Patent Abstract:
A bottle cooler system includes means for using atmospheric water condensate from the evaporator to draw heat from the condenser.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Benefit is claimed of U.S. Patent Application 60/663,912, entitled “CONDENSATE HEAT TRANSFER FOR TRANSCRITICAL CARBON DIOXIDE REFRIGERATION SYSTEM” and filed Mar. 18, 2005. Copending application docket 05-258, entitled HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM and filed on even date herewith, discloses prior art and inventive cooler systems. The present application discloses possible modifications to such systems. The disclosures of said applications are incorporated by reference herein as if set forth at length. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to refrigeration. More particularly, the invention relates to beverage coolers. 
         [0003]    As a natural and environmentally benign refrigerant, CO 2  (R-744) is attracting significant attention. In most air-conditioning operating ranges, CO 2  systems operate in transcritical mode. An example of a transcritical vapor compression system utilizing CO 2  as working fluid comprises a compressor, a gas cooler, an expansion device, an evaporator and the like (see  FIG. 1 ). The major difference between transcritical and conventional operation is that heat rejection in the gas cooler is in the supercritical region because the critical temperature for CO 2  is 87.8 F. Consequently, pressure is not solely dependent on temperature and this opens additional control and optimization issues for system operation. 
         [0004]      FIG. 1  schematically shows transcritical vapor compression system  20  utilizing CO 2  as working fluid. The system comprises a compressor  22 , a gas cooler  24 , an expansion device  26 , and an evaporator  28 . The exemplary gas cooler and evaporator may each take the form of a refrigerant-to-air heat exchanger. Airflows across one or both of these heat exchangers may be forced. For example, one or more fans  30  and  32  may drive respective airflows  34  and  36  across the two heat exchangers. A refrigerant flow path  40  includes a suction line extending from an outlet of the evaporator  28  to an inlet  42  of the compressor  22 . A discharge line extends from an outlet  44  of the compressor to an inlet of the gas cooler. Additional lines connect the gas cooler outlet to expansion device inlet and expansion device outlet to evaporator inlet. 
         [0005]    An electronic expansion valve is usually used as the device  26  to control the high side pressure to optimize the COP of the CO 2  vapor compression system. An electronic expansion valve typically comprises a stepper motor attached to a needle valve to vary the effective valve opening or flow capacity to a large number of possible positions (typically over one hundred). This provides good control of the high side pressure over a large range of operating conditions. The opening of the valve is electronically controlled by a controller  50  to match the actual high side pressure to the desired set point. The controller  50  is coupled to a sensor  52  for measuring the high side pressure. 
         [0006]    As the airflow  36  passes over the heat exchanger  28 , cooling of the airflow  36  causes the condensation of water out of that airflow. Disposal of that water may need to be addressed. One way involves using the heat rejection heat exchanger to heat the water to induce its evaporation. An example of such a system  60  is shown in  FIG. 2 . 
         [0007]    In the illustrated system  60 , components similar to those of the system  20  are shown with like numerals. For illustration, the control and sensor components are hidden. The gas cooler  62  is split into first and second sections  64  and  66 . Along the refrigerant flowpath  66 , the first section  64  is upstream of the second section  66 . The sections  64  and  66  may be along a common air flowpath to receive a common airflow  68  (e.g., driven by a fan  70 ) or may be on separate air flowpaths (e.g., driven by separate fans). If on a common air flowpath, the first section may be upstream/downstream of the second section. 
         [0008]    Water condensed from the airflow  36  is collected by a collection system  80 . An exemplary system  80  includes a pan  82  to which the water is delivered. A portion of the first section  64  is positioned to be immersed in a water accumulation in the pan. Heating of the water by the first section  64  encourages evaporation of the water. 
       SUMMARY OF THE INVENTION 
       [0009]    For advantageous performance, however, the condensate may preferably be exposed to a more downstream section of the heat rejection heat exchanger. A bottle cooler system includes means for using atmospheric water condensate from the evaporator to draw heat from the condenser. 
         [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic view of a prior art refrigeration system. 
           [0012]      FIG. 2  is a schematic view of another prior art refrigeration system. 
           [0013]      FIG. 3  is a schematic view of an inventive refrigeration system. 
           [0014]      FIG. 4  is a side schematic view of a display case bottle cooler including a refrigeration and air management cassette. 
           [0015]      FIG. 5  is a view of a refrigeration and air management cassette. 
           [0016]      FIG. 6  is a partial side schematic view of an alternative cassette. 
           [0017]      FIG. 7  is a partial side schematic view of an alternative cassette. 
