Heat engines, systems for providing pressurized refrigerant, and related methods

Abstract

A method for generating power from a heat source includes mixing a refrigerant in a liquid phase with a lubricating oil, heating the mixture to evaporate the refrigerant, mixing the heated mixture with additional refrigerant in a superheated phase, and atomizing the lubricating oil to disperse the lubricating oil within the refrigerant. The atomized lubricating oil and the refrigerant are passed through a decompressor to generate an electrical current. The refrigerant may be an organic material having a boiling point below about −35 C. Related systems and heat engines are also disclosed.

What is claimed is:  
     
       1. A method comprising:
 mixing a lubricating oil with a first portion of a refrigerant in a bypass zone of a heat engine to form a mixture, the first portion of the refrigerant in a liquid phase;   heating the mixture of the lubricating oil and the first portion of the refrigerant in a high-pressure zone of the heat engine to form a heated mixture, wherein at least a portion of the first portion of the refrigerant is in a gaseous phase, wherein the refrigerant exhibits a boiling point below −35° C.;   mixing the heated mixture with a second portion of the refrigerant, the second portion of the refrigerant in a superheated phase;   atomizing the lubricating oil in an atomizer comprising a mixing media to disperse the lubricating oil within the refrigerant; and   cooling the refrigerant in a low-pressure zone of the heat engine through at least one heat sink;   wherein the high-pressure zone, the low-pressure zone, and the bypass zone form a closed-loop path for the refrigerant.   
     
     
       2. The method of  claim 1 , wherein atomizing the lubricating oil comprises passing the lubricating oil and the refrigerant through a metal mesh. 
     
     
       3. The method of  claim 1 , wherein heating the mixture of the lubricating oil and the first portion of the refrigerant to form a heated mixture comprises transferring heat to the mixture from at least one source selected from the group consisting of a waste heat source, an exhaust gas, a compressor intercooler, biomass, a geothermal heat source, and a solar array. 
     
     
       4. The method of  claim 1 , further comprising:
 passing the atomized lubricating oil and the refrigerant through a decompressor operatively associated with an electrical generator to decrease a pressure of the refrigerant and generate an electrical current;   separating at least a portion of the lubricating oil from the refrigerant; and   condensing at least a portion of the refrigerant to re-form the first portion of the refrigerant.   
     
     
       5. The method of  claim 4 , wherein the at least one heat sink comprises a first heat sink and a second heat sink, and wherein condensing at least a portion of the refrigerant to form the first portion of the refrigerant comprises transferring heat from the refrigerant to each of the first heat sink and the second heat sink. 
     
     
       6. The method of  claim 1 , wherein heating the mixture of the lubricating oil and the first portion of the refrigerant to form a heated mixture comprises increasing a specific volume of the mixture. 
     
     
       7. The method of  claim 1 , wherein atomizing the lubricating oil comprises maintaining the lubricating oil and the refrigerant at constant pressure. 
     
     
       8. The method of  claim 1 , further comprising mixing an additive with the mixture, the additive exhibiting a higher lubricity than the lubricating oil. 
     
     
       9. The method of  claim 1 , wherein mixing a lubricating oil with a first portion of a refrigerant to form a mixture comprises mixing the first portion of the refrigerant in a liquid phase with the lubricating oil downstream of a pump circulating the first portion of the refrigerant. 
     
     
       10. A heat engine, comprising:
 a high-pressure zone configured to transfer heat from at least one heat source to a refrigerant and configured to contain a first portion of the refrigerant in a gaseous phase, the refrigerant exhibiting a boiling point below −35° C.;   a low-pressure zone configured to transfer heat from the refrigerant to at least one heat sink and configured to contain a second portion of the refrigerant in a liquid phase;   a bypass zone configured to mix a third portion of the refrigerant with a lubricating oil, the third portion of the refrigerant and the lubricating oil in a liquid phase; and   an atomizer comprising a mixing media configured to atomize the lubricating oil and disperse the lubricating oil within the first and third portions of the refrigerant;   wherein a closed-loop path for the refrigerant comprises the high-pressure zone, the low-pressure zone, and the bypass zone.   
     
     
       11. The heat engine of  claim 10 , wherein the heat engine is configured to circulate the refrigerant in a Rankine cycle. 
     
     
       12. The heat engine of  claim 10 , further comprising a mixing device configured to mix the lubricating oil with the third portion of the refrigerant in the liquid phase. 
     
     
       13. The heat engine of  claim 10 , wherein the high-pressure zone comprises at least one wall of the at least one heat source configured to transfer heat from the at least one heat source to the first portion of the refrigerant in the liquid phase, wherein the at least one heat source is configured to evaporate the first portion of the refrigerant. 
     
     
       14. The heat engine of  claim 10 , further comprising a positive displacement decompressor configured to provide a pressure gradient through which the refrigerant in the gaseous phase flows continuously from the high-pressure zone to the low-pressure zone, the positive displacement decompressor configured to maintain a pressure differential between the high-pressure zone and the low-pressure zone of between 20 bar and 42 bar, the positive displacement decompressor configured to extract mechanical energy due to the pressure gradient. 
     
     
       15. The heat engine of  claim 14 , further comprising an electrical generator coupled to the positive displacement decompressor and configured to convert the extracted mechanical energy to electrical energy. 
     
     
       16. The heat engine of  claim 15 , further comprising a positive displacement hydraulic pump for providing continuous flow of the refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone. 
     
     
       17. The heat engine of  claim 10 , wherein the closed-loop path further comprises at least one heat-transfer conduit external to the heat engine. 
     
