Patent Publication Number: US-2015082793-A1

Title: Device for power generation according to a rankine cycle

Description:
TECHNICAL FIELD 
     The present invention generally relates to a device for power generation according to a Rankine Cycle, in particular to an Organic Rankine Cycle (ORC). 
     BACKGROUND ART 
     Due to the general necessity to reduce CO2 emissions and to the loss of trust in nuclear power plants, devices for producing electricity with low temperature sources are gaining of importance. Such low temperature sources include e.g. industrial waste heat, low temperature geothermal heat sources, low temperature biomass energy and low temperature solar energy, but also novel low temperature heat generators based on chemical or nuclear reactions. 
     Such devices generally work according to a so-called Organic Rankine Cycle (ORC), i.e. a Rankine cycle in which the working fluid is an organic fluid. The working principle underlying the ORC is basically the same as that of the classical Rankine cycle in which the working fluid is water. The main difference is that the ORC uses as working fluid an organic fluid with lower evaporation temperatures than water. It follows that for the same pressure, the evaporation of the organic fluid takes place at a lower temperature than the evaporation of water in a classical Rankine cycle. It follows that the external heat source in an ORC may be in a lower temperature range than the external heat source in a Rankine cycle working with water. 
     A basic ORC comprises following main steps. A condensate pump pressurizes in a liquid phase the condensed organic working fluid collected at a condenser. The pressurized organic working fluid is heated and evaporated in an evaporator, by heat exchange with an external heat source. It will be noted that the evaporation temperature in an ORC is generally lower than 200° C., most often in the range of 100° C. to 160° C., and that the vapour is generally no super-heated. The vapour produced in the evaporator flows through an expansion machine, wherein its expansion generates a torque for driving an electrical generator. At the exhaust of the expansion machine, the vapour is condensed in the condenser, which is cooled by heat exchange with an external cold source. The condensate collected at the condenser is again pressurized in the condensate pump and pumped back into the evaporator. 
     Today, devices for power generation according to an ORC are commercially available mainly in a range starting with 0.3 MW electric power output, but there is an increasing need for such devices with a smaller electric power output too. In particular for the range of 25 kW to 250 kW electric (corresponding to a thermal recuperation range of about 150 kW to 1.5 MW), there seem to be interesting applications for producing electricity with low temperature sources using an ORC. However, with a decreasing nominal power of the device used for power generation, the investment costs per kW installed strongly increase and the efficiency of power generation decreases. 
     It is known that the efficiency of an ORC can be increased by using a so-called regenerator, i.e. a counter-current heat exchanger, which is arranged between the turbine outlet and the condenser inlet. Indeed, if the organic fluid is a “dry fluid”, i.e. if it has a positive or isentropic saturation vapour curve, the vapour of the organic fluid has not reached the two-phase state when it leaves the turbine. It follows that the temperature of the expanded vapour is still considerably higher than the condensing temperature in the condenser. In the regenerator, this temperature difference is used to preheat the pressurized condensate before it enters into the evaporator. 
     If the external heat source is connected into the ORC with a heat carrier medium, which has to be cooled down in an evaporator working as counter-current heat exchanger, it is also known to operate an ORC with more than one evaporator. Each evaporator then works at a different evaporation pressure, i.e. with a different evaporation temperature, in combination either with a separate expansion machine for each evaporator or with a single multi-stage expansion machine, in which the vapour produced in each additional evaporator, is injected into an intermediate stage of the multi-stage expansion machine. Due to the fact that the heat transfer is split between evaporators working at different evaporation temperatures, one can work with a more important temperature differential on the side of the heat carrier medium, i.e. transform more heat into power. For power generation in the kW-range, such solutions are however considered to be a priori too expensive. 
     ORC systems with more than one evaporator are e.g. described in DE 10 2007 044 625 A1. According to a first embodiment, the system comprises several separate ORCs, each of these ORCs comprising an evaporator, a turbine, a condenser and a condensate pump. With regard to the heat carrier fluid, the evaporators are basically connected in series. With each evaporator is associated a turbine comprising its own housing with a nozzle system and blade wheels. These turbines are regrouped in pairs, wherein the blade wheels of a turbine pair have a common shaft. The parallel shafts of two turbine pairs are interconnected by a gear system to drive an electrical generator. According to a second embodiment described in DE 10 2007 044 625 A1, the system comprises two evaporators associated with a two-stage turbine. This two-stage turbine comprises a rotor carrying two axially spaced blade rings, wherein the first blade ring has a smaller diameter than the second blade ring. A first steam flow (i.e. high pressure steam produced by a high pressure evaporator) radially enters into the turbine housing through a high pressure inlet and flows through a first annular channel radially into a first annular nozzle ring, which deflects the flow in an axial direction into the first blade ring, i.e. the blade ring with the smaller diameter. A second steam flow (low pressure steam produced by a low pressure evaporator) radially enters into the turbine housing through a low pressure inlet and flows through a second annular steam channel into a second nozzle ring, which deflects the flow in an axial direction into the second blade ring, i.e. the blade ring with the bigger diameter. The two stages are designed so as to achieve the same end pressure at the outlet of the first and second blade ring, wherein the exhaust streams are only merged in an outlet diffuser of the turbine. It is obvious that such a turbine has a rather low efficiency, when compared e.g. to a typical induction type turbine, i.e. a multi-stage axial turbine in which low pressure steam is induced into the main vapour stream at an intermediate turbine stage and both streams are thereafter commonly expanded. However, for power generation with an ORC in the kW-range, known induction type turbines are considered to be too expensive. 
     The choice of the expansion machine has a major impact on the performance of the ORC, but also on the costs and therefore on the pay-back time of the power generation device. This is in particular true for power generation in the kW-range. The use of turbo-machines, generally axial flow turbines, seems to be limited to power ranges above 0.3 MW. Below 0.3 MW, displacement type machines, most often derived from existing frigorific compressors, are commonly used. Examples of displacement type machines used in ORCs at lower power ranges are e.g.: reciprocating piston machines, volumetric spiral turbines (also called scroll turbines) and screw-type machines. All these displacement type machines have a poor efficiency and generally involve lubrication problems. Furthermore, displacement type machines often cause problems due to a limited tightness. 
     For making power generation with an ORC in the kW-range a really interesting solution, it would be interesting to implement the ORC in a “black box”, i.e. a preassembled ORC circuit that is integrated in a closed container and ready to be connected to the heat carrier fluid and the cooling fluid. 
     Integrated heat exchanger systems for ORC applications have already been proposed. EP 1426565 A1 proposes e.g. an integrated thermal exchanger group for an ORC comprising a regenerator and a condenser, both arranged in a mainly cylindrical container with a horizontal axis. DE 10 2008 038 241 A1 proposes a similar arrangement. These integrated heat exchangers still require that the turbine and the evaporator are installed as separate components. 
     U.S. Pat. No. 5,219,270 describes a recovery assembly for recovering energy from a wet oxidation. The assembly comprises a bulky reaction barrel with rocket nozzles mounted in a vacuum chamber equipped with tubular cooling elements. 
