Abstract:
The present invention involves plastic-rod-screen-fills for use as fill media in any evaporative water cooling and airborne fumes removal apparatuses. The plastic-rod-screen-fill consists of top and bottom frames and several plastic rods suspending from between the top and bottom frames in the shape of a rectangular thin plate as a rod screen. The plastic rods are separated sufficiently apart from each other in one layer and parallel to the length of the rectangular plastic-rod-screen-fill. The plastic rods and top and bottom frames are in one structure. Plastic-rod-screen-fills are assembled by adjoining to each other to fabricate the plastic-rod-screen-fills pack and designed to be installed upright or slantly in the evaporative cooling apparatuses. The plastic-rod-screen-fills have high manufacturing and installation cost competition, compared with those of current film fills and string-screen-fills. The fabrication methods of plastic-rod-screen-fills and plastic-rod-screen fill packs are described in the present invention.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     References Cited 
       [0000]    
       
         U.S. patent documents; 
         U.S. application Ser. No. 13/053,382, Mar. 22, 2011. Park 
         U.S. Application No. 61/726,928, Nov. 21, 2012. Park 
         U.S. Application No. 61/736,646, Dec. 13, 2012. Park 
       
     
       Foreign Patent Documents 
       [0005]      
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 KR 
                 100393126 
                 Jul. 18, 2003 
                 Park 
               
               
                   
                 KR 
                 100516391 
                 Sep. 14, 2005 
                 Park 
               
               
                   
                 KR 
                 100516392 
                 Sep. 14, 2005 
                 Park 
               
               
                   
                 PCT 
                 WO 2005/008159 A1 
                 Jan. 27, 2005 
                 Park 
               
               
                   
                   
               
             
          
         
       
     
       Other Publications 
       [0000]    
       
         Dominick V. Rosato. et al, Injection Molding Handbook, 3 rd  Edition, Kluwer Academic Publishers. Norwell, Mass. 02061, USA 
         Robert A. Malloy, Plastic Part Design for Injection Molding An Introduction, Department of Plastic Engineering, University of Massachusetts, Lowell, Mass. 01854, USA 
         Http://dehwa.comne.kr/mold/mold.htm 
       
     
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0009]    Not Applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0010]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0011]    1. Field of the Invention 
         [0012]    The present invention relates to evaporative water cooling apparatuses utilizing fill media. More precisely, the present invention relates to the screen type plastic rod fills, being able to be used in evaporative cooling apparatus such as open loop cooling towers, evaporative chiller or cooler, and in airborne fumes removal apparatus like ammonia gas removal apparatus used in livestock facilities, which is fabricated with thin plastic rods, using the unique characteristics of the rods: flowing down of water on the surface of the vertical or slanted rods by gravity, surface tension of the rods strong enough to hold the water on the surface of the rod against the strength of draughts in cooling towers or other apparatuses, and capability of contacting water and cooling air with barely resisting air flowing. 
         [0013]    2. Description of the Related Art 
         [0014]    The fill media used in an evaporative water cooling and air cooling apparatuses like cooling tower, evaporative chiller or air cooler, and flue gas removal apparatuses are string screen fills (SSF) pack which is recently applied for US patent (U.S. patent application Ser. No. 13/053,382, application date: Mar. 20, 2011) or honeycomb shaped fabric cooling pad. The SSFs packs are assembled together a plurality of SSFs, which are in thin plate type and made by winding one long string over a rectangular aluminum frame. The aluminum rectangular frame is fabricated by casting of molten aluminum into a rectangular frame mold and then the winding process of string on the frame is accomplished by using winding automation system. By using such manufacturing lines of two step manufacturing, the mass production of SSFs are accomplished, but high manufacturing cost cannot be eluded. To reduce manufacturing cost of the SSFs, one step manufacturing line is required instead of two step lines. To achieve such an objective of manufacturing screen fill medium by using one step manufacturing line, the frame and string wound on the frame must be simultaneously fabricated at the one step. 
         [0015]    One step manufacturing of frame and string screen is possibly accomplished by casting of molten plastics into a plastic-rod-screen-fill molder, which has a hollowed cavity of the PRSF. To do this, high density polyethylene (HDPE) material is a proper material, since it has properties of rigid and can be rugged construction with ability to withstand without its damage or loss of shape, and also it has chemically inert, low melting temperature of 145° C., and UV resistance, other solid and rigid plastic materials are possible. One step manufacturing of screen fill using HDPE, say plastic-rod-screen-fill (PRSF), is accomplished by fabricating of PRSF using a plastic injection molding machine. The plastic injection molding machine has function of injecting of molten HDPE into PRSF molder and usages of several injection machines can make mass production of the PRSFs with low manufacturing cost. 
         [0016]    The plastic rods consisted of within the PRSF are thin and they have spiral corrugated surface. While water is flowing down on the surface of the plastic rod, the water flows down along the corrugated lines so that the water can flow on longer length than on non-corrugated rod. Eventually, the contacting time of air and water on the surface of the spiral corrugated rod is increased, resulting in increasing the cooling effect of rod by that much rate. 
         [0017]    The purpose of the present invention is a fabrication of plastic-rod-screen-fill (PRSF) being able to reduce the manufacturing cost required for fabrication of string screen fill applied to U.S. patent (U.S. patent application Ser. No. 13/053,382) as well as to simplify the manufacturing line. Another purpose of the present invention is the replacement of current commercial evaporative cooling media with the PRSFs of the present invention. The commercial evaporative cooling media are a cooling pad being used in current commercial evaporative coolers and a thin film plastic fills pack in current cooling towers. 
       SUMMARY OF THE INVETION 
       [0018]    To simplify the manufacturing lines and to reduce manufacturing cost of the fabrication of 100 the SSFs, the PRSF of the present invention is invented and proved to adequate for replacement of the SSFs, since they have several advantages given as follows:
   1. They can be simply fabricated without great efforts through one step automatic manufacturing line using high press molten plastic injection machine.   2. They have a high water cooling efficiencies.   3. They are not attacked by any water chemicals because they are made of inert materials like high density polyethylene.   4. Their service lives are more than 25 years.   5. They deploy a large surface area of contacting water and air in a relatively small volume, thereby maximizing cooling of water.   6. They are of very solid construction without their damage or loss of shape.   7. They are light weight.   8. Their materials are non-toxic, non-hazardous, and suitable for easy and safe disposal at the end of service life.   
 
