Abstract:
The improved refrigeration system of the present invention includes an accumulator with a diffuser pipe extending downwardly into the upper end of a vapor refrigerant tank, the diffuser pipe extending from an evaporator and discharging vapor refrigerant therefrom into the tank. The diffuser pipe includes a lower end located within the interior of the tank which is expanded in diameter relative to the upper end, thereby reducing the velocity of fluid flowing through the pipe and entering the accumulator tank. A diffusion plate is mounted in the lower end of the diffuser pipe, to further diffuse fluid flowing therethrough.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a divisional application of Ser. No. 09/659,315 filed Sep. 12, 2000, entitled “Improved Refrigeration System”, U.S. Pat. No. 6,349,564. 
    
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     (Not applicable) 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates generally to industrial refrigeration systems, and more particularly to an improved dry suction ammonia refrigeration system having a modified accumulator connection. 
     (2) Background Information 
     A major drawback of industrial and commercial refrigeration systems which utilize ammonia as a refrigerant is a high cost of installation, operation, and maintenance. Conventional two stage refrigeration systems utilize a first stage which will provide refrigerant gas having a pressure of about 15 inches HG-0 psig from a low stage accumulator to a compressor, which will compress the gas to approximately 25-30 psi and discharge the compressed gas to a desuperheating coil, then through an oil separator to the second stage. The second stage will take this pressurized gas through a second compressor which increases the pressure to approximately 185 psig. This high pressure gas is then run through a condenser. 
     The inventors herein have found that a change in design of the accumulator assists in diffusing superheated gases to thereby cause liquid within the gas to accumulate within the accumulator vessel. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore a general object of the present invention to provide an improved ammonia refrigeration system. 
     A further object is to provide an improved ammonia refrigeration system which reduces operating costs, installation costs, and maintenance costs as compared to conventional ammonia refrigeration systems. 
     Yet another object is to provide a refrigeration system with an improved accumulator design. 
     These and other objects of the present invention will be apparent to those skilled in the art. 
     The improved refrigeration system of the present invention includes an accumulator with a diffuser and velocity reducer pipe extending downwardly into the upper end of a vapor refrigerant tank, the return pipe extending from an evaporator and discharging vapor refrigerant therefrom into the tank. The diffuser pipe includes a lower end located within the interior of the tank which is expanded in diameter relative to the upper end, thereby reducing the velocity of fluid flowing through the pipe and entering the accumulator tank. A diffusion plate is mounted in the diffuser pipe, to further diffuse fluid flowing therethrough. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The preferred embodiment of the invention is illustrated in the accompanying drawings, in which similar or corresponding parts are identified with the same reference numeral throughout the several views, and in which: 
     FIG. 1 is a detailed flow diagram of a single stage refrigeration system of the present invention; 
     FIG. 2 is an enlarged schematic view of the accumulator of the system shown in FIG. 1; 
     FIG. 3 is an enlarged elevational view of the accumulator shown in FIG. 2; 
     FIG. 4 is a super enlarged sectional view through the diffuser pipe of the accumulator shown in FIG. 3; 
     FIG. 5 is a plan view of the diffusion plate installed within the diffuser pipe shown in FIG. 4; 
     FIG. 5A is a sectional view taken at lines A—A in FIG. 5; 
     FIG. 6 is an enlarged schematic view of the condenser used in the system of FIG. 1; 
     FIG. 7 is a block flow diagram of a two stage refrigeration system; 
     FIG. 8 is a detailed schematic view of a two stage refrigeration system; and 
     FIG. 9 is an enlarged schematic view of the two stage system condenser showing a desuperheating coil. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to FIG. 1, a dry suction ammonia refrigeration system is designated generally at  10 , and a general flow diagram is schematically shown. Beginning at the control pressure receiver  12 , liquid refrigerant, preferably ammonia, is pushed to evaporators designated generally at  14 . The evaporators include processing units  14   a,  cooler units  14   b,  and a chiller  14   c.  Obviously, other types of uses are encompassed within the scope of this invention, although not detailed in this drawing. At each evaporator unit  14   a,    14   b,  and  14   c,  the flow of liquid is completely evaporated to form a dry suction gas. In order to distinguish between the forms of the refrigerant, solid line  16  indicates refrigerant in a liquid form, and dashed line  18  shows refrigerant in a dry suction gas form. The dry suction gas is moved from the evaporators  14  to accumulator  20 , where the gas is then drawn by a compressor  22 . At the compressor, the refrigerant gas is compressed and pumped to condenser  24 . Once condenser  24  transforms the gas back to a liquid, it is returned to receiver  12  for another cycle. 
     Referring now to FIG. 2, the accumulator  20  of the present invention is shown in enlarged schematic form. Accumulator  20  is of a relatively radical design that is not used in standard systems. Suction gas coming back from the plant would enter via conduit  26 , at a pressure of approximately 25-30 psi. Gas traveling to compressor  22  (shown in FIG. 1) would exit accumulator  20  via pipe  28 . 
