Abstract:
A jumper tube for connecting a flow restricting capillary tube and an evaporator in a refrigerator system includes a transition portion in between a cavity portion and a cylindrical portion. The transition portion is crimped and folds a portion of the jumper tube sidewall onto itself to form a passage in the shape of clam shell. The transition portion prevents the creation of popping sounds in the jumper tube due to uncontrolled expansion of refrigerant exiting the capillary tube.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to refrigeration systems and, more particularly, to a noise suppressing jumper tube for connecting a refrigeration condenser and evaporator. 
     One type of refrigeration system includes, in closed series fluid communication, an evaporator, a compressor, a condenser, a capillary tube, and a jumper tube. The compressor receives a refrigerant from the evaporator and compresses the refrigerant. The compressed refrigerant is supplied to the condenser. Refrigerant flowing out of the condenser enters the capillary tube, which restricts flow of refrigerant from the condenser and maintains a pressure differential between the evaporator and the condenser. The jumper tube connects the capillary tube and the evaporator and provides a transition from the small diameter capillary tube passage and the large diameter passage in the evaporator. 
     The refrigerant discharged from the capillary tube may be in the form of a liquid, a gas, or a combination of liquid and gas. A portion of the refrigerant vaporizes as it is discharged from the capillary tube into the relatively low pressure environment of the evaporator via the jumper tube. The pressure difference between the refrigerant in the capillary tube and the refrigerant in the evaporator causes liquid refrigerant flowing subsonically through the capillary tube to flow near or above supersonic velocities as it is discharged from the capillary tube and vaporizes. It is believed that the transition between subsonic and supersonic flows and/or the vaporization process, causes a popping noise similar to the sound of a woodpecker pecking on wood (sometimes referred to as woodpecker noise or “WPN”) as the refrigerant expands in the jumper tube and in the evaporator. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the invention, a jumper tube for a refrigeration system includes a transition portion which facilitates reduction, and possibly even elimination, of woodpecker noise as well as reducing or eliminating refrigerant groaning or rushing noises. Specifically, the jumper tube transition portion includes a crimp which forms a restricted passage and a transition angle from the smallest section of the crimped portion to a cylindrical portion of the tube that is greater than 7° measured from the longitudinal axis of the jumper tube. It is believed that by selecting the transition angle to be greater than 7°, refrigerant can be continuously expanded within the transition portion without generating noise. 
     The jumper tube also includes a bend section a short distance downstream of the transition portion. The bend section affects flow of refrigerant moving downwardly through the jumper tube when the jumper tube is connected to an evaporator. Also, the downstream end of the bend is inclined upward when the jumper tube is connected to the evaporator, further affecting the behavior of the refrigerant through the jumper tube. It is believed that the combination of the transition angle, the downward flow of the refrigerant through the transition portion, the bend in the cylindrical portion, and the upward flow from the bend into the evaporator tube prevent generation of woodpecker noise in the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a refrigeration system including a jumper tube; 
     FIG. 2 is an front cross-sectional view of the jumper tube shown in FIG. 1; 
     FIG. 3 is a top plan view of a refrigerator evaporator connected to the jumper tube shown in FIG. 2; 
     FIG. 4 is side plan view of the evaporator shown in FIG. 3; 
     FIG. 5 is a magnified side view of the jumper tube shown in FIG. 2; and 
     FIG. 6 is a cross sectional view of the jumper tube shown in FIG. 5 taken along line  6 — 6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 schematically illustrates a refrigeration system  10 , or circuit, including a compressor  12 , a condenser  14 , a flow restrictor, such as a capillary tube  16 , a jumper tube  18 , and an evaporator  20  connected in closed series flow relationship. Compressor  12  draws refrigerant vapor from evaporator  20  and discharges compressed refrigerant to condenser  14 . High pressure refrigerant condensed in condenser  14  flows to evaporator  20  through capillary tube  16  and jumper tube  18 . 
     Capillary tube  16  restricts the flow of liquid refrigerant to evaporator  20  and maintains a pressure differential between condenser  14  and evaporator  20 . Specifically, an inner diameter of capillary tube  16  is much smaller than the inner diameter of other fluid passages in system  10 . Jumper tube  18  connects the small passage of capillary tube  16  to the larger passage of evaporator  20 . 
