Volumetric energy recovery system with three stage expansion

Abstract

A method for generating mechanical work via a closed-loop Rankine cycle includes heating a working fluid to at least a partial vapor state, generating useful work at a first expansion stage by expanding the working fluid as the working fluid passes through the first expansion stage, generating useful work at a second expansion stage by expanding the working fluid as the working fluid passes through the second expansion stage, generating useful work at a third expansion stage by expanding the working fluid as the working fluid passes through the third expansion stage, and condensing the working fluid to a liquid state.

What is claimed is: 
     
         1 . A method of generating mechanical work via a closed-loop Rankine cycle, the method comprising:
 heating a working fluid to at least a partial vapor state;   generating useful work at a first expansion stage by expanding the working fluid as the working fluid passes through the first expansion stage;   generating useful work at a second expansion stage by expanding the working fluid as the working fluid passes through the second expansion stage;   generating useful work at a third expansion stage by expanding the working fluid as the working fluid passes through the third expansion stage; and   condensing the working fluid to a liquid state.   
     
     
         2 . A method for generating mechanical work via a closed-loop Rankine cycle, the method comprising:
 passing the working fluid through a heat exchanging device to increase the temperature of the working fluid;   passing the working fluid through a first volumetric fluid expansion stage to decrease the temperature and pressure of the working fluid and to create a third mechanical work;   passing a working fluid through a second volumetric fluid expansion stage to decrease a temperature and pressure of the working fluid and to create a first mechanical work;   passing the working fluid through a third volumetric fluid expansion stage to decrease the temperature and pressure of the working fluid and to create a second mechanical work;   condensing the working fluid; and   returning the working fluid to the first volumetric fluid expansion stage.   
     
     
         3 . The method of  claim 2 , wherein the step of passing the working fluid through the heat exchanging device comprises:
 receiving, by the heat exchanging device, a heat stream from a power plant; and   transferring, by the heat exchanging device, heat from the heat stream to the working fluid.   
     
     
         4 . The method of  claim 2 , wherein the step of passing the working fluid through the heat exchanging device comprises providing a first heat exchanger arranged between the first volumetric fluid expansion stage and the second volumetric fluid expansion stage,
 the method further comprising:
 passing the working fluid through the first heat exchanger to increase the temperature of the working fluid, wherein the first heat exchanger is configured to receive a heat stream from a power plant and transfer heat from the heat stream to the working fluid. 
   
     
     
         5 . The method of  claim 4 , further comprising, after condensing the working fluid, passing the working fluid through a second heat exchanger to increase the temperature of the working fluid. 
     
     
         6 . The method of  claim 5 , wherein the step of passing the working fluid through the heat exchanging device comprises providing a third heat exchanger arranged downstream of the second heat exchanger to receive the working fluid from the second heat exchanger,
 the method further comprising:
 passing the working fluid through the third heat exchanger to increase the temperature of the working fluid, wherein the third heat exchanger is configured to receive a heat stream from a power plant and transfer heat from the heat stream to the working fluid. 
   
     
     
         7 . The method of  claim 5 , wherein the step of passing the working fluid through the heat exchanging device comprises providing a third heat exchanger arranged downstream of the second heat exchanger to receive the working fluid from the second heat exchanger,
 the method further comprising:
 passing the working fluid through the third heat exchanger to increase the temperature of the working fluid, wherein the third heat exchanger is configured to receive the heat stream from the first heat exchanger and transfer heat from the heat stream to the working fluid. 
   
     
     
         8 . The method of  claim 6 , wherein the step of passing the working fluid through the heat exchanging device comprises providing a fourth heat exchanger arranged downstream of the third heat exchanger to receive the working fluid from the third heat exchanger,
 the method further comprising:
 passing the working fluid through the fourth heat exchanger to increase the temperature of the working fluid, wherein the fourth heat exchanger is configured to receive a heat stream from a power plant and transfer heat from the heat stream to the working fluid. 
   
     
     
         9 . A system used to generate mechanical work via a closed-loop Rankine cycle, the system comprising:
 a power plant producing a heat stream and having a heat outlet through which the heat stream exits;   a heat exchanging device configured to transfer heat from the heat stream to a working fluid steam;   a first volumetric fluid expansion stage configured to receive the working fluid stream from the heat exchanging device;   a second volumetric fluid expansion stage configured to receive the working fluid stream from the first volumetric fluid expansion stage; and   a third volumetric fluid expansion stage configured to receive the working fluid stream from the second volumetric fluid expansion stage;   wherein each of the first, second, and third volumetric fluid expansion stages is configured to generate mechanical work from the working fluid stream.   
     
     
         10 . The system of  claim 9 , further comprising a condenser configured to receive the working fluid from the third volumetric fluid expansion stage and condense the working fluid. 
     
     
         11 . The system of  claim 10 , further comprising a pump configured to receive the working fluid from the condenser and pump the working fluid in the cycle. 
     
     
         12 . The system of  claim 10 , wherein the heat exchanging device includes a first heat exchanger configured to receive the heat stream from the power plant, receive the working fluid from the first volumetric fluid expansion stage, transfer heat from the heat stream to the working fluid steam, and provide the working fluid stream to the second volumetric fluid expansion stage. 
     
     
         13 . The system of  claim 10 , wherein the heat exchanging device includes a second heat exchanger configured to receive the working fluid discharged from the second volumetric fluid expansion stage, wherein the working fluid exiting the second heat exchanger flows into the condenser, the second heat exchanger further configured to receive the working fluid discharged from the condenser and transfer heat from the working fluid discharged from the third volumetric fluid expansion stage to the working fluid discharged from the condenser. 
     
     
         14 . The system of  claim 13 , wherein the heat exchanging device includes a third heat exchanger configured to receive the heat stream from the first heat exchanger and the working fluid from the second heat exchanger, the third heat exchanger configured to transfer heat from the heat stream to the working fluid discharged from the second heat exchanger. 
     
     
         15 . The system of  claim 14 , wherein the heat exchanging device includes a fourth heat exchanger configured to receive the heat stream from the power plant and the working fluid from the third heat exchanger, the fourth heat exchanger configured to transfer heat from the heat stream to the working fluid discharged from the third heat exchanger. 
     
     
         16 . The system of  claim 15 , wherein the first volumetric fluid expansion stage is arranged between the fourth heat exchanger and the first heat exchanger and configured to receive the working fluid discharged from the fourth heat exchanger and discharge the working fluid to the first heat exchanger.