     An electronic expansion valve  30  is installed upstream of accumulator  20  along conduit  26 , with probes  32  located to monitor the super heated gas entering accumulator  20 . Expansion valve  30  is installed along a line  34  which is tapped into the conduit  36  carrying liquid from the controlled pressure receiver  12  to the evaporators  14 . Expansion valve  30  is designed to protect the compressor  22  from overheating due to excessive super heated gas coming back from the plant. If the temperature of the super heated gas entering accumulator  20  becomes too high, the expansion valve  30  injects an amount of liquid refrigerant into the gas stream in conduit  26  to quench the excess heat. 
     Referring now to FIG. 3, accumulator  20  is shown in more detail. The accumulator  20  includes a containment vessel  38  having an upper portion  38   a  and a lower portion  38   b.  As shown in FIG. 2, accumulator  20  is designed to accumulate any refrigerant in the form of liquid within lower portion  38   b  and includes a fluid level control apparatus  40  of a conventional type to maintain the liquid level within lower portion  38   b.  A diffuser pipe  42  enters the upper end of vessel upper portion  38   a  and has an upper end connected to conduit  26 , to direct super heated gas into accumulator  20 . 
     As shown in FIG. 4, diffuser pipe  42  includes an upper end  42   a  connected to conduit  26  and equal in diameter to conduit  26 . Diffuser pipe includes a concentric reducer  42   b  downstream of upper portion  42   a,  which increases in diameter from its upper end to its lower end to approximately twice the diameter of upper portion  42   a  at its lower end. A lower portion  42   c  of diffuser pipe  42  extends vertically downward from the enlarged lower end of reducer  42   b.  Preferably, the lower end  42   c  of diffuser pipe  42  extends downward a distance approximately one-half the height of vessel upper portion  38   a,  but spaced above the liquid level in the vessel lower portion  38   b,  as shown in FIG.  3 . This diffuser pipe length assists in diffusing the super heated gas and causing it to swirl about within the vessel, thereby causing any liquid within the gas to accumulate within the vessel lower portion  38   b.    
     Referring once again to FIG. 4, reducer  42   b  will cause the velocity of refrigerant entering accumulator  20  from conduit  26  to reduce, because of the increase in diameter of the pipe from the upper portion  42   a  to the lower portion  42   c  in reducer  42   b.  This decrease in velocity also serves to diffuse the gas and assists in removing liquid from the gas. 
     In order to assist in diffusion, diffusion plate  44  may be installed within the upper end of lower portion  42   c  of diffuser pipe  42 . Diffusion plate  44  includes a plurality of apertures  46 , as shown in FIG. 5, with the area of apertures  46  being approximately 1.5 times the cross-sectional inside area of conduit  26  and/or diffusion pipe upper portion  42   a.  For example, if conduit  26  has a diameter of six inches, diffusion plate  44  should have apertures with a cross-sectional; area equal to about 1.5 times the cross-sectional area (about 29 square inches) of conduit  26 , equal to slightly more than 43 square inches. In addition, the side walls of each aperture  46  are preferably chamfered on the lower side, to function similar to reducer  42   b,  as refrigerant passes through each aperture  46 , as shown in FIG.  5 A. 
     Referring once again to FIG. 3, accumulator vessel upper portion  38   a  includes dual outlet pipes  48  extending vertically out of vessel upper portion  38   a  and thence connected together and to outlet pipe  28 , as shown in FIG.  2 . While dual outlet pipes  48  are shown in the drawings, dual outlets are not a requirement for the invention, and a single outlet pipe would function adequately. FIG. 3 additionally discloses reinforcing rings  50  mounted on vessel upper portion  38   a  around each of the outlet pipes  48  and the upper portion  42   a  of diffuser pipe  42  where it enters accumulator  20 . 
     Referring now to FIG. 6, the condenser  24  of the refrigeration system  10  is shown in enlarged schematic form. Condenser  24  is of conventional manufacture, but significant changes in the piping are used in the refrigeration system of this invention. Refrigerant in the form of gas having a pressure of approximately 110-185 psi is conveyed from compressor  28  (shown in FIG. 1) via inlet pipe  50 , to condenser  24 . The outlet pipe  52  is connected to the stem  54   a  of a full size tee  54  which is oriented with the stem  54   a  extending horizontally, and arms  54   b  and  54   c  extending vertically in opposing directions. The upper arm  54   b  of tee  54  has a full extension  56  of approximately 8-10 inches, which is capped. A purge valve  58  off of the cap of extension  56  is piped to a conventional purger. This feature allows a significant amount of noncondensable gases to accumulate and be purged. This improvement is necessary to remove noncondensable gases when condenser outlets are installed with mechanical traps. Once condenser  24  has condensed the refrigerant gas to liquid form, it exits the condenser through outlet pipe  52 . The noncondensable gases will collect in tee upper arm  54   b  and extension  56  for purging, while the condensed liquid refrigerant continues through the tee lower arm  54   c,  thence through a trap  60 , a check valve  62 , and thence via pipe  64  to the receiver, at a pressure of approximately 55-60 psi. 
