Abstract:
Provided are a pileus-gills type helium condenser and an apparatus, including the same, for condensing helium. The pileus-gills type helium condenser includes: a body having a hemispheric shape and formed of a highly thermally conductive metal; a plurality of cooling fins collectively having a pileus gills-like shape and arranged along the circumference of the body to be spaced apart from one another; and a through-hole formed in the center of the body to be adjacent to the cooling fins.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0003739, filed on Jan. 16, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a helium condenser for recondensing helium gas resulting from the evaporation of liquid helium contained in an insulated tank, and an apparatus including the helium condenser. 
         [0004]    The present invention is derived from a research project supported by the Atomic Energy Research &amp; Development (R&amp;D) Program of the Ministry of Education, Science, and Technology [M2070605000108M060500110, Development of Superconducting Cyclotron Main Technology]. 
         [0005]    2. Description of the Related Art 
         [0006]    In general, liquid helium boils at a temperature of 4 K, and is used in a device, such as a small measuring device requiring a very low temperature, an electromagnet for a magnetic resonance imaging device, or a superconducting cyclotron. 
         [0007]    However, liquid helium contained in a tank tends to evaporate into helium gas because it is practically difficult to maintain the temperature of the tank below 4 K. If the liquid helium contained in the tank continuously evaporates into the helium gas, however, the water level of the liquid helium contained in the tank is lowered due to the pressure of the helium gas resulting from the evaporation of the liquid helium, such that a sufficient amount of liquid helium cannot be injected into the liquid helium. Also, if the helium gas leaks outside of the tank, there is an economic loss because helium is expensive. 
         [0008]    In order to overcome such problems, a conventional apparatus for condensing helium is disposed in the tank. 
         [0009]    The conventional apparatus is configured such that the helium gas resulting from the evaporation of the liquid helium in the tank is extracted from the tank by a pump, is liquefied by a separate device, which is located outside the tank and uses a large heat exchanger, and then is injected again in liquid form in the tank. 
         [0010]    However, the conventional apparatus is complex, large, and expensive, and takes up much space because it needs to be installed outside the tank. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides a helium condenser, which is disposed in a helium tank, has a small size, and provides high cooling efficiency, and an apparatus for condensing helium, the apparatus including the helium condenser. 
         [0012]    According to an aspect of the present invention, there is provided a pileus-gills type helium condenser comprising: a body having a hemispheric shape and formed of a highly thermally conductive metal; a plurality of cooling fins collectively having a pileus gills-like shape and arranged along the circumference of the body to be spaced apart from one another; and a through-hole formed in the center of the body to be adjacent to the cooling fins. 
         [0013]    The pileus-gills type helium condenser may further comprise an auxiliary cooling cap coupled to an upper portion of the body and covering the cooling fins to be spaced apart from the cooling fins. 
         [0014]    The pileus-gills type helium condenser may further comprise: a helium guide part having a conical shape and inserted into the through-hole; and a connecting part coupled to the auxiliary cooling cap. 
         [0015]    According another aspect of the present invention, there is provided an apparatus for condensing helium, the apparatus comprising the pileus-gills type helium condenser. 
         [0016]    The apparatus may further comprise a helium retrieving pipe disposed under the pileus-gills type helium condenser and comprising a taper part whose cross-sectional area increases toward the pileus-gills type helium condenser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0018]      FIG. 1  is a cross-sectional view of an apparatus for condensing helium, according to an embodiment of the present invention; 
           [0019]      FIG. 2  is an exploded perspective view of a pileus-gills type helium condenser of the apparatus of  FIG. 1 , according to an embodiment of the present invention; 
           [0020]      FIG. 3  is an assembled perspective view of the pileus-gills type helium condenser of  FIG. 2 ; 
           [0021]      FIG. 4  is an enlarged view of portion “A” of  FIG. 3 ; 
           [0022]      FIG. 5  is a perspective view of the pileus-gills type helium condenser of  FIG. 3  viewed in a different direction from that in which the pileus-gills type helium condenser of  FIG. 3  is viewed; 
           [0023]      FIG. 6  is a perspective view illustrating cooling fins of the pileus-gills type helium condenser of  FIG. 2 ; and 
           [0024]      FIG. 7  is a partial cutaway view of the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0026]      FIG. 1  is a cross-sectional view of an apparatus  10  for condensing helium, according to an embodiment of the present invention.  FIG. 2  is an exploded perspective view of a pileus-gills type helium condenser  20  of the apparatus  10  of  FIG. 1 , according to an embodiment of the present invention.  FIG. 3  is an assembled perspective view of the pileus-gills type helium condenser  20  of  FIG. 2 .  FIG. 4  is an enlarged view of portion “A” of  FIG. 3 .  FIG. 5  is a perspective view of the pileus-gills type helium condenser  20  of  FIG. 3  viewed in a different direction from that in which the pileus-gills type helium condenser of  FIG. 3  is viewed.  FIG. 6  is a perspective view illustrating cooling fins  24  of the pileus-gills type helium condenser  20  of  FIG. 2 .  FIG. 7  is a partial cutaway view of the apparatus  10  of  FIG. 1 . 