         [0027]    &lt;Designing and Fabrication of PRSF and PRSFs Pack&gt; The PRSF of the present invention is shown in  FIG. 1  and the schematic picture of the PRSFs Pack is illustrated in  FIG. 2 .  FIGS. 1 and 2  show a single unit of PRSF and an assembled pack by joining several single units of PRSF, respectively, and  FIG. 3-1  shows a top view of rod configuration in the top and bottom plates of the assembled pack, PRSFs pack.  FIG. 3-2  schematically illustrates the picture of the top plate enlarging a part of the top view of the PRSFs pack more in detail. The single unit of plastic-rod-screen-fill, PRSF, shown in  FIG. 1 , is in one structure as shown in  FIGS. 4-1 ,  4 - 2 , and  4 - 3 . The dimension of the standard PRSF shown in  FIG. 1  is 260(Length)×765(Height)×15(Thickness) mm and the diameter and effective length of rod used are 15 mm and 750 mm (750=765−7.5(thickness of perforated plate)×2), respectively. 
         [0028]    Assembling  20  units of the standard PRSFs shown in FIGS.  1  and  4 - 1  and two side  125  support panels of 10 mm thick shown in  FIG. 5 , the standard PRSFs pack as shown in  FIG. 2  is fabricated, whose dimension is 320(Width)×765(Height)×260(Length) mm and top view is schematically illustrated as shown in  FIG. 3-1 . When a longer distance between the rods than that shown in  FIG. 3-1  is required, a gap supporter shown in  FIGS. 6-1  and  6 - 2  is inserted between the PRSF frames. The fabrication of PRSF in one structure of the present invention is accomplished by a plastic injection molding machine. The dies forming one structure of PRSF shown in  FIGS. 4-1 ,  4 - 2  and  4 - 3  are made and then installed in the plastic injection molding machine. The molten plastic melted in the plastic injection molding machine is injected into the dies by high pressing pressure. After enough cooling down in the dies, the skeleton PRSF is taken out of the dies and put into cooling tank enough to be cooled for handling it. To fabricate PRSF with the longer distance between adjacent rods, additional dies for fabricating the gap supporter are necessary and made to simultaneously be used with the PRSF fabrication dies. 
         [0029]    &lt;Fabrication of molders&gt; Fabricating of PRSF without gap supporters needs two half molders. One of these is a molder fabricating the half part of a PRSF shown in  FIGS. 4-1 ,  4 - 2 , and  4 - 3  and the other for fabricating the opposite half part of the PRSF. Each of these is one half piece of molder to be overlapped and designed to easily remove the completely formed PRSF out of the molder. On each half piece of molder, a half part of a PRSF shape is,hollowed and the corrugated lines are carved on the surface of the hollowed half rods as shown in  FIG. 4-1 . The slant corrugated lines are carved to keep the slant angle (15 to 30 degree, other degrees possible) to the length of rod. When the two pieces of the molders are joined together, the carved corrugated lines are smoothly connected without any disconnected lines. For fabricating PRSF with gap supporters, additional molders for fabricating the gap supporter are made. A detailed description of fabrication of molders is given in the section of Detailed Description of Preferred Embodiment. 
         [0030]    &lt;Effect of corrugated lines on surface of plastic rod&gt; The plastic rods consisted of within the PRSF are thin in range of 2.5 to 15 mm in diameter, other diameter is possible, and it has spiral corrugated surface with a 3 to 10 lines on its surface. The spiral corrugated rod is schematically illustrated in  FIG. 7 . As shown in  FIG. 7 , the spiral corrugated lines are slanted to the length of rod. The spiral corrugated lines have effective slant angles of 10 to 30 degree to the length of the plastic rod. When the slant angle is greater than 35 degree, the water flowing on the surface of the plastic rod flows straightly down over the corrugated lines instead of flowing down along the corrugated lines, while the corrugated lines of slant angle less than 10 degree does not make a significant difference between the lengths of corrugated lines and plastic rod. The slant angles preferred in the present invention are 15 to 30 degree. While water is flowing down on the surface of the corrugated plastic rod, the water flows down along the corrugated lines, so that the water can flow on longer length by around 3 to 15% than on non-corrugated rod, since the spiral corrugated lines are longer by about 3 to 15% than the lengths of plastic rod with slant angles of 15 to 30 degrees, respectively. Eventually, the contacting time of air and water on the surface of the spiral corrugated rod increases by 3 to 15% compared with that of the non-spiral corrugated rod. Another effect of the spiral corrugated lines created on the surface of the plastic rod is that the PRSF gets more rigid and stronger. The spiral corrugated lines shown in  FIG. 7  has a shape of triangle hump. Usually a matter  165  in triangle shape is stronger and more rigid than non-triangle shape. Hence, the spiral corrugated rod can be expected to be stronger and more rigid, resulting in getting the PRSF more rigid and stronger 
         [0031]    &lt;Determination of plastic material&gt; The material fabricating the plastic rod used in the present invention is a polystyrene, polypropylene, and polyethylene which have excellent physical and chemical properties such as high melting temperature, high resistance to most chemicals, high tenacity for stretching and shrinking, resistant to ultra violate, and high durability, so that they are suitable for fabrication of PRSF. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1-1  is a schematic picture of perfect PRSF plastic rod screen fill without side panels. 
           [0033]      FIG. 1-2  is a schematic picture of perfect PRSF plastic rod screen fill with side panels. 
           [0034]      FIG. 2  illustrates a schematic picture of PRSFs pack fabricated by assembling several units of PRSFs of 320(Width)×765(Height)×260(Length)mm assembled  20  of PRSFs and with 10 mm thick left and right side panels attached 
           [0035]      FIG. 3-1  shows a partial schematic picture of top and bottom view of PRSFs pack shown in  FIG. 2  whose dimension is 320(Width)×765(Height)×260(Length)mm assembled  20  of PRSFs and left and right side panels (10 mm thick top and bottom frame and 2 mm thick panel) on both sides of PRSFs pack. 
           [0036]      FIG. 3-2  illustrates a schematic picture of enlarged part of top and bottom view of PRSFs pack shown in  FIG. 3-1 . 
           [0037]      FIG. 4-1  illustrates a schematic picture of left and right sides of PRSF shown in  FIG. 1 .  FIG. 4-2  illustrates a schematic picture of the top view of the top frame of PRSF shown in FIGS.  1  and  4 - 1 . 
           [0038]      FIG. 4-3  illustrates a schematic picture of the bottom view of the bottom frame of PRSF shown in FIGS.  1  and  4 - 1 . 
           [0039]      FIG. 5  illustrates a schematic picture of left and right sides of PRSFs pack side panel. 
           [0040]      FIG. 6-1  shows a side view of gap supporter which includes top, bottom, and side frames. 
           [0041]      FIG. 6-2  shows a top view of top and bottom frames of the gap supporter. 
           [0042]      FIG. 7  illustrates the schematic drawing of side view of spiral corrugated lines on the plastic rod. 
           [0043]      FIG. 8  illustrates a top view of perforated top and bottom plates of PRSFs pack assembled a plurality of PRSFs with gap supporters inserted between PRSFs. 
           [0044]      FIG. 9  is a schematic picture of the installation of PRSFs packs in trapezoidal cooling heat exchanging media zone of a trapezoidal type cooling facilities. 
           [0045]      FIG. 10-1  shows a simple illustration of the regular pentagon cooling heat exchanging media using a trapezoidal PRSFs pack. 
           [0046]      FIG. 10-2  shows an enlarged assembling configuration of triangle shape PRSFs packs and rectangular PRSFs pack around the edge of the trapezoidal PRSFs pack cooling media. 
           [0047]      FIG. 10-3  schematically illustrates the top view of one side of the trapezoidal perforated top and bottom plates of the PRSFs pack cooling media as shown in  FIG. 10-1  and  FIG. 10-2  fabricated by assembling trapezoidal shape PRSFs shown in  FIG. 10-4  and  FIG. 10-5 . 
           [0048]      FIG. 10-4  shows the top view of the top and bottom frame of the male trapezoidal PRSF including 2 rods. 
           [0049]      FIG. 10-5  shows the top view of the top and bottom frame of the female trapezoidal PRSF including 4 rods. 
           [0050]      FIG. 11  shows the schematic picture of left and right sides of the trapezoidal PRSFs pack side panel. 
           [0051]      FIG. 12  shows a cross sectional view of a slanted PRSFs pack fabricated by assembling several slanted PRSFs. 
           [0052]      FIG. 13-1  illustrates a top view of half PRSF skeleton hollowed on the lower part of PRSF fabrication molder. 
           [0053]      FIG. 13-2  shows a cross section view of the cavity of top and bottom frames of PRSF created by combining upper and lower parts of PRSF fabrication molder. 
           [0054]      FIG. 14-1  shows a cross sectional view of the male slanted PRFS fabrication molder when the lower and upper parts of the male slanted molder are jointed together. 
           [0055]      FIG. 14-2  shows a top view of the top frame of the male slanted PRSF fabrication molder when the lower and upper parts of the male slanted molder are jointed together. 
           [0056]      FIG. 14-3  shows a bottom view of the bottom frame of the male slanted PRSF fabrication molder when the lower and upper parts of the male slanted molder are jointed together. 
           [0057]      FIG. 15-1  shows a cross sectional view of the female slanted PRSF fabrication molder when the lower and upper parts of the female slanted molder are jointed together. 
           [0058]      FIG. 15-2  shows a top view of the top frame of the female slanted PRSF fabrication molder when the lower and upper parts of the female slanted molder are jointed together. 
           [0059]      FIG. 15-3  shows a bottom view of the bottom frame of the female slanted PRSF fabrication molder when the lower and upper parts of the female slanted molder are jointed together. 
           [0060]      FIG. 16-1  shows an internal top view of the upper part of PRSFs pack side panel fabrication molder. 
           [0061]      FIG. 16-2  shows an internal top view of the lower part of PRSFs pack side panel fabrication molder. 
           [0062]      FIG. 16-3  illustrates a side view of the cross section of PRSFs pack side panel fabrication molder including cavity of PRSFs pack side panel combining the lower and upper parts of the PRSFs pack side panel fabrication molder. 
           [0063]      FIG. 16-4  illustrates a cross sectional view of the cavity of top and bottom frames of PRSFs pack side panel fabrication molder combining lower and upper parts of the PRSFs pack side panel fabrication molder. 
           [0064]      FIG. 17-1  shows the internal top view of upper and lower part of trapezoidal PRSFs pack side panel molder. 
           [0065]      FIG. 17-2  shows the side cross section view of trapezoidal PRSFs pack side panel fabrication molder combined lower and upper parts of molder. 
           [0066]      FIG. 17-3  shows the cross section view of top and bottom frame of trapezoidal PRSFs pack side panel fabrication molder combined power and upper parts of molder. 
           [0067]      FIG. 18  shows the part of plastic rod and the rectangular plane of circumference of plastic rod×length of plastic rod, C(width)×H(length) mm, and rectangular diagonal line showing one circle of spiral corrugated line on rod. 
           [0068]      FIG. 19  shows a schematic picture of die-caster in the shape of the plate type rectangular box for production of 2 of PRSFs at one shot of injection. 
           [0069]      FIG. 20  shows a schematic picture of die-caster in the shape of the plate type rectangular box for production of 4 of PRSFs at one shot of injection. 
       