     FIG. 2 is an enlarged view of jumper tube  18 . Jumper tube  18  includes an inlet portion  22 , a cavity portion  24 , a cylindrical portion  26 , and a transition portion  28 . Inlet portion  22  has circular cross-sectional shape and an inlet passage  30  having an inner diameter slightly larger than the inner diameter of capillary tube  16 . Capillary tube  16  is inserted through inlet portion  22  during use in refrigeration system  10  (FIG.  1 ). Refrigerant flows from condenser  14  (FIG. 1) in a downstream direction through jumper tube from right to left in FIG. 2, and ultimately to evaporator  20  (FIG.  1 ). 
     Cavity portion  24  extends from inlet portion  22  and includes a first end  32 , a second end  34 , and a passage  36 , or cavity, therethrough. Passage  36  increases in size, i.e., the cross sectional area of passage  36  increases, from cavity portion first end  32  to cavity portion second end  34 . Thus, passage  36  forms an expanded area or cavity around capillary tube  16  for deposit of material produced by brazing, soldering, or other joining methods that can be used to form a leakproof connection between capillary tube  16  and cavity portion  24 . Also, capillary tube  16  extends through cavity portion  24  to prevent materials from clogging capillary tube  16 . While cavity portion  24  as illustrated has a substantially conical shaped deposit cavity, in alternative embodiments the deposit cavity could have many other shapes without adversely affecting WPN suppression and still serve the functional purpose of containing capillary tube attachment byproducts and preventing capillary tube  16  from being clogged. 
     Transition portion  28  extends from cavity portion second end  34  and includes a first end  38 , a crimped portion  40 , a second end  42 , and a transition passage  44  therethrough. Crimped portion  40  is formed with a crimper, either by hand or with a machine, and has an hour glass shape. Transition passage  44  decreases in cross sectional area to a section  46  where transition passage  44  has a cross-sectional area smaller than inlet passage  30 . On either side of section  46 , transition passage  44  has a larger cross sectional area. Transition passage  44  continuously increases, i.e., not a step increase, in cross sectional area at transition portion second end to a cylindrical passage  48  of cylindrical portion  26  extending from transition portion second end  42 . Cylindrical portion  26  is dimensioned for connection to evaporator  20  (FIG.  1 ), and includes a longitudinal axis  50  which also extends through inlet portion  22 , cavity portion  24  and transition portion  28 . In alternative embodiments, one or more of inlet portion  22 , cavity portion  24 , and transition portion  28  are offset from longitudinal axis  50  of cylindrical portion  26 . 
     When connected to system  10  (FIG.  1 ), transition portion  28  forms a stop for capillary tube  16  which is inserted through inlet portion  22  and cavity portion  24 . The shape of transition passage  44  also facilitates preventing WPN when refrigerant flows through jumper tube  18 , and crimped portion  24  supports capillary tube  16  and prevents vibration of capillary tube  16 . However, it has been observed that WPN is also suppressed in alternative embodiments where capillary tube is not supported by crimped portion  40 . 
     Unlike known jumper tubes, jumper tube  18  has a maximum transition angle in the flow path of refrigerant measured from longitudinal axis  50  between section  46  and second end  42  of crimped portion  40  (i.e., the angle at which an imaginary line tangential to the greatest sloped segment of the crimped portion  40  would intersect the longitudinal axis  50 ) greater than 7°. Typically, the maximum transition angle is selected from the range of 20° to 49°, and more typically, from the range of 34° to 39°. 
