Patent Publication Number: US-2003226360-A1

Title: Heat energy conversion apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to an apparatus for converting heat into mechanical energy.  
       [0003] 2. Prior Art  
       [0004] Various arrangements have been proposed heretofore for converting waste heat, such as from an internal combustion engine, into useful mechanical energy. For example, U.S. Pat. No. 4,069,672 to Milling discloses taking part of the ammonia in an engine&#39;s water-ammonia coolant to run a turbine. Other arrangements for similar purposes are disclosed in Murphy 4,019,325, Wang 4,472,939, Arvola et al 4,800,722, and ElDifrawi 4,266,404.  
       SUMMARY OF THE INVENTION  
       [0005] The present invention is directed to a novel apparatus for converting heat energy, typically waste heat, into mechanical energy that can be used for any chosen purpose.  
       [0006] In accordance with this invention, a heating fluid, such as hot air, is introduced into a heat exchanger where it heats a cooler gaseous second fluid, such as ambient air, that is pumped into the heat exchanger by a gas pump, and after being heated and pressurized in the heat exchanger drives a gas motor. The gas motor drives the pump as well as one or more other load devices performing useful work. The gas motor passes the heated, pressurized gaseous second fluid from the heat exchanger at a higher volumetric flow rate than the pump is introducing it in its unheated state into the heat exchanger. This volumetric flow rate difference is achieved either by the particular drive arrangement from the gas motor to the gas pump that provides a mechanical advantage of the motor over the pump or by the comparative sizes of the two  
       [0007] A principal object of this invention is to provide a novel and advantageous apparatus for converting heat energy into useful mechanical energy.  
       [0008] Another object of this invention is to provide such an apparatus of relatively simple construction using operating components of ready availability that have proved their reliability in a wide variety of other applications.  
       [0009] Further objects and advantages of this invention will be apparent from the following detailed description of certain presently preferred embodiments thereof, with reference to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 is a schematic cross-sectional view of a first embodiment of this invention;  
     [0011]FIG. 2 is a partial schematic cross-section showing the gas motor and the gas pump in a second embodiment of the invention; and  
     [0012]FIG. 3 is a view similar to FIG. 1 and showing a third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0013] Before explaining the present invention in detail it is to be understood that the invention is not limited in its application to the particular arrangements shown and described since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.  
     [0014] Referring to FIG. 1, in broad outline this embodiment of the present invention comprises a heat exchanger  10 , a gas motor  11 , a gas pump  12 , and an endless belt  13  driving the pump from the motor. Both the motor  11  and the pump  12  are of the type known as root pumps or roots blowers, having two high speed counter-rotating lobes of figure-eight cross-section which mesh without actually touching. When operating as a pump, this type of rotary lobe apparatus is capable of transferring gas at a relatively low compression ratio. When operating as a fluid motor, the gas pressure on its inlet side cause the figure-eight lobes to rotate. The gas motor  11  and the gas pump  12  are the same size in this embodiment of the invention. In FIG. 1 the gaseous fluid being pumped into the heat exchanger by pump  12  is unheated ambient air.  
     [0015] Heat exchanger  10  has chamber  14  with an inlet  15  connected directly to the outlet of pump  12  and an outlet  17  connected directly to the inlet of motor  11 . Inside the heat exchanger chamber  14  is a heat transfer conduit  18  of suitable construction for heating the air or other gaseous fluid coming into chamber from pump  12 . Conduit  18  may have external fins (not shown) to enhance the heat transfer effect. Conduit  18  has an inlet  19  for receiving air or other gaseous or liquid heating fluid after it has been heated by any suitable heat source, such as an automotive engine or air conditioner, the sun, or a combustible fuel. This incoming heating fluid passes along the interior of conduit  18  to an exhaust outlet  20 , transferring heat to the surrounding air or other gaseous second fluid in chamber  14 . Thus, it will be seen that conduit  18  provides a pathway for the heating fluid while the surrounding interior of heat exchanger  10  provides a separate pathway for the gaseous second fluid that is being pumped in by pump  12  to be heated and pressurized by heat transfer from the heating fluid in conduit  18 .  
     [0016] As a result of its being heated, as described, the pressure of the air or other gaseous second fluid in heat exchange chamber  14  increases to a value such that this pressure causes the lobes of gas motor  11  to rotate. One of these rotary lobes is attached to a small diameter pulley  21  driving the endless belt  13 . One of the rotary lobes of gas pump  12  is attached to a larger diameter pulley  22  which is driven by belt  13 . This provides a mechanical advantage for motor  11  over pump  12  so that the lobes of motor  11  rotate faster than the lobes of pump  12 . Consequently, the fluid motor  11  transfers the heated air or other gaseous second fluid out of the heat exchanger  10  at a higher volumetric flow rate than the pump  12  is pumping the unheated second gaseous fluid in its unheated state into the heat exchanger.  
     [0017] Either rotary lobe of the gas motor  11  or either rotary lobe of the gas pump  12  may be coupled to a power outlet drive arrangement to one or more external load devices (not shown).  
     [0018] In place of the pulleys  21  and  22  and the endless belt  13 , the gas motor  11  can drive the gas pump through suitable gearing that provides the desired mechanical advantage of the motor over the pump.  
     [0019]FIG. 2 shows a second embodiment of this invention having a gas motor  111  that is larger than the gas pump  112 , and one rotary lobe of the motor is connected directly to one smaller rotary lobe of the pump by a rigid shaft S. In this embodiment, the larger size of the motor  111  provides it the desired mechanical advantage over the pump  112 , whereby the volumetric flow rate of the heated second gaseous fluid from the heat exchanger through motor  111  is higher than the volumetric flow rate of the unheated gaseous second fluid delivered to the heat exchanger by pump  112 .  
     [0020] If desired, the conduit  18  in FIG. 1 may be omitted and the heating fluid may be introduced into the heat exchanger chamber for direct contact with the gaseous second fluid that is to be heated by heat transfer from the heating fluid. For example, the heating fluid may be hot oil droplets sprayed into the interior of the heat exchanger.  
     [0021] In the embodiment of FIG. 3 a feedback conduit  30  with heat-radiating fins  31  connects the outlet of gas motor  11  to the inlet of pump  12  to recirculate and cool the gaseous second fluid expelled from motor  11  and then re-introduce it to pump  12 . Any other suitable cooling arrangement in place of, or in addition to, the cooling fins may be provided to lower the temperature of the gaseous second fluid before it returns to pump  12 . In other respects, the embodiment of FIG. 3 is shown identical to the embodiment of FIG. 1. However, it is to be understood that the reccirculation conduit  30  may be provided with a gas motor and pump combination arranged as shown in FIG. 2.  
     [0022] It is to be understood that either the gas pump or the gas motor, or both, may be of a different type, either rotary or reciprocating, than the roots pump or blower shown in the drawings.