WO2017092922A1

WO2017092922A1 - Thermodynamic system

Info

Publication number: WO2017092922A1
Application number: PCT/EP2016/074921
Authority: WO
Inventors: Pierre CONVERT
Original assignee: Aqylon
Priority date: 2015-12-01
Filing date: 2016-10-18
Publication date: 2017-06-08
Also published as: FR3044351B1; FR3044351A1; EP3384136A1

Abstract

The invention relates to a thermodynamic system (10) comprising a loop (21 – 26) for the circulation of a working fluid, said loop (21 – 26) comprising a pump (40) intended to increase the pressure of the said working fluid when it is in the liquid phase and a condenser (30) intended to condense the said working fluid upstream of the said pump (40) when the said working fluid is in the gaseous phase, the said loop (21 – 26) further comprising a regenerator (60), the said regenerator (60) being positioned in a part of the loop (23 – 24; 26 – 21) that is configured for the circulation of the fluid in the liquid phase, the said regenerator (60) being configured to exchange heat energy between the said working fluid downstream of the said condenser (30) and the said working fluid downstream of the said pump (40), the said regenerator (60) being intended to lower the temperature of the said working fluid upstream of the said pump (40).

Description

Thermodynamic system

The invention relates to a thermodynamic system, in particular a system implementing a thermodynamic Rankine cycle.

It is known, in systems implementing a Rankine thermodynamic cycle, to provide a pump and a condenser. Said pump has the function of creating a pressure difference within the system, and to ensure the circulation of a working fluid within said system. Said condenser has the function of liquefying the working fluid before it enters into communication with said pump.

Such pumps are likely to be deteriorated, in particular by cavitation. Therefore, a protection of said pump is to be expected.

The NPSH - net positive suction head in English - measures the difference between the pressure of the liquid at a point in the thermodynamic system and the saturation vapor pressure at the temperature of the working fluid. Cavitation in a pump appears if the fluid pressure passes locally below the vaporization pressure of said fluid, so if the NPSH is too low.

To avoid this phenomenon, there are complex solutions to implement. For example, it is possible to increase the static pressure (by placing the condenser at a certain height relative to the pump) or to decrease the speed of the working fluid (which has an influence on the total pressure).

One of the objectives of the invention is to avoid the phenomenon of cavitation of a pump intended to be integrated in a thermodynamic system, in particular with the aid of a simplified solution.

Thus, the invention relates to a thermodynamic system, in particular a system implementing a Rankine thermodynamic cycle, comprising a circulation loop of a working fluid, said loop comprising a pump intended to increase the pressure of said working fluid when it is in the liquid phase and a condenser for condensing said working fluid upstream of said pump when said working fluid is in the gas phase.

According to the invention, said loop further comprises a regenerator, said regenerator being positioned in a part of the loop configured for the circulation of the fluid in the liquid phase, said regenerator being configured to exchange thermal energy between said working fluid in downstream of said condenser and said working fluid downstream of said pump, said regenerator being adapted to lower the temperature of said working fluid upstream of said pump, said loop further comprising a heat exchanger for lowering the temperature of said working fluid downstream of said regenerator, said heat exchanger being connected in series between said regenerator and said pump.

The invention consists in cooling the working fluid after it has been condensed, in particular to ensure the absence of any traces of fluid in the gaseous state before it enters the pump and n causes it to deteriorate.

The advantage of acting on the temperature of the working fluid by subcooling thereof, at the outlet of the condenser, makes it possible to shift its vaporization pressure and thus to overcome complex solutions known from the prior art. , such as that of physically shifting the condenser in height relative to the pump in order to increase the static pressure in the calculation of the NPSH of the pump.

According to various embodiments of the invention, which may be taken together or separately:

said regenerator is mounted on the one hand, between said condenser and said heat exchanger and on the other hand, between said pump and an evaporator, said evaporator being configured to evaporate the working fluid when it is in the liquid phase,

the system of the invention comprises a circulation loop for a cooling fluid, the condenser and the heat exchanger being traversed by said cooling fluid,

said loop for circulating a cooling fluid is configured on the one hand for liquefying the working fluid through said condenser and, on the other hand, for cooling said working fluid through said heat exchanger,

the system of the invention comprises two circulation loops for two cooling fluids, the condenser being traversed by one of said two cooling fluids and the heat exchanger being traversed by the other of said two cooling fluids,

said circulation loops of said two cooling fluids are configured on the one hand to liquefy the working fluid through said condenser and on the other hand for cooling said working fluid through said heat exchanger.

The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent in the following detailed explanatory description of at least one embodiment of the invention given to As a purely illustrative and non-limiting example, with reference to the attached schematic drawings according to:

FIG. 1 is a schematic representation of an embodiment of a system according to the invention,

FIG. 2 is a diagram illustrating an example of fluid temperatures in a system according to the invention, in particular that illustrated in FIG.

The invention relates to a thermodynamic system 10, in particular a system 10 implementing a thermodynamic Rankine cycle. This system 10 comprises a circulation loop 21 -26 of a working fluid.