         [0027]    Referring to  FIGS. 1 through 7 , the apparatus  10  uses natural convection, and thus it does not require a separate pump. 
         [0028]    The apparatus  10  includes a tank  12  containing liquid helium, and a Gifford-McMahon refrigerator (referred to as a refrigerator hereinafter) disposed over the tank  12  and maintaining the temperature of the pileus-gills type helium condenser  20  below 4 K. The refrigerator  14  is commonly known and thus a detailed explanation thereof will not be given. A liquid helium supply pipe  16  and a liquid helium retrieving pipe  50  are installed in the tank  12 . The liquid helium supply pipe  16  supplies liquid helium to the tank  12 . The liquid helium retrieving pipe  50  retrieves helium gas resulting from the evaporation of the liquid helium from the tank  12  and supplies the retrieved helium gas to the pileus-gills type helium condenser  20 . 
         [0029]    The apparatus  10  includes the pileus-gills type helium condenser  20 . 
         [0030]    The pileus-gills type helium condenser  20  includes a body  2 , cooling fins  24 , an auxiliary cooling cap  30 , and a connecting member  40 . 
         [0031]    The body  22  is formed of highly thermally conductive oxygen-free copper. Here, oxygen-free copper refers to high quality copper that has a purity of higher than 99.99%, an oxygen content of less than 10 ppm, an electrical conductivity of higher than 101% international annealed copper standard (IACS). Also, the oxygen-free copper has high electrical conductivity, thermal conductivity, formability, bendability, resistance to hydrogen embrittlement, and processability. 
         [0032]    The body  22  has a hemispheric shape. A through-hole  28  is formed in the center of the body  22 . The through-hole  28  is adjacent to the cooling fins  24 . A plurality of coupling grooves  26  are formed in an upper portion of the body  22 . A female screw is formed on an inner circumferential surface of each of the coupling grooves  26 . The auxiliary cooling cap  30  and the connecting member  40  are coupled to the body  22  by the coupling grooves  26 . 
         [0033]    The cooling fins  24  are integrally formed with the body  22 . The cooling fins  24  increase an area contacting helium. The cooling fins  24  have a pileus gills-like shape. That is, as shown in  FIG. 6 , the cooling fins  22  consist of a plurality of pieces that are arranged along the circumference of the body  22  and are divided by slits. The cooling fins  24  act as heat exchangers. Upper portions of the cooling fins  24  are integrally formed with the body  22 . The cooling fins  24  may be formed by laser beam machining or discharge machining. 
         [0034]    The auxiliary cooling cap  30  covers the upper portion of the body  22 . The auxiliary cooling cap  30  has a hemispheric shape. The auxiliary cooling cap  30  may be formed of oxygen-free copper like the body  22 . The auxiliary cooling cap  30  is coupled to the upper portion of the body  22 . That is, the auxiliary cooling cap  30  includes a plurality of first coupling holes  32 . The first coupling holes  32  are formed to correspond in position to the coupling grooves  26  formed in the body  22 . The auxiliary cooling cap  30  covers the cooling fins  24  in such a manner that the auxiliary cooling cap is spaced by a small distance from the cooling fins  24 .  FIG. 4  is an enlarged view illustrating that the cooling fins  24  and the auxiliary cooling cap  30  are spaced apart from each other by the small distance. 
         [0035]    The body  22  is connected to the refrigerator  14  by the connecting member  40 . The connecting member  40  may be formed of oxygen-free copper like the body  22 . The connecting member  40  includes a helium guide part  42 , second coupling holes  44 , and a flange  46 . The helium guide part  42  has a conical shape, and is inserted into the through-hole  28 . The helium guide part  42  enables helium gas, which results from the evaporation of liquid helium contained in the tank  12 , to naturally collide with the cooling fins  24 . In detail, the helium guide part  42  guides the helium gas so that the helium gas can more easily flow between the cooling fins  24 . 