    
    
     DESCRIPTION OF NUMBER IN THE DRAWINGS 
       [0070]      1  PRSF without side panels (frames),  1 - 1  PRSF with side panels (frames),  2  upper perforated frame,  3  lower perforated frame,  4  hole,  5  spiral corrugated plastic rod,  6  left side panel (frame),  7  right side panel(frame),  8  PRSFs pack,  9  PRSF with plastic rod much closer to the left side edge of PRSF as shown in  FIG. 4-1 ,  10  PRSF with plastic rod less close to the right side edge of PRSF as shown in  FIG. 4-1 ,  11  size reduction gap,  12  PRSFs pack side panel,  13  female attachment tab,  14  male attachment tab,  15  spiral corrugated line,  16  2 mm panel,  17  upper frame of PRSFs pack side panel,  18  lower frame of PRSFs pack side panel,  19  hump for preserving hole,  20  rod cavity for making plastic rod,  21  gap supporter,  22  upper frame of gap supporter,  23  lower frame of gap supporter,  24  PRSFs pack assembled a plurality of PRSFs with gap supporters inserted between PRSFs,  25  image  260  line of side panel,  26  trapezoidal cooling media,  27  stair shape open space,  28  cooling media of regular pentagon cooling facilities,  29  side panel of trapezoidal cooling media,  30  triangle PRSFs pack,  31  trapezoidal PRSF,  32  upper frame of trapezoidal cooling media,  33  lower frame of trapezoidal cooling media,  34  slanted PRSFs pack,  35  male slanted PRSF,  36  female slanted PRSF,  37  PRSF fabrication molder,  38  upper part of PRSF fabrication molder,  39  lower part of PRSF fabrication molder,  40  inlet port of molten plastics,  41  outlet port of molten plastics,  42  cavity of top and bottom frame of PRSF,  43  joining line of upper and lower parts of PRSF fabrication molder,  44  male slanted PRSF fabrication molder,  45  upper part of slanted PRSF fabrication molder,  46  image line of slanted PRSF cavity,  47  lower part of slanted PRSF fabrication molder,  48  female slanted PRSF fabrication molder,  49  upper part of slanted PRSF fabrication molder,  50  lower part of slanted PRSF fabrication molder,  51  joining line of upper and lower parts of slanted PRSF fabrication molder,  52  PRSFs pack side panel fabrication molder,  53  panel cavity hollowed on upper part of PRSFs pack side panel fabrication molder,  53 - 1  inner slight dark flat part  53 - 1  of the lower part molder shown in  FIG. 16-2 ,  54  upper part of PRSFs pack side panel fabrication molder,  55  lower part of PRSFs pack side panel fabrication molder,  56  hollowed hole for preserving hole,  57  humped hole for preserving hole,  58  cavity of PRSFs pack side panel,  59  top frame of PRSFs pack side panel cavity,  60  bottom frame of PRSFs pack side panel cavity,  61  top and bottom frame cavity of PRSFs pack side panel,  62  side panel image of PRSFs pack side panel,  63  side panel image line of PRSFs pack side panel,  64  trapezoidal PRSFs pack side panel fabrication molder,  65 , upper part of trapezoidal PRSFs pack side panel fabrication molder,  66  lower part of trapezoidal PRSFs pack side panel fabrication molder,  67  die-caster in the shape of the plate type rectangular box for production of 2 of PRSFs at one shot of injection,  68  die-caster in the shape of the plate type rectangular box for production of 4 of PRSFs at one shot of injection,  69  PRSF fabrication molder supporter,  70  molten plastic injector,  71  molten plastic inlet port,  72  molten plastic distributor. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0071]    The string screen fills (SSFs) invented by the present inventor have a disadvantage in manufacturing of the SSFs, since they are fabricated through separated two manufacturing lines of molding fabrication of SSF frame and webbing fabrication of winding strings over the SSF frame. Such manufacturing lines have a problem limiting more reduction of the manufacturing cost of SSFs. To complement such a problem, a one step manufacturing line, described above, of the present invention is invented. One step manufacturing means a manufacturing of SSF frame and string winding over the frame within one manufacturing line at a same time instead of individual fabrication through two different manufacturing lines, In other word, the SSF frame and loading string on the frame are completely accomplished in one step same manufacturing. Therefore, one step manufacturing line can reduce by nearly one half of manufacturing time and cost required in the previous manufacturing process claimed in US patent recently applied (U.S. patent application Ser. No. 13/053,382). To meet this object, the strings on the frame are simultaneously formed when the frame of the SSF is fabricated by molding in the first step manufacturing line of the SSF manufacturing process, resulting in no usage of the second step manufacturing line. To do this, materials able to be melt at low temperature are employed instead of string materials. 
         [0072]    There are several factors for designing of the PRSF and PRSFs pack to be determined by conducting experiments and using out sources. The designing factors are extensively examined and determined by conducting several experiments employing SSPs packs in U.S. patent (application Ser. No. 13/053,382) recently applied by the inventor of the present invention. Since the plastic rods used in the present invention are similar materials with polyester strings, those results are applied to designing and fabrication of the PRSFs and PRSFs packs without any significant modification. Only for the verification of the slant angle of plastic rod able to hold the flowing down water on the surface of the plastic rod when the plastic rod is slanted, a simple experiment was carried out. The result shows that the flowing down water is held on the surface of the plastic rod up to slant angle 38 degree. 
         [0073]    The factors for designing the PRSF and PRSFs pack are the number of plastic rods per unit cross section of the PRSFs pack, diameter of the plastic rod holes on the top surface of the PRSFs pack, diameter of the plastic rods, effective length of the rods for effectively cooling water, verification of flying away of water out of rod due to the air blowing rate of fan, and the effect of the corrugated lines on the surface of the plastic rods. Such factors are essential for the effective and economical designing of the PRSF and tabulated in Table 1. 
         [0074]    &lt;Function of PRSFs Pack on Contacting Water and Air&gt; The function of the PRSFs pack  8  to contact water with air on the surface of the rods  5  described in U.S. patent application Ser. No. 13/053,382 and briefly described here. The water is sprayed on the top of the PRSFs pack  8  which has uniformly distributed holes  4  on it and passing through the holes  4 , and then flowing down on the surface of the rods  5  suspending between the top  2  and bottom  3  sides of the PRSFs pack  8 . While the water is flowing down on the surface of plastic rods  5 , the water is cooling warm or hot air by contacting with the air entering the PRSFs pack  8  from its one side and passing through the PRSFs pack  8  towards the opposite side. 
         [0075]    &lt;Determination of Optimum Number of Rods in PRSF&gt; The wider the surface of water to be contacted with air is, the colder the water can be cooled, so that the more number of rods  5  should be used in the PRSF  1  to provide much larger contacting surface between air and water. But too many rods  5  may cause to increase the air pressure drop over the PRSFs pack  8  because the rods  5  are too close each other. Since air pressure drop means a reducing of air flowing rate, the cooling rate of water is decreased, resulting in that outlet water is not cooled enough. To avoid this problem, an optimum number of rods  5  should be used in the PRSF  1 . The optimum number of rods  5  means the maximum number of rods  5  per unit cross area not to resist flowing of air as well as to maximize contacting surface of the rods, The optimum number of rods used in the present invention is 12 rods 
         [0000]                                                                                                                  TABLE 1                   Design Factors of PRSF and PRSFs Pack.            Item   Design Factor                    Diameter   4.5   7.5   10.0   12.5       of Rod (mm)            Hole Diameter   8.7   6.4   14.4   10.6   19.2   14.12   24.1   17.7       on Perforated       Plate (mm)       Specific   15.0   19.0   13.7   19.2   13.0   19.0   12.2   18.0       Surface Area       (ft 2 /ft 3)              Rod #/unit   9/30(9.6 mm hole)   9/46(14.43 mm hole)       area (#of       holes/cm 2)              Effective   150        Length (cm)       Slant Angle   35       (degree)       Standard   300(W) × 750(H) × 7.5(Thickness)       PRS (mm)       Rod # in Stan-   18       dard ORSF(ea)       Standard   300(W) × 750(H) × 300(Thickness)       PRSFs       Pack (mm)                    
per 90 cm 2  for the rod  5  of 1.5 cm in diameter and 1.5 cm between surfaces of rods  5  by employing the data used in other field related with optimum number of rods  5 . Using longer distance between rods  5 , the specific number of rods  5  is 5 rods/90 cm 2  for the rods  5  of 1.5 cm in diameter and 1.83 cm between surfaces of rods  5 .
 
