IT201600080087A1 - VOLUMETRIC EXPANDER, SYSTEM WITH CLOSED CYCLE USED AS THE EXPANDER, PROCEDURE FOR STARTING THE VOLUMETRIC EXPANDER AND PROCEDURE FOR THE CONVERSION OF THERMAL ENERGY IN ELECTRICAL ENERGY BY MEANS OF THIS SYSTEM - Google Patents

Description

VOLUMETRIC EXPANDER, CLOSED-CYCLE SYSTEM USING SAID EXPANDER, START-UP PROCEDURE OF SAID VOLUMETRIC EXPANDER AND PROCESS OF CONVERSION OF THERMAL ENERGY INTO ELECTRIC ENERGY THROUGH SAID SYSTEM "

FIELD OF THE TROVATO

The present invention relates to a volumetric expander and a closed cycle plant, for example a Rankine cycle, using said expander for the generation of electrical and / or mechanical energy by means of heat recovery and conversion; the present invention also relates to a process for starting the volumetric expander and a process for converting thermal energy into electrical energy by means of said system.

The present invention can be used in biogas / biomass plants for the recovery of waste heat from the cogeneration process, in geothermal plants for the exploitation of medium / small heat sources, in industrial plants for the recovery of thermal waste (conversion of waste heat from industrial processes), in the home for the production of electricity and the exploitation of heat for sanitary use. Further use of the expander and the related system may concern both domestic and industrial systems, in which the heat source is provided by solar energy collection systems. The plant may also be used in the automotive sector, for example for the recovery of heat from the engine.

STATE OF THE ART

Rankine cycle systems are known which use a volumetric expander for the recovery of thermal energy and the subsequent production of electrical energy.

An embodiment of such systems provides for the use of one or more turbines as an expansion chamber. However, this solution has some constraints and drawbacks, well known to the skilled in the art, and which are:

- high cost of the turbine and of the connected control organs;

- need for frequent maintenance with consequent charges of various types;

- maximum efficiency which is obtained only at a very precise flow rate of the expanding fluid and with a defined rotation speed; in particular this is perhaps the greatest limitation of turbine systems since if the rotation speed undergoes even a slight variation with respect to the optimal value, the efficiency of the turbine declines drastically.

It should also be noted that generally available heat sources have a medium / low temperature. The conversion of the heat supplied by these sources into electrical energy is, through the use of turbines, excessively expensive in relation to the energy produced: the turbines are not very suitable for the exploitation of medium / low temperature thermal sources which also generally have a widely variable heat output, a condition that makes the use of turbines for the conversion of thermal energy even more inconvenient (as described above, turbines allow maximum efficiency to be obtained at a very precise flow rate of the expanding fluid).

Due to the low capacity of exploitation of medium / low temperature sources, the latter are used in a limited way only for professional uses while they are not used in the domestic environment. In fact, today most of the medium / low temperature sources are dispersed in the environment and therefore wasted. The most common heat sources, referred to here, are available both as a derivative of human activity and in nature, such as the heat contained in industrial waste products or the heat contained in biomass if the latter are burned. .

To overcome the drawbacks described above, it is known to use volumetric expanders, alternative or rotary, capable of operating with relatively modest flow rates of fluid without excessive reduction in power and efficiency. The volumetric expanders, operating at lower thermal powers, work at a number of revolutions (cycles) considerably lower than the rotation speed of the turbines, which eliminates the risk of damage to the moving parts in the event that there was the passage of liquid (drops due to to incorrect vaporization of the working fluid) in the expansion chamber. The volumetric expanders also have a lower structural complexity than that of turbines with a consequent reduction in costs. In addition to their reduced complexity, volumetric expanders are more compact than turbines, which facilitates their construction, assembly and installation.

Examples of volumetric expanders used for the conversion of thermal energy into electrical energy - making use of low temperature heat sources - are described in patent applications US2012 / 0267898A1 and W02014141072.

Although known alternative volumetric expanders are better than turbines in conditions of medium / low temperature heat sources, the Applicant believes that such known volumetric expanders can be further improved under various aspects.

Known volumetric expanders - in particular expanders adapted to operate according to a Rankine cycle - are generally used discontinuously: the systems on which these expanders operate undergo continuous stops and starts. During a condition of inactivity of the expander, the working fluid present in the same condenses (particularly in environments where there is a low external temperature) thus forming liquid condensates. The condensed working fluid prevents the expander from restarting, thus making it impossible to restart from the entire system unless previously eliminating said liquid condensates. To obviate this inconvenience, in the past real extraordinary maintenance procedures were envisaged which forced the personnel in charge of the extemporaneous heating of the expander by means of electric resistances placed outside the latter or by means of rudimentary systems such as the heating with flame of the expander body. However, the use of resistors or other extemporaneous systems requires extremely long operating times as well as a high energy consumption which negatively affects the overall performance of the system.

Alternatively, the staff was called upon to purge the unwanted liquid present inside the expander. Even this maintenance procedure - in addition to requiring specialized personnel - requires very long operating times that weigh heavily on the downtime of the system.

PURPOSE OF THE FOUND

The aim of the present invention is therefore to substantially solve at least one of the drawbacks and / or limitations of the previous solutions.

A first objective of the present invention is to provide a volumetric expander and a relative high efficiency plant, in particular which allow to obtain high yields also through the conversion of variable thermal energy at medium / low temperature. It is also an object of the present invention to provide a volumetric expander and a relative plant, for example with a Rankine cycle, adaptable to the different working conditions in such a way as to be able to effectively exploit the available heat sources and deliver maximum power. with excellent returns.

The object of the present invention is also to provide a volumetric expander and a relative plant, for example with a Rankine cycle, of simple and compact construction capable of allowing easy installation and consequently having extremely high production, maintenance and assembly costs. reduced.

It is also the aim of the invention to provide a volumetric expander that can be easily and quickly installed on a system for the conversion of thermal energy into electrical energy; in particular, the purpose of this document is to provide a volumetric expander that can be quickly disassembled and / or removed (for example in the case of installation, replacement or repair) so that any downtime of the system can be reduced to minimum.

It is also an object of the present invention to provide a volumetric expander having a structure capable of guaranteeing a rapid and effective start-up of the same; in particular, the purpose of the present invention is to provide a volumetric expander that does not require the consumption of electricity or energy from external sources for starting the same.

In particular, the aim of the present invention is to provide a volumetric expander and a related plant, for example a Rankine cycle, which can be implemented without the need for complex modifications to conventional systems for converting thermal energy into electricity. A further objective of the present invention is to provide a process capable of effectively exploiting the expander and the plant mentioned above; in particular, the aim of the present invention is to provide a process for converting thermal energy into electrical energy that is easily implemented and through which it is possible to obtain excellent energy conversion yields.

These objects and others, which will become more apparent from the following description, are substantially achieved by a volumetric expander, a closed-cycle plant and a process for converting energy to electrical energy in accordance with what is expressed in one or more of the appended claims and / or the following aspects, taken alone or in any combination with each other or in combination with any of the appended claims and / or in combination with any of the further aspects or features described below.

SUMMARY

Aspects of the invention are described below. In a 1st aspect a volumetric expander (4) is provided for a closed cycle plant, in particular a Rankine cycle, said volumetric expander (4) comprising:

> at least one enclosure (50) having at least one general inlet (51) configured to allow the introduction of a working fluid inside the enclosure (50) and at least one general outlet (52) configured to allow expulsion of the working fluid from said casing (50),

> at least one piston (6) operating inside the casing and able to define an expansion chamber (7) with variable volume,

> a main shaft (11) kinematically connected to the piston (6) and configured to rotate around a main axis (X), said main shaft (11) being housed at least partially inside the casing (50) ,> at least one valve (10) configured to selectively open and close an inlet and an outlet (8, 9) to the expansion chamber (7) allowing at least: o a condition for the introduction of the working fluid into the expansion chamber (7 ),

or an expansion condition of the working fluid in the expansion chamber (7), ed

or a condition of discharge of the working fluid from said expansion chamber (7)

wherein the casing (50) defines internally a discharge chamber in fluid communication with the general outlet (52), the discharge chamber being further configured to be placed in fluid communication with the outlet (9) of the chamber expansion (7) during the condition of discharge of the working fluid from the expansion chamber (7) itself.

In a 2nd aspect in accordance with the 1st aspect in which the casing (50) internally defines a discharge chamber in direct fluid communication with the general outlet (52).

In a 3rd aspect in accordance with any of the preceding aspects the discharge chamber is configured to be placed in direct fluid communication with the outlet (9) of the expansion chamber (7) during the working fluid discharge condition from the expansion chamber (7) itself.

In a 4th aspect according to any of the preceding aspects, the expander comprises a transmission member (53) connected - on one side - to the valve (10) and - on the other side - to the main shaft (11), called transmission member (53) being configured to synchronize the inlet condition, the expansion condition and the discharge condition of the working fluid with the rotation of the main shaft (11),

and in which the transmission member (53) is arranged in the casing (50) inside the discharge chamber of the working fluid.

In a 5th aspect in accordance with any of the preceding aspects, the casing (50) comprises a side wall extending between a first and a second longitudinal end portion (50a, 50b), said side wall extending in thickness between a surface external and an internal surface of the casing, said internal surface delimiting an internal cavity of the casing (50) defining at least part of the discharge chamber arranged inside the casing (50) itself.

In a 6th aspect in accordance with the preceding aspect, the transmission member (53) is arranged at least partially inside the internal cavity of the casing (50) between the first and second longitudinal end portion (50a, 50b).

In a 7th aspect in accordance with any of the preceding aspects, the variable volume of each expansion chamber (7) is delimited by a respective jacket (5), operating inside the casing (50), and by said piston (6) , slidably housed in said liner, said inlet (8) and outlet (9) being placed on said liner which defines a seat (22), for example a cylindrical seat (22).

In an 8th aspect in accordance with the previous aspect, the seat (22) is defined on the side wall of the casing (50), the piston (6) is movable with reciprocating motion and sliding inside the seat.

In a 9th aspect in accordance with the 7th or 8th aspect, the seat (22) of the jacket (5) extends along the thickness of the side wall of the casing (50), in particular starting from the inner surface of the casing up to a respective valve (10).

In a 10th aspect in accordance with any of the preceding aspects, the expander (4) comprises at least one crank mechanism (37) constrained on one side to the piston (6) and on the other hand constrained to the main shaft (11), called crank mechanism (37) being configured to rotate the main shaft (11) around the axis (X) following the reciprocating sliding motion of the piston (6), in particular inside the respective expansion chamber (7) .

