Abstract:
The present invention overcomes several disadvantages inherent in the operation of heat generating systems, particularly in the operation of engine-generators sets. The present apparatuses and methods increase the efficiency of these systems and provide means to economize fuel in their operation. The present invention applies to many type of engines and engines set combinations, but particularly to engine generator sets that run on fuels. Heat generating systems such as an engine-generator set are immersed in a medium similar, but not necessarily equal to, one used on oil cooled or liquid filled electrical transformers with high thermal conductivity and a high voltage rating. The medium in the unit recovers wasted heat (thermal energy). The heat recovered is transferred with a heat transfer unit or heat exchanger and utilized directly, as useful energy, for many purposes, such as heating, or cooling with the use of absorption or adsorption chillers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/519,638 filed 26 May 2011, the entire contents and substance of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to heat recovery from the operation of a heat generating system immersed in a medium. More particularly, the present invention relates to heat recovery, and the dampening of noise, generated by an internal combustion engine-generator set, enclosed in a thermally insulated housing, and immersed in a non-combustible medium with a high heat transfer value and a high level of electrical isolation capacity. The present invention allows recovery of wasted heat energy from the engine-generator set and dampens noise generated by the engine-generator set. 
         [0004]    2. Description of the Related Art 
         [0005]    Engine-generator sets are used in countless applications where a ready source of electrical power is either inconvenient or unavailable. These sets are often used at construction sites, or outdoors where adverse weather conditions are unpredictable or unavoidable. Engine-generator sets are also often used as backup electrical power sources at businesses and homes. In these types of conditions, loss of electrical power due to the failure of the engine-generator set can result in a significant economic loss. Therefore, reliability of the components is extremely important. 
         [0006]    Internal combustion engines have been used to drive electric generators that convert mechanical energy of the engines into electricity for use in the field for many purposes. One problem plaguing the use of generator sets of this type is that these devices are noisy and uneconomical to operate. Since they must be run continuously to supply electricity, the noise generated by the internal combustion engine is unsuitable for many purposes, including their use in residential areas. Although many attempts have been made to enclose or house these units in special noise attenuation enclosures, these attempts have not been entirely satisfactory because, in addition to other problems, the level of noise reduction is not sufficient to effectively quiet the noise from the internal combustion engine. Noise abatement structures applied externally to the engine-generator set results in bulky and expensive noise control systems. Enclosures or housings supplied to reduce noise also tend to vibrate, thereby resulting in secondary noise emissions. In addition, problems have been experienced with the air cooling systems in such enclosed generator sets. 
         [0007]    Even though such enclosures have disadvantages, a housing surrounding the engine-generator set does reduce the noise created by the operating system, protect users from coming into contact with heated parts, and protect the engine-generator set from adverse weather conditions. Yet by enclosing the heat generating components, such as the internal combustion engine and alternator, with heat sensitive components, such as the starting battery and electrical controls, serious reliability issues arise. 
         [0008]    Using an air cooled engine for a small enclosed stand-by engine-generator set is very cost effective compared to fluid cooled engines, however using an air cooled engine creates significant design issues related to purging the housing of the air rejected from an air cooled engine. Another significant design issue is to prevent heated air from recirculation back into the engine air intake, especially in areas containing heat sensitive components. 
         [0009]    While noise and housing problems exist, another potentially more serious problem with the present design of electrical generator sets is that while a generator set is in operation, approximately 60 to 70 percent of the fuel used in the engine is converted into waste heat. This waste heat, or waste energy, is dissipated and lost into the atmosphere, or expelled as unburned hydrocarbons. This waste heat severely limits the efficiency of the generator set. If recovered, the conventionally wasted heat could be used, for example, for heating a building during the winter months or through an absorption or adsorption chiller to cool the same building during the summer months. Thus, it can be seen that there is a need for a method and apparatus that can both provide electric power and heat recovery for cogeneration and a quieter system as well. 
         [0010]    The present invention provides a method and apparatus for improving the efficiency of the operation of an electrical engine-generator set. The present invention further provides a method for recuperating, and efficiently using, the waste heat produced by the conventional internal combustion engine and the electrical generator during the operation of the system. The present invention further provides a method and apparatus for dampening the noise generated by the operation of an electrical engine-generator set. The present invention further provides a weather resistant enclosure that provides an improved heat recovery system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    Various embodiments of the present invention are directed towards apparatuses and methods for recovering heat generated during the operation of a heat generating system. 
         [0012]    Broadly described, an aspect of the present invention comprises a thermally insulated housing at least partially enclosing a heat generating system, a medium in heat transfer communication with at least a portion of the heat generating system, and a heat recovery subsystem to recover heat from the medium. The medium can comprise a heat adsorbing, high-voltage rated, fluid. In an embodiment of the present invention, the heat recovery subsystem can comprise a heat exchanger. In another embodiment of the present invention, the heat generating system can comprise an engine-generator set. The recovered heat can be transferred to an adsorption chiller. In another embodiment of the present invention, the recovered heat can be transferred to a heater. 