         [0076]    &lt;Designing and Installation of rectangular PRSF and PRSs Pack&gt; The schematic pictures of the PRSF  1  and PRSFs pack  8  of the present invention are shown in  FIGS. 1 and 2 , respectively.  FIG. 1  shows a standard unit of single PRSF  1  and  FIG. 2  a PRSFs pack  8  fabricated by assembling a plurality of standard unit PRSFs  1 , which is a standard PRSFs Pack  8  using for a cooling heat exchange media to be installed in the cooling tower.  FIG. 3-1  illustrates the top view of top  2  and bottom  3  plates of the standard PRSFs pack  8  fabricated by assembling of 100 standard unit of PRSFs  1 . The unit standard PRSF  1  has a structure as shown in  FIG. 1  and is schematically illustrated in  FIGS. 4-1 ,  4 - 2 , and  4 - 3 . The standard PRSF  1  shown in  FIG. 4-1  has a dimension of 260(Length)×765(Height)×15(Thickness) mm, other dimensions are possible, and is in the shape of plastic rod  5  screen plate consisting of 5 plastic rods  5  of 15 mm in diameter. The plastic rods  5  in the screen plate are separated from each other with an interval of 30 mm between centers of the adjacent rods  5 , which indicates the interval of 20 mm between surfaces of the adjacent rods  5 . As shown in  FIG. 3-1 , the plastic rod  5  at the end of upper side of the PRSF  1  is apart from the edge of the rod  5  screen by 5.6 mm (interval between surface of the rod  5  and the edge of the rod  5  screen, 13.1 mm between the edge of the rod  5  screen and center of the rod). The second plastic rod  5  is apart from the first one by 51.96 mm between the centers of the plastic rods  5  and next plastic rods  5  are located in the same intervals as between the first and second rods  5 . The plastic rod  5  at the lower end of the rod  5  screen is apart by 38.98 mm from the edge of the plastic rod  5  screen.  FIG. 3-1  shows the left and right parts of the PRSF  1  and  FIG. 3-2  shows a schematic illustration in detail of partial configuration of rods  5  and holes  4  in the top  2  and bottom  3  plates of the PRSFs pack  8  by enlarging a part of the top  2  view of the PRSFs pack  8  shown in  FIG. 3-1 .  FIGS. 3-1  and  3 - 2  show the configuration of the staggered arrangement of holes  4  and rods  5 , and also  FIG. 3-2  shows how to attach the rods  5  on the holes  4  being able to hold the rods  5  at the center of the holes  4 . The size of open hole  4  around the rod  5  is determined enough water to flow down over the surface of the rods  5  and its thickness is 3 mm preferred in the present invention for the rod  5  of 15 mm in diameter. When the PRSFs  8  shown in FIGS.  1  and  4 - 1  are assembled to fabricate the PRSFs pack  8 , the top view of the top frame  2  of the PRSF  1  shown in  FIG. 4-2  is shown as indicated by number  9  as shown in  FIG. 3-2 . On the contrary, when the PRSF  1  shown in  FIG. 4-1  is horizontally rotated by 180 degree and assembled with previous one, the rotated PRSF  1  becomes the PRSF  1  indicated by  10  as shown in  FIG. 3-2 . Hence, the PRSFs  8  of one kind fabricated as shown in  FIG. 4-1  are assembled by horizontally rotating one of them by 180 degree to fabricate PRSFs pack  8  as shown in  FIG. 2 , whose top  2  and bottom  3  plates are shown in  FIG. 3-1 . To accomplish such fabrication of the PRSF pack  8 , 3 female attachment tabs  13  are made properly separated and located on the left side of the top  2  and bottom  3  frames of the PRSF  1 , and 3 male attachment tabs  14  on the right side of the top  2  and bottom  3  frames. The 3 male  14  and female  13  attachment tabs are made respectively on the same locations from the right and left ends of the PRSF top  2  and bottom  3  frames in order to be easily joined by aligning male  14  or female  13  attachment tabs with and being inserted into their counterpart tabs  13  or  14  by pressing them. And also for the strong installation of the PRSFs packs  8  and attaching the PRSFs packs  8  on side of each other, male  14  and female  13  attachment tabs are made on both ends of top  2  and bottom  3  frame of the PRSFs  1  as shown in  FIGS. 4-2  and  4 - 3  and the piling attachment tabs  13 ,  14  are made on the top  2  and bottom  3  frames as shown in  FIGS. 4-2  and  4 - 3 . The spiral corrugated lines  15  are made on the surface of the plastic rods  5  for water to spirally flow down on the surface of the plastic rods  5 , while the water is flowing down on the surface of the plastic rods  5 . For the water sprayed on the top perforated plate  2  of the PRSFs pack  8  to be uniformly imbibed through the holes  4  and flow down on the surface of the plastic rods  5 , the plastic rods  5  are fixed to be located at the center of the holes  4  of the top  2  and bottom  3  perforated plates as shown in  FIG. 3-2 . 
         [0077]    The top perforated plate  2  of the PRSFs pack  8  fabricated by assembling a plurality of the PRSFs  1  shown in  FIG. 4-1  using the assembly method described above is schematically shown in  FIG. 3-1 . The plastic rods  5  are located at the vertex of an equilateral triangle as shown in  FIG. 3 . Such arrangement of the plastic rods  5  in the equilateral triangle position maximizes the effective contacting area of the water flowing down on the surface of the rods  5  and air transversely traveling through the plastic rods  5 , resulting in maximizing the cooling effect of the hot water or air.  FIG. 3-2  shows that the arrangement of the plastic rods  5  is in a zigzag shape, which increases the cooling effect of the hot water or air. The hole  4  around the rod  5  should be thick enough to smoothly imbibe and flow down the water around the rod  5 . For the rod  5  of 15 mm in diameter, the hole  4  thickness of 3 mm is preferred, other thickness is possible. The standard PRSF  1  of 260(Width)×765(Height)×15(thickness) mm, fabricated using plastic rods  5  of 15 mm in diameter, hole  4  thickness of 3 mm, and intervals of 10 mm between the surface of the adjacent plastic rods  5 , has 15 mm thickness, 15×7.5 mm cross section of top  2  and bottom  3  frames, 5 plastic rods  5  between the top  2  and bottom  3  frames, and 750 mm actual effective length of plastic rod  5 . By assembling  20  of such standard PRSFs  1  shown in  FIG. 4-1 , the PRSFs pack  8  of 300 (Width)×765(Height)×260(Length) mm is fabricated like open side PRSFs pack  8  which is same with the one detached the side panels of the PRSFs pack  8  as shown in  FIG. 2 . The PRSFs pack  8  fabricated as described above does not have side panels  12 , so that the side panels  12  are separately fabricated and attached on the sides of the open side PRSFs pack  8 . The side panel  12  consists of one large panel  16  and top  17  and bottom  18  frames which are on both sides of the panel  12  as shown in  FIG. 5 . When the side panel  12  is attached on the both sides of the PRSF top  2  and bottom  3  frames, insides of the top  17  and bottom  18  frames of the side panel  12  are made to fit the one side of the top  2  and bottom  3  frames of the PRSF  1  and to fit its opposite side by rotating the side panel  12  180 degree like panels  12  attached on both sides of the PRSFs pack  8  as shown in  FIG. 3-1 . The side panels  12  are attached on both sides of the PRSFs pack  8  to provide open sides to the staggered direction of rods as shown in  FIG. 3-1 . 