           [0018]      FIG. 8  is a partial side schematic view of an alternative cassette. 
       
    
    
       [0019]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0020]      FIG. 3  shows a system  100  having a compressor  22 , expansion device  26 , and heat absorption heat exchanger (evaporator)  28 . These may be similar to corresponding components of the systems of  FIGS. 1 and 2 . For illustration, the control and sensor components are hidden. The gas cooler  102  is split into first and second sections  104  and  106 . Along the refrigerant flowpath  66 , the first section  104  is upstream of the second section  106 . The sections  104  and  106  may be along a common air flowpath to receive a common airflow  108  (e.g., driven by a fan  110 ) or may be on separate air flowpaths (e.g., driven by separate fans). In the exemplary system, the first section  104  is upstream of the second section  106  with the fan  110  intervening. 
         [0021]    Water condensed from the airflow  36  is collected by a collection system  112 . An exemplary system  112  includes a pan  122  to which the water is delivered. A portion of the second section  106  is positioned to be immersed in a water accumulation in the pan  122 . Heating of the water by the second section  64  may encourage evaporation of the water. Contrasted with the system of  FIG. 2 , the section of the gas cooler which gives up heat to the condensate is relatively downstream along the refrigerant flow path (e.g., in the cooler half or quarter of the temperature drop prior to the expansion device). This is intended to reduce the refrigerant temperature as much as possible by exposing the coldest refrigerant to the condensate. For a transcritical CO 2  refrigeration system, to maintain peak efficiencies it is critical to minimize the temperature at the exit of the high-side (gas cooler) heat exchanger. 
         [0022]    It is even more critical to minimize this exit temperature for a CO 2  bottle cooler refrigeration system. Manufacture costs are of particular concern. The result is that low cost/relatively lower efficiency heat exchangers (including but not limiting to wire-on-tube heat exchanger, plate-on-tube heat exchanger, finless heat exchanger etc.) are particularly useful for to control bottle cooler manufacture costs. 
         [0023]    Thus, a particular area for implementation of the condensate heat exchange is in bottle coolers, including those which may be positioned outdoors or must have the capability to be outdoors (presenting large variations in ambient temperature).  FIG. 4  shows an exemplary cooler  200  having a removable cassette  202  containing the refrigerant and air handling systems. The exemplary cassette  202  is mounted in a compartment of a base  204  of a housing. The housing has an interior volume  206  between left and right side walls, a rear wall/duct  216 , a top wall/duct  218 , a front door  220 , and the base compartment. The interior contains a vertical array of shelves  222  holding beverage containers  224 . 
         [0024]    The exemplary cassette  202  draws the air flow  108  through a front grille in the base  224  and discharges the air flow  108  from a rear of the base. The cassette may be extractable through the base front by removing or opening the grille. The exemplary cassette drives the air flow  36  on a recirculating flow path through the interior  206  via the rear duct  210  and top duct  218 . 
         [0025]      FIG. 5  shows further details of an exemplary cassette  202 . The heat exchanger  28  is positioned in a well  240  defined by an insulated wall  242 . The heat exchanger  28  is shown positioned mostly in an upper rear quadrant of the cassette and oriented to pass the air flow  36  generally rearwardly, with an upturn after exiting the heat exchanger so as to discharge from a rear portion o the cassette upper end. A drain  250  may extend through a bottom of the wall  242  to pass water condensed from the flow  36  to the drain pan  122 . A water accumulation  254  is shown in the pan  122 . The pan  122  is along an air duct  256  passing the flow  108  downstream of the heat exchanger first section  104 . The heat exchanger second section  106  is positioned to be at least partially immersed in the accumulation  254 . Exposure of the accumulation  254  to the immersed second section  106  and to the heated air in the flow  108  may encourage evaporation. 
         [0026]    In an exemplary, coil routing of the second section  106 , the second section is divided into a first portion normally above the accumulation and in the airflow  108  and a second portion normally immersed. The refrigerant flow path may pass generally downstream along the air flow  108  through the first portion and then pass into the second portion before proceeding to the expansion device. 
         [0027]    The  FIG. 5  arrangement is consistent with a basic reengineering of a baseline cassette having a single heat rejection heat exchanger located where the first section  104  is and nothing where the second section  106  is. It is also consistent with a reengineering of a split system where the hotter section is in that latter position. However, the illustrated configuration has the disadvantage that the cooler section is downstream of the hotter section along the air flow path. Accordingly, it may be desirable to reverse the air flow to become back-to-front. A portion of this back-to-front air flow could be directed to flow over the cooler door window to avoid window fogging. 