         [0013]    In another embodiment of the present invention, a method of recovering heat from a heat generating system can comprise: providing a medium capable of transferring heat, in heat transfer communication with at least a portion of a heat generating system, transferring heat from the heat generating system to the medium, and recovering heat from the medium. The medium can comprises a heat adsorbing, high-voltage rated, fluid. In an embodiment of the present invention, the transferring of heat from the heat generating system to the medium can comprise the use of a heat exchanger. In another embodiment, the heat may be transferred to a device capable of utilizing heat from the medium. The heat generating system can comprise an engine-generator set. 
         [0014]    In another embodiment of the present invention, an apparatus for the recovery of heat and dampening of noise generated during the operation of an engine-generator set can comprise: a thermally insulated housing at least partially enclosing an engine-generator set, a medium in heat transfer communication with at least a portion of the engine-generator set, a dampening subsystem to dampen at least a portion of the noise generated by the engine-generator set, and a heat recovery subsystem to recover heat from the medium. The medium can comprise a heat adsorbing, high-voltage rated, medium. In an embodiment of the present invention, the heat recovery subsystem can comprise a heat exchanger. In another embodiment of the present invention, the medium can be in heat transfer communication with at least a portion of exhaust generated by the engine-generator set. In another embodiment of the present invention, at least a portion of medium passes through the generator via apertures therein. In an embodiment of the present invention, the dampening subsystem can comprise a muffler. In another embodiment of the present invention, the dampening subsystem can comprise at least a portion of the medium. 
         [0015]    In another embodiment of the present invention, at least one component of the set can be not enclosed in the thermally insulated housing. The recovered heat can be transferred to an adsorption chiller. In another embodiment of the present invention, the recovered heat can be transferred to a heater. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0016]    The various embodiments of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the various embodiments of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0017]      FIG. 1  is a side, sectional view of a preferred embodiment of the present invention where an engine-generator set is surrounded by a thermally insulated housing, and completely immersed in medium, according to an exemplary embodiment of the present invention. 
           [0018]      FIG. 2  is a side, sectional view of another preferred embodiment of the present invention where an exhaust pipe guides exhaust gases into a muffler, according to an exemplary embodiment of the present invention. 
           [0019]      FIG. 3  is a side, sectional view of the flow pattern of heat absorbing medium according to the proposed embodiment of the invention shown in  FIG. 1 . 
           [0020]      FIG. 4  is a side, sectional view of a heat exchanger, according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    Although preferred embodiments of the invention are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the invention is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity. 
         [0022]    It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. 
         [0023]    Also, in describing the preferred embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
         [0024]    By “comprising” it is meant that at least the named element, or method step is present in the apparatus or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named. 
         [0025]    It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified. 
         [0026]    Various embodiments of the present invention are directed towards apparatuses and methods for recovering heat generated during the operation of a heat generating system. 
         [0027]    An embodiment of the present invention is an apparatus comprising a thermally insulated housing at least partially enclosing a heat generating system, a medium in heat transfer communication with at least a portion of the heat generating system, and a heat recovery subsystem to recover heat from the medium. 
         [0028]    In an embodiment of the present invention, the heat generating system can comprise an engine-generator set.  FIG. 1  shows the present invention in a preferred embodiment of the set  10 , comprising an engine  20  that drives a generator  30 , both of which are contained within a thermally insulated housing  100 . The thermally insulated housing  100  is filled with a heat absorbing, high voltage rated, medium  90 . Preferably the engine  20  is a conventional internal combustion engine modified to run on natural gas, although the same could run on any type of fuel if so equipped. The generator set is used to supply electrical power to designated areas or equipments. 
         [0029]    As illustrated in  FIG. 1 , the present unit engine-generator set can be completely immersed in a medium  90 . The heat generated by the conventional engine-generator set that is typically lost as waste heat is recovered by the medium  90  in which the engine-generator set is immersed. 
         [0030]    The medium  90  serves to internally cool the entire set  10 , in particular the engine  20  and the generator  30 . The medium  90  also serves to absorb heat from the exhaust gases of the engine  20  by means of a heat exchanger  32 . 
         [0031]    The term “medium” is used herein for convenience and refers generically to many solids, liquids, gases, solutions, suspensions, powders, gels, dispersions, or combination thereof comprising at least one of the foregoing. The medium  90  should be high voltage resistant with good heat absorbing qualities, and the housing  100  should be thermally insulated to the external ambient. The medium should comprises cooling characteristics similar or better than the medium used to cool electrical high voltage transformers, with high voltage rating and excellent heat absorbing characteristics. The medium can comprise stable silicon-based or fluorinated hydrocarbons, combustion-resistant vegetable oil-based dielectric coolants, synthetic pentaerythritol tetra fatty acid esters, or naphthenic mineral oil. 
