Patent Publication Number: US-6701733-B2

Title: Air conditioning system for marine applications

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Benefit is herein claimed of the filing date under 35 USC §119 and/or §120 and CFR 1.78 to U.S. Provisional Patent Application Serial No. 60/394,594, filed on Jul. 9, 2002, entitled “Air Conditioning System for Marine Applications.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to marine air conditioning systems and relates specifically to a system having a water-cooled condenser. 
     2. Description of the Related Art 
     For many years, air conditioning units have been installed on boats to provide comfortable areas on the boat during warm weather. Various methods of cooling the air on the boat have been used, including non-refrigerant cooling systems. However, a system using a compressed refrigerant is the most effective system in widespread use today. 
     In typical marine air conditioning systems, an electric motor drives a compressor for compressing refrigerant within a closed-system. The refrigerant becomes heated as it is compressed, and it then passes through a condenser for cooling the refrigerant. The condenser may be an air-cooled unit, in which air passes over tubing in the condenser for drawing heat from the refrigerant as it passed through the condenser. Another type uses water to cool the refrigerant, in which a pump draws water through a hole in the hull of the boat and over the condenser tubes. Either method sufficiently cools the refrigerant. 
     One disadvantage of using the current systems is that the electric motor typically requires the boat to be docked and connected to an outboard electrical source or to have an onboard generator. Without a generator, the system cannot be used when the boat is away from a dock. A disadvantage of a water-cooled system is that the system requires a separate water pump to pass water through the condenser. A related disadvantage is the additional holes in the hull that are required for the inlet and outlet of the pump for the condenser. 
     Many systems are available that use engine-driven compressors for compressing the refrigerant. However, these systems also use air-cooled condensers or water-cooled condensers that utilize a water pump in addition to that providing water to cool the engine. 
     Therefore, there is a need for a marine air conditioning system having a water-cooled condenser and that eliminates the need for a separate water pump for the condenser and the associated additional holes in the hull. There is also a need for such a system that is operable while away from a dock. 
     BRIEF SUMMARY OF THE INVENTION 
     A marine air conditioning system for installation on a boat comprises a compressor, a water-cooled condenser, and an evaporator. The compressor is preferably directly driven by an engine used for propelling the boat. The condenser is installed inline in a cooling-water intake tube, through which a pump draws raw water from outside of the hull for cooling the engine. The raw water from the intake tube is drawn through a portion of the condenser in thermal communication with the refrigerant for transferring heat from the refrigerant to the water. The raw water then continues into the engine cooling system and is exhausted through a discharge tube. The refrigerant passes through an expansion valve, and then into the evaporator. Air is passed through the evaporator for cooling the air, and the refrigerant returns to the compressor for recirculation in the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings. 
     FIG. 1 is a schematic view of an air conditioning system according to the invention and installed on a boat. 
     FIG. 2 is a perspective view of the condenser of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a boat  11  having an air conditioning system  13  installed thereon. System  13  is a sealed system containing a refrigerant (not shown) used in a refrigeration cycle. System  13  is engine-driven and water-cooled to provide cool air to a passenger cabin, helm, or other desired location on boat  11  without the need for an external power source to be connected to boat  11 . The main components of system  13  are compressor  15 , condenser  17 , and evaporator  19 . 
     Compressor  15  is mounted on or near engine  21 . A belt pulley  23  on engine  21  is connected by belt  25  to a belt pulley  27  on compressor  15 . When engine  21  is operating, pulley  23  rotates with engine  21 , turning belt  25  and pulley  27 . Pulley  25  is operably connected to a reciprocating piston (not shown), rotary valve, or other means located within compressor  15  for compressing the refrigerant within system  13 . A clutch or other type of controller (not shown) selectively controls the output of compressor  15 . The refrigerant enters compressor  15  through hose  29 , which extends from evaporator  19 , and exits compressor  15  through hose  31 , which extends to condenser  17 . 
     A pump  32 , which may be driven by engine  21 , as shown, or by other means, is used to draw raw water for cooling engine  21  into an intake tube  33 , through engine  21 , and out of discharge tube  35 . Though shown as drawing water through a hole formed in the hull of boat  11 , intake tube  33  may alternatively draw water from an outdrive portion of the propulsion system. Discharge tube  35  typically incorporates an outlet for exhaust gases from engine  21  and may discharge water through the hull, as shown, or at other locations on boat  11 . Alternatively, water drawn through intake tube  33  may pass through a liquid-to-liquid heat exchanger for transferring heat from a separate, closed cooling system for engine  21 , the raw water exiting out of discharge tube  35  without passing through engine  21 . 
