Method and device for converting thermal energy of a low temperature heat source to mechanical energy

Abstract

In a method and device ( 1 ) for converting thermal energy of a low temperature heat source ( 20 ) into mechanical energy in a closed circuit, a liquid working agent is heated by transmitting heat from the low temperature source ( 20 ) and partially evaporating it in an expansion device ( 3 ). Erosion to the condenser ( 8 ) for condensing the partially evaporated working agent can be prevented by separating the liquid phase from the evaporator phase in the partially evaporated working agent that is directly in front of the condenser ( 8 ), and only the evaporator phase is transferred to the condenser ( 8 ) for condensing and subsequently, the condensed evaporator phase and the liquid phase are merged.

1 . A method for conversion of heat energy from a low-temperature heat source to mechanical energy in a closed circuit comprising the following steps:
 a) increasing the pressure of a liquid agent,   b) heating of the increased-pressure, liquid agent by transferring heat from the low-temperature heat source to the agent, without vaporizing the agent,   c) expanding the heated, liquid agent, wherein an expanded, partially vaporized agent with a vapor phase and a liquid phase is produced by partial vaporization of the agent, and heat energy in the agent is converted to mechanical energy,   d) condensing the vapor phase produced in step c) in a condenser in order to produce the liquid agent from step a), wherein   in the case of the expanded, partially vaporized agent produced in step c), the liquid phase is separated from the vapor phase immediately before the condenser   only the vapor phase is supplied to the condenser,   the condensed vapor. phase and the liquid phase are combined after the condenser but before step a), in order to produce the liquid agent.   
     
     
         2 . The method according to  claim 1 , wherein
 the pressure of the agent in the condenser is set to an optimum between the droplets of the liquid phase in the vapor phase of the agent being as small as possible and the mechanical energy produced being as great as possible in step c).   
     
     
         3 . The method according to  claim 1 , wherein
 the condensed vapor phase and the liquid phase are combined in an agent reservoir.   
     
     
         4 . The method according to  claim 1 , wherein
 the low-temperature source is at a temperature of less than 400° C.   
     
     
         5 . An apparatus for conversion of heat energy from a low-temperature heat source to mechanical energy in a closed circuit, comprising
 a pump for increasing the pressure of a liquid agent,   a heat exchanger for heating the increased-pressure, liquid agent by transferring heat from the low-temperature heat source to the agent, without vaporizing the agent,   an expansion device for expanding the heated, liquid agent, wherein an expanded, partially vaporized agent with a liquid phase and a vapor phase can be produced by partial vaporization of the agent in the expansion device, and heat energy in the agent can be converted to mechanical energy,   a condenser for condensation of the vapor phase of the partially vaporized agent in order to produce the liquid agent,   a separator for separation of the liquid phase from the vapor phase of the expanded, partially vaporized agent, wherein the separator is arranged immediately before the condenser in the flow direction of the agent, and is connected to the condenser in order to supply the vapor phase to the condenser, and   a combination means for combining the liquid phase and the condensed vapor phase of the partially vaporized agent, wherein the combination means is arranged before the pump in the flow direction of the agent and is connected to the separator in order to supply the liquid phase, and to the condenser in order to supply the condensed vapor phase, to the combination means.   
     
     
         6 . The apparatus according to  claim 5 , wherein
 the pressure of the agent in the condenser can be set to an optimum between the droplets of the liquid phase in the vapor phase of the agent being as small as possible and the mechanical energy produced being as great as possible in the expansion device.   
     
     
         7 . The apparatus according to  claim 5 , wherein
 the combination means is in the form of an agent reservoir.   
     
     
         8 . The apparatus according to  claim 5 , wherein a nozzle and a turbine are arranged successively in the flow direction of the agent in the expansion device. 
     
     
         9 . The apparatus according to  claim 5 , wherein the nozzle and the turbine form a single physical unit. 
     
     
         10 . The apparatus according to  claim 5 , wherein the low-temperature source is at a temperature of less than 400° C. 
     
     
         11 . A system for conversion of heat energy from a low-temperature heat source to mechanical energy in a closed circuit, comprising
 means for increasing the pressure of a liquid agent,   a low-temperature heat source from which heat is transferred to the increased-pressure, liquid agent without vaporizing the agent,   means for expanding the heated, liquid agent, wherein an expanded, partially vaporized agent with a vapor phase and a liquid phase is produced by partial vaporization of the agent, and heat energy in the agent is converted to mechanical energy, and   a condenser to condense the vapor phase in order to produce the liquid agent, wherein in the case of the expanded, partially vaporized agent, the liquid phase is separated from the vapor phase immediately before the condenser and only the vapor phase is supplied to the condenser, the condensed vapor phase and the liquid phase are combined after the condenser in order to produce the liquid agent.   
     
     
         12 . The system according to  claim 11 , wherein the pressure of the agent in the condenser is set to an optimum between the droplets of the liquid phase in the vapor phase of the agent being as small as possible and the mechanical energy produced being as great as possible. 
     
     
         13 . The system according to  claim 11 , wherein the condensed vapor phase and the liquid phase are combined in an agent reservoir. 
     
     
         14 . The system according to  claim 11 , wherein the low-temperature source is at a temperature of less than 400° C.