Abstract:
A package marine air conditioning unit places an evaporator coil on the inlet side of an enclosing cabinet, an axial supply fan on an opposing outlet side of the cabinet, and a compressor disposed between the evaporator coil and the supply fan. Locating the compressor within the air stream on the leaving air side of the evaporator coil allows cold air to flow around the compressor thereby providing beneficial compressor cooling. An axial flow supply fan located downstream of the compressor functions to draw return air in a generally lineal flow path across the evaporator coil and around the compressor, for discharge in an axial direction thereby resulting in a generally linear air flow path through the unit. A cabinet is provided to enclose the components thereby allowing for the installation of electric heating elements. Enclosing the components within a cabinet avoids the need to paint or otherwise coat the enclosed components thereby reducing manufacturing costs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/166,308 filed on Apr. 3, 2009. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       COPYRIGHT NOTICE 
       [0003]    A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise retains all copyright and all other rights reserved. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates generally to marine air conditioning systems, and more particularly to a compact, self-contained water cooled package air conditioning system for the marine industry. 
         [0006]    2. Description of Related Art 
         [0007]    Air conditioning (“A/C”) systems have been installed on marine vessels for many years. Marine air conditioning systems are typically comprised of water cooled vapor-compression refrigeration system, configured as packaged or split systems that function in either straight cool or heat pump modes. These systems are typically specially designed for installation on marine vessels wherein space is extremely limited and quiet operation is required. The installation of air conditioning systems in marine vessels is wrought with difficulties and limitations that are unique to such applications. 
         [0008]    As used herein the term “package system” shall mean an air conditioning system wherein the compressor, condenser coil, evaporator coil, and evaporator fan are installed in close proximity, typically manufactured as an installable unit. As used there the term “split system” shall mean an air conditioning system wherein at least the compressor is mounted remote from the evaporator coil. 
         [0009]    In marine vessel installations, the use of split systems is primarily driven by a desire to locate the compressor in a remote area, such as the engine room, in order to reduce noise transmission to the occupied cabins and parts of the vessel. The use of split systems results in significantly increased installation costs, and requires running refrigerant lines throughout the vessel to connect the compressor to a remotely located evaporator coil. Accordingly, there is a strong preference for the use of package systems. 
         [0010]    One significant limitation presented when attempting to install package A/C units on a marine vessel involves is a lack of space. More particularly, space on marine vessels is very limited, and interior rooms and cabins often present little or no unused or free space to accommodate the installation of an air conditioning unit. Accordingly, an important characteristic of a marine air conditioning unit is compact size. Another problem experienced with marine air conditioning units involves excessive sound/noise levels. Space limitations often dictate that marine air conditioning systems be installed in proximity to frequently occupied spaces such as cabins and sleeping quarters. For example, package A/C units are often installed under seats, benches, and beds, within rooms and spaces that are frequently occupied. As a result of such limitations, advancements in marine air conditioning units that result in quieter operation are important. 
         [0011]    A further problem experienced with conventional marine air conditioning units relate to performance. Efforts to minimize the size marine A/C systems have resulted in component configurations wherein the distance between the evaporator coil and the evaporator fan inlet is very small. Such configurations have been found to perform unsatisfactorily. A common problem experienced with such configurations is the formation of ice on the evaporator coil. The icing problem is a result from uneven air flow across the coil due to the close spacing of the evaporator coil and the supply fan inlet, which causes low face velocities along the coil periphery. In an attempt to rectify such problems, some models incorporate complex control schemes that temporarily terminate cooling mode operation in an attempt to de-frost the evaporator coil thereby interrupting the flow of cold air to the conditioned space. Another problem associated with package marine air conditioning units in the art involves the migration of moisture from the coil into the discharge airstream resulting from localized excessive air velocity across the coil. Moisture drawn from the coil into the discharge airstream is supplied to the conditioned space thereby raising the humidity level. 
         [0012]    A further problem found in package marine air conditioners in the art involves the location of the compressor. More particularly, prior art designs (both packaged and split systems) typically locate the compressor in an area that is not exposed to air flow thereby failing to cool the compressor leading to compressor overheating. In other designs the compressor is located upstream of the evaporator coil and thus is exposed to relatively warm return air. Both of said locations fail to provide the compressor with adequate ambient cooling resulting in performance degradation. 