         [0078]    To fabricate the PRSFs pack  8  with longer distance between the adjacent rods  5  using the same size rods  5  than the interval between adjacent rods  5  of PRSFs pack  8  fabricated by using the direct attaching of PRSFs  1  with their thickness of rod diameter as shown in  FIGS. 3-1  and  3 - 2 , a gap supporter  21  shown in  FIGS. 6-1  and  6 - 2  is inserted between the PRSFs  1 .  FIG. 6-1  shows the side view of the gap supporter  21  frame and  FIG. 6-2  top view of the top  6  and bottom  7  frames of the gap supporters  21 . The shapes of both sides of the top  6  and bottom  7  frame of the gap supporter  21  are designed to be in the same shape before rotation when the gap supporter  21  is rotated by 180 degree as shown in  FIG. 3-2 . Such a side shape of the top  6  and bottom  7  frame of the gap supporter  21  is designed to be perfectly joined together with the side of the top  2  and bottom  3  frame of the PRSF  1 . The PRSF  1  used to fabricate the PRSFs pack  8  with longer distance between the adjacent rods  5  has side frames of 2 mm thick on left and right ends of the PRSF frame  9 ,  10  shown in  FIG. 4-1 . Hence, the gap supporter  21  also has the side frames  21  of 2 mm thick as shown in  FIG. 6-1 . By assembling several PRSFs  1  and gap supporters  21  in a way as attaching two PRSFs  1  on both side  6 ,  7  of one gap supporter  21  by horizontally rotating one of two PRSFs  1  by 180 degree, the PRSFs pack  8  shown in  FIG. 2  is fabricated, whose top view is schematically illustrated in  FIG. 8 . The PRSFs pack  8  shown in  FIG. 8  has the dimension of 300 (Width)×765 (Height)×340 (Length) mm, whose diameter of rod  5 , hole  4  thickness, interval between surfaces of the adjacent rods  5 , and specific number of rods  5  are 15, 5, 18.3 mm, and 5/90 cm 2 , respectively. The rods  5  are located at the vertexes of equilateral triangle, which are in the zigzag shape to the direction of air traveling. 
         [0079]    The standard PRSFs pack  8  is used for the fabrication of the required size of the PRSFs heat exchange cooling media by joining several standard PRSFs packs  8  side by side in the horizontal  435  direction, and piling them on top of the previous PRSFs packs  8  in the vertical direction. The evaporative water cooling media to be installed in the evaporative cooling apparatuses like cooling tower, water evaporative cooling chiller, etc., can be fabricated in several shapes, depending on the shapes of the water cooling apparatuses. Such a topic is extensively described in U.S. patents application Ser. No. 13/053,382, 61/728,928, and 61/736,646 recently applied by the inventor of the present invention, including rectangular and trapezoidal cooling media  26  for a cross-current cooling tower, such as rectangular, square, regular pentagon, and regular hexagonal cooling tower, and V-type and X-type cooling media for a counter current cooling tower. For the installation of PRSFs packs  8  in the rectangular and square cooling towers and evaporative water chiller, which have the rectangular cooling media, the rectangular PRSFs packs  8  are used. However, the shapes of cooling  445  media for the regular pentagon and hexagonal cooling towers are trapezoidal, so that both edges of cooling media are in the trapezoidal shape. Hence, the rectangular PRSFs packs  8  are installed in the shape of stairs near to the side panels of the trapezoidal cooling media  26  and the stair shape open spaces  27  are covered with triangular plastic plates to prevent passing of water as shown in  FIG. 9 . Another method is a direct installation method of trapezoidal PRSFs  31 , which is described in the following section. 
         [0080]    &lt;Designing and Installation of trapezoidal PRSFs&gt; As shown in  FIG. 10-1 , the regular pentagon shape water cooling media consists of 5 of trapezoidal cooling media  26 .  FIG. 10-2  is a schematic picture of the enlarged side panel area joined the left and right sides of the trapezoidal cooling media  26 , which shows a detailed configuration of assembling by combination of rectangular PRSFs packs  8  and triangle PRSFs packs  30  to fit the triangle space of the left or right side area of the trapezoidal cooing media  26 . The triangle PRSFs pack  30  is schematically illustrated in  FIG. 10-3 . The combination of the rectangular  8  and triangle PRSFs packs  30  to fit the triangle space of the left or right side of the trapezoidal cooling media  26  has a good advantage to leave no open spaces, compared with installation method of employment of rectangular PRSFs packs  8  only, which leaves open space like stairs as shown in  FIG. 9 . However, the combination method requires a fabrication of trapezoidal PRSF  31  to be assembled to fabricate the triangle PRSFs pack  30  as shown in  FIG. 10-3 . The trapezoidal PRSFs  31  are fabricated to have top and bottom trapezoidal shape surfaces and short and long widths of the rectangular PRSF  1  as shown in  FIGS. 10-4  and  10 - 5  able to fit the triangle space of the triangle PRSFs pack  30 , which illustrate the top and bottom surface view of the PRSFs  31  short and long in width, respectively. The triangle PRSFs pack  30  shown in  FIG. 10-3  is fabricated by assembling several trapezoidal PRSFs  31  in different width to be arranged in a right triangle shape and by attaching a trapezoidal PRSFs pack side panel  29  onto a hypotenuse of right triangle. The picture of trapezoidal PRFs pack side panel  29  is shown in  FIG. 11 , which shows the left and right sides of the panel. The trapezoidal PRSFs pack side panel  29  consists of a top  32  and bottom  33  square frame and thin panel between the frames, and on the both sides of the top  32  and bottom  33  square frame are several semi holes  19  and male  14  attachment tabs properly separated being able to be jointed with the hypotenuse of the right triangle PRSFs pack  30 . 
         [0081]    &lt;Installation of Slanted PRSFs pack&gt; The V-type and X-type cooling media are constructed by installing the slanted PRSFs packs  34  in V shape and X shape as described in U.S. patent application Ser. No. 13/053,382, respectively. The slanted PRSFs pack and PRSF  35  of the present invention have the slant angle of 30 degree to the vertical direction of the cooling tower, which are in the same shape with string-screen-fills and string-screen-fills pack whose fabrications are described in U.S. patent application Ser. No. 13/053,382. The side view of the slanted PRSFs pack  34  assembled several single units of the slanted PRSF  35 ,  36  is shown in  FIG. 12 , which illustrates a method to assemble several single units of slanted PRSFs  35 ,  36  for the fabrication of PRSFs pack  34  by joining the rear side of male slanted PRSF  35  onto the front side of female PRSF  36  without any rotations being able to keep top surfaces of the slanted PRSFs horizontal as shown in  FIG. 12 . Such slanted PRSFs packs  34  shown in  FIG. 12  are used for fabrication V- and X-type PRSFs pack cooling media of the counter current cooling tower by assembling them in V-shape and X-shape. 