     GB 1,027,223 describes a multi-stage turbine, wherein a separate condenser is associated with each turbine stage. The turbine stages are axially spaced along a common shaft. Each turbine stage discharges the expanded vapour directly into a chamber containing its separate condenser. The turbine itself is not further described. 
     DE 10 2007 037 889 A1 describes a generator, a turbine, an evaporator and a condenser all mounted in a common housing. The turbine is of a mechanically rather complicated and thermodynamically rather inefficient design, generating for example high pressure drops in the steam circuit. 
     SUMMARY OF INVENTION 
     A device for power generation according to a Rankine cycle (RC), in particular according to an organic Rankine cycle (ORC), comprises a turbine for expanding a vapour of a working fluid and at least one heat exchanger, such as a regenerator and/or a condenser, through which the expanded vapour has to flow. In accordance with the invention, the device further comprises a vapour tight container containing the turbine and the at least one heat exchanger. The turbine is a radial-outward-flow type turbine having: a shaft that is led in a sealed manner out of the container; an axial vapour inlet port arranged opposite the shaft so as to be located inside the container; and a stator exhaust ring with stator exhaust blades defining peripheral vapour exhaust openings for discharging the expanded vapour directly into the vapour tight container, in which the expanded vapour flows through the at least one heat exchanger. It will be appreciated that the invention combines in a very efficient way, a very compact, but very efficient radial-outward-flow type turbine and at least one heat exchanger, which is to be traversed by the vapour expanded in the turbine, in a common vapour tight containment. The axial vapour inlet port is hereby arranged opposite the shaft and located inside the container, where it can be very easily connected to an internal vapour generator. The direct peripheral expanded vapour discharge through the stator exhaust ring with its stator exhaust blades into the common container substantially reduces pressure losses between the turbine and the at least one heat exchanger. The common container also reduces the risk of (organic) vapour losses to the atmosphere. The fact that a separate, vapour tight turbine housing is not necessary, reduces the costs and makes an up-sizing or down-sizing of the turbine much easier. 
     In a preferred embodiment, the container has the form of a vertical cylinder with a top end and a bottom end. In this case, the turbine is advantageously centred in the top end of the container, and the at least one heat exchanger is located below the turbine. It will be appreciated that this design provides ideal flow conditions for the expanded vapour between the exhaust of the turbine and the at least one heat exchanger. 
     A preferred embodiment of the turbine is a radial-outward-flow type multi-stage turbine with vapour induction in at least one intermediary stage. In this embodiment, an annular vapour inlet port advantageously surrounds the axial vapour inlet port, and is arranged in the turbine so as to annularly induce, in an intermediary stage of the turbine, a vapour stream from a second evaporator into an already partially expanded vapour stream from a first evaporator. It will be appreciated that the proposed radial-outward-flow type, multi-stage turbine can be very easily configured as an induction type turbine, wherein the manufacturing costs for the induction type turbine are not much higher than for a turbine with a single vapour inlet. 
     In a preferred embodiment, the device further includes a first evaporator and, optionally, a second evaporator. The first evaporator and, if present, the second evaporator are advantageously arranged in the container, axially below the axial vapour inlet port of the turbine. The at least one heat exchanger is then advantageously arranged annularly around the first evaporator and, if the second evaporator is present, annularly around the first and second evaporator. With such an arrangement, the device gets particularly compact. Furthermore, the intergration of the evaporator(s) into a common container with the turbine and at least one heat exchanger located downstream of the turbine, further reduces the risk of (organic) vapour losses to the atmosphere. Arranging the the evaporator(s) axially below the axial vapour inlet port of the turbine also allows to reduce pressure and heat losses between the evaporator(s) and the turbine. It remains to be noted that the evaporator that is arranged in the common container may also be a vapour generator comprising an internal heat source, e.g. a novel type of low temperature heat source, which is based on chemical or nuclear reactions. 
     A preferred embodiment of the device further comprises a first vapour drum that is located in axial extension of the axial vapour inlet port and directly connected to the latter without any intermediate piping. If the turbine is a multi-stage turbine with vapour induction in an intermediary stage, this embodiment further comprises a second vapour drum that is located in axial extension of the annular vapour inlet port and directly connected to the latter without any intermediate piping. In this case, the second vapour drum is a compartment inside the first vapour drum, or the first vapour drum is a compartment inside the second vapour drum. In such an embodiment, the axial vapour inlet port is advantageously formed by a first tubular vapour inlet connection, which is engaged in a sliding and sealed manner by the first vapour drum; and the annular vapour inlet port, if present, is advantageously formed by a second tubular vapour inlet connection surrounding the first tubular vapour inlet connection, wherein the second tubular vapour inlet connection is advantageously engaged in a sliding and sealed manner by the second vapour drum. If the first evaporator and second evaporator are—in this preferred embodiment—arranged axially below the axial vapour inlet port of the turbine, the first vapour drum and/or the second vapour drum are advantageously supported by the first evaporator and/or second evaporator or by a support structure associated with the first evaporator and/or second evaporator. Such combined low and high pressure vapour drums, which are connected without any intermediate piping and, preferably, with sliding connections to the turbine vapour inlets, reduce pressure losses at the vapour inlet(s) of the turbine, allow to easily achieve a superheating of the low pressure vapour by the high pressure vapour, thereby increasing efficiency of the Rankine cycle, make the device more compact, facilitate its assembling and reduce its costs. 
     In a preferred embodiment, the at least one heat exchanger includes a first regenerator that is arranged in the container so that the exhaust vapour of the turbine flows directly through it; this first regenerator being connected to a fluid inlet port of a first evaporator, so as to reheat the fluid with heat extracted from the exhaust vapour flowing through the first regenerator. The at least one heat exchanger may further include a second regenerator that is arranged in the container so that the vapour having crossed the first regenerator flows through it; this second regenerator being connected to a fluid inlet port of a second evaporator, so as to reheat the fluid with heat extracted from the vapour flowing through the second regenerator. Such a double-stage regeneration allows to significantly increase the efficiency of the Rankine cycle. 
     The at least one heat exchanger may also include a condenser in which the expanded vapour is condensed, wherein, if present, the first regenerator, the second generator and the condenser are arranged below the turbine, vertically one above the other. This configuration is not only very compact. It also provides nearly ideal flow conditions for the vapour between the exhaust of the turbine, the regenerators and the condenser. 
     In a preferred embodiment, the device further includes a first evaporator connected to an axial vapour inlet port of the turbine, a second evaporator working at a lower evaporation pressure than the first evaporator and connected to an annular vapour inlet port of the turbine for inducing lower pressure vapour into an intermediary stage of the turbine; for the first evaporator, a first heat carrier fluid inlet port and a first heat carrier fluid outlet port; for the second evaporator, a second heat carrier fluid inlet port and a second heat carrier fluid outlet port; a connection pipe connecting the first heat carrier fluid outlet port to the second heat carrier fluid inlet port; and optionally, a bypass-valve connected between the second heat carrier fluid inlet port and the second heat carrier fluid outlet port, for adjusting the flow rate of the heat carrier fluid in the second evaporator. Such a configuration allows to further optimize the RC, and in particular the ORC. 