In an 11th aspect in accordance with any of the previous aspects, at least part of the main shaft (11) is housed in the housing discharge chamber (50). In a 12th aspect in accordance with the 10th or 11th aspect, the entire crank mechanism (37) is housed in the discharge chamber of the casing (50).

In a 13th aspect in accordance with any of the 8th to 10th aspects the main shaft (11) comprises an engaging portion (11 a) spaced from the axis of rotation (X) of the same main shaft ( 11), in which the crank mechanism (37) includes:

> a base element (38) constrained, in particular hinged, to the engagement portion (11 a) of the main shaft (11), said base element (38) being movable by rotation around the axis (X) of the 'main shaft (11),

> a thrust element (39) directly connected - on one side - to the base element (38) and - on the other side - to the piston (6).

In a 14th aspect in accordance with the previous aspect, the engagement portion (11a) of the main shaft (11) includes a pin, the base element (38) being incinerated to said pin.

In a 15th aspect in accordance with any of the preceding aspects the valve (10) comprises:

> an internally hollow valve body (24) presenting:

or a housing seat (25), for example having a substantially cylindrical shape, developing inside the valve body,

or at least a first and a second passage (26, 27) respectively in fluid communication, in particular direct, with the inlet (8) and the outlet (9) of the expansion chamber (7),

> at least one distribution body (28) engaged for rotation inside the housing seat (25) of the valve body and comprising:

or at least one inlet channel (29) in fluid communication with the general inlet (51) of the casing (50),

or at least one emission channel (30) in fluid communication with the discharge chamber of the casing (50) and therefore with the general outlet (52) of the latter, or at least a first channel (31) in communication of fluid directed with the inlet channel (29), the first channel (31) comprising at least one lateral opening (31a) configured to be placed in fluid communication with the first passage (26) of the valve body (24) ,

or at least a second channel (32), distinct and separated from the first channel (31), in direct fluid communication with the emission channel (30), the second channel (32) comprising at least one respective lateral opening (32a) - angularly offset with respect to the lateral opening (31 a) of the first channel (31) with respect to a rotation axis (Z) of the distribution body - configured to be placed in fluid communication with the second passage (26) of the valve body (24),

the distribution body (28), following the rotation inside the housing seat (25) around its own axis (Z), being configured to selectively determine the conditions of inlet, expansion and discharge of the volumetric expander (4 ).

In a 16th aspect in accordance with the previous aspect, the lateral openings (31a, 32a) - respectively of the first and second channels (31, 32) of the distribution body - are configured to be placed in direct fluid communication with the expansion chamber (7), in particular with the seat (22) of the jacket (5).

In a 17th aspect in accordance with the 15th or 16th aspect, the transmission member (53) is at least partially arranged inside the valve body (24) and directly engaged with the distribution body (28) of the valve (10) .

In an 18th aspect in accordance with any of the aspects from the 15th to the 17th the transmission organ (53) includes:

> at least one first toothed wheel (54) keyed to the distribution body (28) of the valve (10),

> at least one second toothed wheel (55) keyed onto the main shaft (11),> at least one intermediate member (56) - for example a toothed wheel (56) - configured to connect the first and second toothed wheels (54) in motion , 55).

In a 19th aspect in accordance with any of the preceding aspects, the expander comprises a plurality of pistons (6) operating inside the casing.

In a 20th aspect in accordance with the previous aspect each piston (6) is housed in a respective jacket (5) defined internally to the casing (50).

In a 21st aspect in accordance with the 19th or 20th aspect the pistons (6) are angularly offset from each other with respect to the axis of rotation (X) of the main shaft (11), in particular to define a radial expander or also called stellar expander.

In a 22 ° aspect in accordance with any of the aspects from the 19th to the 21st the volumetric expander (4) comprises a number of pistons (6) equal to or greater than 3, in particular in a number equal to or between 3 and 12 , even more particularly between 3 and 9.

In a 23rd aspect in accordance with any of the previous aspects, the expander (4) comprises a valve (10) for each expansion chamber (7) of each piston (6).

In a 24th aspect in accordance with any of the 19th to 23rd aspects the crank mechanism (37) comprises a thrust element (39) for each piston (6), each thrust element (39) is constrained to a single base element (38). In a 25th aspect in accordance with any of the aspects from the 15th to the 24th the transmission organ (53) - for each piston (6) - includes:

> at least one first toothed wheel (54) keyed to the distribution body (28) of the valve (10),

> at least one second sprocket (55) keyed onto the main shaft (11),> at least one intermediate member (56) - for example a sprocket (56) - configured to connect the first and second sprockets (54, 55 ), said transmission member (53) being configured for:

o synchronize - for each piston (6) - at least the inlet condition and the discharge condition of the working fluid with respect to the expansion chamber (7) with the rotation of the main shaft (11),

or synchronize at least the inlet condition and the discharge condition of the working fluid of the various expansion chambers (7) in such a way that the inlet condition, or respectively the discharge condition, of an expansion chamber (7) is temporally offset with respect to an inlet condition, or respectively to an unloading condition, of another expansion chamber (7).

In a 26th aspect in accordance with any of the 5th to 25th aspects, the envelope (50) includes:

> in correspondence with the first portion of the longitudinal end (50a), a front closure element (57),

> in correspondence with the second portion of the longitudinal end (50b), a rear closing element (58),

the internal surface of the side wall of the casing (50), together with said front and rear closure elements, delimiting the internal cavity of the casing (50) itself.

In a 21st aspect in accordance with the previous aspect, the front element (57) is engaged to the rest of the shell (50) of the expander in a removable way.

In a 28th aspect in accordance with the 26th or 21st aspect, the rear element (58) is engaged to the rest of the shell (50) of the expander (4) in a removable way.

In a 29th aspect in accordance with the general inlet (51) it is defined on the front element (57) or on the rear element (58), and in which the general outlet (52) is defined on the front element ( 57) or on the rear element (58).

In a 30th aspect in accordance with any of the 26th to 29th aspects the general inlet (51) and general outlet (52) are both defined on the front element (57) or on the rear element (58 ).

In a 31st aspect in accordance with any of the 15th to 30th aspects in which:> the general inlet (51) is in fluid communication, in particular direct, exclusively with the inlet channel (29) of the valve (optionally of each valve), the general inlet (51) communicating directly neither with the exhaust chamber nor with the general outlet (52), and

> in which the general outlet (52) communicates, in particular directly, with the discharge chamber which is in direct fluid communication with the emission channel (30) of the valve (10).

In a 32 ° aspect in accordance with any of the preceding aspects, the casing (50) comprises at least one auxiliary inlet (59) which results exclusively in fluid communication, in particular direct, with the discharge chamber and therefore, through this the latter, with the general outlet (52), the auxiliary inlet (59) being configured to allow the introduction of working fluid, in particular directly, into the enclosure (50).

In a 33rd aspect in accordance with the previous aspect, the auxiliary input (59) is not in fluid communication, in particular direct, with the general input (51).

In a 34th aspect in accordance with the 32nd or 33rd aspect the auxiliary inlet (59) being configured to allow the direct introduction and subsequent circulation of working fluid in the gaseous state in the discharge chamber inside the enclosure (50 ).

In a 35 ° aspect in accordance with any of the aspects from 32 ° to 34 ° the auxiliary input (59) is defined on the front element (57) or on the rear element (58) of the casing (50).

In a 36th aspect in accordance with any of the 32nd to 35th aspects the general input (51), the general output (52) and the auxiliary input (59) are defined on the front element (57) .

In a 37th aspect in accordance with any of the 32nd to 36th aspects the generate input (51) and the auxiliary input (59) are both arranged on the front closing element (57) or both on the element rear closure (58) of the casing (50).

In a 38th aspect in accordance with any one of the 5th to 37th aspects the casing (50) comprises a hollow tubular body having a through opening extending between the first and the second longitudinal end portion (50a, 50b ) and delimited at least in part by the internal surface, at the first and second end portions (50a, 50b) the casing (50) has a first and a second access respectively.

In a 39 ° aspect in accordance with the previous aspect, the front closure element (57) is engaged in correspondence with the first access and being configured to define, in cooperation with the inner surface of the enclosure (50) itself, a closure fluid tight.

In a 40th aspect in accordance with any of the preceding aspects, the casing (50) comprises at least a first and a second through connection duct (60, 61) extending from the inner surface of the casing (50) up to a respective valve (10), the valve (10) being in fluid communication with the first and second through-connecting conduits (60, 61), wherein the first through-connecting conduit (60) is in direct fluid communication with the 'general inlet (51), the first connection duct (60) does not communicate directly with the exhaust chamber and with the general outlet (52), in which the second through connection duct (61) is in direct fluid communication with the discharge chamber, optionally in which the first and second through ducts (60, 61) are not in direct fluid communication with each other.

In a 41st aspect in accordance with any of the aspects from the 26th to the 40th, the front closure element (57) includes:

- a support portion (62) abutting a front wall (50c) of the envelope (50), said support portion (62) being configured to completely cover the first access of the envelope (50),

- a graft portion (63) emerging from the support portion (62) inside the envelope cavity (50) and bounded by an external surface counter-shaped to the internal surface of the envelope (50).

In a 42 ° aspect in accordance with the aspect preceding the general entrance (51) - defined on the front closing element (57) - it includes:

- an attachment portion (51 a) defining a blind cavity through the thickness of the support portion (62) and at least part of the graft portion (63) of the front closure element (57),

- at least one distribution channel (51 b) in fluid communication with the attachment portion (51 a) and emerging transversely from the latter up to the external surface of the coupling portion (63).

In a 43 ° aspect in accordance with the previous aspect, the distribution channel (51 b) is in fluid communication with the first through duct (60) of the envelope (50). In a 44 ° aspect in accordance with any one of the 40 ° to 43 ° aspects the inlet channel (29) of the valve (10) is in fluid communication, in particular direct, with the first through connection duct (60 ) of the casing (50), the emission channel (30) of the valve (10) being in fluid communication, in particular direct, with the second through connection duct (61) of the casing (50).

In a 45 ° aspect in accordance with any of the aspects from 26 ° to 44 ° the rear closing element (58) includes:

> a support portion (68) abutting a front wall (50d) of the envelope (50), said support portion (68) being configured to completely cover the second access of the envelope (50),

> at least one seat passing through the support portion (68) and configured to allow the passage of the main shaft (11) which is arranged partly inside and partly outside the casing (50).

