Abstract:
A ultrasonic transducer is associated with a heat exchanger and is operable to vibrate a tube associated with the heat exchanger to break up accumulated solids which may have formed on an outer periphery of the tube. A gas flow passes over the tube to remove the pulverized solids.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a heat exchanger, which operates to cryogenically cool a gas flow, such as air, and wherein an ultrasonic vibrator is associated with the heat exchanger to cause the breakup of accumulated solids which have been separated from the gas flow. 
         [0002]    Heat exchangers to cryogenically cool a gas flow are known for various reasons. In one application, air may be cryogenically cooled. 
         [0003]    In another application, air being processed for use in an enclosed space, such as a spacecraft or spacesuit, must be processed. It is known to use alternate sieve beds to absorb carbon dioxide and water from the airflow in one sieve bed, and at the same time recycle the sieve material through a desorb process in an alternate sieve bed. 
         [0004]    These applications require somewhat large space, and are unduly complex. 
         [0005]    It is known to associate an ultrasonic transducer with a heat exchanger for cleaning the heat exchanger. However, in general, these systems have used the ultrasonic transducer as a separate tool periodically brought in to clean the heat exchanger surfaces. 
       SUMMARY OF THE INVENTION 
       [0006]    In a disclosed embodiment of this invention, a gas flow is cooled at a heat exchanger. An ultrasonic vibrator vibrates the heat exchanger to break up accumulated solids which have been removed from the gas flow. A working fluid passes over the heat exchanger while the vibration is occurring to remove the broken up solids. In one disclosed embodiment, the gas flow may be air, and cryogenic cooling can remove CO 2  and water from the air flow. The buildup of accumulated CO 2  and water can greatly diminish the heat transfer effect, and by breaking up the accumulations the heat transfer characteristics are maintained. 
         [0007]    In another disclosed embodiment, a pair of heat exchangers is associated with valves such that an air flow is passed over a first cooling heat exchanger in a “removal” step, while an alternate flow of purge gas passes over the second heat exchanger. CO 2  and water freeze out of the airflow and accumulate on the heat exchanger. The heat exchanger being purged is subjected to ultrasonic vibrations such that accumulated CO 2  and water solids are broken away from the heat exchanger, and removed by the purge gas. 
         [0008]    In this manner, carbon dioxide and water can be removed from an airflow to very low levels, such that the air flow can be used as air in an enclosed space, such as an aircraft or a space suit. 
         [0009]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  schematically shows a heat exchanger. 
           [0011]      FIG. 2A  shows a first heat exchanger tube with accumulated solids. 
           [0012]      FIG. 2B  shows broken up or pulverized solids after vibration has been applied. 
           [0013]      FIG. 3  shows one application for the inventive system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]      FIG. 1  schematically shows a heat exchanger  10  having an outer housing  12  and a plurality of tubes  14 . Air passes between the housing and the tubes and a sub-cooled refrigerant passes through the tubes  14 . The refrigerant cools the gas flow. In disclosed embodiments, the refrigerant cryogenically cools the gas flow, but other cooling temperatures which “freeze” components from a gas flow come within the scope of this invention. 
         [0015]    A ultrasonic transducer  15  is attached to the housing, and either continuously or periodically vibrates the housing. While many different transducers can be used, a 20 khz vibrating cleaner available as a Brandon Ultrasonic Cleaner, may be utilized. 
         [0016]    As shown in  FIG. 2A , accumulated solids  18  can build up on an outer surface  16  of the tubes  14 . As an example, CO 2  and water can freeze out of the air flowing over the tubes  14 . 
         [0017]    When subject to ultrasonic vibration, as shown in  FIG. 2B , the solids pulverize or otherwise breakup at  20 . Gas flowing over the tubes such as the air to be cooled, can then remove the pulverized solids. In one application, the gas flowing over the tubes  14  may be air to be cryogenically cooled. When air is cryogenically cooled, CO 2  and water freeze out of the air, and can form the solids such as shown at  18  in  FIG. 2A . By continuously vibrating the heat exchanger  10 , the solids are pulverized, and will flow with the airflow heading to a downstream use. The vibration can also occur periodically. In this manner, the cryogenic cooling of the air can occur quite efficiently. Testing of this application shows that the vibration removes substantially all of the solids. 
         [0018]      FIG. 3  shows a system  40  which utilizes this ultrasonic vibration to process a gas flow. As shown, a first heat exchanger  42  and a second heat exchanger  44  each include tubing  46 . Tubing  46  each communicate with a refrigerant system such that they cryogenically cool gas flowing over them within the heat exchangers  42  and  44 . A valve  48  alternately routes air from a source  50  through one of the heat exchangers and through a second valve  52  to an outlet  54 . Outlet  54  may head into an enclosed air usage, such as a spacecraft or space suit. 
         [0019]    On the other hand, a source of purge gas, which could be nitrogen, passes through the valve  52 , across the heat exchanger  44  which is not receiving the air, and back through the valve  48  to a downstream use  58  such as being delivered outside of the environment. Other valving systems to alternate the gas flows may be used. 
         [0020]    Now, air which is to be delivered into the use  54  passes over the heat exchanger  42 . The air is cryogenically cooled, and carbon dioxide and water are removed from the airflow as buildup on the tube  46 . At the same time, the other heat exchanger  44  is subject to ultrasonic vibration, and the previously accumulated CO 2  and water on its heat exchanger  46  is pulverized, and carried away by the purge gas  56 . After a period of time, the valves  48  and  52  are reversed, and the heat exchanger  42  will move into a purge mode, while the heat exchanger moves into a CO 2  and water removal mode. A control controls the vibrators  15  to run on the heat exchanger in the purge mode and not run vibrator on the heat exchanger removing CO 2  and water. 
         [0021]    By utilizing this basic convention to assist in removing carbon dioxide and water, air to be supplied into an enclosed space can be properly treated to remove carbon dioxide and water to acceptable levels with a very unique and efficient system. 
         [0022]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.