     In a preferred embodiment, the at least one heat exchanger includes a condenser, and a condensate collector is arranged under the condenser in the container. In this embodiment: a condensate outlet port is advantageously connected to the condensate collector; a first condensate inlet is advantageously connected either directly or through a first regenerator to a first evaporator; a second condensate inlet is advantageously connected, either directly or through a second regenerator, to a second evaporator; and a condensate pump is advantageously connected with its suction side to the condensate collector, and with its pressure side via a first valve to the first condensate inlet and via a second valve to the second condensate inlet. Such a configuration allows to further optimize the RC, and in particular the ORC. 
     In an alternative embodiment, the device includes an air-cooled condenser arranged outside the container connected to the container by means of a large diameter vapour pipe. The at least one heat exchanger then includes at least one regenerator arranged in the container so that the expanded vapour flows through it before being channelled through the large diameter pipe into the air-cooled condenser. It will be appreciated that even with an external air-cooled condenser, the device can remain very compact. 
     A preferred embodiment of the turbine comprises: a substantially plate-shaped first turbine housing part including the axial vapour inlet port; a set of stator rings with stator blades, the stator rings having increasing diameters and being preferably fixed with screws onto the first turbine housing part; a stator exhaust ring with stator exhaust blades, the stator exhaust ring radially surrounding the stator ring with the biggest diameter and being preferably fixed with screws onto the first turbine housing part, the stator exhaust blades defining the vapour exhaust openings for discharging the expanded vapour into the container; a substantially plate-shaped second turbine housing part including a shaft outlet neck; the second turbine housing part being preferably fixed with screws onto the stator exhaust ring; a turbine shaft rotatably supported within the shaft outlet neck; a rotor disk supported in a cantilever manner by the turbine shaft between the first turbine housing part and the second turbine housing part; for each stator ring, a rotor ring with rotor blades, the rotor ring radially surrounding the corresponding stator ring and being fixed with screws onto the rotor disk. A main advantage of such a turbine design is that the turbine may be easily up-sized or down-sized, and that it may be easily fine-tuned to specific working parameters. Hence, an optimal turbine efficiency may nearly always be warranted. 
     The turbine advantageously includes an annular vapour inlet port formed in the first turbine housing part as a ring-zone with through-holes, the ring-zone separating a first ring-shaped flange, which supports a first set of stator rings, from a second ring-shaped flange, which supports a second set of stator rings. A vapour induction port may thus be added to the turbine with very simple means and at very low costs. 
     In a preferred embodiment, the turbine is an induction turbine comprising: a first turbine housing part including the axial vapour inlet port; a set of stator rings with stator blades supported by the first turbine housing part; a turbine shaft supporting in a cantilever manner a rotor disk; for each stator ring, a rotor ring with rotor blades, the rotor ring radially surrounding the corresponding stator ring and being supported by the rotor disk; an annular vapour inlet port formed in the first turbine housing part as a ring-zone with through-holes. These through-holes advantageously open onto an outer rim of one of the rotor rings, this outer rim having a width decreasing towards its periphery, and forming an annular, preferably concave, surface, which defines with an annular, preferably convex, surface on the next stator ring, a ring-shaped converging nozzle, for annularly inducing, into the next stator ring, a vapour stream from the through-holes into a vapour stream flowing through the preceding rotor ring. Thus, vapour induction is fluidically optimized at relatively low costs. 
     In a preferred embodiment of the turbine, the first turbine housing part supports an end-cap, which forms a vapour inlet deflection surface opposite the axial vapour inlet port; this vapour inlet deflection surface being a revolution surface centred on the central axis of the turbine; wherein a first stator ring is integrated into the end-cap. 
     In a preferred embodiment, the second turbine housing part is mounted in a sealed manner in an opening of the container, so that a shaft outlet neck of the second turbine housing part is located outside the container. In this embodiment, the turbine adavantageously further includes: rolling contact bearings in the shaft outlet neck for supporting and locating the turbine shaft therein; and a shaft sealing device located adjacent to the rolling contact bearings, so that the rolling contact bearings are sealed from the vapour in the turbine. Hence, the shaft bearings may be rather standard rolling contact bearings, which are easily accessible outside the common container for monitoring and maintenance purposes. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The afore-described and other features, aspects and advantages of the invention will be better understood with regard to the following description of an embodiment of the invention and upon reference to the attached drawings, wherein: 
         FIG. 1 : is a block diagram schematically illustrating how different components of a preferred device for power generation according to an improved organic Rankine cycle (ORC) are interconnected; 
         FIG. 2 : is a schematic sectional view of a multi-stage turbine, in which low pressure vapour is induced at a low pressure turbine stage, the section plane containing the central axis of the turbine; 
         FIG. 3 : is an enlarged detail of  FIG. 2 ; 
         FIG. 4 : is a schematic sectional view of a turbine as shown in  FIG. 2 , the section plane being this time perpendicular to the central axis of the turbine; 
         FIG. 5 : is a schematic sectional view of the turbine as in  FIG. 2 , further schematically showing a first arrangement of a high pressure vapour drum and a low pressure vapour drum directly connected to the turbine; 
         FIG. 6 : is a schematic sectional view as in  FIG. 5 , showing a slightly modified embodiment; 
         FIG. 7 : is a schematic sectional view as in  FIG. 5 , showing a further possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine; 
         FIG. 8 : is a schematic sectional view as in  FIG. 5 , showing an additional possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine; 
         FIG. 9 : is a schematic sectional view of a device in accordance with the invention, the section plane being a vertical plane; and 
         FIG. 10 : is a schematic sectional view of as indicated by line  9 - 9 ′ in  FIG. 9 ; 
         FIG. 9 : is a schematic sectional view of a device in accordance with the invention, which is equipped with an air cooled condenser. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
     It will be understood that the following description and the drawings to which it refers describe by way of example preferred embodiments of the claimed subject matter for illustration purposes. The description and drawings shall not further limit the scope, nature or spirit of the claimed subject matter. 
       FIG. 1  is a block diagram schematically illustrating how different components of device for power generation according to an improved Organic Rankine Cycle (ORC) are interconnected. This device comprises following main components arranged within a closed vapour tight container  10 : a first or high pressure evaporator  12 , a second or low pressure evaporator  14 ; a turbine  16 ; a condenser  18  and two regenerators  20 ,  22 . It further comprises a condensate pump  24  and an electrical generator  26 , which are preferably arranged outside of the container  10 . 
     The preferred device comprises moreover following fluid inlet and outlet ports:
         a first heat carrier fluid inlet port  30 , respectively outlet port  30 ′, connected to the heat carrier fluid inlet, respectively the heat carrier fluid outlet of the first evaporator  12 ;   a second heat carrier fluid inlet port  32 , respectively outlet port  32 ′, connected to the heat carrier fluid inlet, respectively the heat carrier fluid outlet of the second evaporator  14 ;   a cooling fluid inlet port  34 , respectively outlet port  34 ′ connected to the cooling fluid inlet, respectively the cooling fluid outlet of the condenser  18 ;   a condensate outlet port  36 ;   a first condensate inlet port  38 ; and   a second condensate inlet port  40 .       

