Abstract:
A cold trap heat exchanger with a horizontal and vertical arrangement of vaporization chambers, with vibration pads for vehicle use. Vaporization pipes each have a series of thermo vanes mounted on horizontal arranged pipes. This fluid controls the vaporization of the liquid fluid and surface area causing a liquid film on surface area varies of both tubes and pipes to occur, and this increases the facilitate refrigeration. The pneumatic chambers are filled with liquid N 2 . These gases are controlled through regulated orifice for back pressure on gas turbines used to move atmosphere circuits across cold trap tubes and veins and flow through vanes for cooling control of designed areas and chambers in cooling application that may be required for cooling.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a non-provisional application of U.S. Provisional Application No. 61/802/806, filed Mar. 18, 2013, entitled: LIQUID NITROGEN &amp; CARBON DIOXIDE THERMO VANES COLD TRAP EXCHANGER AND, and claims the filing priority and benefit of the provisional application, the disclosure of which is incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention is to clean up the atmosphere and improve natural cycling for plant life. 
         [0003]    A number of refrigerants and processes being used for refrigeration systems contribute pollution to the atmosphere. The present cryogenic process eliminates the release of Freon and other gases that are harmful to air and natural photon cycling. 
         [0004]    After cooling with liquid nitrogen, the liquid nitrogen is transformed to a gas and the heat exchanger process is complete. This releases only pure nitrogen to the atmosphere. Nitrogen is clean and it accelerates nitrogen fixation for natural growth of nature&#39;s plants. 
         [0005]    This invention relates to a liquid nitrogen thermo vane heat exchanger that is particularly well suited for refrigerated transportation storage containers. 
         [0006]    Refrigerated trucks and other refrigerated transportation containers typically use conventional refrigerating systems operated by diesel engines. In such systems, a compressor operated by the diesel engine compresses a gaseous refrigerant until it is transformed into a liquid. The pressure on the liquid is then released through an expansion valve, and the refrigerant is passed through a heat exchanger, and this absorbs heat and chills the heat exchanger coils, thus cooling the container. While this system is in use widely, there are a number of drawbacks with this system. 
         [0007]    Diesel engines are noisy, dirty and require fuel and need repairs from time to time. They also produce undesirable gaseous emissions. The refrigerating units themselves typically use fluro-chemical type compounds, which are an undesirable pollutant when released occasionally into the atmosphere. At present, no safety alarms are needed for this condition. The newest version uses a process known as Thermo Cycling. The process turns on or off the cooling unit when specific temperatures are reached. This process allows the food container atmosphere to maintain temperatures as low as 20 degrees. This process, along with the practice of running the devices at a higher average temperature, are methods employed to save on fuel costs, without losing safety of food. 
         [0008]    A number of refrigerants and processes can be used for refrigeration systems. Liquid nitrogen is one such refrigerant. Liquid nitrogen vaporizes at a much lower temperature than the currently used gaseous refrigerant and thus provides a much colder refrigerant than the conventional gaseous refrigerant when released through a heat exchanger. Liquid nitrogen is available in pressurized containers and can be released through a thermo vane heat exchanger and then can provide power for gas turbines before being released to the atmosphere. Since nitrogen is a major component of air, the release of nitrogen poses no pollution threat. 
         [0009]    It is an object of the present invention to provide a liquid nitrogen refrigeration system having improved and controlled cooling characteristics which is also useful in cold traps for a food processor. 
       SUMMARY OF THE INVENTION 
       [0010]    A liquid nitrogen thermo vane heat exchanger comprises a vertical array of alternating vaporization chambers and pressure control chambers connected together in series. The vaporization chambers each have a plurality of thermo vanes mounted in exterior loops along the exterior of the chamber. The thermo vane tubes provide a controlled rate of vaporization of the liquid nitrogen and an increased exterior surface area to facilitate refrigeration. 
         [0011]    In the present invention, the liquid nitrogen vane cooling exchanger comprises a plurality of separate heat exchanger chambers in the form of flat blades mounted in a vertically spaced relationship in a rack. The chambers having thermo vanes on the exterior are alternately positioned with adjacent chambers which are designed with deflector blades in the various chambers. 