     Referring now to FIG. 7, a two stage refrigeration system is shown in a block flow diagram, with a first stage having a lower pressure and lower temperature, and a second stage having a higher pressure and higher temperature. The high stage of the system of FIG. 7 is identical to the single stage version of the invention shown. in FIG. 1, and for this reason all components will be identified with the same reference numerals. Starting once again at the controlled pressure receiver  12 , liquid refrigerant is pushed to evaporators  14 , wherein the refrigerant is completely evaporated to a dry suction gas. The dry suction gas is moved to the accumulator  20  where it is then drawn in by compressor  22 . The refrigerant gas is compressed at compressor  22  and pumped to condenser  24  where the gas is condensed back to a liquid and flows back to the controlled pressure receiver  12 . 
     Liquid refrigerant from control pressure receiver  12  is pushed through a pipe to the low stage receiver  66 . The liquid refrigerant in low stage receiver  66  is pushed to the low temperature evaporator units  68 , where the liquid is completely evaporated to form a dry suction gas. The dry suction gas from evaporators  68  is brought to the low stage accumulator  70  where the gas is then drawn by the low stage compressor  72 . The gas is compressed in compressor  72 , and pumped to a desuperheating coil  74  within the high stage condenser  24 . After desuperheating the gas, the gas is brought back through an optional oil separator  76  to the high stage accumulator  20 . Excess liquid in the low stage accumulator  70  is pushed through a pipe to the suction of the high stage accumulator  20  utilizing a transfer system. 
     FIG. 8 is similar to FIG. 7, but utilizes component designations for the various boxes in the flow diagram of FIG.  7 . This dual stage refrigeration system utilizes a high temperature stage for things such as processing units, cooler units, and chillers, and a low temperature stage for evaporators, such as blast freezers, where a very low temperature is desired. Beginning with the high stage compressor, ammonia gas is pumped from the high stage accumulator  20  to the condenser  24 . At the condenser  24 , water and air are used to condense the ammonia gas back to a liquid. The liquid is pushed down to control pressure receiver  12 , which pushes the liquid through the plant to the various evaporators  14   a,    14   b,  and  14   c.  At each evaporator  14   a,    14   b,  and  14   c,  an electronic expansion valve is utilized to meter the flow of liquid to the exact proportions needed to do maximum cooling, without over feeding and causing liquid carryover. For extremely low temperature applications, such as a blast freezer where a temperature of 0° F. or lower is desired, the ammonia liquid is pushed from receiver  12  to a low temperature low pressure receiver  66 . Receivers  12  and  66  take the majority of the “flash” out of liquid ammonia, thereby making evaporators  14   a,    14   b,  and  14   c  and low temperatures evaporators  68   a  and  68   b,  more efficient. “Flash” has been a major problem for ammonia refrigeration systems, and has been known to cause an evaporator coil to lose as much as 10 percent of its capacity. The refrigeration system  10  greatly reduces this problem, and uses the pressure of the receivers to “pump” the liquid. This pressure is typically equal to the pressure a modern liquid ammonia pump would output, so that the efficiency of the “pumping” would not be compromised compared to the conventional liquid pumps. 
     Once the liquid ammonia is evaporated in the various evaporators  14   a,    14   b,    14   c,    68   a  and  68   b,  the ammonia gas is motivated back to the high stage accumulator  20  from evaporators  14   a,    14   b,  and  14   c,  and to low stage accumulator  70  from low temperature evaporators  68   a  and  68   b,  respectively. Once in accumulators  20  and  70 , the gas is simply suctioned back into the associated compressors  22  and  72 , respectively. 
     Referring now to FIG. 9, condenser  24  in the dual stage refrigeration system, includes the standard portion  24  which condenses gas from the high stage compressors via inlet pipe  50  and returns the condensed liquid through trap  60  and pipe  64 . The desuperheating coil  74  is located proximal condenser  24 , and takes gas from the low stage compressor  72  (shown in FIGS. 7 and 8) via line  78 , and removes heat via the desuperheating coil before the gas reaches the high stage accumulator  20 . To facilitate the efficient removal of oil, an oil separator  76  may be mounted in outlet line  80  from the desuperheating coil  74 . 
     Prior art dual stage refrigeration systems may pump high stage gas of approximately 185 psi through a coil to remove oil, and thence through a condenser. The present desuperheating coil differs significantly from this prior art in that the desuperheating coil is located after the low stage compression and prior to the high stage suction. This reduction of heat in the gas requires less horsepower for the high stage compressor to compress the gas from 30 psi to 185 psi, thereby extending the life of the compressor and increasing the efficiency of the system. 
     Whereas the invention has been shown and described in connection with the preferred embodiment thereof, many modifications, substitutions and additions may be made which are within the intended broad scope of the appended claims.