         [0032]    As shown in  FIG. 1 , internal combustion engine  20  draws air from the atmosphere through an intake pipe  22  having an air filter  24 , where ambient air serves as the combustion air for engine  20 . Intake pipe  22  protrudes through and above the hermetically closed housing  100 . 
         [0033]    The engine exhaust pipe  26  also protrudes through and out of housing  100 . 
         [0034]    In another embodiment of the present invention, the heat recovery subsystem can comprise a heat exchanger. As shown in  FIG. 2 , exhaust pipe  26  can guide exhaust gases from internal combustion engine  20 , after passing through heat recovery unit  32 , into a muffler  62 , which dampens the noise of the set  10 . Hot exhaust gases exit muffler  62  through muffler exhaust pipe  64 . The muffler exhaust pipe  64  expels the exhaust gases into the atmosphere. The heat recovery unit  32  transferred the recovered heat into medium  90 . 
         [0035]    Cooling of engine  20  and generator  30  is provided by the surrounding medium  90 , which is pumped throughout the system using pump  34 . Thus neither units, engine  20  nor generator  30 , need to incorporate individual cooling methods. 
         [0036]    In another embodiment of the present invention, as shown in  FIG. 1  and  FIG. 3 , medium  90  is sucked into the system by pump  34  through inlet  36 . Pump  34  can be driven directly from engine  20  or through an alternate method. Medium  90  continues to flow through heat exchanger intake  38  to heat exchanger  32 . Upon exiting the heat exchanger  32 , medium  90  can be directed to an end user or device through supply line  52  or pumped back to the housing  100 . The end device can be, for example, an absorption chiller (to cool) or to an air handling unit (to heat), or to any other device or means of utilizing the recovered heat energy. 
         [0037]    In the event of an air-cooled engine  20 , pump  34  can serve to pump the medium  90  through a special set of baffles (not shown) that forces the medium  90  through a set of fins (not shown) that are conventionally incorporated around the engine  20  in order to cool the engine  20  by the flow of medium  90 . Medium  90  is also forced through generator  30  to recover the heat generated by this unit during its operation. 
         [0038]    Generally the preferred embodiments are shown as  FIG. 1-4  of the present invention, however it will be understood by those skilled in the art that components of the present invention shown inside the housing  100  (thus immersed in medium  90 ) can be located outside the housing  100 , and conversely, some of those elements shown outside housing  100  can be located inside housing  100 . Only the engine  20  and generator  30  and appropriate piping must be immersed in medium  90 . For example, heat exchanger  32  can be inside or outside housing  100 , as can muffler  62 , air filter  24 , pump  42  or flow control valve  44 . All heat generated by the various components inside housing  100  is absorbed by medium  90 . In a preferred embodiment, medium  90  exits housing  100 , transfers its heat to an end device, or ambient, and return to set  10  through pipe  54  to continue the constant heat exchange with the submerged components. In another preferred embodiment shown in  FIG. 4 , the heat generated inside housing  100  can be directly transferred into a medium by means of a heat exchanger (H) build right into the housing  100 . This way the medium needed to cool the combination engine-generator set can be restricted to housing  100  and the medium to be utilized in heat recovery could be used, by means of pump (K), to transfer the recovered heat to do useful work outside the housing  100 . 
         [0039]    The means for passing the medium  90  through the heat exchanger  32  is illustrated in  FIG. 1  and  FIG. 2 , and described as preferably comprising pump  34 , intake  36  and exchanger intake  38 . Other embodiments of the means of passing the medium  90  through the heat exchanger  32  include an additional pump at the intake of heat exchanger  32  or running the returning medium from pipe  54  directly to the exhaust heat exchanger  32  and discharging the medium  90  back into the housing  100 . In the event that the medium  90  inside the housing  100  becomes too hot, a flow control valve  44  can reroute medium  90 , totally or partially, through radiator  46 . Radiator fan  48  can dissipate the heat of medium  90  into the surrounding space, and medium  90  can be returned into housing  100 . 
         [0040]    The electrical generator  30  can be a high efficiency alternator type that supplies alternating current to an electronic section, not shown, in enclosure  100 . The electronic section can transform the supplied alternating current into a stabilized alternating current with a desired voltage and or frequency or into a stabilized direct current with a desired voltage. A constant speed, brushless generator is also contemplated maintaining the output frequency at a constant value of 50 or 60 cycles, as desired. 
         [0041]    In a preferred embodiment, electrical generator  30  has a rotor with permanent magnets, or brushless, and openings for passing cooling medium through the inside of the unit. The stator of the electrical generator carries the electrical windings and includes sufficient clearance to let the cooling medium  90  flow freely throughout the unit. 
         [0042]    Electrical heaters  60  and  61  shown in  FIG. 1  will come into operation, individually, by means of relays if additional thermal energy is required. They will operate directly from the electric power generated by the unit otherwise the electric power generated will be sold to the power company. 
         [0043]    It should be understood, of course, that the foregoing relates only to preferred embodiments of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the claims.