Closed circuit functioning according to a Rankine cycle with a device for the emergency stopping of the circuit, and method using such a circuit

Abstract

The present invention relates to a closed circuit operating on a Rankine cycle, the circuit comprising at least one compression and circulation pump for a working fluid in liquid form, a heat exchanger over which a hot source is swept in order to evaporate the fluid, means for expanding the fluid in the form of a vapor, a cooling exchanger swept by a cold source to condense the working fluid, a reservoir of working fluid, and working fluid circulation pipes for circulating the fluid between the pump, the heat exchanger, the expansion means, the condenser and the reservoir. The circuit comprises a device for draining the fluid contained in the heat exchanger.

Claims

1. A method for controlling a closed circuit operating on a Rankine cycle, the circuit comprising at least one compression and circulation pump with an inlet and an outlet for a working fluid in liquid form, a heat exchanger over which a hot source is swept in order to evaporate the fluid circulating between an inlet and an outlet of the heat exchanger, an expansion device for expanding the fluid in the form of a vapor, a cooling exchanger swept by a cold source to condense the working fluid circulating between an inlet and an outlet of the cooling exchanger, a reservoir of working fluid, working fluid circulation pipes for circulating the fluid between the pump, the heat exchanger, the expansion means, the condenser and the reservoir, a bypass device for the hot source which passes through the heat exchanger, the bypass device comprising a bypass pipeline connected between an upstream line for carrying the hot source to the heat exchanger and a downstream line for carrying the hot source from the heat exchanger, the bypass device bypassing the heat exchanger, the bypass pipeline bearing a three-way valve provided at a junction of the pipeline with the upstream line of the heat exchanger, and a nonreturn check-valve placed in a vicinity of the outlet of the at least one compression and circulation pump, the method comprising, upon occurrence of an emergency shutdown of the circuit initiated by detection of at least one of overpressure and overheating, transferring the fluid contained in the heat exchanger to the part of the circuit between the upstream side of the pump and the reservoir, and commanding the three-way valve into a position such that the hot source bypasses the heat exchanger through the bypass pipeline.

2. The method as claimed in claim 1, wherein, upon the occurrence of the emergency shutdown of the circuit, the fluid contained in the heat exchanger is transferred toward the reservoir.

3. The method as claimed in claim 1, wherein, upon the occurrence of the emergency shutdown of the circuit, the fluid contained in the heat exchanger is transferred toward a pipe connecting the upstream side of the pump and the reservoir through a drain pipe.

4. The method as claimed in claim 3, wherein the circulation of the working fluid in the drain pipe is controlled by a directional-control means.

5. The method as claimed in claim 1, wherein the hot source swept over the heat exchanger comprises exhaust gas of an internal combustion engine, engine coolant of an internal combustion engine or cooling fluid of an industrial furnace.

6. The method as claimed in claim 1, wherein, upon the occurrence of the emergency shutdown, a circuit control unit shuts down the at least one compression and circulation pump and activates transfer of the fluid contained in the heat exchanger to the part of the circuit between the upstream side of the pump and the reservoir.

7. The method as claimed in claim 1, wherein, upon the occurrence of the emergency shutdown, a circuit control unit shuts down the at least one compression and circulation pump, activates transfer of the fluid contained in the heat exchanger to the part of the circuit between the upstream side of the pump and the reservoir, and activates bypass flow of the hot source so that it bypasses the heat exchanger.

Description

(1) The other features and advantages of the invention will become apparent from reading the following description, given solely by way of nonlimiting illustration, and to which are attached:

(2) FIG. 1 which illustrates a closed circuit operating on a Rankine cycle according to the invention and

(3) FIG. 2 which illustrates an alternative form of the closed circuit operating on a Rankine cycle according to FIG. 1.

(4) FIGS. 1 and 2 illustrate one embodiment of a closed circuit Rankine cycle 10 which is advantageously of the ORC (Organic Rankine Cycle) type and which uses an organic working fluid or mixtures of organic fluids such as butane, ethanol, hydrofluorocarbons, etc.

(5) Of course the closed circuit may also operate on a fluid such as ammonia, water, carbon dioxide, etc.

(6) This circuit comprises a pump 12 for compressing and circulating the working fluid, referred to in the remainder of the description as the circulation pump, with an inlet 14 for working fluid in liquid form and an outlet 16 for this working fluid, likewise in liquid form, but compressed to a high pressure. This pump is advantageously rotationally driven by any means, such as an electric motor (not depicted).

(7) This circuit also comprises a heat exchanger 18, referred to as evaporator, through which the compressed working fluid passes between an inlet 20 for this liquid fluid and an outlet 22 through which the working fluid re-emerges from this evaporator in the form of compressed vapor. This evaporator also has passing through it a hot source 23 in liquid or gaseous form, carried by a line 24 between an inlet 25a and an outlet 25b so that it can release its heat to the working fluid.

(8) This hot source may for example stem from the exhaust gases of an internal combustion engine, from the engine coolant of an internal combustion engine, from the cooling fluid of an industrial furnace, or from the heat-transfer fluid heated up in thermal installations or by a burner.

(9) This circuit also comprises an expansion machine 26 which via its inlet 28 receives the working fluid in the form of a high-pressure compressed vapor, this fluid reemerging via the outlet 30 of this machine in the form of low-pressure expanded vapor.

(10) Advantageously, this expansion machine takes the form of an expansion turbine the rotor shaft of which is rotationally driven by the working fluid in vapor form, by causing a connecting shaft 32 to rotate. For preference, this shaft allows the energy recuperated from the working fluid to be transmitted to any conversion device, such as, for example, an electric generator (not depicted).