     Reference number  42  identifies an external heat transfer circuit, associated e.g. with a low temperature external heat source. In this external heat transfer circuit  42  circulates a heat carrier fluid, such as a heat-transfer-oil, which transports the heat energy to be transformed by the ORC in mechanical energy. The heat carrier fluid enters through the first heat carrier fluid inlet port  30  into the first evaporator  12 , traverses the latter, thereby heating and evaporating an organic working fluid flowing through the first evaporator  12 . Thereafter, the heat carrier fluid leaves the container  10  through the first heat carrier fluid outlet port  30 ′, to be channelled through an external connection conduit  44  to the second heat carrier fluid inlet port  32 . Through this second heat carrier fluid inlet port  32 , the heat carrier fluid enters into the second evaporator  14 , traverses the latter, thereby heating and evaporating the organic working fluid flowing through the second evaporator  14 . Thereafter, the heat carrier fluid definitively leaves the container  10  through the second heat carrier fluid outlet port  32 ′. 
     As an alternative to the external connection conduit  44 , it is possible to foresee an internal connection conduit (not shown) located within the container  10 , which would eliminate the first heat carrier fluid outlet port  30 ′ and the second heat carrier fluid inlet port  32 . However, the solution with the external first heat carrier fluid outlet port  30 ′ and the second heat carrier fluid inlet port  32  warrants a greater flexibility. Thus, instead of connecting the first and second evaporator  12 ,  14  in series with regard to the heat carrier fluid, it is e.g. possible to connect the first evaporator  12  to a first heat transfer circuit (not shown), and the second evaporator  14  to a separate second heat transfer circuit (not shown). 
     In the embodiment shown in  FIG. 1 , a bypass-valve  45  is moreover connected between the second heat carrier fluid inlet and outlet ports  32 ,  32 ′. This bypass-valve  45  allows limiting the flow of heat carrier fluid through the second evaporator  14 , thereby limiting the At of the heat carrier fluid between the ports  30  and  32 ′. The more the bypass-valve  45  is opened, the higher the outlet temperature of the heat carrier fluid at port  32 ′ and, consequently, the lower the At of the heat carrier fluid between the ports  30  and  32 ′ will be. 
     The organic fluid vapour produced in the first evaporator  12 , called hereinafter high pressure vapour, is channelled into a high pressure vapour drum  46 , which is directly, i.e. without any intermediate piping, connected to a high pressure inlet of the turbine  16 . The organic vapour produced in the second evaporator  14 , which has a lower pressure than the organic vapour produced in the first evaporator  12  and is therefore called low pressure vapour, is channelled into a low pressure vapour drum  48 , which is directly, i.e. without any intermediate piping, connected to a low pressure inlet of the turbine  16 . In the turbine  16 , both vapour streams are expanded to generate a torque for driving the generator  26  coupled to the turbine  16 . 
     To protect the turbine  16  against damage by organic fluid droplets impacting onto the turbine blades, the ORC cycle is generally designed so that the vapour at the turbine exhaust has not yet reached a two-phase state (to achieve this aim the organic fluid should preferably be a “dry” ORC working fluid, i.e. it should have a positive or isentropic saturation vapour curve). It follows that the temperature of the vapour at the outlet of the turbine  16  is still much higher than the condensing temperature in the condenser  18 . In the two regenerators  20  and  22 , this temperature difference is efficiently used to preheat the condensate before it enters into evaporator  12  or  14 . More particularly, the first regenerator  20 , which is heated directly with the exhaust vapour of the turbine  16 , preheats the condensate stream pumped through the first evaporator  12 , which works at a higher pressure and consequently also with a higher evaporating temperature than the second evaporator  14 . The second regenerator  22 , which is heated with the vapour already cooled down in the first regenerator  20 , preheats the condensate stream pumped through the second evaporator  14 , which works at a lower evaporating temperature. It will be appreciated that this two-stage regeneration allows a more efficient heat exchange in the regenerators  20 ,  22  and the evaporators  12 ,  14  than a single-stage regeneration. 
     In the condenser  18 , the organic working fluid is condensed by means of an external cooling circuit  50  connected to the cooling fluid inlet port  34  and outlet port  34 ′ of the condenser  18 . Such an external cooling circuit  50  may e.g. comprise a dry or a wet cooling tower (not shown). 
     The condensate pump  24  pressurizes the condensed organic working fluid collected at the condenser  18  and pumps it through the regenerators  20 ,  22  to the two evaporators  12 ,  14 . More particularly, at the outlet of the condensate pump  24 , the pressurized condensate is split in two separate condensate streams. A first condensate stream is pumped through a first valve  52 , which is connected to the first condensate inlet port  38 . This first condensate stream flows through the first regenerator  20 , wherein it is pre-heated by the exhaust vapour of the turbine  16 , into the first evaporator  12 . A second condensate stream is pumped through a second valve  54 , which is connected the second condensate inlet port  40 . This second condensate stream flows through the second regenerator  22 , wherein it is pre-heated by the expanded vapour, into the second evaporator  14 . The first and second valve  52 ,  54  allow to adjust the pressures in the evaporator  12  and  14  independently from one another. Alternatively, two separate condensate pumps can be used, one for pumping the first condensate flow through the first regenerator  20  into the first evaporator  12 , and the other for pumping the second condensate flow through the second regenerator  22  into the second evaporator  14 . 
     It will be understood that the pressures and temperatures depend on the characteristics of the heat carrier circuit  42 , on the type of organic working fluid used in the ORC, on the characteristics of the available cooling circuit  50 , and on the dimensioning of the heat exchangers  12 ,  14 ,  18 ,  20 ,  22 , the turbine  16 , and the condensate pump  24 . Following values are listed for illustrating the ORC presented with a realistic example: 
     Heat Carrier Fluid in the External Heat Transfer Circuit  42 : 
     Type: customary heat-transfer-oil
 