In a 46th aspect, a closed cycle plant (1) is provided, in particular a Rankine cycle, for the conversion of thermal energy into electrical energy comprising:> a closed circuit (2) inside which at least one fluid circulates work in accordance with a predetermined direction of circulation,

> at least one volumetric expander (4) in accordance with any of the preceding aspects active on the closed circuit (2) and configured to receive working fluid in the gaseous state at the inlet,

> at least one electricity generator (12) connected to the main shaft (11) of the volumetric expander (4), said generator (12) being configured to generate electricity following the rotation of the main shaft (11). In a 47th aspect in accordance with the previous aspect regretted (1) it includes:> at least one pump (13) engaged on the closed circuit (2) and predisposed to impose on the working fluid said predetermined direction of circulation,

> at least one first heat exchanger (3) active on the closed circuit (2) and located downstream of the pump (13) with respect to the direction of circulation of the working fluid, said first heat exchanger (3) being arranged to receive the working fluid and being configured to receive heat from a hot source (H) and allow the working fluid to heat up to determine its passage from the liquid to the gaseous state,

the volumetric expander (4) being connected downstream of the first heat exchanger (3), with respect to the direction of circulation of the working fluid inside the closed circuit (2), and being configured to receive the working fluid at the inlet gaseous state generated in the first exchanger (3).

In a 48th aspect in accordance with the regressed 46th or 47th aspect, it comprises at least a second heat exchanger (16) active on the closed circuit (2) and interposed between the expander (4) and the pump (13), called second heat exchanger (16) being able to receive in passage the working fluid leaving said expander (4), said second heat exchanger (16) being configured to communicate with a cold source (C) and allow the condensation of the working fluid to define its complete transition from the gaseous state to the liquid state.

In a 49th aspect in accordance with the previous aspect, the plant (1) comprises at least one collection tank (17) active on the closed circuit (2) and interposed between the pump (13) and the second exchanger (16), said collection tank (17) being configured to contain the working fluid in the liquid state leaving said second exchanger (16), the pump (13) being connected to the collecting tank (17) and being able to send the work in the liquid state in the direction of the first heat exchanger (3).

In a 50th aspect in accordance with any one of the aspects from the 46th to the 49th regret it comprises at least a third heat exchanger (18) operatively active on the circuit (2) upstream of the first heat exchanger (3) and able to receive in passage said working fluid, said third heat exchanger (18) being furthermore configured to receive heat from a hot source (H) and to allow preheating of the working fluid before the latter is introduced into the first heat exchanger.

In a 51st aspect in accordance with the previous aspect, the third heat exchanger (18) is configured to preheat the working fluid up to a saturated liquid condition.

In a 52 ° aspect in accordance with any one of the aspects from 46 ° to 51 ° the first heat exchanger (3) is adapted to receive the working fluid in the condition of saturated liquid and to supply the working fluid in the vapor condition. saturated.

In a 53 ° aspect in accordance with any of the aspects from 50 ° to 52 ° the first and third heat exchangers (3, 18) are immediately consecutively arranged with respect to each other according to a direction of circulation of the working fluid , said first and third heat exchanger (3, 18) being configured to receive heat from the same hot source (H).

In a 54 ° aspect in accordance with the previous aspect regretted (1) it comprises a heating circuit (19) developing between an inlet (20) and an outlet (21) and inside which at least one heating fluid coming from said hot source (H), said first and third heat exchanger (3, 18) being operationally active on the heating circuit (19) and interposed between the inlet (20) and the outlet (21) of said heating circuit (19), the heating fluid, circulating from the inlet (20) in the direction of the outlet (21), passing consecutively through the first and third heat exchanger (3, 18). In a 55th aspect a process is provided for the conversion of thermal energy into electrical energy comprising the following steps:

> prepare a system (1) according to any of the aspects from the 46th to the 54th; > recirculate the working fluid inside the circuit (2);

> heat, through the first heat exchanger (3), the working fluid in passage from the latter until this fluid is evaporated and is in a saturated steam condition;

> expand the working fluid inside the volumetric expander (4) in order to move each piston (6) with consequent rotation of the main shaft (11) and production of electricity by the generator (12),> condense the working fluid leaving the volumetric expander (4),

> sending the condensed working fluid to the first heat exchanger (3), the process comprising at least one phase of emission of the working fluid, leaving each expansion chamber, into the discharge chamber inside the casing, so such that said working fluid invests at least part of the transmission member (53) arranged inside the casing (50) of the volumetric expander (4).

In a 56 ° aspect in accordance with the previous aspect, the heating phase of the working fluid, by means of the first heat exchanger (3), brings the working fluid to a temperature below 150 ° C, in particular below 90 ° C, even more particularly between 25 ° C and 85 ° C, and in which the phase of sending the fluid, by means of the pump (13), imposes a pressure jump to the working fluid between 4 bar and 30 bars, in particular between 4 bars and 25 bars, even more particularly between 7 bars and 25 bars.

In a 57th aspect in accordance with the 56th or 57th aspect the heating phase of the working fluid comprises a sub-phase of preheating the working fluid by means of the third heat exchanger (18) before the latter is introduced in the first heat exchanger (3), the preheating phase bringing the working fluid to a temperature between 20 ° C and 100 ° C, in particular between 20 ° C and 80 ° C, the heating phase allowing to maintain this 'last in a condition of saturated liquid.

In a 58th aspect a start-up process of a volumetric expander (4) is provided in accordance with any one of the aspects from the 1st to the 45th, said process comprises at least the following steps:

> introduce working fluid in a gaseous state into the discharge chamber of the casing (50) through the additional inlet (59) in order to at least partially heat the casing (50) and the valve (10),

> optionally, by means of the working fluid in the gaseous state introduced through the further inlet (59), any working fluid in the liquid state present in the casing (50) in such a way as to allow, for at least part of said working fluid in the liquid state, the transition from liquid to gaseous,> terminate the phase of inlet of the working fluid in the gaseous state through the further inlet (59) and proceed with the inlet of the working fluid in the gaseous state through the general input (51) in such a way as to determine a starting condition of the volumetric expander (4).

In a 59 ° aspect in accordance with the previous aspect, the step of introducing the working fluid in the gaseous state through the further inlet (59) heats at least in part the transmission member (53), the piston (6), the expansion chamber, the valve (10) and the crank mechanism (37).

In a 60 ° aspect in accordance with the 58 ° or 59 ° aspect, the working fluid in the gaseous state introduced into the discharge chamber through the further inlet (59) has a temperature below 150 ° C, in particular between 25 ° C and 100 ° C. In a 61 ° aspect in accordance with any of the aspects from 58 ° to 60 ° the working fluid in the gaseous state is introduced under pressure into the discharge chamber through the further inlet (59) at a pressure between 4 bar and 30 bars, in particular between 4 bars and 25 bars, even more particularly between 7 bars and 25 bars.

In a 62 ° aspect in accordance with any of the aspects from 58 ° to 61 ° the working fluid comprises at least one fluid of an organic type, optionally the organic fluid of the working fluid is present in a percentage comprised between 90% and 99%, in particular between 95% and 99%, even more particularly around 98%.

In a 63rd aspect in accordance with the previous aspect, the organic fluid includes at least one selected from the group of the following fluids: R134A, 245FA, R1234FY, R1234FZ.

In a 64th aspect in accordance with the 62nd or 63rd aspect, the organic fluid comprises one or more hydrocarbons, preferably halogenated hydrocarbons, even more preferably fluorinated hydrocarbons, said working fluid having:

> melting temperature between -110 ° C and - 95 ° C at atmospheric pressure; > boiling temperature between -30 ° C and -20 ° C at atmospheric pressure; > density between 1.15 g / cm <3> and 1.25 g / cm <3> at a temperature of 25 ° C;

> vapor pressure between 600000 Pa and 700000 Pa at a temperature of 25 ° C.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments and some aspects of the invention will be described hereinafter with reference to the accompanying drawings, provided for indicative purposes only and therefore not limitative in which:

Figure 1 is a basic diagram of a closed-loop plant in a first embodiment in accordance with the present invention;

> Figure 2 is a basic diagram of a closed-loop plant in a second embodiment in accordance with the present invention;

Figure 3 is a perspective view of a volumetric expander according to the present invention;

Figure 4 is a perspective view of a volumetric expander according to the present invention associated with an electric generator;

Figure 5 is an exploded view of a volumetric expander according to the present invention;

> Figure 5A is an exploded schematic view of a part of the volumetric expander in accordance with the present invention;

> Figure 5B is a schematic front view of a part of the volumetric expander in accordance with the present invention;

Figure 6 is a further exploded view of a volumetric expander according to the present invention;

Figure 7 is a side view of a volumetric expander according to the present invention;

> Figure 8 is a sectional view, along the trace VIII-VIII, of the volumetric expander of figure 7;

Figure 9 is a perspective view of a closure element of a volumetric expander according to the present invention;

Figure 10 is a longitudinal sectional view of a volumetric expander according to the present invention;

> Figure 11 is a longitudinal sectional view of a volumetric expander in accordance with the present invention in which a condition of fluid entry into the expander is schematised;

> Figure 12 is a longitudinal sectional view of a volumetric expander in accordance with the present invention in which a condition of fluid emission from the expander is schematised;

Figure 12A is a detail view of a volumetric expander according to the present invention;

Figure 13 is a cross-sectional view of a volumetric expander according to the present invention;

Figure 14 is an exploded view of a valve of a volumetric expander according to the present invention.

DEFINITIONS AND CONVENTIONS

It should be noted that in the present detailed description corresponding parts illustrated in the various figures are indicated with the same numerical references.

The figures could illustrate the object of the invention by means of non-scale representations; therefore, parts and components illustrated in the figures relating to the object of the invention could only concern schematic representations.

In the following description and in the claims the terms upstream and downstream refer to a sense of circulation of a working fluid within a closed circuit.

The term direct fluid communication between two elements means a continuous communication of the working fluid flow between said elements without the same flow being interrupted by one or more fluid interception elements. Between two elements in direct fluid communication, no fluid interception device is provided - in interposition between these latter elements - which could somehow interrupt the flow of fluid between said two elements.

The term working fluid refers to an organic type fluid (ORC fluid). Preferably, the working fluid comprises an amount of organic fluid comprised between 90% and 99%, in particular between 95% and 99%, even more particularly around 98%. The organic fluid is mixed with at least one oil configured to allow the lubrication of moving elements inside the volumetric expander. For example, the organic fluids used can comprise at least one selected from the group of the following fluids: R134A, 245FA, R1234FY, R1234FZ.

DETAILED DESCRIPTION

General embodiment of a closed-cycle plant for the production of electricity.

With 1, a closed cycle plant, in particular a Rankine cycle, for the conversion of thermal energy into electrical energy has been indicated. Plant 1 is used, for example, in biogas / biomass plants for the recovery of waste heat from the cogeneration process, in geothermal plants for the exploitation of medium / small heat sources, in industrial plants for the recovery of thermal waste ( conversion of heat waste from industrial processes), in the domestic environment for the production of electricity and the exploitation of heat for sanitary use. A further use of plant 1 may concern both domestic and industrial systems, in which the heat source is provided by solar energy capture systems. The plant may also be used in the automotive sector, for example for the recovery of heat from the engine.

