Abstract:
A refrigeration unit having a jet pump with an automatically adjustable cross-section for the control of refrigerant flow that provides a more economical refrigeration process. The circulation of thermotransfering materials, such as a refrigerant, through the jet pump&#39;s evaporator facilitates a more efficient cooling effect.

Description:
The present invention relates to jet pumps and their application to cooling and heating systems for thermal control processes. 
    
    
     BACKGROUND OF THE INVENTION 
     Human productivity and quality of life has been substantially increased in recent years by the use of efficient climate control equipment, such as air conditioning. The growing demands for food preservation on the one hand and energy-saving requirements on the other hand could be satisfied only with effective and economical thermal control systems. There are existing refrigeration systems which consist of a refrigerant vapor compressor discharging into a condenser which liquefies the refrigerant while it emits heat to the surroundings. This is followed by partially vaporizing the liquid refrigerant and lowering its temperature by means of absorbing its latent heat of vaporization. The refrigerant then passes through the evaporator which vaporizes the remaining liquid and absorbs the heat from the cooling object. The produced vapor then returns to the compressor to repeat the cycle again. The circulation of the thermotransfering materials such as a refrigerant through the evaporator makes the process of absorbing heat from the cooling object more efficient. 
     Suitable forms of jet pumps for the circulating refrigerant are comprised of a suction inlet for entering liquid which is then lifted by the pump into the mixing chamber, a jet with an inlet for the introduction of high-pressure liquid. The high-pressure liquid, called working liquid, flows into the mixing chamber and creates a suction effect at the suction inlet. The low-pressure liquid, called secondary liquid, is lifted by the pump and sucked into the mixing chamber. 
     An early example of a jet pump is disclosed in U.S. Pat. No. 607,849 by Hampson in 1898. Subsequently, multiple attempts to increase efficiency of conventional jet pumps for refrigerating systems were made. For example in the U.S. Pat. Nos. 3,199,310 by Schlichting, 2,301,839 by Work, and 3,277,660 by Kemper disclosed the idea of using different liquids as secondary and working liquids to increase the efficiency of the jet pump. In U.S. Pat. No. 3,680,327 by Stein disclosed a “compound ejector” for use in steam-jet refrigeration that introduces multiple primary jets through stationary nozzles in order to mix secondary and working liquids. In U.S. Pat. No. 4,378,681 by Modisette, U.S. Pat. No. 4,748,826 by Lauman, and U.S. Pat. No. 5,647,221 by Garris, Jr. are disclosed the idea of using virtual flow for increasing the efficiency of a jet pump or an ejector. 
     It is known that heat loading on the cooling system during the refrigeration or freezing process is variable and the quantity of the refrigerant circulating through a freezer or a refrigerator changes to large extent throughout the process. The greatest quantity of the refrigerant circulates at the beginning of the process. Some time later, the quantity of the refrigerant must be reduced due to the decreasing amount of heat transferring from cooled object and refrigerant. The final step of the process requires further reduction of the feeding refrigerant. Obviously, the optimum process should allow adjusting the quantity of the feeding refrigerant according to the amount of heat exchanged. 
     All of described types of the jet pumps have a constant cross section of the nozzles. Therefore they can not change the quantity of a refrigerant introduced into an evaporator and thus cannot reduce the time of the refrigeration process. Accordingly, a need exists for improving the jet pump for circulating refrigerant in order to increase the effectiveness of the refrigeration process. 
     SUMMARY OF THE INVENTION 
     The present invention provides improvement of the construction of jet pumps. The cross section of the nozzle of the jet pump varies during the refrigeration process depending upon the pressure inside an evaporator. This effect is achieved by placing a movable piston into a narrowing of the output channel of the pump. The movable piston changes the cross-section of the jet pump through which the high pressure refrigerant (working liquid) passes through to the mixing chamber of the jet pump. That piston is in dynamic equilibrium by means of its weight and the difference in pressure of the refrigerant before and after flowing around the piston. Therefore the variation in the diameter of the ring-shaped nozzle is the result of the change in the distance between the margin of the upper part of the piston and the wall of the narrowing channel through which high-pressure refrigerant is introduced. 
     According to the second embodiment of the present invention the piston is in dynamic equilibrium by means of its weight, resistance of a buffer placed between the stopper and the screen, and the difference in pressure of the refrigerant before and after the piston. Therefore the variation in the diameter of the ring-shaped nozzle is the result of the change in the distance between the margin of the upper part of the piston and the wall of the narrowing channel through which high-pressure refrigerant is introduced. 
     According to the third embodiment of the present invention the piston is placed on the pipe which introduces the low-pressure refrigerant to the mixing chamber. The pipe is positioned within the body of the jet pump so that the output channel is at the narrowing portion of the body of the jet pump. At the output channel high-pressure refrigerant is introduced into the mixing chamber. 
     The above described and many other features and attendant advantages of the present invention will become apparent as the invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Detailed descriptions of the preferred embodiments of the present invention will be made preference to the accompanying drawings. 
     FIG. 1 shows the cross-section view of the jet pump in accordance with the first embodiment of the present invention. 