         [0028]    An alternative implementation might eliminate the physical separateness of the first section  104 . One example would be to only have a single heat rejecting heat exchanger unit positioned as represented by the second section  106  in  FIG. 5 . The immersed portion of that exchanger unit could serve the role of the second section  106  while the exposed portion could serve the role of the first section  104  (see  FIG. 6  below). Another simple variation could involve heat exchanger positioning so that water dripping from the drain flows over a leading portion of the heat exchanger (i.e., at the upstream end of the warm air flow). 
         [0029]    Various implementations may further maximize heat transfer via a counterflow exchange of condensate water and the refrigerant. This counterflow may be the exclusive method of heat exchange between the condensate and the refrigerant, or may supplement pan immersion or another mechanism.  FIG. 6  shows such a system, wherein the drain  250  having an outlet  260 . A length  262  of the refrigerant line extends upward to the outlet. The length  262  is positioned to guide/wick droplets of water from the outlet  260  downwardly along the length  262  to the drain pan. With refrigerant flowing upward through the length  324 , the refrigerant and water are in counterflow heat exchange. A more upstream (along the refrigerant flow path) length  264  (or portion of the heat rejection heat exchanger) may be immersed in the water  254  in the pan. a yet more upstream portion  270  may be in the air flow 
         [0030]    In another example of a supplementary situation, a relatively small downstream section of the gas cooler may run through/in the drain pan  122 . A smaller yet more downstream portion may run up into the to evaporator drain in a counterflow heat exchange (both along its length and/or merely a two step counterflow in combination with the portion in the pan). In the  FIG. 7  example, the drain  250  is replaced by a more convoluted drain  300 . The drain  300  has an upwardly directed U-portion  302  defining a water trap containing a water slug  304 . The drain  300  and slug  304  may prevent air leakage between the hot and cold air flows and might be used independently in place of the simpler drain  250 . The slug is continuously replenished by condensate flowing into the drain  300  and continuously discharges condensate down toward the pan  122 . A portion  306  of the refrigerant line extends from a remainder of the second section  106  and through the drain  300 . The expansion device (not shown) may be positioned between the downstream end of the line portion  306  and the evaporator  28 . Thus refrigerant flowing through the line portion  306  is in counterflow heat exchange with the condensate flowing through the drain  300 . Although shown piercing the drain  300 , the line portion  306  may enter the drain outlet  308  and/or exit the drain inlet  310  and more closely follow the path of the drain. 
         [0031]      FIG. 8  shows an alternate drain  320  having an outlet  322 . A length  324  of the refrigerant line extends upward to the outlet. The length  324  is positioned to guide/wick droplets of water from the outlet  322  downwardly along the length  324  to the drain pan. With refrigerant flowing upward through the length  324 , the refrigerant and water are in counterflow heat exchange. A more upstream (along the refrigerant flow path) portion of the heat rejection heat exchanger may be immersed in the water in the pan. 
         [0032]    In other implementations, the condensate could be delivered to air flow (e.g.,  108 ) just prior to its passing over the last portion of the heat rejecting heat exchanger (i.e., the gas cooler which would be a condenser if conditions were appropriate) so that the heat transfer is enhanced and hence the refrigerant temperature is reduced. This may be particularly effective in dry climates where evaporative cooling of the air flow is particularly relevant. 
         [0033]    This condensate to air delivery could be done in several ways. A wick could be placed upstream of the relevant section of the heat exchanger along the air flow. A spray device could be similarly positioned to introduce the spray of condensate to the air flow. Such a spray could also or alternatively directly contact the relevant heat exchanger portion to cool via evaporative or conventional cooling. Similarly, a wick could contact the heat exchanger to transport the water and provide conventional and/or evaporative cooling. 
         [0034]    Thus, it is seen that for transcritical bottle cooler applications, the water being condensed on evaporator surfaces is useful for refrigerant cooling to maintain efficiency. This approach especially provides additional efficiency for low cost, fouling resistant, heat exchangers like wire-on-tube, plate-on-tube, finless heat exchangers, and the like. This may enable performance comparable to high efficiency finned-tube conventional heat exchangers currently being used for bottle cooler applications. The protective coating typically present on low cost heat exchangers (wire-on-tube, plate-on-tube, etc.) may provide effective resistance to corrosion from the condensate to which the heat exchanger is exposed. 
         [0035]    One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when implemented as a remanufacturing of an existing system or reengineering of an existing system configuration, details of the existing configuration may influence details of the implementation. Exemplary baseline systems could be transcritical CO2 systems or could have other operational domains and/or other refrigerants. Accordingly, other embodiments are within the scope of the following claims.

Technology Classification (CPC): 5