         [0013]    Yet another limitation present with commercially available package marine A/C units involves air flow paths. In particular, conventional package marine A/C units typically use centrifugal fans to draw air across the evaporator coil and supply cold air to the conditioned space. A centrifugal fan typically draws air in from one direction and discharges the air in a direction that is generally perpendicular to the inlet direction. Accordingly, the air flow path through such package A/C units follows an L-shaped (i.e. 90-degree) path. The present inventor has found that an L-shaped air-flow path renders installation exceedingly difficult in a large number of cases wherein the available space is long and narrow leaving little if any room to re-direct the air 90-degrees from the evaporator coil inlet to the supply fan outlet. 
         [0014]    An example of a package prior art marine U.S. Pat. No. 5,848,536, issued to Dodge et al., which discloses a self-contained marine air conditioner having the limitations and disadvantages discussed above. Dodge discloses a self-contained marine air conditioning unit wherein, in an effort to minimize overall size, the distance between the evaporator coil and evaporator fan intake is relatively small. The design disclosed by Dodge, however, failed to significantly reduce noise as a result of positioning the blower in close proximity to the evaporator coil thereby allowing blower sound to propagate from the unit. The design disclosed by Dodge, is further burdened by evaporator coil freeze-up (e.g. icing) resulting from the close spacing between the evaporator coil and blower inlet in the draw-thru configuration (e.g. wherein air is drawn across the evaporator coil), which configuration results in uneven airflow across the coil. Finally, the Dodge system places the compressor outside of the air stream thereby relying on solely on internal refrigerant flow to cool the compressor. It has been found, however, that in warm operating conditions this system is prone to compressor overheating, and in cold operating conditions liquid refrigerant has been found to migrate back to the compressor, both undesirable situations can lead to compressor failure. A further limitation present with the configuration disclosed by Dodge, as well as all other configurations that do not incorporate a cabinet or enclosure to house the components is the inability to incorporate electric heat. As seen in the Dodge reference, the major components, namely the compressor, evaporator coil, condenser, etc. are mounted on a base frame or chasis essentially exposed without a protective cabinet. One disadvantage of exposing the components involves the inability to incorporate electric heating elements due as exposed heating coils would be a fire hazard. 
         [0015]    As should now be apparent, self-contained marine air conditioning units, such as the one disclosed by Dodge, are burdened with significant limitations and disadvantages. Accordingly, there thus exists a need for an improved, compact, self-contained marine air conditioning unit that is more practical, reliable, quieter, cost effective, and smaller, than units currently available. 
       BRIEF SUMMARY OF THE INVENTION 
       [0016]    The present invention overcomes the limitations and disadvantages present in the art by providing an improved compact package marine A/C system particularly well adapted for installation and use within marine vessels, while providing a system that is more practical, reliable, quieter, and smaller. A package marine A/C unit in accordance with the present invention places the evaporator coil on the inlet side of the unit with the compressor between the evaporator coil leaving air side and the supply fan inlet. Locating the compressor within the conditioned air stream on the leaving air side of the evaporator coil allows cold air to flow around the compressor thereby providing beneficial compressor cooling. An axial flow supply fan is located downstream of the compressor and functions to draw return air in a generally lineal flow path across the evaporator coil and around the compressor, for discharge in an axial direction thereby resulting in a generally linear air flow path through the unit. A spiral wound tubular refrigerant-to-water condenser is preferably disposed surrounding relation with the axial flow supply fan thereby minimizing space requirements. A cabinet is provided to enclose the components thereby allowing for the installation of electric heating elements. Enclosing the components within a cabinet avoids the need to paint or otherwise coat the enclosed components thereby reducing manufacturing costs. 
         [0017]    A marine A/C unit in accordance with the present invention significantly overcomes the limitations and disadvantages present in the art. Locating the compressor between the evaporator coil and supply fan creates increased separation between the evaporator coil and supply fan inlet, as compared with prior art marine air conditioners, such that even air flow across the evaporator coil is achieved thereby eliminating evaporator coil icing. In order to take full advantage of the available space, the present invention relocates virtually all the refrigeration and electrical components between the evaporator and the fan intake without significantly interfering with airflow across the coil. In addition, providing sufficient space between the evaporator coil and supply fan eliminates localized high evaporator coil air flow velocities such that water does not become entrained in the leaving air stream. The use of an axial flow fan allows for the air to travel through the unit in a generally linear air flow path thereby avoiding the L-shaped flow paths associated with prior art devices. Mounting the compressor in the interior of the unit, namely between the evaporator coil and the supply fan, functions to significantly reduce compressor noise propagation, and providing a cabinet enclosure results in further noise reduction. Placement of the compressor on the leaving air side of the evaporator coil causes cold, approximately 58° F., air to circulate around the compressor thereby providing improved external cooling leading to greater efficiency and longer compressor life. Finally, providing the unit with a cabinet to enclose the various components not only functions to reduce noise, but allows for the installation of electric heating elements safely within the confines of the housing. 