(11) The circuit further comprises a cooling exchanger 34, or condenser, with an inlet 36 for the expanded low-pressure vapor and an outlet 38 for the low-pressure working fluid converted into liquid form after passing through this condenser.

(12) This condenser is swept by a cold source, generally a flow of ambient air or of cooling water, so as to cool the expanded vapor so that it condenses and is converted into a liquid.

(13) Of course, any other cooling cold source, such as another cooling liquid or cold air, can be used to cause the vapor to condense.

(14) This circuit also comprises, between the condenser and the circulating pump, a closed reservoir 40 for keeping the working fluid in the liquid state.

(15) Advantageously, the circuit comprises a nonreturn check-valve 42 placed in the vicinity of the outlet 16 from the pump 12, and a filter (not depicted), such as a cartridge filter, for filtering the working fluid leaving the reservoir before it enters the pump.

(16) Of course, the various elements of the circuit are connected to one another by fluid circulation pipes 44, 46, 48, 50, 52, 54, successively connecting the pump to the check-valve (check-valve pipe 44), the check-valve to the evaporator (evaporator pipe 46), the evaporator to the turbine (turbine pipe 48), this turbine to the condenser (condenser pipe 50), the condenser to the reservoir (reservoir pipe 52), the reservoir to the pump (pump pipe 54) so that the working fluid circulates in a clockwise direction as indicated in the figures by the arrows F.

(17) This circuit further comprises a draining device 56 for draining the fluid contained in the heat exchanger 18 and which, in the event of a circuit emergency shutdown, allows the pressurized liquid contained in this exchanger to be transferred to the reservoir or to that part of the circuit that is situated between this reservoir and the upstream side of the pump.

(18) By way of example illustrated in the figure, this draining device 56 comprises a drain pipe 58, which starts at a connecting point 60 of the circuit upstream of the evaporator and downstream of the pump (when considering the direction in which the working fluid circulates according to the arrows F) on the pipe or 46 where the fluid is in liquid form and ends at another connecting point 62 of this circuit upstream of the pump and downstream of the condenser on one of the pipes 52 or 54 where the fluid is likewise in liquid form.

(19) More specifically, and as better illustrated in the figures, this pipe starts at a point 60 of the circuit between the nonreturn check-valve 42 and the inlet 20 of the evaporator and ends at a point 62 on the circuit positioned between the outlet of the reservoir 40 and the inlet 14 of the pump 12.

(20) In the example of the figures, a directional-control means 64 makes it possible to control the circulation of the working fluid in liquid form that circulates in this pipe.

(21) This directional-control means is a two-way valve 66 in the case of FIG. 1 and is situated on the pipe 58 some distance from the two connecting points.

(22) As illustrated in FIG. 2, the directional-control means 64 is a three-way valve 68 which is positioned on the point 60 of connection to the pipe 46.

(23) These two types of valve can be controlled by any known means, such as electrical, pneumatic, hydraulic, etc. means.

(24) Advantageously, these valves can also be electrically-operated valves, in particular electrically-operated solenoid valves.

(25) Thus, this drain pipe and the valve that controls its actuation, are subjected only to a moderate temperature. The choice of materials for this valve is therefore less restrictive.

(26) In addition, the fact that the draining device 56 is designed to pass working fluid in the liquid state between the pipes 46 and 62 means that recourse can be had to a valve that is smaller in size than in the usual circuit designs, thereby making it possible to reduce the cost and bulk thereof.

(27) Advantageously, although this is not compulsory, a bypass device 70 for the hot source 24 which passes through the evaporator 18 (bypass illustrated in dotted line in the figures) may be positioned in the path of this source so that it bypasses this evaporator. By way of example, this device comprises a pipeline 72 bypassing the evaporator and situated between the hot-source inlet 25a to the evaporator and its outlet 25b. This pipeline bears a directional-control means 74, in this instance a three-way valve, which is placed on the line 24 upstream of the evaporator and at the junction with the pipeline 72 thus making it possible to control the circulation of the hot source through this bypass pipeline.

(28) Of course, like the directional-control means 64, this valve may be controlled by any known means, such as electrical, pneumatic, hydraulic, etc. means.

(29) In the event of the emergency shutdown procedure being activated, the circuit control unit, that any closed circuit habitually has, proceeds to shut down the pump 12. During this emergency shutdown the draining device 56 is activated by commanding the directional-control means 64 to open so that the working fluid circulates in the pipe 58 in the direction indicated by the arrow C. This then makes it possible to drain the fluid contained in the evaporator 18 toward that part of the circuit (in this instance the branch 54) situated between the pump and the reservoir so that this fluid is then introduced into this reservoir.

(30) Additionally, this control unit activates the evaporator bypass device 70 by commanding the valve 74 into a position such that the hot source bypasses the evaporator.

(31) Thus, under the effect of the pressure of the working fluid present in the evaporator 18 and in the pipes 46 and 48 between the outlet 16 of the pump 12 (and its nonreturn check-valve 42) and the inlet 28 of the turbine 26, the opening of the valve of the draining device causes a large proportion of the working fluid, present in the evaporator in liquid state, to flow back toward the reservoir through the pipe 58.

(32) This is notably achieved thanks to the presence of the check-valve 42 which prevents the working fluid from circulating towards the outlet side of the pump.

(33) Thus deprived of a good proportion of its supply of working fluid, vapor production within the evaporator quickly disappears. The turbine is in turn deprived of a supply of gaseous working fluid and energy production by the circuit quickly comes to a halt.

(34) It should be noted that this emergency shutdown procedure can be brought into action through various means, such as detection of a circuit malfunction (overpressure, overheating, etc.), manual shutdown, etc.