As shown in Figure 1, the plant 1 includes a closed circuit 2 inside which a working fluid circulates.

As can be seen for example from the schematizations of Figures 1 and 2, the plant 1 comprises at least one pump 13 engaged on the circuit 2 and arranged to impose a predetermined direction of circulation on the working fluid. In a preferential but not limiting form of the plant 1, the pump 13 comprises a gear pump.

The working fluid entering the pump 13 is in the liquid state at a predetermined pressure corresponding to a minimum pressure of the circuit. The pump 13 is configured to impose a predetermined pressure jump on the working fluid and bring it to a maximum pressure of the circuit 2. The pressure jump imposed by the pump 13 depends on the sizing of the latter and is higher than 5 bar, in particularly between 5 bar and 25 bar, even more particularly between 5 bar and 20 bar. Thanks to the pressure jump imposed by the pump 13, the working fluid circulates in the circuit 2 and in particular at its outlet reaches a first heat exchanger or evaporator 3 active on the circuit 2. In fact, the working fluid in the state liquid sent by the pump 13, is introduced into the evaporator 3 which is configured to heat said fluid until it defines its transition from the liquid to the gaseous state.

More in detail, the evaporator 3 is arranged to receive the working fluid in passage and also to receive heat from a hot source H adapted to allow the heating of said fluid up to the transition of state: at the outlet from the evaporator 3 the work is in a saturated steam condition. From a structural point of view, the evaporator 3 can for example comprise a heat exchanger adapted to exploit, as a hot source H, a further working fluid arriving from a different industrial plant. Alternatively, the evaporator 3 can comprise a boiler designed to allow the transition of state of the working fluid by means of a hot source H obtained by combustion.

Continuing along the direction of circulation of the working fluid, it is possible to observe that the working fluid in the gaseous state leaving the first heat exchanger 3 enters a volumetric expander 4 configured to transform the thermal energy of the working fluid in mechanical energy.

The volumetric expander 4 comprises at least one piston 6 designed to cooperatively define an expansion chamber 7 with variable volume (see for example Figure 10). As will be better described below, the volumetric expander 4 also comprises a crank mechanism 37 connected on one side to the piston 6 and on the other hand is associated with a main shaft 11 configured to rotate around an X axis (see figure 10).

The expander 4 also has an inlet 8 and an outlet 9 respectively adapted to allow the entry and discharge of the working fluid from the expansion chamber 7 (Figure 10). In particular, the volumetric expander 4 comprises at least one valve 10 configured to selectively allow the entry and discharge of the working fluid from the expansion chamber 7 through the inlet 8 and the outlet 9 and generate the movement of the piston 6: in this way it is possible to rotate the main shaft 11 around the axis (Figure 10). The volumetric expander 4 will be described in detail below.

As can be seen for example from Figures 1 and 2, the plant 1 also includes at least one electricity generator 12 connected to the main shaft 11 which is able to transform the rotation of the latter into electricity. In particular, the generator 12 can comprise at least one rotor connected to the main shaft 11 which is movable by rotation with respect to a stator. The relative movement between rotor and stator allows the development of a predetermined quantity of electrical energy.

Continuing along the direction of travel of the working fluid it is possible to observe that the plant 1 also comprises at least a second heat exchanger or condenser 16 active on the circuit 2. The condenser 16, as visible for example in Figure 1, is interposed between the expander 4 and the pump 13; the second heat exchanger 16 is designed to receive the working fluid coming out of the expander 4 in transit and allow it to pass from the gaseous to the liquid state. More in detail, the condenser 16 is configured to receive the working fluid in passage and also communicate with a cold source C which is adapted to remove heat from the fluid passing through said second heat exchanger 16. The working fluid leaving the condenser 16 is fed back into pump 13: the circuit thus defined represents a closed cycle, in particular a Rankine cycle.

Preferred embodiment of a closed-cycle plant for the production of electricity.

A preferential but not limiting embodiment of the plant 1 is illustrated in Figure 2. Said plant 1, in addition to the general embodiment, comprises an economizer 36 arranged downstream of both the pump 13 and the volumetric expander 4. In greater detail, the economizer 36 comprises a heat exchanger arranged to receive the working fluid leaving the volumetric expander 4 and the working fluid leaving the pump 13. The economizer 36 actually allows preheating of the working fluid in output from pump 13 thanks to the heat recovery of the working fluid leaving the volumetric expander 4.

As can also be seen from Figure 2, regression 1 also comprises a third heat exchanger or preheater 18 active on the circuit 2 upstream of the first heat exchanger 3 and in particular interposed between the economizer 36 and the evaporator 3. The third heat exchanger heat 18 is configured to receive in passage the working fluid leaving the pump 13 and preheated by the economizer 36. The third heat exchanger 18 is also configured to receive heat from a hot source H and to allow further preheating of the working fluid before the latter is introduced into the first heat exchanger 3. In the embodiments illustrated in the accompanying figures, the third heat exchanger 18 consists, in a non-limiting way, of a distinct (separate) element from the economizer 36 and from the evaporator 3. Alternatively, the preheater 18 could be integrated with the evaporator 3 to substantially form an "all- in-one ”(condition not illustrated in the accompanying figures); in the latter condition described, regret 1 can include only two exchangers ("all-in-one" exchanger and economizer 36) or only one exchanger (only "all-in-one" exchanger) if heat recovery is renounced by the economizer 36.

Preferably, the plant 1 comprises at least one heating circuit 19 in fluid communication with both the first heat exchanger 3 and the third heat exchanger 18; the circuit is designed to allow the circulation of at least one heating fluid coming from the hot source H.

The heating circuit 19 comprises, but is not limited to, a hydraulic circuit developing between an inlet 20 and an outlet 21. The hot source H may, for example, comprise a source of heated water capable of circulating from the inlet 20 until it comes out of the circuit 19 through outlet 21. Advantageously, the direction of circulation of the heating fluid of the hot source H (in the preferential form of heated water) is in countercurrent with respect to the direction of travel of the working fluid inside the circuit 2.

In the embodiment of Figure 2, the evaporator 3 is a liquid (heated water) and gas (working fluid in the gaseous state) heat exchanger. The third heat exchanger 18, also active on the heating circuit 19, uses the heat of the same hot source H used for the evaporation 3 of the working fluid; since the working fluid of the circuit 2 in countercurrent with the heating fluid (hot water) of the circuit 19, the latter fluid has a temperature which decreases during the passage from the revaporizer 3 to the preheater 18. Advantageously in the "all in" condition one ”, the integration of the preheater 18 with the evaporator 3 allows to form a single heat exchanger which allows to considerably reduce the pressure drops on the side of the heating circuit 19.

The heating fluid entering the circuit 19 can have a temperature lower than 150 ° C, in particular between 25 ° C and 130 ° C. The temperature of the heating fluid is suitable to allow revaporization of the working fluid. At the outlet of the evaporator 3 the heating fluid has a lower temperature than the temperature of the same at the inlet from said evaporator 3: this lowering of temperature is due to the transfer of heat by the heating fluid to the working fluid. In particular, the heating fluid entering the third exchanger 18 can have a temperature lower than 100 ° C, in particular between 20 ° C and 90 ° C.

The first and third heat exchangers 3, 18 are structurally dimensioned in such a way that the working fluid passing by the latter is kept in a saturated liquid condition inside the third heat exchanger 18 while the change of state of the work from liquid to gaseous takes place entirely in the first exchanger 3.

As can be seen from Figure 2, the system advantageously comprises at least a first temperature sensor 39 active on the heating circuit 19 and interposed between the inlet 20 and the evaporator 3. The first temperature sensor 39 is configured to generate a relative control signal at the temperature of the hot fluid entering the evaporator 3.

The system 1 can also comprise a second temperature sensor 40 (Figure 2) active on the heating circuit 19 and interposed between the output 21 and the preheater 18. The second temperature sensor 40 is configured to generate a relative control signal at the temperature of the hot fluid leaving the preheater 18. As can be seen from Figure 2, the unit 1 advantageously comprises a first pressure sensor 34 active on the circuit 2 and interposed between the evaporator 3 and the volumetric expander 4. The first pressure sensor 34 is configured to generate a control signal relating to the pressure of the working fluid entering the volumetric expander 4, or to the maximum pressure of the circuit 2.

As can also be seen from Figure 2, the unit 1 also comprises a second pressure sensor 35 arranged upstream of the pump 13 and configured to generate a control signal relating to the pressure of the working fluid entering the latter, i.e. relative to the pressure of circuit minimum.

Advantageously, the plant 1 comprises a control unit 33 which is connected with the first and second temperature sensors 39, 40 (see the connection lines "h" and "m" in figure 2) and with the first and second pressure sensor 34, 35 (see connection lines “c” and “d” in figure 2). The control unit 33 is configured to receive the control signals of the sensors 39 and 40 and determine the temperature of the hot source H entering and leaving the evaporator 3 and the preheater 18 respectively: in this way the control unit 33 is able to monitor the hot source H and consequently the heat supplied to the exchangers. As previously mentioned, the control unit 33 is also connected with the first and second pressure sensors 34 and 35; said unit 33 is configured to receive the control signals of the sensors 34 and 35 to determine the pressure of the working fluid entering and leaving the volumetric expander 4 and the pump 13 respectively, i.e. the maximum and minimum pressure of the circuit 2. In this way the control unit 33 can monitor the pressure values of the working fluid in circuit 2.

Preferably, the control unit 33 is also configured to compare the pressure entering the expander 4 with a predetermined reference value, for example referred to a minimum required pressure value, and to determine an intervention or alarm condition in the event in which the measured pressure value is lower than the reference value. In fact, the monitoring carried out by the control unit is used to set / check the difference between the saturation temperature and the working temperature of the fluid, i.e. to establish whether the working fluid is in a saturated vapor condition or whether is still in phase transition (in transition from the liquid to the gas phase). Advantageously, the unit 1 can be equipped with a bypass circuit 41 in fluid communication with the circuit 2 and adapted to allow the bypass of the volumetric expander 4. More in detail, the bypass circuit 41 is connected upstream and downstream of the expander 4 and thanks to the presence of interception elements 42 (solenoid valves) both on the circuit 2 and on the bypass circuit 41 it is possible to manage the path of the working fluid and possibly bypass the volumetric expander 4.