Inlet temperature at  30 : 180° C.
 
Outlet temperature at  32 ′: 75° C.
 
     Organic Working Fluid: 
     Type: Solkane® 365mfc produced by SOLVAY
 
First evaporation temperature: 158° C. (20 bar)
 
Second evaporation temperature: 86° C. (4.5 bar)
 
Vapour outlet temperature of the turbine  16 : 74° C.
 
Vapour outlet temperature of the first regenerator  20 : 60° C.
 
Vapour outlet temperature of the second regenerator  22 : 45° C.
 
Condensate temperature at the outlet of condenser  18 : 35° C.
 
Condensate temperature at the inlet of first evaporator  12 : 68° C.
 
Condensate temperature at the inlet of second evaporator  14 : 55° C.
 
The efficiency of this two-stage ORC is about 15% for a Δt of 100° C., but about 11% of the available energy in the heat carrier fluid is converted into mechanical energy. Without the low pressure circuit (i.e. without the second evaporator  14 , the second regenerator  22 , the low pressure vapour drum  48  and the low pressure vapour inlet of the turbine  16 ), the efficiency of the single stage ORC would be about 21%, but only about 7% of the available energy in the heat carrier fluid would be converted into mechanical energy.
 
     Typical temperature ranges for the heat carrier fluid are e.g.: 
     Inlet temperature of the heat carrier fluid: 140° C. to 350° C.
 
Outlet temperature of the heat carrier fluid: 66 to 150° C.
 