Said loop will advantageously comprise a power generation means (not shown here). Said energy production means will advantageously comprise a turbine. Said turbine is intended to be driven by the expansion of said working fluid in the gas phase.

It should be noted that said power generation means may advantageously comprise an electric energy generator coupled to said turbine.

In Figure 1, these elements not shown are between sections 21 and 22 of said loop 21 -26.

Between said sections 21 and 22, said loop 21 -26 will comprise a first section (not shown here), in which circulates the working fluid in the vapor state, high temperature and high pressure. This first section drives the working fluid to the turbine, through which it relaxes, while driving the turbine in a rotational movement, movement advantageously transmitted to the generator via a transmission shaft.

On the other hand, it is expected that the working fluid leaves said turbine and circulates in a second section in the vapor state, high temperature and low pressure. This second section is that which is marked 22 in FIG. Said second section 22 conducts the fluid to a condenser 30 whose function is to condense said fluid.

Once condensed, said working fluid flows from the condenser 30 to a pump 40, in particular via a first succession of sections 23, 24, 25. Said working fluid is then in the liquid state, low temperature and low pressure. After passing through said pump 40, the working fluid is still in the state of liquid, low temperature but at high pressure.

It is circulated via a second succession of sections 26, 21 in the direction of an evaporator (not shown here) from which it leaves in the form of steam, high temperature and high pressure, to then be directed to the turbine, in particular via the first section not illustrated here and already mentioned above.

According to the invention, said loop 21 -26 advantageously comprises a heat exchanger 50 intended to lower the temperature of said working fluid downstream of said condenser 30, said heat exchanger 50 being connected in series between said condenser 30 and said pump 40.

As illustrated in Figure 1, said heat exchanger 50 is positioned at the first succession of sections 23, 24, 25, wherein said working fluid is in the liquid state, low temperature and low pressure. More specifically, said heat exchanger 50 is positioned between sections 24 and 25; it makes it possible to reduce the temperature of said working fluid, downstream of the condenser 30 and upstream of the pump 40, for example by a few degrees Celsius. The term "a few degrees Celsius" means a number less than 25 ° C, for example a figure substantially of the order of 5 ° C.

Advantageously, said fluid first passes through a regenerator 60 before being driven, via the intermediate section 24, to said pump 40.

Thus, according to the invention, said loop 21 -26 advantageously comprises a regenerator 60 positioned in a part of the loop configured for the circulation of the fluid in the liquid phase, between the sections 23 and 24, but also between the sections 26 and 21. Said regenerator 60 is configured to exchange thermal energy between said working fluid upstream of said heat exchanger 50 and said working fluid downstream of said pump 40. The objective of using said regenerator 60 is the lowering the temperature of said working fluid upstream of the pump 40, in particular upstream of said heat exchanger 50, so as to increase the NPSH mentioned in the preamble. In the example illustrated here, said regenerator 60 is mounted between the condenser 30 and the heat exchanger 50, thus between the sections 23 and 24. Thus, the exchanger 50 is connected in series between the regenerator 60 and the pump 40.

Said regenerator 60 is also mounted between said pump 40 and an evaporator (shown above but not shown here), thus between sections 26 and 21 of FIG.

Said regenerator 60 therefore makes it possible to exchange thermal energy between said working fluid when it is in the liquid phase upstream of the pump 40, more precisely upstream of the heat exchanger 50, and said working fluid when it is in the liquid phase, downstream of said pump 40.

This is why said regenerator 60 can advantageously be described as an internal exchanger.

The lowering of the temperature in said heat exchanger 50 makes it possible to ensure a temperature difference between the two sides of the regenerator 60 to allow heat exchange and thus lower the temperature of the working fluid between the outlet of the condenser 30 and the inlet of the pump 40.

The regenerator 60 makes it possible to reduce the temperature of the working fluid between the condenser 30 and the pump 40. This reduction will advantageously be of the order of a few degrees Celsius, preferably of the order of a few tens of degrees Celsius. The term "a few tens of degrees Celsius" means a number between 10 ° C and 50 ° C.

Said regenerator 60 thus participates in the protection of the pump by avoiding all the more the risk of cavitation of the latter. In other words, said regenerator 60 makes it possible to increase said NPSH by further decreasing the temperature of said working fluid at its inlet.

An advantage of the system according to the invention therefore lies in the fact that the working fluid is cooled before entering the pump 40 so as to avoid any deterioration thereof, in particular by cavitation.

On the other hand, the working fluid will have to be reheated after passing through the pump to be evaporated. It would be counterproductive to cool it unduly before it passes into the pump 40 and then have to heat it up to evaporation, which is not the case of subcooling obtained here through said regenerator 60. By way of example, in the case where the working fluid is Toluene and its temperature is of the order of 65 ° C. at the outlet of the condenser 30, in particular in section 23 of FIG. 1, the system 10 of the invention will advantageously be configured so that:

said toluene is cooled through the regenerator 60 to be measured at its outlet at around 29 ° C., in particular in section 24 of FIG. 1, and in such a way that

said toluene is cooled through the heat exchanger 50 to be measured at its outlet at around 26 ° C., in particular in section 25 of FIG.