         [0012]    The thermo vanes are an important feature of the present invention. They provide a controlled rate of vaporization of the nitrogen while at the same time providing the equivalent of a cooling surface on the heat exchanger to provide added exterior surface area for improving the cooling capacity of the cold trap. Because of the small designed flat surface, liquid nitrogen in the thermo vane tubes cannot flash or boil turbulently in the tubes. Instead, the vanes have a controlling effect on liquid nitrogen that controls the vaporization of the liquid nitrogen. When the nitrogen can vaporize in thermo vanes by the process of film boiling under other conditions as well, when nitrogen vaporizes in thermo vanes by the process of film boiling, a thicker than normal layer of vapor or gas is formed at the wall of the vanes and this insulates the liquid nitrogen from the much warmer wall of the surface. This slows the vaporization rate of the nitrogen. At the same time, the vapor adjacent the walls flows in a laminar flow pattern to the outlet of the thermo vanes and then into the larger interior of the heat exchanger. The laminar flow improves the refrigeration effectiveness of the cold trap. In short, the thermo vanes provide an effective way of controlled vaporization of an otherwise very volatile liquid. 
         [0013]    These and other features and advantages of the present invention are described below in connection with a detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a liquid nitrogen capillary heat exchanger constructed in accordance with the present invention. 
           [0015]      FIG. 2  is a front elevational view of the capillary heat exchanger. 
           [0016]      FIG. 3  is an end view of one of the chambers taken along lines  3 - 3  of  FIG. 2 . 
           [0017]      FIG. 4  is a perspective view showing a cooling tube with capillary tubes employing the capillary tube covering fins of the present invention, with only one representation capillary tube set and cover being shown. 
           [0018]      FIG. 5 , consisting of  FIGS. 5   a    5   b  and  5   c  are schematic diagrams of alternate embodiments of the capillary tube heat exchange of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The basic construction of the heat exchanger of the present invention is similar to the heat exchanger disclosed in applicant&#39;s U.S. Pat. No. 5,582,015, which is incorporated herein by reference and described below. 
         [0020]    Referring to the drawings and more particularly  FIG. 1 , a heat exchanger  10  in which the present invention is employed comprises a series of heat exchanger chambers  12 ,  14  spaced vertically apart in alternating arrangement in a support rack  16 . Support rack  16  comprises a pair of spaced vertical support members  18  positioned at each end of the rack and interconnected by cross-members  20  and longitudinal members  21 . A base  22  is connected at the bottom of the support members and extends outwardly from each side thereof in order to provide support for the rack. 
         [0021]    Chambers  12  and  14  are substantially the same in construction, with the exception that chambers  12  have a series of capillary tubes  24  and  26  spaced along the longitudinal length of each chamber. Chambers  12  desirably are copper pipes  28  having a four and one-half inch O.D. and a wall thickness of ¼ inches. The pipes in the preferred embodiment are about 56 inches long. Caps  30  are removably fitted on the ends of the pipes by welded ends on the pipes and on the interior of the caps or by such suitable fasteners. A pressure tight fit is essential. The pipes are mounted in the rack with the end caps  30  resting on cross-members  20  of the rack and with flexible metal bands  32  extending from the cross-member one side of the cap over the top of each cap and then down into attachment with the cross-member on the other side of the cap. The bands are held in place by removable fasteners. 
         [0022]    While the pipes for chambers  12  and  14  are substantially the same, with the exception of the capillary tubes  32 , for convention, the pipe for chamber  12  will be referred to as pipe  28  and the pipe for chamber  14  will be referred to as pipe  29 . 