     FIG. 3 illustrates the connection of jumper tube  18  to evaporator  20 . Jumper tube inlet portion  22 , cavity portion  24  and transition portion  28  are positioned above an evaporator inlet  54 . A bend section  52 , such as the 84° bend shown, in cylindrical portion  26  is located a short distance, for example, about 1.5 inches from transition portion  28 , and results in refrigerant flowing through jumper tube  18  to be flowing upward at a 6° angle relative to evaporator  20  immediately after bend section  52 . Bend section  52  therefore affects the propagation of refrigerant through jumper tube  18  and is believed to facilitate avoidance of WPN. Of course, the angle of bend  52  and/or the 6° upward slope may be varied to optimize flow conditions for a given refrigerant in a given system, including bends of 90° or larger. Thus, refrigerant flows through jumper tube  18  into evaporator inlet  54 , through evaporator coils  56 , and back to compressor  12  (FIG. 1) through evaporator outlet conduit  58 . 
     FIG. 4 is a side view of the connection of jumper tube  18  to evaporator  20  that allows refrigerant to flow from jumper tube  18  to evaporator coils  56  through evaporator inlet conduit  54  and then back to compressor  12  (FIG. 1) through evaporator outlet conduit  58 . From this view, crimped portion  40  of jumper tube  18  is bulb-shaped. 
     FIG. 5 is an enlarged view of jumper tube  18  from the perspective of FIG.  4 . As shown in FIG. 5, a portion of jumper tube  18  is outwardly displaced from longitudinal axis  50  at crimped portion  40 . 
     FIG. 6 is a cross-sectional view of crimped portion  40  at section  46  (FIG.  2 ), showing transition passage  44  formed by crimped sidewall  62  of jumper tube  18 . A portion of jumper tube sidewall  62  is folded or crimped on each side of transition passage  44  so that an inner face  64  of sidewall  62  forms transition passage  44  with inner surface  64  of folding sidewalls  66  contacting one another. The contacting inner surface  64  of sidewalls  66  provides transition passage  44  with the shape of a clam shell, i.e., having two substantially arched sections inverted relative to one another and substantially intersecting at the sides of transition passage  44  where folding sidewalls  66  contact one another. The separation of the arched sections, i.e., the height of the passage, is smaller than the inner diameter of capillary tube  16  to form a stop for capillary tube  16 , such as a passage height of 0.032 inches to 0.053 inches. 
     In an exemplary embodiment, jumper tube  18  is fabricated from aluminum, plastic, or a metal, such as copper, and has an inlet portion axial length of about 0.25 inches and a cavity portion  24  axial length of about 0.75 inches. Transition passage  44  has a nominal minimum diameter of about 0.040 inches, slightly larger than the capillary tube inner diameter of approximately 0.026 inches, and much smaller than the capillary tube outer diameter of 0.076 inches. The bend is formed about 1.5 inches from crimped portion  40 . Cavity portion is crimped so that crimped portion  40  is located about 1 inch from the inlet portion end of jumper tube  18 . Crimped portion  40  is formed manually with a pneumatic hand tool that resembles a pair of scissors with the scissor blades replaced by a pair of appropriately shaped dies that crush jumper tube sidewall  66  to form the clam shell shaped transition passage. Pneumatic hand tools for crimping are well known in the art. 
     When jumper tube  18  is connected to evaporator  20 , capillary tube  16  is inserted into inlet portion  22  and connected to jumper tube  18  by conventional methods, e.g., by soldering or brazing, with deposit materials from the connection process contained in cavity portion  24 . Connecting jumper tube  18  to condenser  14  includes the step of inserting capillary tube  16  into jumper tube  18  through inlet portion  22  and into tube cavity portion  24  until capillary tube  16  contacts crimped portion  40  of jumper tube  18 . Capillary tube  16  and jumper tube  18  are then joined to form a leakproof joint. 
     In operation, refrigerant flows downwardly through capillary tube 16 , and into jumper tube transition portion  28 . Refrigerant continuously expands along the jumper tube sidewalls within transition portion  28  and flows downwardly into cylindrical portion  26 . A short distance later, refrigerant enters bend section  52  and then flows upward at an angle of about 6° or greater. It is believed that the combination of bend section  52  and the upward turn causes refrigerant to pool in the bottom of the bend and either prevents WPN or affects propagation of WPN by dispersing it or absorbing it so that the noise does not penetrate the sidewalls of jumper tube  18 . From bend section  52 , refrigerant flows upwardly into evaporator inlet conduit  54 . 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.