The pump 40 will then compress said toluene, for example to 15bar, and the regenerator 60 will then heat up to about 63.4 ° C.

It should be noted, on the other hand, that the condenser 30 is connected to a first cooling circuit 71 -73 which comprises at least one cold source (not shown here); said cooling circuit 71 -73 is advantageously a circuit external to the loop 21 -26.

It should be noted, also, that the heat exchanger 50 is also in connection with a cooling circuit, which circuit may be independent of said first cooling circuit 71 -73 (case not shown here).

Here, the condenser 30 and the heat exchanger 50 are traversed by the same cooling fluid. In other words, the condenser 30 and the heat exchanger 50 are advantageously connected to the same cooling circuit 71 -73.

Said circulation loop 71 -73 of a cooling fluid is here configured, on the one hand for liquefying the working fluid through said condenser 30 and, on the other hand for cooling said working fluid through said heat exchanger. 50. Said single 71 -73 circulation loop, simplifies the integration of the system 10 of the invention, for example on site.

FIG. 2 illustrates an example of temperatures measured, in the context of the example of the system of FIG. 1, for the working fluid on the one hand, and for the cooling fluid on the other hand, especially in the case where the condenser 30 and the heat exchanger 50 are traversed by the same cooling fluid. This FIG. 2 comprises a first curve C1 which represents the evolution of the temperature of the working fluid within the thermodynamic system of the invention. This curve C1 shows the effects on the temperature of the working fluid:

condenser 30, namely a drop of a few degrees Celsius,

regenerator 60 upstream of the pump 40, namely a drop of approximately 30 degrees Celsius,

- The heat exchanger 50, also upstream of the pump 40, namely a drop of a few degrees Celsius,

- Regenerator 60 downstream of the pump 40, an increase of about 30 degrees Celsius.

FIG. 2 also includes a second curve C2 which represents the evolution of the temperature of a said cooling fluid within the cooling loop 71 -73 illustrated in FIG. This curve C2 shows the variations in the temperature of said cooling fluid:

through the condenser 30, namely an increase of about 20 degrees Celsius, which corresponds to the thermal energy conceded by the working fluid, and

- Through the heat exchanger 50, namely an increase of a few degrees Celsius, which also corresponds to the thermal energy conceded by the working fluid.

The system 10 of the invention therefore makes it possible to favor a thermal height rather than a geometrical height of pressure, in particular to increase the NPSH of the pump 40.

The system 10 of the invention therefore proposes an easy solution to implement, on site for example. On the other hand, favoring a geometric pressure height to increase the NPSH of the pump 40 entails strong integration constraints; for example burial constraints of the pump over several meters, or constraints of elevation of the condenser relative to the pump.

Claims

claims

1. Thermodynamic system (10), in particular a system using a Rankine thermodynamic cycle, comprising a circulation loop (21 -26) of a working fluid, said loop (21 -26) comprising a pump (40) intended to increase the pressure of said working fluid when in the liquid phase and a condenser (30) for condensing said working fluid upstream of said pump (40) when said working fluid is in the gas phase, said loop (21 -26 ) further comprising a regenerator (60), said regenerator (60) being positioned in a portion of the loop (23-24; 26-21) configured for liquid phase fluid flow, said regenerator (60) being configured to exchanging thermal energy between said working fluid downstream of said condenser (30) and said working fluid downstream of said pump (40), said regenerator (60) being adapted to lower the temperature of said working fluid upstream of said said pump (40), said loop (21-26) further comprising a heat exchanger (50) for lowering the temperature of said working fluid downstream of said regenerator (60), said heat exchanger (50) being mounted in series between said regenerator (60) and said pump (40).

2. System (10) according to the preceding claim, wherein said regenerator (60) is mounted on the one hand, between said condenser (30) and said heat exchanger (50) and on the other hand, between said pump (40) and an evaporator, said evaporator being configured to evaporate the working fluid when in the liquid phase.

3. System (10) according to any one of the preceding claims, comprising a circulation loop of a cooling fluid (71 -73), the condenser (30) and the heat exchanger (50) being traversed by said cooling fluid.

4. System (10) according to the preceding claim, wherein said circulation loop of said cooling fluid (71 -73) is configured on the one hand for liquefying the working fluid through said condenser (30) and, on the other hand for cooling said working fluid through said heat exchanger (50).

System (10) according to any one of claims 1 or 2, comprising two circulation loops of two cooling fluids, the condenser (30) being traversed by one of said two cooling fluids and the heat exchanger (50) being traveled by the other of said two cooling fluids.

System (10) according to the preceding claim, wherein said circulation loops of said two cooling fluids are configured on the one hand for liquefying the working fluid through said condenser (30) and, on the other hand for cooling said fluid of working through said heat exchanger (50).