         [0023]    Referring to the construction of chamber  12 , pipe  28  includes a series of small openings one-quarter inch in diameter at four separate angularly spaced locations at each of  51  axial positions along the pipe, with each series of openings preferably being spaced axially apart by a distance of one inch. The first three inches at each end of the pipe has no openings. As shown in  FIG. 3 , the openings in pipe  28  comprise a horizontal opening  36  at the left hand side of the pipe, an opening  38  positioned downwardly therefrom by an angle of 45 degrees, an opening  40  positioned downwardly form opening  36  a distance of 78 degrees, and an opening  42  positioned upwardly to the right from a vertical position by a distance of 35 degrees. Capillary tubes  24  and  26 , which are about nine inches long, form elongated loops as shown and are fitted and welded into these openings. Each capillary tube is formed of copper and preferably has a one-quarter inch O.D. and a one-sixteenth ( 1/16) inch I.D. The capillary tubes extend all the way through the walls of the pipes so that the interior of the capillary tubes is in communication with the interior of the pipes. All chambers  12  are of substantially the same construction. 
         [0024]    Pipes  29  have no capillary tubes attached to the outside thereof but can be filled with a heat transmissive particulate material, preferably copper filings  31 . The copper filings improve the heat transfer in the interior of the pipe and also serve to slow down the flow of refrigerant through the pipe so as to maximize heat transferring the interior of the pipe and also serve to slow down the flow of refrigerant through the pipe so as to maximize heat transfer. It is desirable to have the flow of refrigerant through the system be slow enough that the amount of heat that the refrigerant can absorb from the exterior environment is maximized and the back pressure caused by vaporization is controlled. 
         [0025]    As shown in  FIG. 2 , all of the chambers are connected in series, starting from the first chamber at the bottom of the rack (the numbers of the chambers and tubes in serial order from bottom to the top being indicated in parenthesis after the number of the chamber or tube) to the last chamber or ninth chamber at the top of the rack. Pipe  28 ( 1 ) has an inlet  44  at the left hand end ( FIG. 2 ), which is connected through an inlet orifice valve  46  to a conduit  48  leading upwardly thorough relief valve  49  to a suitable source of liquid nitrogen, which is maintained under pressure in a conventional pressurized tank  51  of the type that can be purchased commercially from any number of vendors. The right hand end of pipe  2891 ) is connected through openings in the end cap to a larger pipe  50  and a smaller pipe  52  leading upwardly to corresponding openings in the right hand end cap of pipe  29 ( 2 ). Pipe  50  has a three-quarter inch O.D. and pipe  52  has a one-quarter inch O.D. As shown in  FIG. 2 , the level of liquid nitrogen  54  in pipe  28 ( 1 ) covers the bottom of the pipe and does not fill the entire pipe. And inlet  56  of pipe  50  extends inwardly into the interior of pipe  28 ( 1 ) and then downwardly under the surface of the liquid nitrogen  11  in the pipe, so that pipe  50  will be filled with liquid. The smaller pipe  52  is in communication with the vapor portion of the interior of pipe  28 ( 1 ) and conveys vapor into the next adjacent pipe. Pipe  52  enters the end cape of pipe  29 ( 2 ) in an opening  33  on the left hand side of the end cap on the horizontal axis, while pipe  50  enters the pipe at an opening  35  at the axis ( FIG. 4 ). 
         [0026]    On the left hand side of pipe  29 ( 2 ), a large pipe  58  corresponding with pipe  50  exits pipe  29 ( 2 ) and extends upwardly to the left hand end of  29 ( 3 ), with the pipe exiting from the axis of the pipe and entering in the axis of the next adjacent pipe. A smaller pipe  60  exits from an opening  62  on the right hand side of the end cap at the horizontal axis and extends upwardly into an opening  64  in the upper portion of the end cap on the vertical axis. 
         [0027]    All of the pipes in the heat exchanger are connected in the same way, so that liquid nitrogen enters the heat exchanger in the left hand end of the lowermost pipe for level control, extends backwardly and forwardly through each of the pipes as it moves upwardly through the heat exchanger, and then exits from an outlet opening  66  at the right hand end of the uppermost pipe  2999 ). The movement of the liquid and the gas through the heat exchangers is caused by the vapor pressure of nitrogen as it evaporates in the system. 
         [0028]    Pressure gauges  70 ( 1 )- 70 ( 9 ) are mounted on the respective pipes  28  or  29  ( 1 )-( 9 ) in order to monitor the pressure in each of the pipes. Since back pressure is a critical factor in this system, it is important to maintain proper pressure in each of the pipes. In addition, a pressure valve  72  is connected to outlet  66  of the heat exchanger. This sets the threshold pressure for release of nitrogen. 
         [0029]    The desired pressures in each of the pipes, as indicated by the pressure gauges and the pressure at the outlet pressure valve  72  are set forth in the following table. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 70(1) 
                 24.7 psig 
               
