Organic rankine cycle system with lubrication circuit

Abstract

A Rankine cycle system including a Rankine cycle working circuit and a lubrication circuit is disclosed. The lubrication circuit and the Rankine cycle working circuit include a shared segment including a mixture of Rankine cycle working fluid from the Rankine cycle working circuit and lubricant from the lubrication circuit. A separator receives the mixture of Rankine cycle working fluid and lubricant from the shared segment and separates the Rankine cycle working fluid from the lubricant. The separated Rankine cycle working fluid is directed along the Rankine cycle working circuit from the separator to the heating zone and the separated lubricant is directed along the lubrication circuit from the separator to a mechanical expander. The working fluid and lubricant are recombined after passing separately through the expander and are then introduced to the condensing zone.

What is claimed is: 
     
         1 . A Rankine cycle system comprising:
 a. a separator for separating a working fluid from a lubricant, the separator having a first inlet for receiving a working fluid and lubricant mixture, a first outlet for discharging the working fluid, and a second outlet for discharging the lubricant;   b. a mechanical expander having a working fluid inlet in fluid communication with the separator first outlet, a lubricant circuit inlet in fluid communication with the separator second outlet, a working fluid outlet, and a lubricant circuit outlet in direct fluid communication with the working fluid outlet;   c. a mixing location at which the lubricant from the lubricant circuit outlet is mixed with the working fluid from the working fluid outlet to form the working fluid and lubricant mixture;   d. a condenser in direct fluid communication with the mixing location; and   e. a fluid pump in fluid communication with the condenser and the separator, the fluid pump being for receiving the working fluid and lubricant mixture from the condenser and discharging the working fluid and lubricant mixture to the separator.   
     
     
         2 . The Rankine cycle system of  claim 1 , wherein:
 a. the system is configured such that the mechanical separator lubricant inlet is above the first outlet of the separator.   
     
     
         3 . The Rankine cycle system of  claim 1 , wherein the separator includes a pipe directing the working fluid and lubricant mixture around an inside surface of the separator. 
     
     
         4 . The Rankine cycle system of  claim 1 , wherein the separator includes a diverter plate. 
     
     
         5 . The Rankine cycle system of  claim 4 , wherein the diverter plate includes an open center. 
     
     
         6 . The Ranking cycle system of  claim 1 , wherein the separator includes a plurality of converging inlet branches extending from an interior volume of the separator to the separator first outlet. 
     
     
         7 . The Rankine cycle system of  claim 1 , further including a control valve located between the separator second outlet and the mechanical expander lubricant circuit inlet, the control valve being configured to regulate a flow rate of lubricant through the mechanical expander. 
     
     
         8 . The Rankine cycle system of  claim 1 , wherein the Rankine cycle working circuit is an organic Rankine cycle working circuit. 
     
     
         9 . The Rankine cycle system of  claim 1 , wherein the Rankine cycle working fluid is an organic solvent. 
     
     
         10 . The Rankine cycle system of  claim 9 , wherein the Rankine cycle working fluid is selected from the group consisting of ethanol, n-pentane, and toluene. 
     
     
         11 . The Rankine cycle system of  claim 1 , wherein the lubricant is an oil. 
     
     
         12 . The Rankine cycle system of  claim 1 , wherein the Rankine cycle working fluid is heated at a heating zone by waste heat from a prime mover. 
     
     
         13 . The Rankine cycle system of  claim 12 , wherein the prime mover is selected from the group consisting of an internal combustion engine and a fuel cell. 
     
     
         14 . The Rankine cycle system of  claim 1 , wherein the mechanical expander includes a fixed displacement expander. 
     
     
         15 . The Rankine cycle system of  claim 14 , wherein the mechanical expander is a three stage volumetric expander. 
     
     
         16 . A Rankine cycle system comprising:
 a. an organic working fluid;   b. a condenser for condensing the organic working fluid to form condensed organic working fluid;   c. a heat exchanger for heating the organic working fluid to form heated organic working fluid;   d. a fixed displacement mechanical expansion device for extracting energy from the organic working fluid, the mechanical expansion device including first and second interleaved non-contacting rotors each having an equal number of a plurality of lobes mounted on a shaft, the mechanical expansion device including intermeshing timing gears that coordinate rotation of the rotors and prevent the lobes of the first and second interleaved rotors from contacting each other, the mechanical expansion device including a housing having an inlet, an outlet, and an interior region that provides fluid communication between the inlet and the outlet, the interior region including first and second rotor bores in which the first and second rotors are respectively positioned, the first and second rotors defining fluid transfer volumes between the lobes that transfer the working fluid circumferentially about the bores from the inlet to the outlet, and at least one of the shafts defining an output shaft;   e. a pump positioned between the condenser and the heat exchanger for pumping the condensed organic working fluid received from the condenser to the heat exchanger, wherein the heated organic working fluid flows from the heat exchanger to the inlet of the mechanical expansion device, and wherein expanded working fluid flows from the outlet of the mechanical expansion device to the condenser;   f. the condenser, the heat exchanger, and the fixed displacement mechanical expansion device being part of a Rankine cycle working circuit through which the organic working fluid is circulated;   g. a lubrication circuit for lubricating the fixed displacement mechanical expansion device;   h. the lubrication circuit and the Rankine cycle working circuit including a shared segment including a mixture of the organic working fluid from the Rankine cycle working circuit and lubricant from the lubrication circuit; and   i. a separator that receives the mixture of organic working fluid and lubricant from the shared segment and separates the organic working fluid from the lubricant, wherein the separated organic working fluid is directed along the Rankine cycle working circuit from the separator to the heat exchanger and the separated lubricant is directed along the lubrication circuit from the separator to the fixed displacement mechanical expansion device.   
     
     
         17 . The Rankine cycle system of  claim 16 , wherein the pump drives flow of the organic working fluid through the Rankine cycle working circuit and also drives flow of the lubricant through the lubrication circuit. 
     
     
         18 . The Rankine cycle system of  claim 16 , wherein the pump is positioned along the shared segment. 
     
     
         19 . The Rankine cycle system of  claim 16 , wherein the lubricant leaving the expansion device is combined with the organic working fluid leaving the expansion device at a location between the condenser and the pump. 
     
     
         20 . The Rankine cycle system of  claim 1 , further including a control valve located between the separator second outlet and the mechanical expander lubricant circuit inlet, the control valve being configured to regulate a flow rate of lubricant through the mechanical expander.