Advantageously, the control unit 33 is connected to the interception elements 42 (see the connection lines "a" in figure 2): thanks to the pressure monitoring the control unit 33 is configured to determine a possible condition intervention (as previously described, for example a condition in which the maximum pressure of the working fluid is below a predetermined limit) and command the bypass of the expander 4 until the circulation pressure of the working fluid is exceeds a predetermined level: in this way it is possible to prevent the working fluid from being introduced into the expander 4 at a too low pressure.

The control unit 33 can also be advantageously connected to the pump 13 (see the connection line "b" in figure 2); the control unit is configured to command the activation of the pump 13 and in particular to manage its operation in such a way as to be able to consequently control the maximum pressure value of the working fluid. The control unit 33 can also be advantageously connected to the generator 12 (see the connection line "g" in figure 2); the control unit 33 is configured to monitor the operation of the generator 12 and determine the amount of electricity generated. The control unit 33 is also advantageously connected to the capacitor 16 (see the connection line "f in figure 2); the control unit 33 is configured to command the activation of the condenser 16 and in particular to manage its operation in such a way as to be able to control the condensation temperature of the working fluid. For example, the control unit can be connected to one or more ventilation (cooling) elements of the condenser 16 and configured to manage the rotation speed of the fans; in this way the unit 33, by controlling the rotation speed of the fans, is able to regulate the cooling capacity of the ventilation elements and therefore the condensing capacity of the condenser 16.

A further additional component of the system of figure 2 is represented by the collection tank 17; the latter is active on the circuit 2 between the condenser 16 and the pump 13. The collection tank 17 has the function of collecting and containing the working fluid in the liquid state coming out of the condenser 16 so that the pump 13 is guaranteed the draft of liquid. In particular, the tank 17 prevents the pumping of working fluid loaded with air bubbles which could cause a malfunction of the internal system 1.

Volumetric expander.

The subject of the present invention is a volumetric expander 4 configured to transform the thermal energy of the working fluid into mechanical energy. The expander 4 comprises a casing 50 having at least one general inlet 51 configured to allow the introduction of a working fluid inside the casing 50 and at least one general outlet 52 configured to allow the expulsion of the working fluid from said casing 50.

As can be seen from the accompanying figures, inside the casing 50 are housed:

- at least one piston 6 suitable for defining the variable volume expansion chamber 7, - at least part of the main shaft 11 kinematically connected to the piston 6 and configured to rotate around a main axis X, - at least one configured valve 10 to selectively open and close an inlet and an outlet 8, 9 of the expansion chamber 7 allowing at least one condition for introducing the working fluid into the expansion chamber 7, an expansion condition of the working fluid in the expansion chamber 7, and a condition of discharge of the working fluid from said expansion chamber 7,

- a transmission member 53 connected - on one side - to the valve 10 and - on the other side - to the main shaft 11. The transmission member 53 is configured to synchronize the input condition, the expansion condition and the discharge of the working fluid with the rotation of the main shaft 11.

The general inlet 51, through the circuit 2, allows the introduction of the working fluid into the casing 50 arriving from the evaporator 3 while the general outlet 52, again through the circuit 2, allows the discharge of the working fluid in output from casing 50 into capacitor 16.

In greater detail and as visible for example in figures 3 and 4, the casing 50 comprises a side wall extending between a first and a second longitudinal end portion 50a, 50b; the side wall extends in thickness between an external surface and an internal surface. The internal surface delimits an internal cavity of the casing 50 defining at least in part a discharge chamber for the working fluid inside the casing 50 and in direct fluid communication with the outlet 52. The general outlet 52 is in fluid communication directed exclusively with the discharge chamber of the casing 50. In the accompanying figures an internal surface of the casing 50 with a circular section has been shown in a non-limiting way (see for example Figure 5).

In a preferential but non-limiting embodiment of the invention, the casing 50 comprises a hollow tubular body having a through opening extending between the first and second longitudinal end portion 50a, 50b and delimited at least in part by the internal surface : at the first and second end portions 50a, 50b the casing 50 has a first and a second access respectively.

As visible for example in figures 3 and 4, the casing 50 includes a front closure element 57 at the first longitudinal end portion 50a while at the second end portion 50b it comprises a rear closure element 58; the closing elements 57 and 58 are configured to close - in particular hermetically - the first and second accesses respectively and to cooperate with the internal surface of the casing to delimit the discharge chamber.

In greater detail, the front closing element 57 comprises a resting portion 62 abutting a front wall 50c of the casing 50. The supporting portion 62 is configured to completely cover the first access of the casing 50. The supporting portion 62 presents, in a non-limiting way, a circular shape and extends along a prevailing development plan. The front element 57 also comprises a coupling portion 63 integrally joined to the support portion and emerging from the latter inside the cavity of the casing 50. The coupling portion 63 also has a circular shape and has a maximum radial overall dimensions - measured along the development plane of the support portion 62 - less than the maximum overall dimensions of the latter. In particular, the coupling portion 63 comprises a cylinder concentric to the circular plate of the support portion 62 and having a diameter smaller than the diameter of the support portion 62 (Figure 9). In still greater detail, the coupling portion 63 is delimited by an external cylindrical surface substantially counter-shaped to the internal surface of the casing 50.

In particular, the external surface of the coupling portion 63 is at least partially counter-shaped and substantially abutting the internal surface of the casing 50; the external surface extends starting from the support portion 62 along a direction orthogonal to the development plane of the latter. As can be seen in Figure 9, the external surface of the coupling portion 63 has a first and a second radial groove 63a, 63b extending along the entire length of the diameter of the portion 63 and defining a housing seat for a sealing element, for example a gasket, configured to cooperate with the inner surface of the casing 50 to ensure the fluid-tight closure of the first access. As can be seen in Figure 9, the first and second radial grooves 63a, 63b are spaced apart along the orthogonal direction of the portion 63; in interposition between said grooves 63a, 63b, the external surface has a radial groove 63c; the hole defines in cooperation with the internal surface of the casing 50 a distribution duct 67 (Figure 8) whose function will be better described later.

The front closing element 57 is reversibly engaged to the casing 50 so that the same element 57 can be easily removed to allow quick access to the housing elements inside the casing 50. In particular, the supporting portion 62 of the element 57 has a series of through holes 64 configured to allow the passage and engagement of screws 66 configured to be constrained and threaded holes 65 made on the front wall 50c of the casing 50. As described above, the casing also comprises a rear element 58 configured to hermetically close the second access of the enclosure.

The rear closing element 58 comprises a respective support portion 68 (Figure 6) abutting to a rear wall 50d of the casing 50. The supporting portion 68 is configured to completely cover the second access of the casing 50. support 68 has, in a non-limiting way, a circular shape extending along a prevailing development plane. The rear element 58 is reversibly engaged to the casing 50 so that the same element 58 can be easily removed to allow quick access to the housing elements inside the casing 50. In particular, the supporting portion 68 of the The element 58 has a series of through holes 69 configured to allow the passage and engagement of screws (Figure 4) configured to be constrained and threaded holes 71 made on the rear wall 50d of the casing 50.

As visible from figure 6, the rear element 58 includes a through seat 72 configured to allow the passage of the main shaft 11 which is arranged partly inside and partly outside the casing 50.

As can be seen in Figure 5, the casing 50 comprises for each piston 6 and in particular for each expansion chamber 7, at least a first and a second through connection duct 60, 61 extending from the inner surface of the casing up to of the valve 10 associated with the respective piston 6. In particular, as will be better described below, the expander 4 comprises a plurality of pistons 6 adapted to define, in cooperation with the casing 50, a plurality of expansion chambers 7; for each expansion chamber 7, the casing 50 comprises a first and a second through connection duct 60, 61 in fluid communication with the valve 10 associated with the respective chamber 7.

The first through duct 60 may comprise a circular hole in direct fluid communication with the general inlet 51: the first connecting duct 60 does not communicate directly with the discharge chamber and with the general outlet 52. The first duct 60 is in in particular in direct fluid communication with the distribution duct 67 (Figure 8) defined between the internal surface of the casing and the coupling portion 63 of the front closure element.

The second through duct 61 is distinct and spaced from the first duct 60 and comprises a notch having, in a non-limiting way, a rectangular shape. The second conduit is in direct fluid communication with the discharge chamber: the first and second through conduits 60, 61 are not in direct fluid communication with each other. The first and second connecting ducts are separated from each other by means of the valve 10.

As described above, the casing 50 includes the general entrance and exit 51, 52. The general entrance 51 can be defined on the front closing element 57 or on the rear closing element 58; likewise, the general outlet 52 can be defined on the front closing element 57 or on the rear closing element 58. In a preferential but not limiting embodiment of the invention, general inlet and outlet 51, 52 are defined on the same closing element. In particular, the accompanying figures show a preferential configuration of the invention in which the general inlet and outlet 51, 52 are both arranged on the front closure element 57.

In greater detail, the general inlet 51 comprises an attachment portion 51 a (Figure 10) defining a blind cavity through the thickness of the resting portion 62 and at least part of the coupling portion 63 of the front closure element 57. L The general inlet 51 also comprises at least one distribution channel 51 b in fluid communication with the attachment portion 51 a and transversely emerging from the latter up to the external surface of the coupling portion 63. In particular, the distribution channel 51 b starts from the attachment portion 51 a and ends inside the distribution duct 67. In this way the working fluid entering the expander is introduced through the attachment portion 51 a, reaches the distribution channel 51 b, it is leads into the distribution duct 67, reaches the first through connection duct 60 which carries the fluid to the respective valve 10. A configuration of the expander 4 having four pistons and four respective valves is not limiting; in this configuration, the casing 50 comprises four distinct first ducts 60 which are in communication with the distribution duct and configured to carry the working fluid from the distribution duct 67 to the respective valve 10 (Figure 8).

The working fluid entering the valve 10 is then sent to the respective expansion chamber 7 and discharged into the respective second through duct 61. The casing comprises as many second ducts 61 as there are valves 10 of the expander 4 and therefore the number of pistons 6. In the condition illustrated in the accompanying figures, the casing comprises four second ducts 61 which communicate with the respective valve 10 and directly with the discharge chamber. Each second duct 62 is configured to allow the working fluid to be sent - out of the expansion chamber and therefore from the valve - to the discharge chamber of the casing 50. The working fluid in the working chamber is in direct fluid communication with general exit 52.

As can be seen from the accompanying figures, the casing 50 comprises at least one auxiliary inlet 59 which is exclusively in direct communication with the discharge chamber of the casing 50 and therefore, through the latter, with the general outlet 52: the inlet auxiliary 59 is configured to allow the introduction of the working fluid directly inside the casing 50. The auxiliary inlet 59 is not in direct fluid communication with the general inlet 51 but communicates exclusively directly with the discharge and with the general outlet 52. The auxiliary inlet 59 can be defined on the front closing element 57 and / or on the rear closing element 58. In a preferential but not limiting embodiment of the invention, the auxiliary input 59 is arranged on the closing element on which the general input 51 is arranged, in particular general input 51 and auxiliary input 59 are both arranged on the closing element front 57. In a preferred embodiment of the invention, generating input 51, auxiliary input 59 and general output 52 are arranged on the front closing element 57.