         [0036]    The second coupling holes  44  are formed to correspond in position to the first coupling holes  32  of the auxiliary cooling cap  30  and the coupling grooves  26  of the body  22 . As shown in  FIG. 3 , the connecting member  40 , the auxiliary cooling cap  30 , and the body  22  are screwed to the pileus-gills type helium condenser  20  by sequentially passing fastening means, such as bolts, through the second coupling holes  44  and the first coupling holes  32 . The flange  46  is an upper portion of the connecting member  40 . The refrigerator  14  and the pileus-gills type helium condenser  20  are coupled to each other by the flange  46 . A plurality of insertion holes  48  for coupling the tank  12  to the pileus-gills type helium condenser  20  are formed in the flange  46 . The tank  12  and the pileus-gills type helium condenser  20  are coupled to each other by passing fastening means, such as bolts, through the insertion holes  48 . A plurality of assembly holes  49  for coupling the refrigerator  14  to the pileus-gills type helium condenser  20  are formed in the center of the flange  48 . 
         [0037]    The liquid helium retrieving pipe  50  is disposed under the pileus-gills type helium condenser  20 . The liquid helium retrieving pipe  50  includes a taper part  52  whose cross-sectional area increases toward the pileus-gills type helium condenser  20 . The taper part  52  enables the helium gas resulting from the evaporation of the liquid helium contained in the tank  12  to effectively flow into the pileus-gills type helium condenser  20 . 
         [0038]    The operation of the apparatus  10  constructed as described above will now be explained with reference to a path through which helium flows when the helium condenser  20  is installed in the apparatus  10 . It is assumed that the helium condenser  20  is installed in the tank  12  as shown in  FIG. 1 . 
         [0039]    Helium molecules of liquid helium contained in the tank  12  evaporate from a water surface into helium gas. The helium gas moves upward in the tank  12 . The helium gas collides with the cooling fins  24  of the pileus-gills type helium condenser  20  which are installed in an upper portion of the tank  12 . The temperature of the cooling fins  24  is maintained below 4 K by the refrigerator  14 . Since the cooling fins  24  have a very large surface area, the cooling fins  24  effectively transfer heat of the helium gas and help the helium gas to be liquefied. In this process, the helium guide part  42  naturally guides the helium gas to the cooling fins  24 . The helium gas passing through the slits formed between the pieces of the cooling fins  24  collides with the auxiliary cooling cap  30  covering the cooling fins  24 . Since the temperature of the auxiliary cooling cap  30  is maintained below 4 K by the refrigerator  14 , the helium gas is liquefied. The helium gas colliding with the cooling fins  24  and the auxiliary cooling cap  30  transfers its heat to the cooling fins  24  and the auxiliary cooling cap  30 , is liquefied, and is retrieved to the tank  12 . The taper part  52  formed on the liquid helium retrieving pipe  50  more effectively guides the helium gas from the tank  12  to the pileus-gills type helium condenser  20 . 
         [0040]    Since the apparatus  10  has a maximum cooling area due to the pileus-gills type helium condenser  20 , the heat of the helium gas can be effectively transferred to the cooling fins  24  and the helium gas can be liquefied with high yield. Also, the helium guide part  42  can naturally guide the helium gas to the cooling fins  24  that are cooling media. Also, the auxiliary cooling cap  30  can additionally cool and liquefy some of the helium gas not contacting the cooling fins  24 . 
         [0041]    Although the pileus-gills type helium condenser  20  of  FIGS. 1 through 7  includes the auxiliary cooling cap  30  that is coupled to the upper portion of the body  2 , is spaced apart from the cooling fins  24 , and covers the cooling fins  24 , the present invention is not limited thereto and the auxiliary cooling cap  30  may be omitted. 
         [0042]    Although the pileus-gills type helium condenser  20  of  FIGS. 1 through 7  includes the connecting member  40  that includes the conical helium guide part  42  inserted into the through-hole  28  and is coupled to the auxiliary cooling cap  30 , the present invention is not limited thereto and the connecting member  40  may be omitted as long as the refrigerator  14  can be properly coupled to the pileus-gills type helium condenser  20 . 
         [0043]    Although the apparatus  10  of  FIGS. 1 through 7  includes the helium retrieving pipe  50  that is disposed under the pileus-gills type helium condenser  20  and includes the taper part  52  whose cross-sectional area increases toward the pileus-gills type helium condenser  20 , the present invention is not limited thereto and the taper part  52  may be omitted. 
         [0044]    As described above, the pileus-gills type helium condenser according to the present invention can achieve maximum cooling efficiency, even with a small structure, by significantly increasing the surface area of the cooling fins contacting and cooling helium. 
         [0045]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.