     In an alternative embodiment (not shown), the circuit of  FIG. 1  only comprises the first regenerator  20 , i.e. the second condensate inlet port  40  is directly connected to the second evaporator  14 , without passing by a regenerator. In certain cases it may moreover be interesting to work without any regenerator. In this case, the first condensate inlet port  40  is directly connected to the first evaporator  14 , and the second condensate inlet port  40  is directly connected to the second evaporator  14 , without passing by a regenerator. 
     In a further embodiment (not shown), the circuit comprises in addition to the high pressure evaporator  12  more than one low pressure evaporator, each of these low pressure evaporators supplying the turbine  16  with vapour at a different intermediate pressure, which is induced into the turbine at a stage in which the pressure of the expanded vapour is about equal to the pressure of the induced vapour. In this multi-induction embodiment, a regenerator can be associated with each evaporator or only with one or more selected evaporators. 
     Finally, if the possible or desired At for the heat carrier fluid is rather small, it is also possible to work solely with the high pressure evaporator  12  and a turbine without low pressure inlet. 
       FIG. 2  is a schematic cross-section through an embodiment of the turbine  16  that is particularly suited for being used in an ORC as described above. It will first be noted that the turbine  16  is a multi-stage (here a three-stage) radial-outward-flow type turbine, i.e. the vapour axially enters into the turbine  16  and then flows in a radial direction outward through the different stages of the turbine  16 , which are substantially concentric. The turbine is furthermore of the induction type, i.e. a secondary flow of low pressure vapour is induced at a low pressure stage into the turbine  16 . Finally, the turbine is of the impulse type, i.e. the vapour is mainly expanded as it passes through the stator of the turbine  16 . 
     As best seen in the cross-section of  FIG. 4 , each of the three turbine stages comprises a stator ring  56   1 ,  56   2 ,  56   3 , with increasing diameter and curved stator blades  58   1 ,  58   2 ,  58   3 , and a rotor ring  60   1 ,  60   2 ,  60   3 , with increasing diameter and curved rotor blades  62   1 ,  62   2 ,  62   3 . The inlet stator ring  56   1  and the first rotor ring  60   1  form the first stage of the turbine  16 . The second stator ring  56   2  and the second rotor ring  60   2  form the second stage of the turbine  16 . The third stator ring  56   3  and the third rotor ring  60   3  form the third stage of the turbine  16 . A fourth ring  56   4  surrounds the third or last stage of the turbine  16 , to form a stator exhaust ring  56   4 , with stator exhaust blades  58   4 . It will of course be understood that the turbine  16  may also be designed with 4 stages or more, by adding one or more pairs of stator and rotor rings. 
     Referring now to  FIG. 2 , it will be noted that the rotor rings  60   1 ,  60   2 ,  60   3  are supported by a rotor disk  64 , which is fixed to a free end of a turbine shaft  66 . The turbine shaft  66  with the rotor disk  64  is rotatably supported in a cantilever fashion in a shaft outlet neck  72  by means of a bearing arrangement, preferably built up with rolling contact bearings. Reference number  68  points to a schematic representation of such a rolling contact bearing. Reference number  70  identifies a schematic representation of a sealing device, which seals the shaft  66  in the shaft outlet neck  72 , between the rotor disk  64  and the bearing arrangement. 
     Reference number  74  identifies the central axis of the turbine shaft  66 , which is also the central axis of all rotor rings  60   1 ,  60   2 ,  60   3  (and of all stator rings  56   1 ,  56   2 ,  56   3 ,  56   4 ), since all these rings are coaxial with the turbine shaft  66 . It will be noted that the rotor disk  64  is axially secured to the turbine shaft  66 , e.g. by means of a nut  75  or a screw (not shown), and that the torque is transmitted from the rotor disk  64  to the turbine shaft  66  by means of a form-fit or keyed assembly (not shown). The rotor rings  60   1 ,  60   2 ,  60   3  are fixed with screws  76  to the rotor disk  64 , so that they are easily exchangeable. 
     Still referring to  FIG. 2 , the stator rings  56   1 ,  56   2 ,  56   3  are fixed with screws  78  to a plate-shaped first turbine housing part  80 . This first turbine housing part  80  comprises a first and a second tubular vapour inlet connection  82 ,  84 , a first and a second ring-shaped flange  88 ,  90  and a perforated ring zone  92 . The first tubular vapour inlet connection  82  is centred on the central axis  74  of the turbine  16 . The second tubular vapour inlet connection  84  surrounds the first tubular vapour inlet connection  82 , so as to define with the latter an annular space  86 , wherein the perforated ring zone  92  is contained in this annular space  86 . The first ring-shaped flange  88  forms a shoulder around the first tubular vapour inlet connection  82 . The second ring-shaped flange  90  forms a shoulder around the second tubular vapour inlet connection  84 . The perforated ring zone  92  joins the first flange  88  and the second ring-shaped flange  90  and is provided with through-holes  94 . 
     It will be noted that instead of being integral with the first turbine housing part  80 , the first and/or second tubular vapour inlet connection  82 ,  84  could also be flanged to the first turbine housing part  80 . In this case, the first turbine housing part  80  mainly consists of the first ring-shaped flange  88 , the second ring-shaped flange  90  and the perforated ring zone  92 , which joins the first and the second ring-shaped flange  88 ,  90 . In this embodiment, the first ring-shaped flange  88  advantageously comprises a first connection means for flanging a removable first vapour inlet connection thereto, and the second ring-shaped flange  90  advantageously comprises a second connection means for flanging a removable second vapour inlet connection thereto (not shown in the drawings). 
     The first ring-shaped flange  88  supports the first and the second stator ring  56   1 ,  56   2 . The first stator ring  56   1  is advantageously part of an end-cap  96 , which forms a vapour inlet deflection surface  98  at the end of the first tubular vapour inlet connection  82 . This vapour inlet deflection surface  98  is a revolution surface centred on the central axis  74  of the turbine  16 , so as to annularly deflect the axial vapour stream in the first tubular vapour inlet connection  82  by 90° into the first stator ring  56   1 . 
     The second ring-shaped flange  90  supports the third stator ring  56   3 , as well as the exhaust stator ring  56   4 . By means of the exhaust stator ring  56   4 , the first turbine housing part  80  is fixed to a plate-shaped second turbine housing part  100 . The rotor disk  64  with the rotor rings  60   1 ,  60   2 ,  60   3  is hereby located axially between the first housing part  80  and the second housing part  100 . In the radial direction, the first rotor ring  60   1  is located between the first and the second stator ring  56   1  and  56   2 ; the second rotor ring  60   2  is located between the second and the third stator ring  56   2  and  56   3 ; and the third rotor ring  60   3  is located between the third stator ring  56   3  and the exhaust stator ring  56   4 . It will be appreciated that—with this sandwich design—the height of the stator blades  58   1 ,  58   2 ,  58   3  and rotor blades  62   1 ,  62   2 ,  62   3  can be modified, by simply exchanging the removable stator rings  56  and rotor rings  60 . Consequently, with one size for the first and second turbine housing part  80  and  100 , the rotor disk  64  and the turbine shaft  66 , one may already cover a large range of pressures and flow rates. Thus, it will be e.g. be possible to cover the electric power range of 25 kW to 100 kW with one unique size for the first and second turbine housing part  80  and  100 , the rotor disk  64  and the turbine shaft  66 . In most cases it will even not be necessary to change the form of the rotor and stator blades  58 ,  62 . A broad electric power range may be covered by simply changing the height of the rotor and stator blades  58 ,  62 , all other geometric characteristics of the rotor and stator rings  56 ,  60  and blades  58 ,  62  remaining unchanged. Furthermore, if the available heat energy increases or decreases during lifetime of the turbine, the latter may be easily reconfigured for the new operating conditions by simply exchanging its rotor and stator rings  56 ,  60 . 
     As is best seen in  FIG. 3 , each of the three stator rings  56   1 ,  56   2 ,  56   3  includes at its base an annular shoulder  102   1 ,  102   2 ,  102   3 , which forms a labyrinth joint  10   6  with an opposite grooved surface located on an annular outer rim  104   1 ,  104   2 ,  104   3  of the corresponding rotor ring  60   1 ,  60   2 ,  60   3 . Similarly, each of the first two rotor rings  60   1 ,  60   2  includes at its base an annular shoulder  108   1 ,  108   2 , which forms a labyrinth joint  112  with an opposite grooved surface located on an annular outer rim  110   2 ,  110   3  of the corresponding stator ring  56   2 ,  56   3 . Thus, vapour tightness in the radial direction between the rotating and stationary parts is solely achieved by easily machinable surfaces on the removable stator rings  56   1 ,  56   2 ,  56   3  and rotor rings  60   1 ,  60   2 , and necessitates neither complicated machining on the turbine housing parts  80 ,  100  or the rotor disk  64 , nor separate sealing elements. Furthermore, if the removable rotor and stator rings  56 ,  60  are replaced, all sealing surfaces in the turbine are replaced too. Alternatively, the removable stator rings  56   1 ,  56   2 ,  56   3  and rotor rings  60   1 ,  60   2 , may be designed without the aforementioned annular shoulder, wherein the outer rims  104   1 ,  104   2 ,  104   3  of the rotor rings  60   1 ,  60   2 ,  60   3  and the outer rims  110   2 ,  110   3  of the stator rings  56   2 ,  56   3  cooperate directly with corresponding annular surfaces on the housing part  80  and the rotor disk  64  to form labyrinth joints. 
     It will further be noted that the annular shoulder  102   2  of the second stator ring  56   2  is smaller than the other two annular shoulders  102   1 ,  102   3 , thereby leaving uncovered the through-holes  94  in the perforated ring zone  92  of the first turbine housing part  80 . The width of the annular outer rim  104   2  of the second rotor ring  60   2 , which is located just behind the perforated ring zone  92 , decreases towards its periphery, so as to define with the opposite surface of the third stator ring  56   3  a ring-shaped converging nozzle  114 , which is delimited, on one side, by an annular concave surface  116  defined by the second rotor ring  60   2  and, on the other side, by an annular convex surface  118  defined by the third stator ring  56   3 . This ring-shaped nozzle  114  deflects the low pressure vapour stream, which flows from the annular space  86  in an axial direction through the through-holes  94 , by an angle of 90° into the third stator ring  56   3 . In this third stator ring  56   3 , this low pressure vapour stream is induced into the main vapour stream that has already been expanded in the first and second stage of the turbine  16 , so that both vapour streams have substantially the same pressure when they merge in the third stator ring  56   3 . 