In greater detail, the auxiliary inlet comprises an opening through the front closing element 57, for example identical to the general outlet 52. The through opening of the inlet 59 passes through the entire thickness of the front closing element 57 (passing through the support portion and the coupling portion) without interfering with the general inlet 51. As will be better described below, the auxiliary inlet is configured to allow the introduction of hot working fluid in the gaseous state directly in the discharge chamber: auxiliary inlet 59, discharge chamber and general outlet 52 essentially define a by-pass circuit which allows the passage of working fluid inside the casing without the movement of the main shaft 11 being triggered; in this way, the working fluid in passage can heat any condensed working fluid formed inside the casing to allow it to change from the liquid state to the gaseous state.

As briefly mentioned above, the expander includes at least one piston 6 operating inside the casing and designed to define a variable volume expansion chamber (7). In particular, the expander 4 comprises a plurality of pistons 6 and related expansion chambers 7. In the accompanying figures an expander 4 comprising four pistons 6 has been shown in a non-limiting way; the expander may however include a number of pistons 6 equal to or between 3 and 12, in particular equal to or between 4 and 9.

In the accompanying figures, a preferential but not limiting embodiment of the invention has been illustrated in which the variable volume of each expansion chamber is delimited by a respective jacket 5, operating inside the casing 50, and a respective piston 6, housed slidingly in the jacket 5: the inlet 8 and the outlet 9 are placed on said jacket 5 which defines a seat 22, in particular a cylindrical seat, defined on the side wall of the casing 50 and inside which it is movable reciprocating motion and sliding of the piston 6. As can be seen for example in Figure 10, the seat 22 of the jacket 5 extends along the thickness of the side wall of the casing 50, in particular starting from the internal surface of the casing 50 up to the respective valve 10.

The accompanying figures illustrate a volumetric expander 4 defining an expander with radial cylinders or star expander in which the cylinders (expansion chambers 7 and in particular the liners 5) are arranged along radial lines, around the main shaft 11. In the illustrated case in the aforementioned figures, the radial expander 4 is composed of a single "star" with four cylinders or liners 5; however, the expander 4 can be composed of several "stars", that is, by several autonomous series of cylinders (condition not illustrated in the accompanying figures).

As previously mentioned for the transmission of the motion of the piston 6 to the main shaft 11, the expander 4 comprises, regardless of the type of expander 4 used, a crank mechanism 37 (for example a connecting rod) connected on one side to the piston 6 while on the side opposite is constrained to the main shaft 11 which is designed to move by rotary motion around the X axis: this connection allows the piston 6 to determine the rotation of the main shaft 11 around the X axis and therefore to transform the thermal power of the working fluid in mechanical power.

In the case illustrated in the accompanying figures (radial or star expander), the crank mechanism 37 is entirely contained in the casing 50 and in particular entirely housed in the discharge chamber. The crank mechanism 37 essentially comprises a base element 28, for example comprising a plate with a circular shape, hinged to an engagement portion 11a of the main shaft 11 which is spaced from the axis of rotation X of the same main shaft 11: the engagement portion 11a comprises a pin offset with respect to the X axis. The base element 38 is hinged to the engagement portion 11a and movable for rotation around the X axis of the main shaft 11. The base element 38 it is configured to rotate concentrically around the engagement portion 11a and at the same time around the X axis of the main shaft 11.

The crank mechanism 37 also comprises at least one thrust element 39, for example a connecting rod, directly connected - on one side - to the base element 38 and - on the other side - to the piston 6. The crank mechanism 37 comprises a thrust element for each piston 6. The thrust element 39 is connected to the piston and to the base element in a per se known manner. In radial type expanders, a connecting rod is fixed on one side to the base element 38 while on the other side it is hinged to the piston 6. The remaining connecting rods are instead hinged both to the base element and to the respective piston. As previously described, the chamber 7, in particular the jacket 5, has at least one inlet 8 and one outlet 9 respectively adapted to allow the entry and discharge of the working fluid, arriving from the evaporator 3, into the expansion chamber. 7. The volumetric expander 4 is in fluid communication with the circuit 2 by means of said inlet 8 and said outlet 9 which are respectively adapted to allow the entry of the working fluid into the expansion chamber 7 and its subsequent discharge .

In order to determine the movement of each piston 6, the circulation of the working fluid in passage from the volumetric expander, in particular from the expansion chamber 7 must be regulated. For this reason, the volumetric expander 4 comprises a valve 10 arranged, in a non-limiting way, outside the expansion chamber 7 (substantially defining the head of the jacket 5) and configured to selectively allow the inlet and discharge of the fluid. from the expansion chamber 7. In greater detail, the valve 10 is structured in such a way as to be able to define predetermined operating conditions inside the expansion chamber 7, such as:

- an inlet condition in which it allows the passage of fluid from inlet 8 while prohibiting the passage of fluid from outlet 9;

- an expansion condition in which it prohibits the passage of fluid from both the inlet 8 and the outlet 9 of the expansion chamber 7;

- a discharge condition in which it prohibits the passage of fluid from inlet 8 while allowing the passage of fluid from outlet 9.

On the basis of what has been said, it is possible to observe that the working fluid leaving the first heat exchanger or evaporator 3 is not in direct fluid communication with the working fluid leaving the expander 4 itself as there is an interruption of the flow. due to the closure of the inlet and outlet for the definition of the expansion condition.

The succession of the conditions described above defines a work cycle of the fluid inside the expansion chamber 7. Through the alternation of the inlet, expansion and discharge conditions, the valve 10 allows the movement of the piston 6 inside the jacket ( an alternative scroll). From this point of view, the expander 4 basically defines a two-stroke engine that completes a complete cycle of input and discharge in a single revolution of the main shaft.

As described above, the expander comprises a plurality of expansion chambers and relative valves 10; the valves 10, in order to ensure the rotation of the main shaft 11, must synchronize the expansion condition inside the expansion chambers so that the latter do not occur simultaneously (piston timing 6).

Each valve 10 comprises a valve body 24 having a housing seat 25 having, in a non-limiting way, a substantially cylindrical shape, the body 24 of the valve 10 also comprises at least a first and a second passage 26, 27 respectively arranged to put in communication the housing seat 25 with the inlet 8 and outlet 9 of the expansion chamber 7. The valve 10 further comprises at least one distribution body 28 configured to be movably constrained inside the housing seat 25. In fact, the distribution body 28 has, in a non-limiting way, a shape at least partially counter-shaped to the housing seat 25 (substantially cylindrical shape) and is engaged by rotation inside the latter to substantially define a rotary valve.

The distribution body 28 comprises an inlet channel 29 in fluid communication with the general inlet 51 of the casing 50, in particular with the first duct 60 of the casing 50, and an emission channel 30 in fluid communication with the discharge chamber of the casing 50 and therefore with the general outlet 52 of the latter. Inlet and outlet channels are not in fluid communication with each other.

Said body 28 comprises, in correspondence with a side wall, at least a first and a second channel 31, 32 angularly offset from each other with respect to an axis of rotation of the distribution body 28.

The first and second channels 31, 32 are arranged on the distribution body 28 in such a way that, in the condition of engagement between the latter and the body 24 (insertion inside the housing seat 25), these channels 31, 32 are adapted to be in fluid communication with the first and second passages 26 and 27. In particular and as visible in Figure 10, the first channel 31 is in direct fluid communication with the inlet channel 29 of the valve body 24: the first channel 31 comprises a lateral opening 31 a configured to be placed in fluid communication with the first passage 26 of the valve body 24.

The second channel 32, distinct and separated from the first channel 31, is direct fluid communication with the emission channel 30 of the valve body 24; the second channel 32 comprises at least one respective lateral opening 32a - angularly offset with respect to the lateral opening 31 a of the first channel 31 with respect to an axis of rotation Z of the distribution body - configured to be placed in fluid communication with the second passage 26 of the valve body 24. The distribution body 28, following the rotation inside the housing seat 25 around its own axis Z, is configured to selectively determine the conditions of inlet, expansion and discharge of the volumetric expander 4.

The side openings 31 a, 32a - respectively of the first and second channels 31, 32 of the valve body 24 - are configured to be placed in direct fluid communication with the expansion chamber by means of the first and second passage 26, 27 respectively.

During the condition in which the working fluid is introduced into the expansion chamber 7 there is a predetermined positioning of the first and second channels 31, 32. In particular, during this condition the opening 31 a of the first channel 31 faces the inlet 8 of the expansion chamber: with a certain and predefined position of rotation of the distribution body 28, the opening 31 a is arranged in front of the first passage 26, in particular at the inlet 8 (Figures 10 and 11). In this same inlet condition, the lateral opening 32a of the second channel 32 faces opposite to the second passage 27, in particular to the outlet 9. In the unloading condition, on the other hand, the lateral opening 31 a faces the opposite side to the expansion chamber 7 (figure 12) being placed on the opposite side to the first passage 26, in particular to the inlet 8. In this same position of the body 28, the lateral opening 32a faces towards the expansion chamber 7 communicating with fluid with the second passage 27, in particular at exit 9.

Therefore, during the rotation of the distribution body 28, the expansion chamber 7 is put into communication with the outside in an alternating way by means of the first and second channels 31 and 32, in particular of the respective openings 31a and 32a. Therefore, the work flow in the gaseous state, coming from the revaporizer 3 can enter the expansion chamber 7, passing through the housing seat 25, the inlet channel 29, the first channel 31, the first passage 26 and the inlet 8 to end up inside the expansion chamber 7 (figure 11). As regards the working fluid outlet path from the inside of the chamber 7 to the outside, an analogous solution can of course be realized. From inside the chamber 7 the same work flow can flow out through the exit 9, the second passage 27, the second channel 32, the emission channel 30 to end up in the second duct 61 and finally in the discharge chamber. The general inlet 51 of the casing 50 is in direct fluid communication exclusively with the inlet channel 29 of the valve 10: the general inlet 51 does not communicate directly with the discharge chamber and with the general outlet 52 of the casing . The general outlet 52 communicates directly with the discharge chamber of the body 52 which is in direct fluid communication with the emission channel 30 of the valve 10.