         [0018]    Accordingly, it is an object of the present invention to provide a compact marine air conditioning system that overcomes the shortcomings of the prior art systems. 
         [0019]    Another object of the present invention is to provide such a system that is compact while maximizing the distance between the evaporator coil and supply fan inlet. 
         [0020]    Yet another object of the present invention is to provide such a system configured with a generally linear air flow path. 
         [0021]    Still another object of the present invention is to provide such a system wherein the compressor is located downstream from the evaporator coil so as to improve compressor performance and reliability. 
         [0022]    Another object of the present invention is to provide such as system wherein the supply fan comprises an axial flow configuration for maintaining a linear air flow path and supply air discharge. 
         [0023]    Yet another object of the present invention is to provide such a system that is enclosed by a cabinet. 
         [0024]    Still another object of the present invention is to provide such a system capable of being equipped with electric heating elements. 
         [0025]    Another object is to provide a multi configuration marine air conditioning unit that is very quiet, esthetically pleasing since mechanical and electrical components are all enclosed, preventing any damage of exposed components, thus making the unit easier to manufacture because the compressor and related components do not need to be painted. 
         [0026]    In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0027]    Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
           [0028]      FIGS. 1-3  depict a marine air conditioning unit in accordance with the prior art; 
           [0029]      FIG. 4  is a side view schematic diagram of a compact marine air conditioning unit in accordance with the present invention; 
           [0030]      FIG. 5  is a top view schematic thereof; and 
           [0031]      FIG. 6  depicts an alternate embodiment including a supply fan remotely mounted from the main unit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Turning now to the drawings,  FIGS. 1-3  depict a self-contained marine air conditioning unit in accordance with the prior art as disclosed in U.S. Pat. No. 5,848,536, issued to Dodge et al., referenced above. The Dodge A/C unit is generally characterized as having an evaporator coil that functions to transfer heat between refrigerant contained within the coil and return air circulating across the coil. In an effort to minimize unit size, an evaporator fan is mounted with an intake in close proximity with the evaporator coil. In a further attempt to reduce unit size a refrigerant-to-water heat exchanger, which functions as a condenser, is mounted between the evaporator and the blower/supply fan. Various other mechanical and electrical components, including the compressor, and other mechanical and electrical apparatus are mounted along side the evaporator coil. As noted above, the placement of the supply fan inlet in close proximity to the evaporator coil results in uneven airflow across the evaporator coil, particularly at the coil edges and corners. This uneven airflow is known to cause ice to form on the coil thereby leading to coil freeze-up and resulting unit shut down. In addition, since the compressor is not mounted in an air stream, the Dodge unit relies exclusively on internal refrigerant flow to cool the side-mounted compressor. It has been found that in warm operating conditions the unit is prone to overheating, and in cold operating conditions liquid refrigerant has been found to migrate back to the compressor, both situations are present conditions that lead to compressor failure. The blower discharge is angled upward 90-degrees relative to the return air stream thereby complicating installation in a large number of vessels. Finally, the lack of a cabinet to enclose the components exposes the unit to damage. In addition, sales and marketing considerations mandate that the components be painted, which significantly increases manufacturing time and cost. 