         [0082]    &lt;Fabrication of molder&gt; To fabricate the PRSF  1  connecting the top  2  and bottom  3  frames and several plastic rods  5  in one structure as shown in  FIG. 4-1 , an employment of high pressure mold casting injection machine is essential and therefore a PRSF fabrication molder  37  to fabricate the PRSF  1  to be inserted into the injection machine should be fabricated. The PRSF fabrication molder  37  consists of two parts, upper  38  and lower part  39  molders, on which each half part of the PRSF  1  is carved. The lower part molder  39  carved the lower half part of the PRSF  1  on it is schematically illustrated in  FIG. 13-1 , which is the top view of the PRSF  1  shown in FIGS.  1  and  4 - 1 . The upper part molder  38  is exactly same with the lower part molder  39  except for carved corrugated lines  15 .  FIG. 13-2  shows the cross section of the cavity of the top  2  and bottom  3  frame of the PRSF  1  created by joining the upper  38  and lower part  39  molders together. The spiral corrugated lines  15  on the upper  38  and lower part  39  molder are carefully carved to be smoothly connected without any disconnected lines when the upper  38  and lower part  39  molders are jointed together. To firmly join together two PRSFs  1  when the PRSFs pack  8  is assembled, 2 male  13  and female  14  attachment tabs are carved respectively on the left side and right side of the top  2  and bottom  3  frames of the PRSF in the upper part molder, while 2 female  14  and male  13  attachment tabs are carved respectively on the left and right side of the top  2  and bottom  3  frame of the PRSF in the lower part molder  39 . By doing so, the male attachment tabs  13  can join firmly together with female attachment tabs  14  on the same location by pressing them when they are assembled together. The dimension of the PRSF fabrication molder  37  is 40(W)×87(H)×10(Thickness) cm when two parts of molders  38 ,  39  are joined. The fabrication of PRSF fabrication molder  37  described above is related with the molder for the fabrication of non-slanted PRSFs pack  8 . However, contrary to the fabrication of the one-type PRSF fabrication molder  37 , the slanted PRSFs pack  34  requires two-type PRSF molders, since the rotational attachment of the slanted PRSF is not allowed. Namely, the slanted PRSFs  35 ,  36  are joined together without rotation of themselves as shown in  FIG. 10 . To do so, two-type PRSFs are necessary like male  35  and female  36  slanted PRSFs, which are respectively drawn as shown in  FIGS. 14-1 ,  14 - 2 ,  14 - 3  and  15 - 1 ,  15 - 2 ,  15 - 3 . The male slanted PRSF  35  has male attachment tabs  13  on the top  2  and bottom  3  frames of the male slanted PRSF  35  and the female slanted PRSF  36  has female attachment tabs  14  on the top  2  and bottom  3  frames. The male  13  and female  14  attachment tabs are properly located on the surface of the top  2  and bottom  3  frame to adjoin each other for their firm attachments.  FIG. 14-1  shows the side view of cross section of male slanted PRSF fabrication molder  44  joined upper  45  and lower  47  molders with the created cavity of the side view of the male slanted PRSF  35  and  FIGS. 14-2  and  14 - 3  show the top and bottom view of the male slanted PRSF fabrication molder  44  created cavities of top and bottom frame of the male slanted PRSF  35 , respectively.  FIGS. 15-1 ,  15 - 2 , and  15 - 3  also show respectively similar side view, top view, and bottom view of the female slanted PRSF  36  as shown in  FIGS. 14-1 ,  14 - 2 , and  14 - 3 . To join male  35  and female  36  slanted PRSFs together, male attachment tabs  13  are properly carved on one side of the hollowed top  2  and bottom  3  frame of the male slanted PRSF  35  and female attachments  14  on the other side.  FIGS. 16-1 ,  16 - 2 ,  16 - 3 , and  16 - 4  show the illustration of the PRSFs pack side panel fabrication molder  52  for fabrication of the side panel of the rectangular column type PRSFs pack  8  without side panels, which is fabricated by assembling the PRSFs  1  without side frames as shown in FIGS.  1  and  4 - 1 .  FIGS. 16-1  and  16 - 2  show simple illustrations of the top views of the upper  54  and lower  55  part of the PRSFs pack side panel molder, respectively, and  FIGS. 16-3  and  16 - 4  show the cross section view of the side of the PRSFs side panel fabrication molder  52  combined the lower  55  and upper  54  parts of molder and the cross section view of the top  17  and bottom  18  frame of the PRSFs pack side panel fabrication molder  52  combined lower  55  and upper  54  parts of the molder, respectively. Dark park  53  of the upper part molder  52  shown in  FIG. 16-1  is carved to be entirely and flatly hollowed and inner slight dark flat part  53 - 1  of the lower part molder  55  shown in  FIG. 16-2  is jutted out above the lower part molder  55  as shown in  FIG. 16-3 . The top  17  and bottom  18  frames of the side panel  12  are carved on the location shown in  FIG. 16-3  including humps  57  and hollows  56  as shown in  FIG. 16-4 . Combining the upper  54  and lower  55  parts of the molder, the cavity  61  of the PRSFs pack side panel is created as shown in  FIGS. 16-3  and  16 - 4 . The white open space  53  shown in  FIG. 16-3  is the cavity of the side cross section view of the PRSFs pack side panel molder  52  and the dark cavity  61  shown in  FIG. 16-4  is the side view of the top  17  and bottom  18  frames of the PRSFs pack side panel molder  52 .  FIGS. 17-1 ,  17 - 2 , and  17 - 3  show the illustration of the molder for fabrication of the side panel of the trapezoidal cooling media  26  as shown in  FIGS. 10-1  and  11 .  FIG. 17-1  shows a simple illustration of the internal top view of the upper  65  and lower  66  part of the trapezoidal PRSFs pack side panel molder  64  and  FIGS. 17-2  and  17 - 3  show the side view of the cross section of the trapezoidal PRSFs pack side panel molder  64  combined the lower  65  and upper  66  parts of molder and the cross section view of the top  59  and bottom  60  frame of the trapezoidal PRSFs pack side panel molder  64  combined lower  66  and upper  65  parts of the molder, respectively. Central dark part  29  of the upper  65  and lower  66  part molder shown in  FIG. 17-1  is carved to be entirely and flatly hollowed being able to fabricate the panel between top  59  and bottom  60  frame of the trapezoidal PRSFs pack side panel  29 . The top  59  and bottom  60  frames of the trapezoidal PRSFs pack side panel  29  are carved on both left and right sides of the central dark part  29  shown in  FIG. 17-1  including humps  57  and hollows  56  as shown in  FIG. 17-3 . Combining the upper  65  and lower  66  parts of the trapezoidal PRSFs pack side panel fabrication molder  64 , the panel  29  and top and bottom frame  59 ,  60  cavity of the trapezoidal PRSFs pack side panel  64  is created as shown in  FIGS. 17-2  and  17 - 3 . The white open space  29  shown in  FIG. 17-2  is the cavity of the side cross section view of the trapezoidal PRSFs pack side panel  29  and the white open cavity  59 ,  60  shown in  FIG. 17-3  is the cavity of the top view of the top and bottom frames of trapezoidal PRSFs pack side panel  29 . 