As described above, the expander 4 also comprises at least one transmission member 53 arranged in the casing 50, inside the working fluid discharge chamber, connected - on one side - to the valve 10 and - on the other side - to the main shaft 11: the transmission member 53 is configured to synchronize the inlet condition, the expansion condition and the discharge condition of the working fluid with the rotation of the main shaft 11.

In particular, the transmission member 53 is housed at least in part in the cavity of the casing 50 and apparently inside the valve body 24. In greater detail, the transmission member 53 is constrained, on one side, to the body distribution valve 28 of each valve and, on the other side, to the main shaft 11. As can be seen for example in Figure 10 at least part of the member 53 is housed inside the second duct 61 and receives the working fluid leaving the expansion chamber (at the outlet from each expansion chamber).

In still greater detail, the transmission member 53, for each valve 10 of the expander 4 - comprises at least a first toothed wheel 54 keyed to the distribution body 28 of the valve 10. The transmission element 53 comprises at least a second toothed wheel 55 keyed onto the main shaft 11 connected to the first toothed wheel 54 (in particular to each toothed wheel 54). In the accompanying figures, a preferential embodiment of the invention has been illustrated in which the transmission member comprises - for each first toothed wheel 54 - at least one intermediate member 56 - for example a toothed wheel 56 - configured to connect the first and the second toothed wheel 54, 55.

In particular, each first toothed wheel 54 is housed at least partly inside a respective valve body 24 and at least partly inside a respective second duct 61 of the casing 50. The second toothed wheel is instead internally housed in the discharge chamber while each toothed wheel 56 is at least partially housed in the discharge chamber and at least partially inside the respective second duct 61.

The transmission member 53 causes, with each complete rotation of the main shaft 11, the intake opening 31 to rotate for a short interval, included in the same complete rotation, in front of the inlet 8 so as to put in communication permanent chamber 7 with evaporator 3.

In a subsequent interval of the same rotation, the distribution body 28 closes the access to the inlet 8, and connects the chamber 7 with the outlet 9.

In practice, the transmission member 53 is configured to selectively put each expansion chamber 7 of the expander in communication with the first and second passages 26 and 27 for the inlet and discharge of the working fluid according to a sequence synchronized with the movement and position of each piston 6: this sequence of opening / closing of the inlet 8, and opening / closing of the outlet 9 are controlled by, and included in the same single rotation, by the main shaft 11.

In fact, the transmission member is configured to synchronize at least the inlet condition and the discharge condition of the working fluid of the various expansion chambers 7 in such a way that the inlet condition, or respectively the discharge condition, of a expansion chamber 7 is temporally offset with respect to an inlet condition, or respectively to an unloading condition, of another expansion chamber 7.

Therefore, the introduction of a work flow in the gaseous state with an adequate pressure, and with the modalities explained above, inside the expansion chamber 7, a predetermined alternating movement of the piston 6 inside the jacket 5 is obtained; this movement transforms this movement into a rotary movement of the shaft 11, which can be used to drive an electric generator 12, as illustrated in the accompanying figures, generally composed of a rotor, keyed on the main shaft 11 (figure 4), and a stator, known per se.

The electric generator 12 therefore generates one or more electric voltages suitable for supplying, by means of suitable electric connections, not shown, the user devices which can take on an extreme variety of forms, uses and nature. As previously mentioned, regret 100 can comprise a control unit 33; advantageously, this unit 33 is connected to the distribution body 28 and / or to the main shaft 11 and is configured to monitor the position and movement of the latter.

Procedure for the production of electricity.

The present invention also relates to a process for converting thermal energy into electrical energy. The process comprises a phase of circulation of the working fluid whose motion is imparted by the pump 13. The working fluid, pushed by the pump 13 reaches the evaporator 3 which, thanks to the hot source H heats the working fluid up to its evaporation (condition visible in the schematic of figure 1).

The pressure jump imposed by the pump 13 is substantially the jump required by the cycle as a function of the working conditions. In other words, the pump 13 is fed by the fluid in the liquid state at the condensation pressure unless under-cooling. The outlet pressure depends on the evaporation pressure which is equal to the evaporation pressure of the working fluid or on the temperature of the hot source unless overheating. The mass flow rate of the working fluid depends on the available heat output and the imposed superheat. The process can comprise additional steps of heating the fluid preceding the evaporation steps. In particular, the process may include a heat recovery phase by means of economizer 36: this phase allows to heat the working fluid leaving the pump by means of the working fluid leaving the expander.

The process may also present a preheating phase of the working fluid leaving N economizer 36 by means of the third heat exchanger 18. The preheating phase allows the working fluid to be heated without causing the latter to evaporate. The heat for preheating is taken from the hot source H leaving the evaporator 3. In order to correctly optimize the process, it is possible to size the evaporator 3 and the preheater 18 so that they can respectively operate in heat exchange between fluid / gas and fluid / fluid.

After the evaporation phase, the working fluid in the gaseous state reaches the volumetric expander 4: the working fluid passes in succession through the housing seat 25 of the valve 10, the inlet channel 29, the first channel 31, the opening 31a, the first passage 26, the inlet 8 until it enters the expansion chamber 7: these phases determine the condition of inlet of the working fluid.

After the inlet phase, the expander determines the expansion phase (inlet 8 and outlet 9 are closed and consequent expansion of the fluid) thanks to its greater pressure. As a result of this expansion, the piston 6 is urged to move in an alternating (alternative expander) or rotary (rotary expander) direction, in a per se known manner, thus rotating the main shaft 11 and ultimately activating said electric generator 12 .

The gas flow is then expelled from the expansion chamber 7 through the outlet 9, the second passage 27, the opening 32a, the emission channel 30 until it exits from the body 24 of the valve 10 and then from the general outlet 52 housing 50.

From here, the circuit 2 itself conveys the working fluid into the condenser 16 in which this fluid is condensed and sent to the collection tank 17.

The tank 17 is in fluid communication with the pump 13 which draws directly from said tank to make the working fluid circulate again in the circuit. In greater detail, the collection tank 17 is interposed between the condenser 16 and the pump 13 and allows the accumulation of working fluid in the liquid state: in this condition, the tank 17 ensures that the pump 13 draws liquid avoiding the draft. of any air springs thus ensuring a continuous supply of liquid.

Procedure for starting the volumetric expander.

The present invention also relates to a process for starting the volumetric expander 4 in accordance with one or more of the attached claims and / or in accordance with the above description.

The process comprises a step of injecting the gaseous working fluid into the discharge chamber of the casing 50 through the further inlet 59. The working fluid injected through the auxiliary inlet 59 has a temperature below 150 ° C, in particular between 25 ° C and 100 ° C; the working fluid in the gaseous state is introduced under pressure into the discharge chamber through the further inlet 59 at a pressure between 4 bar and 30 bar, in particular between 4 bar and 25 bar, even more particularly between 7 and 25 bar bar. During this inlet phase, the working fluid enters the discharge chamber and exits from the general outlet 52. During this inlet phase, the working fluid does not reach the general inlet 51: during this inlet phase no discharge is provided. introduction of further working fluid through the general inlet 51.

The passage of hot fluid allows to heat at least in part the transmission member 53, the piston 6, the casing 50, the valve 10 and the crank mechanism 37.

The introduction phase allows to heat, by means of the working fluid in the gaseous state introduced through the further inlet 59, any working fluid in the liquid state present in the expander in such a way as to allow, for at least part of said working fluid to liquid state, the transition of state from liquid to gaseous. At the end of the entry phase, the procedure provides for a phase of entry of the working fluid in the gaseous state exclusively through the general inlet 51 in such a way as to determine a starting condition of the volumetric expander 4.

ADVANTAGES OF THE FOUND

The present invention allows to obtain considerable advantages with respect to the solutions of the known art. The volumetric expander 4 as described above comprises at least a piston 6, a valve 10, transmission members 53 and a crank mechanism 37 all arranged inside the casing 50: the expander 4 has a simple and compact structure which facilitates its installation on the system 100. Thanks to the casing 50 which houses a portion of the crankshaft 11, the pistons 6, the transmission elements 53, the valves 10 and the crank mechanism 37 - it is possible (having to carry out any intervention) to disassemble the whole group (expander 4) and insert a new one with minimal actions. It should also be noted that the presence of the transmission unit 53 inside the casing 50 - and in particular at least partially in the discharge chamber - allows the automatic lubrication of these members 53 during the operation of the expander 4 (i.e. during the operating condition in which the main shaft 11 is rotated). In fact, the working fluid leaving the valve 10 strikes the transmission members 53 and enters the discharge chamber. In this way, the expander 4 does not require additional lubrication systems necessary for the moving parts. It should also be noted that the crank mechanism 37 also operates inside the discharge chamber and is hit by the working fluid leaving the expander. The structure of the expander 4 object of the present invention therefore guarantees the automatic and efficient lubrication of all the components inside the casing 50.

Thanks to the invention, it is therefore easy to assemble and disassemble the entire expander 4 in a single piece and an optimal lubrication of all the moving parts is obtained. rapid hot and pressurized working fluid inside the casing 50 even in conditions of stationary expander, i.e. with rotation of the main shaft 11 excluded and without allowing the working fluid to enter the expansion chamber 7.

The further inlet 59 allows the working fluid in the gaseous state to be directly introduced into the discharge chamber: the fluid purges and simultaneously heats all the internal components of the expander in such a way as to allow the passage to the gaseous state of any internal liquid condensates to the expander 4 which can be generated when the expander is stopped.

Since the incoming working fluid is hot, under pressure and in a gaseous state, there is an efficient energy transfer that is far greater than an extemporaneous heating from the outside: at the same time the mechanical purge effect of any liquid phases by the incoming stream. It should also be noted that the auxiliary input 59 allows you to take advantage of the thermal energy available to the working fluid without consuming electricity; in fact, thanks to the presence of the entrance 59 it is possible to avoid the consumption of electricity for heating the expander and in this way keep the efficiency of the entire system 100 high (there is no consumption of electricity which should be subtracted from the electricity produced by plant 100).

Thanks to the invention, it is possible to carry out easier restarting operations of the expander 4 after conditions of possible machine stop since all the moving parts are in a single almost hermetic casing 50 which can be efficiently heated by adding hot fluid inside it.

