side  114  of the tubular moisture exchange cartridge  110  inserted in the shell  182  is sealed by means of the o-ring  160   b  as the cartridge cover  121  is tightly screwed into the device enclosure  120  through the thread  125 , pressing the moisture exchange cartridge  110  into sealing engagement with the o-ring  160   b . The cover  121  is also sealed with the shell  182  by the tightening of the cover  121 . 
     The use of a liquid reservoir  181  pressurized by the air blower  183  through a duct  126  or similar air supply can provide an additional advantage of providing a pressure assisted drinking source from the reservoir  181 . A drinking tube  184  can optionally be installed through the refilling opening  124  of device enclosure  120  and routed, for example, from a waist area location of the device to an area near the user&#39;s mouth. The reservoir  181  can hold potable water. Because the liquid reservoir  181  is under pressure (e.g. about 40 cm of water), the drinkable water is elevated along the tubing  184  extending to the user&#39;s mouth area. With a relatively small suction effort, the user can drink directly from the liquid reservoir  181 . The cooling device  110  can simultaneously serve as a source of drinkable water delivering water on demand with no user hand involvement. 
     In operation, a liquid intended for vaporization is taken by means of mainly a strong capillary action of the capillary tubes, and consequently, from the liquid reservoir  181  and the liquid transport media  150  (sandwiched between the bottom of the liquid reservoir  181  and the intake end  114  of the moisture exchange cartridge  110 ). The liquid transport media  150  is preferably a sponge material, but in any event is selected to have less capillarity than the capillary tubes  112 . The use of the liquid transport media  150  helps to insure a prolonged supply of liquid coolant o the intake side of the cartridge  110  even as fluid levels in the reservoir  181  drop or change due to movement of the user. From the reservoir  181  with or without the liquid transport media  150 , the liquid coolant is drawn into the dead-ended internal capillaries of the hollow tubes  112  and, further, to openings of pores on external surface of the hollow tubes  112  (see  FIG. 2C ). The blower  130 , powered with the replaceable power supply  140 , delivers relatively hot and dry air into the shell  182  and, then, into the cartridge housing  113  of the tubular moisture exchange cartridge  110  through the openings  117 . The air is cooled while flowing within the moisture exchange cartridge  110  through the interstitial space between and among the outer surfaces of the tubes  112  towards the a distribution side  115  due to the adsorption of latent heat required for the liquid evaporation occurring on openings of pores on the hollow fiber external surfaces. 
     The liquid reservoir  181  can also be under pressure developed by the blower  130 , supplied through the duct  126 . As result, a pressure gradient P 2 -P 1  is created between the intake end  114  and the air distribution end  115  of the moisture exchange cartridge  110 , more particularly, between the internal capillaries of the hollow tubes  112  and the housing  113  of the tubular moisture exchange cartridge  110 , in order, first, to enhance liquid transport for a vaporization, and second, to prevent a gasification of internal capillaries of the hollow tubes  112  with the air delivered under the housing  113  by the blower  130 . 
     A liquid coolant refilling of the personal air conditioning device  100  is provided through the liquid refilling opening  124  while the cap  123  of the device enclosure  120  is open. An exchange of the replaceable power supply  140  is accomplished while the utility cover  122  is open. An exchange of the tubular moisture exchange cartridge  110  is performed by means of unscrewing the cartridge cover  121  being replaced from the shell  182  of the device enclosure  120 . 
     As shown in  FIG. 3 , an air conditioning device  190  is preferably configured to be wearable. The device  190  can be stored in a pouch  200  of a garment, such as belted waist pack  210 —sometimes referred to as a fanny pack. A distribution tube  220  can be provided to route cooled air from the device  190  to ventilation channels  230  in a vest  240  for cooling a torso, a ventilated collar  250  for cooling a neck region or a ventilation ring  260  for cooling a head region under a hat or helmet  270 . 
     The device  190  is constructed similarly to the device  100  as shown in  FIG. 1 . However, as an alternative, the liquid coolant reservoir can be provided in a separate container  280 . The separate container  280  is pressured, for example, through a pressure tube  282  supplying air from the blower  284 . The pressurized separate container  280  supplies coolant directly to the moisture exchange cartridge  286  through a tube  290 , which can also provide a drinking tube branch  292  that can be secured to the vest  240  and provide a source of water at shoulder level that is pressure assisted for easier drinking. 
     Although various examples and preferences for implementing aspects of the invention have been described with varying degrees of detail in this disclosure, such details are not intended to limit the scope of the invention. Rather, it is intended that the legal scope of protection for the various aspects of the invention should be determined by the following claims.