     Referring simultaneously to  FIG. 2  and  FIG. 4 , it will be noted that the expansion of the vapour in the second stator ring  56   2  and the third stator ring  56   3  is mainly achieved by increasing the height of the stator blades  58  in the radial direction (i.e. the height of these blades at the outlet is considerably higher than their height at the inlet of the stator ring). Thus, the expansion of the vapour in these stator rings  56   2  and  56   3  is mainly determined by the increasing height of their blades. Consequently, for adapting the turbine to a different vapour throughput or a different inlet pressure in the turbine  16 , it will not be necessary to entirely change the geometry of the rotor or stator blades  58 ,  62 . It will most often simply be sufficient to change the height of the rotor and stator blades  58 ,  62 , all other geometric characteristics of the rotor and stator rings  56 ,  60  and blades  58 ,  62  remaining basically unchanged. 
     It will be appreciated that the turbine as described hereinbefore may achieve an isentropic efficiency as high as 90%. Its rotation speed will preferably be limited to 18,000 rpm, so to be capable of working with rolling contact bearings and common shaft sealing devices. 
       FIG. 5  schematically shows a first arrangement of the high pressure vapour drum  46  and the low pressure vapour drum  48 , both directly located under the turbine  16  and directly connected to latter without any intermediate piping. The high pressure vapour drum  46  is a cylindrical vessel directly flanged to the first turbine housing part  80 . The low pressure vapour drum  48  forms an annular compartment within the high pressure vapour drum  46 . This annular compartment is outwardly delimited by a cylindrical external wall  120  of the high pressure vapour drum  46  and inwardly delimited by a cylindrical internal wall  122 . This cylindrical internal wall  122  engages the first tubular vapour inlet connection  82  of the turbine  16  in a sealed fit, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the cylindrical internal wall  122  and the first tubular vapour inlet connection  82 . The high pressure vapour flows through the axial passage delimited by the cylindrical internal wall  122  into the first tubular vapour inlet connection  82  of the turbine. The low pressure vapour flows directly from the annular low pressure vapour drum  48  into the annular space  86  delimited between the first tubular vapour inlet connection  82  and the second tubular vapour inlet connection  84  of the turbine. Reference number  124  points to a high pressure vapour inlet pipe connected laterally to the high pressure vapour drum  46 , whereas reference number  126  points to a low pressure vapour inlet pipe connected laterally to the low pressure vapour drum  48 . 
     The arrangement of  FIG. 6  distinguishes over the arrangement of  FIG. 5  mainly in that the low pressure vapour inlet pipe  126 ′ traverses the high pressure vapour drum  46  to leave the latter through its bottom wall. This design necessitates that the low pressure vapour inlet pipe  126  and the high pressure vapour drum  46  may freely expand relative to one another. This can e.g. be achieved by connecting the low pressure vapour inlet pipe  126  by means of a bellow expansion joint (not shown) to the closed end of the high pressure vapour drum  46 . 
       FIG. 7  shows a further arrangement of the high pressure vapour drum  46  and the low pressure vapour drum  48  connected to the turbine  16 . The low pressure vapour drum  48  is a cylindrical vessel flanged to the first turbine housing part  80 . The high pressure vapour drum  46  forms a cylindrical compartment within the low pressure vapour drum  48 , separated from the outer wall of the latter by an annular space  130 . It is vertically supported by a support flange  132 , which is welded into the low pressure vapour drum  48 . Through-openings  134  in the support flange  132  allow the intermediate pressure vapour to pass from an inlet compartment  136  of the low pressure vapour drum  48  into the annular space  130 . The high pressure vapour drum  46  engages the first tubular vapour inlet connection  82  of the turbine  16  in a sealed way, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the high pressure vapour drum  46  and the first tubular vapour inlet connection  82 . Similarly as for the pipe  126 ′ in the embodiment of  FIG. 6 , the passage of the pipe  124  through the bottom wall of the low pressure vapour drum  48  is designed for allowing a relative axial expansion of both components. 
     It will be noted that in  FIGS. 5 ,  6  and  7 , the outer vessel is flanged to the first turbine housing part  80  of the turbine  16 , and must consequently be able to axially expand away from the turbine  16 . In  FIG. 8 , the outer vessel  140  is no longer flanged to the first turbine housing part  80  of the turbine  16 . It simply engages the second tubular vapour inlet connection  84  of the turbine  16  in a sealed way, wherein this sealed fit is designed (e.g. with O-rings) to allow a relative axial movement of the outer vessel  140  and the second tubular vapour inlet connection  84 . In this embodiment, the outer vessel  140  (which may be the high pressure vapour drum  46  as in  FIG. 5  or  6 , or the low pressure vapour drum  48  as in  FIG. 7 ) can be vertically supported by a separate vertical support means  142 . Thus, the outer vessel  140  may e.g. be directly supported on the first or second evaporator  12 ,  14 , when the latter are axially arranged under the outer vessel  140 . It will consequently be appreciated that in the embodiment of  FIG. 7 , the turbine  16  must not support the whole weight of the two vapour drums  46 ,  48 . 
     It will be appreciated that in all three arrangements, the low pressure vapour is slightly superheated by contact with one or more walls of the high pressure vapour drum  46 , which may be advantageous for the efficiency of the low pressure cycle. This superheating-effect is more important for the embodiment of  FIG. 7  and may be further amplified by providing the outer wall of the inner cylinder  46  in  FIG. 7  with fins. 
       FIGS. 9 and 10  show a compact device for electric power generation according to an improved ORC, more particularly, to an ORC working with two evaporators  12 ,  14 , two regenerators  20 ,  22  and an induction turbine  16 , so as illustrated with the circuit of  FIG. 1 . The container  10  is a vertical vapour tight cylinder supported on support feet  150 . The turbine  16  is located inside the vertical cylinder  10 , near the top end of the latter. The central axis  74  of the turbine is aligned with the central axis of the container  10 . Referring back to  FIG. 2 , it will be noted that the second turbine housing part  100  is fixed with in a sealed manner to a head-plate  152 , which is a part of the upper container wall. The shaft outlet neck axially protrudes out of an opening  153  of the head-plate  152 . Alternatively, the second turbine housing part  100  may include an annular flange (not shown) with which it is fixed in a sealed manner onto a flange surrounding an axial opening (not shown) in the head of the container  10 . In this case the entire second turbine housing part  100  is located outside the container  10 . A generator  154  is arranged on the top of the vertical cylinder  10  and is coupled to the vertical shaft of the turbine  16 . It will be appreciated that with this arrangement, the bearing arrangement  68  of the turbine shaft  66  is located completely outside the container  10 , which greatly facilitates the design of its lubrication system, but also its maintenance. 
     The high pressure vapour drum  46  and the low pressure vapour drum  48  are arranged axially directly under the turbine  16 . Both vapour drums  46 ,  48  are advantageously connected to the first and second tubular vapour inlet connection  82 ,  84  of the turbine  16  as described e.g. with reference to  FIG. 5  or  6  and  FIG. 8 . The first evaporator  12  and the second evaporator  14  are arranged axially directly under the two vapour drums  46 ,  48 , which can be vertically supported by the two evaporators  12 ,  14 , as described with reference to  FIG. 8 . These two evaporators  12 ,  14  are preferably enclosed in a separate cylindrical compartment  156 . The first and second regenerator  20 ,  22  are arranged annularly around the two vapour drums  46 ,  48 , wherein the second regenerator  22  is arranged directly under the first regenerator  20 . The condenser  18  is arranged annularly around the two evaporators  12 ,  14 . The bottom part of the vertical cylinder  10  forms a condensate collector  158 . 
     The turbine  16 , which is preferably conceived substantially as described hereinbefore, radially discharges the expanded vapour through the stator exhaust ring  56   4  directly into the upper part of the vertical cylinder  10 . An annular deflector (not shown) may be used to deflect the radially discharged vapour axially downwards. This annular deflector may be incorporated into the turbine  16  or be installed as a separate element into the container  10 . The expanded vapour then passes downwards through the first and second regenerator  20 ,  22 , to be finally condensed in the condenser  18 . The condensate is collected in the condensate collector  158  at the bottom of the vertical cylinder  10 . 
     The pipe connections  30 ,  30 ′,  32 ,  32 ′,  34 ,  34 ′,  36  and  38  shown in  FIG. 9  correspond to the inlet/outlet ports with the same reference numbers shown in  FIG. 1 . 
       FIG. 10  is a horizontal cross-section of the device shown in  FIG. 9 . This  FIG. 10  shows that the annular heat-exchangers  18 ,  20 ,  22  do not occupy the whole annular space around the separate cylindrical compartment  156  in which the evaporators  12 ,  14  are arranged. The free space, here an angular segment of about 40°, is used for arranging therein piping and auxiliary equipment, which is only schematically represented in  FIG. 10  and identified therein with reference number  160 . 
       FIG. 11  shows an alternative embodiment with an air-cooled condenser  170  installed outside the container  10 , which still contains the evaporators  12 ,  14 , the regenerators  20 ,  22 , the vapour drums  46 ,  48 , and the turbine  16 , which are advantageously arranged in this container  10  as described hereinbefore with reference to  FIG. 9 . The bottom half of the container  10 , which was occupied by the condenser  18  in the embodiment of  FIG. 9 , is now empty and connected via a large diameter pipe  172  to the air-cooled condenser  170 . The latter includes a central chimney  174  with a closed end  176 , which is connected to at least one upper vapour collector  178 . From this upper vapour collector  178  the vapour streams through at least one air-cooled condensing heat exchanger  180 , which condenses the vapour. The condensate is collected in at least one lower condensate collector  182  and evacuated back into the condensate collector  158  in the container  10  through a condensate line  184 . Condensate that is already formed in the central chimney  174  flows back into the condensate collector  158  in the container  10  through the large diameter pipe  172 . Reference number  186  identifies a fan for creating an air flow  188  through the condensing heat exchanger(s)  180  and along the outer wall of the chimney  174 , which may be equipped with cooling fins too. 
     