         [0033]      FIGS. 4-6  provide schematic illustrations of a compact self-contained marine air conditioning system/unit, generally referenced as  10 , in accordance with the present invention. It should be noted that all refrigerant lines are not shown to simply the illustration. The routing of refrigerant lines between the compressor, evaporator, and condenser, is considered within the ordinary skill in the art, and may be accomplished in any of a variety of configurations. Air conditioning unit  10  comprises a water-cooled package marine air conditioning unit specifically designed for installation on marine vessels. Marine air conditioning unit  10  is preferably manufactured in various sizes and tonnage capacities, including ½ ton (e.g. 6,000 BtuH), 1.0 ton, 1½ ton, 2 ton, etc. Marine air conditioning unit  10  includes an evaporator coil  20 , a refrigerant compressor  30 , a water-cooled condenser  40 , a supply fan  50 , and a cabinet  60  for substantially enclosing the components. Evaporator coil  20  preferably comprises a fin and tube refrigerant-to-air heat exchanger as used in direct expansion vapor compression refrigeration cycle units. Evaporator coil  20  may be any suitable configuration, e.g. flat, L-shaped, A-shaped, etc., and may further be disposed on any suitable side or sides of the cabinet. Compressor  30  preferably comprises a scroll-type refrigerant compressor of the type commonly used in vapor compression refrigeration systems, however, any suitable compressor is considered within the scope of the present invention. Condenser  40  preferably comprises a generally tubular co-axial water-to-refrigerant heat exchanger. Supply fan  50  preferably comprises an axial flow fan that functions to discharge the cooled air in a generally linear flow path, e.g. perpendicular to the evaporator coil face. Accordingly, the present invention draws air in from one direction and discharges the air from the other side in the same direction. Cabinet  60  is preferably thermally insulated and functions to substantially enclose evaporator  20 , compressor  30 , condenser  40 , supply fan  50  (in a first embodiment), and various electrical and control components, such as capacitors. In addition, cabinet  60  further functions to enable marine air conditioner  10  to be equipped with optional electric heating elements, referenced as  70 . 
         [0034]    A number of significant advantages over prior art marine air conditioning units are realized by a marine A/C unit in accordance with the present invention. One advantage relates to eliminating ice formation on the evaporator coil  20  by locating the compressor  30  between evaporator coil  20  and supply fan  50  so as to create increased separation between evaporator coil  20  and the supply fan inlet  52 , as compared with prior art marine air conditioners, such that even air flow across the evaporator coil is achieved. In addition, maximizing the spacing between evaporator coil  20  and supply fan  50  eliminates localized high evaporator coil air flow velocities generated by the supply fan inlet such that water does not become entrained in the leaving air stream. In order to take full advantage of the available space, the present invention locates virtually all the refrigeration and electrical components between the evaporator and the fan intake without significantly interfering with airflow across the coil. Accordingly, electrical components, such as capacitors, contactors, resistors, etc. may be mounted between the leaving air side of the evaporator coil and the supply fan/blower inlet, which location is in the path wherein conditioned (e.g. cooled) air circulates thereby helping to prevent said electrical components from overheating. 
         [0035]    A further significant advantage of the present invention involves the use of an axial flow supply fan. More particularly, the use of an axial flow supply fan allows for the air to travel through the unit in a generally linear air flow path thereby avoiding the L-shaped flow paths associated with prior art devices. As a result air enters the evaporator and is discharged from the unit in generally the same direction, e.g. along a linear flow path from unit inlet to unit discharge. This feature is considered particularly important when installing the unit on a marine vessel wherein such units are often installed below seats, benches, and bunks (e.g. beds) wherein the available space is typically long and narrow. The shape of axial flow supply fan  50  further allows for positioning of a water-to-refrigerant heat exchanger wound in surrounding relation with fan  50 . This configuration maximizes use of the space and minimizes the overall size of the unit. In a contemplated alternate embodiment, fan  50  may be remotely mounted so as to allow for adaptable installation of one or more fans in communication with the unit via air ducts. 
         [0036]    In an alternate embodiment depicted in  FIG. 6 , supply  50  is adapted for installation remote from the main unit and connected by a duct  80 . Duct  80  preferably comprises flexible tubular duct. The embodiment depicted in  FIG. 6 , further minimizes the required installation space for the main unit by replacing the unit mounted supply fan shown in  FIGS. 4 and 5 , with a fan that may be mounted in a suitable remote location, such as in a cabin. As best seen in  FIG. 6 , the condenser coil  40  is configured in surrounding relation with compressor  30 . This configuration allows the condenser inlet and outlet to project from cabinet  60  on the opposite side of evaporator coil  20  (rather than from the side as depicted in the embodiment shown in  FIGS. 4 and 5 ), in a linear direction, e.g. along the air flow path, thereby further facilitating installation of the system within a long but narrow space. 
         [0037]    Yet another significant advantage relates to improved silencing. Mounting the compressor in the interior of an enclosed unit, namely between the evaporator coil and the supply fan, functions to significantly reduce compressor noise propagation, and providing a cabinet enclosure results in further noise reduction. More particularly, locating the compressor between the evaporator fan the and evaporator coil allows the body of the compressor to function as a sound barrier that prevents sound from propagating to the surrounding environment through the evaporator coil. 