     
       18. A method comprising:
 mixing a lubricating oil with a first portion of a refrigerant in a bypass zone of a heat engine to form a mixture, wherein the first portion of the refrigerant is in a liquid phase;   heating the mixture of the lubricating oil and the first portion of the refrigerant in a high-pressure zone of the heat engine to form a heated mixture, wherein at least a portion of the first portion of the refrigerant is in a gaseous phase;   mixing the heated mixture with a second portion of the refrigerant, wherein the second portion of the refrigerant is in a gaseous or superheated phase;   atomizing the lubricating oil in an atomizer holding a mixing media to disperse the lubricating oil within the refrigerant; and   cooling the refrigerant in a low-pressure zone of the heat engine through at least one heat sink,   wherein the high-pressure zone, the low-pressure zone, and the bypass zone form a closed-loop path for the refrigerant.   
     
     
       19. A method comprising:
 mixing a lubricating oil with a first portion of a refrigerant in a bypass zone to form a mixture;   heating the mixture of the lubricating oil and the first portion of the refrigerant to form a heated mixture, wherein at least a portion of the first portion of the refrigerant is in a gaseous phase, and wherein the lubricating oil and the refrigerant are mixed in a mixing device to form the mixture;   mixing the heated mixture with a second portion of the refrigerant, wherein the second portion of the refrigerant is in a gaseous or superheated phase;   atomizing the lubricating oil in an atomizer holding a mixing media to disperse the lubricating oil within the refrigerant; and   cooling the refrigerant through at least one heat sink.   
     
     
       20. The method of  claim 19 , wherein atomizing the lubricating oil includes passing the lubricating oil and the refrigerant through a metal mesh. 
     
     
       21. The method of  claim 19 , wherein heating the mixture of the lubricating oil and the first portion of the refrigerant to form the heated mixture includes transferring heat to the mixture from at least one source selected from the group consisting of a waste heat source, an exhaust gas, a compressor intercooler, biomass, a geothermal heat source, and a solar array. 
     
     
       22. The method of  claim 19 , further comprising:
 passing the atomized lubricating oil and the refrigerant through a decompressor operatively associated with an electrical generator to decrease a pressure of the refrigerant and generate an electrical current;   separating at least a portion of the lubricating oil from the refrigerant; and   condensing at least a portion of the refrigerant to a liquid phase.   
     
     
       23. The method of  claim 22 , wherein:
 the at least one heat sink includes a first heat sink and a second heat sink, and   condensing the portion of the refrigerant to the liquid phase includes transferring heat from the refrigerant to each of the first heat sink and the second heat sink.   
     
     
       24. The method of  claim 19 , wherein heating the mixture of the lubricating oil and the refrigerant to form the heated mixture includes increasing a specific volume of the mixture. 
     
     
       25. The method of  claim 19 , wherein atomizing the lubricating oil includes maintaining the lubricating oil and the refrigerant at constant pressure. 
     
     
       26. The method of  claim 19 , further comprising mixing an additive with the mixture, wherein the additive exhibits a higher lubricity than the lubricating oil. 
     
     
       27. The method of  claim 19 , further comprising mixing the lubricating oil with the first portion of the refrigerant in a liquid phase in the mixing device to form the mixture of the lubricating oil and the first portion of the refrigerant. 
     
     
       28. A heat engine, comprising:
 a high-pressure zone configured to transfer heat from at least one heat source to a refrigerant and configured to contain a first portion of the refrigerant in a gaseous phase;   a low-pressure zone configured to transfer heat from the refrigerant to at least one heat sink and configured to contain a second portion of the refrigerant in a liquid phase,   a bypass zone configured to mix a third portion of the refrigerant with a lubricating oil, the third portion of the refrigerant and the lubricating oil in a liquid phase; and   an atomizer holding a mixing media configured to atomize the lubricating oil and disperse the lubricating oil within the first portion of the refrigerant,   wherein a closed-loop path for the refrigerant includes the high-pressure zone, the low-pressure zone, and the bypass zone.   
     
     
       29. The heat engine of  claim 28 , wherein the heat engine is configured to circulate the refrigerant in a Rankine cycle. 
     
     
       30. The heat engine of  claim 28 , further comprising a mixing device configured to mix the lubricating oil with the third portion of the refrigerant in the liquid phase in the bypass zone. 
     
     
       31. The heat engine of  claim 28 , wherein:
 the high-pressure zone includes at least one wall of the at least one heat source configured to transfer heat from the at least one heat source to the first portion of the refrigerant in the liquid phase, and   the at least one heat source is configured to evaporate the first portion of the refrigerant.   
     
     
       32. The heat engine of  claim 28 , further comprising:
 a positive displacement decompressor configured to provide a pressure gradient through which the refrigerant in the gaseous phase flows continuously from the high-pressure zone to the low-pressure zone,   wherein the positive displacement decompressor is configured to maintain a pressure differential between the high-pressure zone and the low-pressure zone of between 20 bar and 42 bar, and   wherein the positive displacement decompressor is configured to extract mechanical energy due to the pressure gradient.   
     
     
       33. The heat engine of  claim 32 , further comprising an electrical generator coupled to the positive displacement decompressor and configured to convert the extracted mechanical energy to electrical energy. 
     
     
       34. The heat engine of  claim 33 , further comprising a positive displacement hydraulic pump configured to provide continuous flow of the refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone. 
     
     
       35. The heat engine of  claim 28 , wherein the closed-loop path includes at least one heat-transfer conduit external to the heat engine.