       
         
           
               
             
               
                   
               
               
                 Reference signs list 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                  10 
                 container 
               
               
                   
                  12 
                 first evaporator 
               
               
                   
                  14 
                 second evaporator 
               
               
                   
                  16 
                 turbine 
               
               
                   
                  18 
                 condenser 
               
               
                   
                  20 
                 first regenerator 
               
               
                   
                  22 
                 second regenerator 
               
               
                   
                  24 
                 condensate pump 
               
               
                   
                  26 
                 electrical generator 
               
               
                   
                  30 
                 first heat carrier fluid inlet port of 
               
               
                   
                   
                 12 
               
               
                   
                  30′ 
                 second heat carrier fluid inlet 
               
               
                   
                   
                 port of 12 
               
               
                   
                  32 
                 first heat carrier fluid inlet port of 
               
               
                   
                   
                 12 
               
               
                   
                  32′ 
                 second heat carrier fluid inlet 
               
               
                   
                   
                 port of 14 
               
               
                   
                  34 
                 cooling fluid outlet port of 18 
               
               
                   
                  34′ 
                 cooling fluid outlet port of 18 
               
               
                   
                  36 
                 condensate outlet port 
               
               
                   
                  38 
                 first condensate inlet port 
               
               
                   
                  40 
                 second condensate inlet port 
               
               
                   
                  42 
                 external heat transfer circuit in 
               
               
                   
                   
                 which circulates a heat carrier 
               
               
                   
                   
                 fluid 
               
               
                   
                  44 
                 external connection conduit 
               
               
                   
                  45 
                 bypass-valve 
               
               
                   
                  46 
                 high pressure vapour drum 
               
               
                   
                  48 
                 low pressure vapour drum 
               
               
                   
                  50 
                 external cooling circuit of 18 
               
               
                   
                  52 
                 first valve (connected to 38) 
               
               
                   
                  54 
                 second valve (connected to 40) 
               
               
                   
                  56 1 , 
                 first stator ring, 
               
               
                   
                  56 2 , 
                 second stator ring, 
               
               
                   
                  56 3   
                 third stator ring 
               
               
                   
                  56 4   
                 stator exhaust ring (58) 
               
               
                   
                  58 1 , 
                 curved stator blades (58) of 56 1   
               
               
                   
                  58 2 , 
                 curved stator blades (58) of 56 2   
               
               
                   
                  58 3   
                 curved stator blades (58) of 56 3   
               
               
                   
                  58 4   
                 stator exhaust blades 
               
               
                   
                  60 1 , 
                 first rotor ring, 
               
               
                   
                  60 2 , 
                 second rotor ring, 
               
               
                   
                  60 3   
                 third rotor ring 
               
               
                   
                  62 1 , 
                 curved rotor blades of 60 1   
               
               
                   
                  62 2 , 
                 curved rotor blades of 60 2   
               
               
                   
                  62 3   
                 curved rotor blades of 60 3   
               
               
                   
                  64 
                 rotor disk 
               
               
                   
                  66 
                 turbine shaft 
               
               
                   
                  68 
                 bearing 
               
               
                   
                  70 
                 sealing device 
               
               
                   
                  72 
                 shaft outlet neck 
               
               
                   
                  74 
                 central axis of 16 
               
               
                   
                  75 
                 nut 
               
               
                   
                  76 
                 screws for rotor rings 
               
               
                   
                  78 
                 screws for stator rings (56) 
               
               
                   
                  80 
                 first turbine housing part (80) 
               
               
                   
                  82 
                 first tubular vapour inlet 
               
               
                   
                   
                 connection 
               
               
                   
                  84 
                 second tubular vapour inlet 
               
               
                   
                   
                 connection 
               
               
                   
                  86 
                 annular space (between 82 and 
               
               
                   
                   
                 84) 
               
               
                   
                  88 
                 first ring-shaped flange (on 82) 
               
               
                   
                  90 
                 second ring-shaped flange (on 
               
               
                   
                   
                 84) 
               
               
                   
                  92 
                 perforated ring zone 
               
               
                   
                  94 
                 through-holes in 92 
               
               
                   
                  96 
                 end-cap 
               
               
                   
                  98 
                 vapour inlet deflection surface 
               
               
                   
                 100 
                 second turbine housing part 
               
               
                   
                   
                 (100) 
               
               
                   
                 102 1 , 
                 annular shoulder on 56 1 , 56 2 , 
               
               
                   
                 102 2 , 
                 56 3   
               
               
                   
                 102 3   
               
               
                   
                 104 1 , 
                 annular outer rim on 60 1 , 60 2 , 
               
               
                   
                 104 2 , 
                 60 3   
               
               
                   
                 104 3   
               
               
                   
                 106 
                 labyrinth joint 
               
               
                   
                 108 1 , 
                 annular shoulder on 60 1 , 60 2   
               
               
                   
                 108 2   
               
               
                   
                 110 2 , 
                 annular outer rim on 56 2 , 56 3   
               
               
                   
                 110 3   
               
               
                   
                 112 
                 labyrinth joint 
               
               
                   
                 114 
                 ring-shaped nozzle 
               
               
                   
                 116 
                 annular concave surface defined 
               
               
                   
                   
                 by 60 2   
               
               
                   
                 118 
                 annular convex surface defined 
               
               
                   
                   
                 by 56 3   
               
               
                   
                 120 
                 cylindrical external wall 
               
               
                   
                 122 
                 cylindrical internal wall 
               
               
                   
                 124 
                 high pressure vapour inlet pipe 
               
               
                   
                 126 
                 low pressure vapour inlet pipe 
               
               
                   
                 130 
                 annular space 
               
               
                   
                 132 
                 support flange 
               
               
                   
                 134 
                 through openings in 132 
               
               
                   
                 136 
                 inlet compartment 
               
               
                   
                 140 
                 outer vessel 
               
               
                   
                 142 
                 vertical support means 
               
               
                   
                 150 
                 support feet 
               
               
                   
                 154 
                 generator 
               
               
                   
                 156 
                 separate cylindrical 
               
               
                   
                   
                 compartment 
               
               
                   
                 158 
                 condensate collector 
               
               
                   
                 160 
                 piping and auxiliary equipment 
               
               
                   
                 170 
                 air-cooled condenser 
               
               
                   
                 172 
                 large diameter pipe 
               
               
                   
                 174 
                 central chimney 
               
               
                   
                 176 
                 closed end of 174 
               
               
                   
                 178 
                 upper vapour collector 
               
               
                   
                 180 
                 condensing heat exchanger 
               
               
                   
                 182 
                 lower condensate collector 
               
               
                   
                 184 
                 condensate line 
               
               
                   
                 186 
                 fan 
               
               
                   
                 188 
                 air flow