Method and Device for Converting Thermal Energy Into Mechanical Work

Abstract

The invention relates to a method for converting thermal energy into mechanical work. Said method comprises the following steps which are performed as a cycle: A liquid work medium is fed from a supply reservoir ( 1 ) to a work container ( 3 ); the work medium in the work container ( 3 ) is heated by a first heat exchanger ( 5 ); a sub-amount of the work medium flows from the work container ( 3 ) to a pneumatic-hydraulic-converter ( 8 ), a hydraulic medium from the pneumatic-hydraulic-converter ( 8 ) is compressed in a work machine ( 9 ) in order to convert the hydraulic work of the hydraulic medium into mechanical work; the work medium from the pneumatic-hydraulic-converter ( 8 ) is fed back into the supply reservoir ( 1 ) and the hydraulic medium is returned into the pneumatic-hydraulic-converter ( 8 ). The invention also relates to a device for carrying out said method.

1 . A method for converting thermal energy into mechanical work, said method involving the following steps that are performed as a cyclic process:
 supplying a liquid working fluid from a storage reservoir ( 1 ) to a work tank ( 3 );   heating the working fluid in the work tank ( 3 ) via a first heat exchanger ( 5 );   allowing a fraction of the working fluid from the work tank ( 3 ) to overflow into a pneumatic-hydraulic converter ( 8 ), this causing a hydraulic fluid to be urged from the pneumatic-hydraulic converter ( 8 ) into a working machine ( 9 ) for conversion of the hydraulic work of the hydraulic fluid into mechanical work; and   returning the working fluid from the pneumatic-hydraulic converter ( 8 ) into the storage reservoir ( 1 ) by recirculating hydraulic fluid into the pneumatic-hydraulic converter ( 8 ).   
     
     
         2 . The method as set forth in  claim 1 , comprising compressing the working fluid from a first, lower pressure in the storage reservoir ( 1 ) to a second, higher pressure in the work tank ( 3 ). 
     
     
         3 . The method as set forth in  claim 2 , comprising transferring the working fluid in a liquid form from the storage reservoir ( 1 ) to the work tank ( 3 ). 
     
     
         4 . The method as set forth in  claim 3 , wherein the working fluid evaporates partially while being heated in the work tank ( 3 ) and is directed in the gaseous state from the work tank ( 3 ) into the pneumatic-hydraulic converter ( 8 ). 
     
     
         5 . The method as set forth in  claim 4 , comprising heating isochorically the working fluid in the work tank ( 3 ). 
     
     
         6 . The method as set forth in  claim 5 , wherein the connection between the work tank ( 3 ) and the pneumatic-hydraulic converter ( 8 ) is interrupted by a valve ( 7   a ) while the working fluid is being returned from the pneumatic-hydraulic converter ( 8 ) into the storage reservoir ( 1 ). 
     
     
         7 . The method as set forth in  claim 6 , comprising cooling the working fluid by a heat exchanger ( 15 ) while it is being supplied from the storage reservoir ( 1 ) into the work tank ( 3 ). 
     
     
         8 . The method as set forth in  claim 7 , wherein the hydraulic fluid is maintained by a heat exchanger at a temperature that corresponds to the mean temperature of the working fluid in the pneumatic-hydraulic converter ( 8 ). 
     
     
         9 . The method as set forth in  claim 8 , comprising directing the working fluid from the pneumatic-hydraulic converter ( 8 ) through a second heat exchanger ( 16 ). 
     
     
         10 . The method as set forth in  claim 9 , comprising expanding the working fluid coming from the pneumatic-hydraulic converter ( 8 ) to an expansion pressure that is lower than the first pressure in the storage reservoir ( 1 ) and compressing the working fluid to the first pressure thereafter. 
     
     
         11 . An apparatus for converting thermal energy to mechanical work, said apparatus comprising a storage reservoir ( 1 ), a work tank ( 3 ), and a working machine ( 9 ) for converting hydraulic work into mechanical work, wherein the work tank ( 3 ) communicates with a first heat exchanger ( 5 ) in order to heat the working fluid, that the work tank ( 3 ) is further connected to a pneumatic-hydraulic converter ( 8 ) that transfers the pressure of the working fluid to a hydraulic fluid and that there is provided a recirculation line for recirculating the working fluid from the pneumatic-hydraulic converter ( 8 ) into the storage reservoir ( 1 ). 
     
     
         12 . The apparatus as set forth in  claim 11 , including a feed pump ( 2 ) for pumping the working fluid from the storage reservoir ( 1 ) into the work tank ( 3 ). 
     
     
         13 . The apparatus as set forth in  claim 12 , wherein the first heat exchanger ( 5 ) is mounted in the work tank ( 3 ). 
     
     
         14 . The apparatus as set forth in  claim 13 , wherein the working machine ( 9 ) is a hydraulic motor. 
     
     
         15 . The apparatus as set forth in  claim 14 , wherein the pneumatic-hydraulic converter ( 8 ) a bladder accumulator. 
     
     
         16 . The apparatus as set forth in  claim 15 , including a second heat exchanger ( 16 ) interposed between the pneumatic-hydraulic converter ( 8 ) and the storage reservoir ( 1 ). 
     
     
         17 . The apparatus as set forth in  claim 16 , wherein the second heat exchanger ( 16 ) is a condenser. 
     
     
         18 . The apparatus as set forth in  claim 17 , including a booster pump downstream of the second heat exchanger ( 16 ). 
     
     
         19 . The apparatus as set forth in  claim 18 , wherein the work tank ( 3 ) is an evaporator. 
     
     
         20 . The apparatus as set forth in  claim 19 , including a third heat exchanger ( 11 ) in the circuit of the hydraulic fluid. 
     
     
         21 . The apparatus as set forth in  claim 20 , including an internal combustion engine having a cooling system that communicates with the work tank ( 3 ). 
     
     
         22 . The apparatus as set forth in  claim 21 , including a plurality of work tanks ( 3 ) and of pneumatic-hydraulic converters ( 8 ) connected in parallel.