               
                   
                 70(2) 
                 23.2 psig 
               
               
                   
                 70(3) 
                 22.9 psig 
               
               
                   
                 70(4) 
                 21.4 psig 
               
               
                   
                 70(5) 
                 21.3 psig 
               
               
                   
                 70(6) 
                 15.1 psig 
               
               
                   
                 70(7) 
                 12.9 psig 
               
               
                   
                 70(8) 
                  7.5 psig 
               
               
                   
                 70(9) 
                  5.2 psig 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    In addition to the inclusion of copper filings in tubes  29 , it is desirable to include a desiccant to remove moisture from the gas. An aluminum silicate gel, which has the appearance of small pellets works fine for this purpose. 
         [0031]    The tubes  28  do not have the desiccant or copper filings in them but instead are provided with the capillary tubes on the exterior portions of them. The capillary tubes are extremely important features of the present invention. They provide a controlled rate of vaporization of the nitrogen while at the same time providing added exterior surface area for improving the cooling capacity of the heat exchanger. Because of the small diameter of the capillary tubes, liquid nitrogen in the capillary tubes cannot flash or boil turbulently in the tubes. Instead, the capillary tubes have a controlling effect on liquid nitrogen that controls the vaporization of the liquid nitrogen. The nitrogen vaporizes in the capillary tube by a phenomenon known as film boiling. While liquid nitrogen vaporizes by film boiling under other conditions as well, when nitrogen vaporizes in a capillary tube by the process of film boiling, a thicker than normal layer of vapor or gas is formed at the wall of the capillary tube, thus insulating the liquid nitrogen from the much warmer wall of the capillary tube. This slows the vaporization rate of the nitrogen. At the same time, the vapor adjacent the walls flows in a laminar flow pattern to the outlet of the capillary tube and then into the larger interior of the pipe. The laminar flow improves the refrigerating effectiveness of the heat exchanger. In short, the capillary tubes provide an effective way of controlled vaporization of an otherwise very volatile liquid. 
         [0032]    In accordance with the present invention, the construction of the foregoing capillary tube heat exchanger is modified to give the heat exchanger substantially enhanced heat transfer characteristics. In the present invention, the capillary tube loops  24  and  26  are covered with hollow covers or fins  100 , shown in  FIGS. 4 and 5 . Each fin  100  is formed of a heat transmissive material, such as a metal. Copper or other metal with good heat transmission properties is desirable. A somewhat elastic material can be desirable. Fin  100  is a flat, hollow member having spaced sides  104  and  106  and edges  108  joining the sides. The sides may have a rounded outer contour to conform with the rounded outer contours of the capillary tube loops being encased. As shown, a single fin desirably covers both capillary tube loops located at approximately the same axial position on the cooling tube. Separate fins could be used for each loop, but a single fin provides a larger heat transfer surface and is therefore preferred. The fins may be formed of a flexible material that can be deflected somewhat in order to fit the fins over the capillary tube loops. 
         [0033]    The dimensions of the fins corresponds with the dimensions of the capillary tube loops. Desirably, the fins are shaped and the interior sides are spaced apart by a distance sufficient to permit the fin to be inserted over the capillary tube loops with the fin being in at least loose general contact with the loops when installed. 
         [0034]    When the fins are thus installed and in contact with the capillary tubes, the area of the effective cooling surface provided by the capillary tubes is dramatically increased without losing any of the benefits achieved by the narrow size of the capillary tubes. With the construction of the present invention, the effective area of the cooling surface can be increased by as much as 88%. This can result in dramatically decreased cooling tubes for a refrigerator truck. In the refrigerated truck industry, it is desired to be able to drop the refrigerative temperature to −20 degrees in twenty minutes. In one test, a cooling system without cooling fins was able to reduce the temperature only to −18 degrees in this time. With the fins, the temperature was reduced to as low as −40 degrees. While these results are merely exemplary of limited testing, they do reflect that the cooling fins provide a significant improvement in the cooling capabilities of a nitrogen refrigeration system in a truck cooler. 
         [0035]    Heat Exchanger Specifications. The specification of a heat exchange construction in accordance with the present invention are as follows. 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Height 
                    94″ 
               
               
                 Width 
                    72″ 
               
               
                 Depth 
                 72.5″ for thermo vanes, the entire length of trailer 
               
               
                 Weight (empty) 
                 750 lbs. 
               
               
                 Weight (operational) 
                 785 lbs. 
               
               
                 BTU&#39;s (in operation) 
                 48,000 
               
               
                 Operation pressure 
                 20-30 psi (gauged) 
               
               
                 Static Pressure 
                    0 
               
               
                 Barometric Pressure 
                 1009 HPA 
               
               
                 Humidity 
                 Varies with product 
               
               
                 Temp. Control Range 
                 −30° to +170° F. 
               
               
                 Dew Point 
                 Varies with product 
               
               
                 Material 
                 Copper and Stainless Steel 
               
               
                 Gs Type 
                 Liquid Nitrogen 
               
               
                   
               
             
          
         
       
     
         [0036]    A fuel tank for storage and supply of liquid Nitrogen can have the following specifications: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Overall Length 
                 75″ 
               
               
                   
                 Diameter 
                 26′ 
               
               
                   
                 Capacity 
                 100 gal. 
               
               
                   
                 Operating Pressure 
                 20-30 psi (gauged) 
               
               
                   
                 Static Pressure 
                 20-30 psi (gauged) 
               
               
                   
                 Weight (empty) 
                 405 lbs. 
               
               
                   
                 Weight (full) 
                 1195 lbs. 
               
               
                   
                   
               
             
          
         
       
     
         [0037]    One advantage to the use of this cryogenic process for refrigerating vehicles is that gas turbines are running off the exhaust of the fuel source and generating electric power to run electric strip heaters when heat is required for vehicle trailers or storage. As well as the turbines that run the fans of the circulation systems and are released to the atmosphere with 100% heat recovery as well the exhaust from the fans that give cooling efficiency of 100%. Using cooling fins attached to thermo vanes cryogenic activity and heat transfer that is more efficient than existing cooling devices. 
         [0038]    The outlet of thermo vane collectors support the pneumatic supply for control valves and temperatures controls, with 15 psig regulator before exit of system.