         [0038]    Still another object of the present invention related to compressor performance and reliability. Placement of the compressor on the leaving air side of the evaporator coil causes cold, approximately 58-degree, air to circulate around the compressor thereby providing improved cooling leading to greater efficiency and longer compressor life. This configuration results in a number of significant advantages, namely, (1) reduced head pressure; (2) increased sub-cooling; (3) increased cooling capacity; and (4) increased dehumidification. More particularly, head pressure is reduced by mounting the compressor crankcase in contact with the cold air leaving the evaporator coil. This has the effect of decreasing the condensing pressure of the refrigerant and makes the system more efficient by increasing the net cooling capacity of the system due to the increased mass flow of refrigerant through the compressor. In addition, liquid sub-cooling is increased beyond that which would be achieved with a remote mounted compressor (e.g. one not exposed to evaporator coil leaving air) due to the circulation of cold (approx. 58° F.) air around the compressor. The resulting increased liquid sub-cooling increases gross cooling capacity due to lower enthalpy of the refrigerant entering the evaporator. A further advantage realized beyond increased cooling capacity is increased dehumidification due to the increased gross sensible and latent (e.g. total) cooling capacity resulting in lower evaporator coil leaving air temperature thereby causing more moisture to be removed from the air stream. Maximizing dehumidification is particularly important in marine air conditioning applications due to the inherently high humidity geographical locations frequented by marine vessels. Having the compressor located within the conditioned air stream and on the leaving air side of the evaporator coil functions to re-heat the air, a process known to result in increased dehumidification. Further, the provision of a housing  60  results in significant manufacturing cost savings since the internal components need not be painted as is demanded with A/C units that do not include a cabinet or housing. 
         [0039]    Similar efficiency advantages are realized by also placing the condenser coil within the conditioned air stream on the leaving air side of the evaporator coil. More particularly, head pressure is reduced by having the compressor crankcase and high pressure refrigerant hot gas and liquid in the outer tube of the water cooled condenser coil in contact with the cold air leaving the evaporator coil has the effect of increasing the efficiency of the condenser coil, and decreases the condensing pressure of the refrigerant. This also makes the air conditioner more efficient by increasing the net cooling capacity of the air conditioner due to the increased mass flow of refrigerant through the compressor. This configuration further leads to increased sub-cooling since the compressor crankcase and high pressure refrigerant hot gas and liquid in contact with the cold air has the effect of increasing the liquid sub-cooling beyond that which would normally be achieved. As a result, the water cooled condenser coil is more efficient with cold air being drawn across it as opposed to prior art systems wherein the condenser coil is disposed in the ambient environment. The effect of increasing the sub-cooling of the liquid beyond which would normally be achieved increases the gross cooling capacity of the air conditioner. This is due to the lower enthalpy of the refrigerant entering the evaporator. 
         [0040]    A further advantage realized by locating both the compressor and condenser coil in the conditioned air stream is realized. Because refrigerant gas is cooled by the air flowing over the compressor and condenser, even if water is not flowing through the condenser, a high pressure switch is not required to protect the unit against pump failures. 
         [0041]    Finally, providing the unit with a cabinet to enclose the various components not only functions to reduce noise, but allows for the installation of an electric heating coil, referenced as  70 , safely within the confines of the housing. Electric heat is an ideal option for marine air conditioner since the use of reverse cycle or heat pump units is not practical since such systems do not function efficiently if at all with low water temperatures found in cold water environments. Electric heat has been used in the past but the units had to be much too large in order to satisfy UL regulations that require a certain minimum distance between the electric element and the fan to avoid creating a fire hazard. The present invention overcomes this limitation by using the compressor as a shield and distance creating structure to ensure a safe distance between the fan and the electric heating element or heat strip. 
         [0042]    A further and inherent advantage of a marine air conditioner in accordance with the present invention involves ease of installation. As noted above, marine air conditioning units must often be installed below seats, benches, and bunks (e.g. beds) wherein the available space is typically long and narrow. Since marine air conditioning systems of the prior art typically form a 90-degree angled flow path installation has proven difficult. Accordingly, the linear/in-line flow path achieved by a marine air conditioning unit in accordance with the present invention simplifies installation by essentially conforming to commonly available spaces. 
         [0043]    As should be apparent, various advantages of the present invention may be realized independently. In addition, features disclosed herein may be used with straight cool or heat pump systems, including water cooled an air cooled systems. 
         [0044]    The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.