     Condenser  17  is installed in intake tube  33 , the water passing through condenser  17  before passing through engine  21 . The water cools the compressed refrigerant flowing through condenser  17  and cools engine  21  before exiting boat  11  through discharge tube  35 . Though heat is transferred from the refrigerant to the water passing through condenser  17  prior to cooling engine  21 , the amount of heat transferred does not interfere with cooling of engine  21 . At least one oil cooler (not shown) or similar heat exchanger is typically located in intake tube  33 , the coolers preferably being located downstream of condenser  17 . This orientation allows cool intake water to first pass through condenser  17 , increasing the coefficient of performance of system  13 . 
     FIG. 2 shows details of condenser  17 . In the preferred embodiment, condenser  17  has a cylindrical outer body or housing  37 , an inlet  39 , and an outlet  41 . Portions of outer housing  37  are shown removed, revealing tubes  43  located in interior volume  45  within housing  37 . The walls of inlet  39  and outlet  41  are sealingly connected to header plates  47 ,  49 , header plate  47  being visible near inlet  39 . The ends of tubes  43  are connected to header plates  47 ,  49 , creating a chamber, or manifold  51 ,  53 , on each end of condenser  17 . Manifold  51  communicates inlet  39  with tubes  43 , and manifold  53  communicates tubes  43  with outlet  41 , the plurality of tubes  43  providing multiple paths for water to flow between inlet  39  and outlet  41 . Hose  31  and hose  48  are connected to housing  37  and communicate with volume  45  for passing refrigerant through volume  45  and around tubes  43 . Having multiple tubes  43  provides for increased surface area for the thermal interface between the refrigerant in volume  45  and the water in tubes  43 . 
     Referring again to FIG. 1, refrigerant passes from condenser  17  to evaporator  19  through hose  48 . An expansion valve (not shown) is located before evaporator  19 , the valve causing a pressure and temperature drop in the refrigerant. A fan  49  blows air across evaporator  19  for cooling the air through heat transfer to the refrigerant. The refrigerant exits evaporator  19  through hose  29  and flows to compressor  15  for recirculation in system  13 . 
     In operation, engine  21  rotates pulley  23  and operates a water pump to move water into intake  33 , through engine  21 , and out of discharge  35 . Belt  25  connects pulley  27  on compressor  15  to pulley  23 , rotating pulley  27  as pulley  23  rotates. A reciprocating piston or other means, operated by pulley  27 , compresses gaseous refrigerant contained in system  13 . The temperature of the refrigerant increases as it is compressed. 
     The refrigerant flows through hose  31  from compressor  15  to condenser  17 . Condenser is located inline with intake tube  33 , through which the pump draws water for cooling engine  21 . Water flows into condenser  17  through inlet  39 , through tubes  43 , and exits through outlet  41 . Refrigerant flows from hose  31  into volume  45  and passes in and around tubes  43 . Heat is transferred from the warmer, compressed, gaseous refrigerant to the cooler water through the sidewalls of tubes  43 . In the embodiment shown, the heated water flows out of condenser  17 , through engine  21 , and into tube  35  for discharge into the surrounding water, though the water may alternatively flow through a liquid-to-liquid heat exchanger rather than through engine  21 . Condenser  17  condenses the hot, gaseous refrigerant into a cooler, liquid refrigerant. 
     The cooled, liquid refrigerant flows from condenser  17  to evaporator  19  through hose  48 . An expansion valve, located upstream of evaporator  19  and considered part of an evaporator assembly, causes a pressure and temperature drop in the refrigerant, converting the refrigerant to a cold gas. Fan  49  blows ambient air over evaporator  19 , and heat is transferred from the air to the cold refrigerant. The cooled air is then circulated in selected areas of boat  11 . The refrigerant flows out of evaporator  19  as a heated gas and into hose  29  for return to compressor  15  and recirculation through system  13 . This cycle continues while compressor  15  and the water pump are operated by engine  21 . 
     Many advantages are realized from using the present invention. The air conditioning system of the invention uses an engine-driven compressor and a water-cooled condenser to provide cool air to portions of a boat without the need for external power. The condenser is located in the intake for cooling water for the engine, and water is drawn through the condenser by the engine water pump, eliminating the need for a second pump. Existing water conduits for cooling the engine may be used to provide cooling water for the condenser, thus additional holes in the hull, which are undesirable, are not required. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, the condenser may have a different exterior shape or configuration for fluid flow, such as concentric tubes or a single serpentine or coiled tube. Also, the water pump and compressor may be driven by various means, e.g., shafts, gears, etc.