         [0083]    &lt;Determination of length and number of corrugated lines on the surface of plastic rod&gt; The effect of the spiral corrugated lines  15  on the surface of the plastic rods  5  can be determined by straightforward computations of the length of the spiral corrugated lines  15  based on the rod information. The results of the straightforward computations are tabulated in Table 2. To obtain the data given in Table 2, the information on the plastic rod given in  FIG. 18  was used.  FIG. 18  shows the part of plastic rod  5  and the rectangular plane of circumference×length of plastic rod  5 , C(width)×H(length) mm, where C and H are respectively the circumference and length of the plastic rod  5 , and the relationship between the length of plastic rod  5  and one circle of the spiral corrugated line  15  to be formed based on the slant angle of the spiral corrugated line  15 . The rectangular plane of C×H mm is equivalent with the surface of plastic rod  5  down to the length H mm from the end of plastic rod  5 . The one circle of the spiral corrugated line  15  appears as a diagonal line L of the rectangular plane as shown in  FIG. 18 . The comparisons of the one circle L of spiral corrugated line  15  with the length H of the plastic rod  5  are tabulated in the Table 2 with other information on the plastic rods  5  in different diameter. Table 2 shows that the number of pitches decrease for the fixed length of pitch while the length of pitch decreases for the fixed number of pitches as slant angle increases. Such transitions of length and number of pitches depending on the extent of the slant angles are same with plastic rods  5  in different diameter. If the length of pitch is too long or too short, the water flows down cross over the spiral corrugated line  15  instead of following the spiral corrugated lines  15 . Therefore, an optimum length of pitch should be determined for water to flow within spiral corrugated line  15 . To meet such a condition, the corrugation must be deep enough to hold water within the spiral corrugated line  15  with length of pitch determined. However, if the corrugation is too deep, the corrugated rod becomes flexible and then it cannot be used for fabricating a strong PRSFs pack  8 . To avoid such condition of the spiral corrugated line  15  in the present invention, the depth of spiral corrugated line  15  is determined to be one third of diameter of rod, other depth is possible. Considering the optimum length and depth of pitch, the length of pitch should be determined to be not too long and not too short. Too meet such aim, the lengths of pitches are determined to be 3, 5, 7, 9, and 10 mm for the rods of 2.5, 5.0, 7.5, 10.0, and 15.0 mm in diameter, respectively. For each of the lengths of pitches, the number of pitches are determined to be respectively 7, 8, 9, 10, and 12 mm, which are approximately mean values of the number of pitches as shown in Table 2. And also it can be seen that the length of spiral corrugated lines  15  compared to the length of non-corrugated rod increases as does the slant angle of the spiral corrugated line  15  and that such a trend is not affected by the variation of the diameter of plastic rod  5 . Considering the 
         [0000]                                                                                                                                      TABLE 2                   Length and number of pitches on the plastic rod depending on its specifications.                    Increased   Length       Mean #           Ratio   length of   of pitch   # of   of       Specifications of Plastic Rod   of   of corrugated   (# of   pitches   pitches            D   C   S   H   L   L/H   line   pitches)   (length   (length       (mm)   (mm)   (deg)   (mm)   (mm)   (%)   (mm)   (mm)   of pitch)   of pitch)                    2.5   7.85   15   29.3   30.3   1.035   3.5   7.3(4)   9(3)    7(4)                   20   21.6   23.0   1.064   6.4   7.3(3)   7(3)    7(3)   7(3)               25   16.8   18.6   1.103   10.3   6.2(3)   6(3)    7(2.5)               30   13.6   15.7   1.155   15.5   5.2(3)   5(3)    7(2)       5.0   15.3   15   58.6               9.7(6)   11(5)     8(7)               20   43.1               8.6(5)   8(5)    8(5)   8(5)               25   33.7               8.4(4)   6(5)    8(4)               30   27.2               9.0(3)   5(5)    8(3.5)       7.5   23.6   15   88.1               11.0(8)   12(7)     9(10)               20   64.8               10.8(6)   9(7)    9(7)   9(7)               25   50.6               10.1(5)   7(7)    9(5.5)               30   40.9               10.2(4)   6(7)    9(4.5)       10.0   31.4   15   117.2               11.7(10)   13(9)    10(12)               20   86.3               10.8(8)   10(9)    10(8.5)   10(9)                25   67.3               11.2(6)   7(9)   10(7)               30   54.4               10.8(5)   6(9)   10(5.5)       15.0   47.1   15   175.8                   17(10)   12(14)               20   129.4                   13(10)   12(11)   12(10)               25   101.0                   10(10)   12(8.5)               30   81.6                    8(10)   12(7)               Notes:       D = diameter of plastic rod,       C = circumference of cross section of plastic rod,       S = slant angle of corrugated line to form with length of plastic rod,       H = length of plastic rod equivalent with length of one circle of corrugated line,       L = length of one circle of corrugated line.            
optimum conditions of the spiral corrugated line  15  described above, the optimum slant angle is chosen to be 20 degree, which provides the optimum lengths and number of the pitches. As results of such analyses, the optimum slant angle of the plastic rod  5  used for carving the spiral corrugated lines  15  of the plastic rods  5  in the molder of the present invention is 20 degree, other degrees are possible. Using the slant angle of 20 degree and plastic rod  5  of 7.5 mm in diameter, the length and number of pitches on the length of plastic rod  5  equivalent to one circular corrugated line are 7 and 9 mm, respectively, and the spiral corrugated plastic rod  5  has an effect of 6.4% increase of the length of the non-corrugated rod, which means the reduction of the size of evaporative cooling facilities by that much rate.
 