Claims (16)

CLAIMS 1. Volumetric expander (4) for a closed cycle plant, in particular a Rankine cycle, called volumetric expander (4) comprising: > at least one casing (50) having at least one general inlet (51) configured to allow the introduction of a working fluid inside the casing (50) and at least one general outlet (52) configured to allow the expulsion of the fluid working from said casing (50), > a piston (6) housed in said casing (50) and able to define an expansion chamber (7) with variable volume, > a main shaft (11) kinematically connected to the piston (6) and configured to rotate around a main axis (X),> at least one valve (10) associated with the casing (50) configured to selectively open and close an inlet and an outlet (8, 9) of said expansion chamber (7) allowing at least: o a condition of introduction of the working fluid into the expansion chamber (7), or an expansion condition of the working fluid in the expansion chamber (7), ed or a condition of discharge of the working fluid from said expansion chamber (7), wherein the casing (50) internally defines a discharge chamber in direct fluid communication with the general outlet (52), the discharge chamber being further configured to be placed in direct fluid communication with the outlet ( 9) of the expansion chamber (7) during the condition of discharge of the working fluid from the expansion chamber (7) itself, and in which the casing (50) comprises at least one auxiliary inlet (59) which is exclusively in direct communication with the discharge chamber of the casing (50) and therefore, through the latter, with the general outlet (52 ), the auxiliary inlet (59) being configured to allow the introduction of working fluid directly into the enclosure (50). 2. Expander according to claim 1, wherein the auxiliary inlet (59) is not in direct fluid communication with the general inlet (51), said auxiliary inlet (59) being configured to allow direct entry and subsequent circulation of working fluid in the gaseous state in the discharge chamber inside the casing (50). 3. Expander according to any of the preceding claims, in which the envelope (50) comprises: > a lateral wall extending between a first and a second longitudinal end portion (50a, 50b), said lateral wall extending in thickness between an external surface and an internal surface, said internal surface delimiting an internal cavity of the casing (50) defining at least part of the discharge chamber arranged inside the casing (50) itself,> in correspondence with the first longitudinal end portion (50a), a front closure element (57), > in correspondence with the second portion of the longitudinal end (50b), a rear closing element (58), wherein the general inlet (51) of the enclosure (50) is defined on the front closure member (57) or on the rear closure member (58), and in which the general outlet (52) of the enclosure (50) is defined on the front closure member (57) or on the rear closure member (58), and in which the auxiliary input (59) is defined on the front closing element (57) or on the rear closing element (58), optionally in which the internal surface of the side wall of the casing (50), together with said front and rear closure elements, delimit the internal cavity of the casing (50) itself. 4. Expander according to the preceding claim, wherein the generating inlet (51) and the auxiliary inlet (59) are both arranged on the front closing element (57) or both on the rear closing element (58) of the enclosure (50), in particular the general inlet (51) and the general outlet (52) of the casing (50) are both defined on the front closing element (57) or on the rear closing element (58) of the casing (50 ), optionally the general input (51), the general output (52) and the auxiliary input (59) are defined on the front closing element (57). Expander according to claim 3 or 4, wherein the casing (50) comprises a hollow tubular body having a through opening extending between the first and second longitudinal end portion (50a, 50b) and delimited at least in part from the internal surface, in correspondence with the first and second end portions (50a, 50b), the casing (50) has a first and a second access respectively, the front closure element (57) being engaged at the first access and being configured to define, in cooperation with the internal surface of the casing (50) itself, a fluid-tight closure, 6. Expander according to any one of claims 3 to 5, wherein the casing (50) comprises at least a first and a second through connection duct (60, 61) extending between the internal surface and the internal surface of the casing, the valve (10) being engaged in correspondence with the outer surface of the casing (50) and being in fluid communication with the first and second through connection ducts (60, 61), in which the first through connection duct (60) is in direct fluid communication with the general inlet (51), the first connection duct (60) does not communicate directly with the discharge chamber and with the general outlet (52 ), in which the second through connection duct (61) is in direct fluid communication with the discharge chamber, optionally in which the first and second through ducts (60, 61) are not in direct fluid communication with each other. 7. Expander according to any of claims 3 to 6, in which the front closure element (57) comprises: - a support portion (62) abutting a front wall (50c) of the envelope (50), said support portion (62) being configured to completely cover the first access of the envelope (50), - a graft portion (63) emerging from the support portion (62) inside the envelope cavity (50) and bounded by an external surface counter-shaped to the internal surface of the envelope (50), in which the general entrance (51) - defined on the front closing element (57) - includes: - an attachment portion (51 a) defining a blind cavity through the thickness of the support portion (62) and at least part of the graft portion (63) of the front closure element (57), - at least one distribution channel (51 b) in fluid communication with the attachment portion (51 a) and transversely emerging from the latter up to the external surface of the coupling portion (63), optionally in which the distribution channel (51 b) is in fluid communication with the first through duct (60) of the casing (50) Expander according to any one of the preceding claims, wherein the valve (10) comprises: > an internally hollow valve body (24) presenting: or a housing seat (25), for example having a substantially cylindrical shape, extending inside the valve body, or at least a first and a second passage (26, 27) respectively configured to be placed in fluid communication with the inlet (8) and the outlet (9) of the expansion chamber (7), > at least one distribution body (28) engaged for rotation inside the housing seat (25) of the valve body and comprising: or at least one inlet channel (29) in fluid communication with the general inlet (51) of the casing (50), or at least one emission channel (30) in fluid communication with the discharge chamber of the casing (50) and then with the general outlet (52) of the latter, or at least a first channel (31) in direct fluid communication with the inlet channel (29), the first channel (31) comprising at least one side opening (31a) configured to be placed in fluid communication with the first passage (26) of the valve body (24), or at least a second channel (32), distinct and separated from the first channel (31), in direct fluid communication with the emission channel (30), the second channel (32) comprising at least one respective lateral opening (32a) - angularly offset with respect to the lateral opening (31 a) of the first channel (31) with respect to an axis of rotation (Z) of the distribution body - configured to be placed in fluid communication with the second passage (26) of the valve body (24), the distribution body (28), following the rotation inside the housing seat (25) around its own axis (Z), being configured to selectively determine the conditions of inlet, expansion and discharge of the volumetric expander (4 ), in which the general inlet (51) of the casing (50) is in direct fluid communication exclusively with the inlet channel (29) of the valve (10), the general inlet (51) not communicating directly with the chamber and with the general outlet (52) of the casing, ed in which the general outlet (52) communicates directly with the discharge chamber of the casing (50) which is in direct fluid communication with the emission channel (30) of the valve (10). 9. Expander according to the preceding claim, wherein: > the variable volume of each expansion chamber is delimited by a respective jacket (5), operating inside the casing (50), and by said piston (6), slidably housed in said jacket, said inlet (8) and outlet ( 9) being placed on said jacket which defines a seat (22), in particular a cylindrical seat, defined on the side wall of the casing (50) and inside which the piston (6 ), > the seat (22) of the jacket (5) extends for the entire thickness of the side wall of the casing (50) to define a cavity passing through the thickness of said side wall, > the valve (10) is arranged in correspondence with the jacket (5) so that the side openings (31a, 32a) - respectively of the first and second channels (31, 32) of the valve body (24) - are abutting and in direct fluid communication with the through cavity defined by the seat (22) of the jacket (5). Expander according to claim 8 or 9 when claim 8 depends on claim 6 or 7, wherein the inlet channel (29) of the valve (10) is in direct fluid communication with the first through connection duct (60 ) of the casing (50), the emission channel (30) of the valve (10) being in direct fluid communication with the second through connection duct (61) of the casing (50). Expander according to any one of the preceding claims, wherein the main shaft (11) is housed at least partially inside the casing (50), the volumetric expander (4) further comprising at least one transmission member (53 ) connected - on one side - to the valve (10) and - on the other side - to the main shaft (11), said transmission member (53) being configured to synchronize the conditions of inlet, expansion and discharge of the working fluid from the expansion chamber (7) with the rotation of the main shaft (11), in which the transmission member (53) is arranged in the casing (50) inside the discharge chamber of the working fluid, and in which the transmission member (53) is arranged at least in part within the cavity of the casing (50) between the first and second portion of the longitudinal end (50a, 50b), optionally the transmission member (53) is at least partially arranged inside the valve body (24) and directly engaged to the distribution body (28) of the valve (10), the transmission member (53) comprising: > at least one first toothed wheel (54) keyed to the distribution body (28) of the valve (10), > at least one second toothed wheel (55) keyed onto the main shaft (11),> at least one intermediate member (56) - for example a toothed wheel (56) - configured to connect the first and second toothed wheels (54) in motion , 55). 12. Expander according to any one of the preceding claims comprising a crank mechanism (37) constrained on one side to the piston (6) and on the other side constrained to the main shaft (11), said crank mechanism (37) being configured to rotate the 'main shaft (11) around the axis (X) during the sliding of the piston (6), in which at least part of the main shaft (11) and the entire crank mechanism (37) are placed in the housing discharge chamber (50). 13. Procedure for starting the volumetric expander (4) in accordance with any of the preceding claims, said procedure includes at least the following steps: > introduce working fluid in a gaseous state into the discharge chamber of the casing (50) through the additional inlet (59) in order to at least partially heat the casing (50) and the valve (10), > optionally, by means of the working fluid in the gaseous state introduced through the further inlet (59), any working fluid in the liquid state present in the expander in such a way as to allow, for at least part of said working fluid in the liquid state , the change of state from liquid to gaseous, > end the phase of inlet of the working fluid in the gaseous state through the further inlet (59) and proceed with the inlet of the working fluid in the gaseous state through the general inlet (52) of the body in such a way as to determine a starting condition of the volumetric expander (4). 14. Process according to the preceding claim, in which the step of introducing the working fluid in the gaseous state via the further inlet (59) allows the transmission member (53), the piston (6), to be heated at least in part. the casing (50), the valve (10) and the crank mechanism (37). 15. Process according to claim 13 or 14, wherein the working fluid in the gaseous state introduced into the discharge chamber via the further inlet (59) has a temperature lower than 150 ° C, in particular between 25 ° C and 100 ° C, in which the working fluid in the gaseous state is introduced under pressure into the discharge chamber through the further inlet (59) at a pressure between 4 bar and 30 bar, in particular between 4 bar and 25 bar, even more particularly between 7 bar and 25 bar. 16. Process according to any one of claims 13 to 15, wherein the working fluid comprises at least one fluid of organic type, optionally the organic fluid of the working fluid is present in a percentage comprised between 90% and 99%, in particular between 95% and 99%, even more particularly around 98%, optionally the organic fluid comprises at least one selected from the group of the following fluids: R134A, 245FA, R1234FY, R1234FZ; optionally the organic fluid comprises one or more hydrocarbons, preferably halogenated hydrocarbons, even more preferably fluorinated hydrocarbons, said working fluid presenting: > melting temperature between -110 ° C and - 95 ° C at atmospheric pressure; > boiling temperature between -30 ° C and -20 ° C at atmospheric pressure; > density between 1.15 g / cm <3> and 1.25 g / cm <3> at a temperature of 25 ° C; > vapor pressure between 600000 Pa and 700000 Pa at a temperature of 25 ° C.