     FIG. 2 shows the cross-section view of the jet pump in accordance with FIG. 1, further comprised of a buffer. 
     FIG. 3 shows the cross-section of the jet pump with the movable piston located on the pipe introducing the low-pressure refrigerant into the mixing chamber. 
     The above described and many other features and attendant advantages of the present invention will become apparent as the invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following is a detailed description of the best presently known mode of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention. The scope of the invention is defined by the appended claims. 
     Jet pump  1  (see FIG. 1) consists of an evaporator body  2 , a narrowing channel  4  with an inlet  8  and an outlet  12 , a mixing chamber  13  and inlet  11  for the entrance of low-pressure refrigerant, a screen  5  with holes  6 , and a movable piston  3  with a stopper  7  and upper part  9 , a ring-shaped nozzle  10  formed between the margin of the upper part  9  of the movable piston  3  and inside surface of the narrowing channel  4 . 
     High pressure refrigerant enters the jet pump through the inlet  8 , holes  6 , flows around the movable piston  3  and through the ring-shaped nozzle  10  between the inside surface of narrowing channel  4  and the margin of upper part  9  of the piston  3 , into outlet  12  to the mixing chamber  13 . The low-pressure refrigerant is introduced into the mixing chamber  13  through the inlet  11  due to the reducing pressure of high-pressure refrigerant within the outlet  12  and mixes with high-pressure refrigerant. At the beginning of refrigeration the pressure above the piston  3  is higher than below it and causes the piston to move down thereby expanding the cross-section area of the ring-shape nozzle  10 . As refrigeration proceeds the pressure under the piston  3  increases causing the piston to move up thereby reducing the cross-section area of the ring-shape nozzle  10 . The vertical motion of the piston  3  automatically changes the quantity of refrigerant introduced into the evaporator. If the pressure of working liquid (high-pressure refrigerant) rises too rapidly, the stopper  7  prevents the plugging of the outlet  12 . 
     According to the second embodiment of the present invention jet pump  1  (see FIG. 2) consists of a body  2 , a narrowing channel  4  with an inlet  8  and an outlet  12 , a mixing chamber  13  and inlet  11  for the entrance of low-pressure refrigerant, a screen  5  with holes  6 , and a movable piston  3  with a stopper  7  and upper part  9 , a ring-shaped nozzle  10  formed between margin of the upper part  9  of the movable piston  3  and inside surface of the narrowing channel  4 , a buffer  14 . 
     High pressure refrigerant enters the jet pump through the inlet  8 , holes  6 , flows around the movable piston  3  and through the ring-shaped nozzle  10  between the inside surface of narrowing channel  4  and the margin of upper part  9  of the piston  3  into outlet  12  to the mixing chamber  13 . The low-pressure refrigerant is introduced to the mixing chamber  13  through the inlet  11  due to the reducing pressure of high-pressure refrigerant within the outlet  12  and mixes with high-pressure refrigerant. At the beginning of refrigeration the pressure above the piston  3  is higher than below it and causes the piston to move down thereby expanding the cross-section area of the ring-shaped nozzle  10 . As refrigeration proceeds the pressure under the piston  3  increases causing the piston to move up thereby reducing the cross-section area of the ring-shaped nozzle  10 . The vertical motion of the piston  3  automatically changes the quantity of refrigerant introduced into the evaporator. If the pressure of working liquid (high-pressure refrigerant) rises too rapidly, the stopper  7  and the buffer  14  prevent the plugging of the outlet  12 . 
     According to the third embodiment of the present invention jet pump  1  (see FIG. 3) consists of a body  2 , a narrowing channel  4  with outlet  23 , a mixing chamber  24 , and an inlet  18  for the entrance of high-pressure refrigerant, a screen  5 , a pipe  17  with inlet  16 , outlet  22  and flange  21  placed into the channel  4 , and movable piston  25  with upper part  19 . Between the margin of the upper part  19  of the movable piston  25  and the inside surface of the narrowing channel  4  is formed a ring-shaped nozzle  20 . 
     High-pressure refrigerant enters the jet pump through the inlet  18 , flows around the movable piston  25  and through the ring-shaped nozzle  20  between the inside surface of the narrowing channel  4  and the margin of the upper part  19  of the piston  25  into outlet  23  to the mixing chamber  24 . The low-pressure refrigerant is introduced into the mixing chamber  24  through the outlet  22  of the pipe  17  due to the reducing pressure of high-pressure refrigerant and mixes with high-pressure refrigerant. 
     At the beginning of refrigeration the pressure above the piston  25  is higher than below it and causes the piston to move down thereby expanding the cross-section area of the ring-shaped nozzle  20 . As refrigeration proceeds the pressure under the piston  25  increases causing the piston to move up thereby reducing the cross-section area of the ring-shaped nozzle  20 . The vertical motion of the piston automatically changes the quantity of refrigerant introduced into the evaporator. If the pressure of working liquid (high-pressure refrigerant) rises too rapidly, the flange  21  of the pipe  17  prevents the plugging of the ring-shaped nozzle  25 . 
     This invention has been described in its presently contemplated best modes, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.