         [0084]    &lt;Fabrication of PRSF Using Molder and Mass Production&gt; The molding fabrication of a single unit of the PRSF  1  is accomplished by casting of molten plastics by injecting of molten plastic into PRSF molder  37  shown in  FIGS. 13-1  and  13 - 2  mounted on a high temperature injection machine. The production capability of injection machine is determined using a weight of plastic material used for fabrication of manufactured goods. Using the density, 0.75 g/cm 3 , of plastics and size of the PRSF, 300(W)×750(H)×7.5(Thickness) mm, the weight of single unit of the standard PRSF of the present invention is 221 g and the production capacity of the injection machine able to handle the 221 g of PRSF is 160 ton, so that a 160 ton injection machine is required for fabrication of 615 the PRSF  1 . The 160 ton injection machine is categorized to be a small size injection machine (140-300 ton). Therefore, to fabricate several PRSFs  1  at one shot of the injection machine, several PRSF molders must be combined in one fabrication frame, large die-caster, which can be inserted into a medium size injection machine (350-650 ton) or supper size injection machine (700-1400 ton) to fabricate several PRSFs  1  at one injection. Using the small size injection machine of 320 ton, two of PRSFs  1  can be fabricated. The largest medium size injection machine of 640 ton can fabricate four of PRSFs  1 . Therefore, as an exemplary production of the PRSFs using small and medium size injection machines, the large die-casters  67 ,  68  to fabricate two and four PRSFs must be fabricated, respectively. A structure of the die-caster  67 ,  68  to easily release the PRSF  1  out of the molder  37 ,  44 ,  48 ,  52 ,  64  after injection of the molten plastic material is a plate type rectangular box. Hence, the die-casters  67 ,  68  in the shape of the plate type rectangular box for the exemplary multi-production of the PRSFs  1  at one shot of injection are schematically drawn in  FIGS. 19 and 20 , which are the die-caster  67 ,  68  for production of 2 and 4 PRSFs  1 . The die-caster  67 ,  68  consists of support system  69 , molder, cast release system, injector of molten plastics  70 , and distributing controlling lines  72  of molten plastics. The support system  69  contains the other parts within the inside of the support system  69  and supports the other parts to work, and the molder is the one shown in  FIG. 13-1 ,  14 - 1 , or  15 - 1 . The cast release system releases the casted PRSF  1  out of the die-caster  67 ,  68  and the injector of molten plastics  70  transfers the molten plastic injected from the injection system to the distributing controller of molten plastics. The distributing controlling lines  72  of the molten plastics are the lines to distribute the molten plastics to the every hollowed PRSF carved in the PRSF fabrication molder  37 . The functions of the support system are to receive the molten plastics injected from the injection system at the entrance of the receiver  71  and to transfer the molten plastics to every hollowed PRSF  37  after passing through the distribute controlling lines  72 . And also the support system has the functions of cooling the molten plastics by circulating cold water surrounding the molten plastics filled the hollowed PRSF  37  and ejecting the cooled PRSF from the PRSF fabrication molder  37 . Every injection machine has an injection molding cycle which is an elapse time between the injection time of molten plastics and the ejection time of the product and most plastic injection machines have the injection molding cycle of 10 to 100 seconds. More detailed information of the injection molding cycle of the plastic injection machines is described in the non-patent references. Supposing the injection molding cycle of the fabrication of one PRSF  1  is 100 seconds, 160 PRSFs  1  per hour can be fabricated by using one 500 ton injection machine. Therefore, when several decades of the injection machines are simultaneously operated, a mass production of the PRSFs  1  is possible to meet a required industrial demand of the products. 
         [0085]    While the present invention has been described as having an exemplary design, this invention may be further modified within the concept and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention relates.