Plate heat exchanger module for which the channels integrate as input a uniform flow distribution zone and a fluid bifurcation zone

Abstract

A heat exchanger module with a longitudinal axis including a stack of plates defining at least two fluid circuits, at least a portion of the plates each including fluid circulation channels each delimited, at least in part, by a groove. A communication is produced between the channels within a same plate and between all the plates of a same circuit, in a feed or pre-collector zone, with a succession of channel groupings, two-by-two, in the form of bifurcations.

Claims

1. A heat exchanger module with longitudinal axis (X) comprising a stack of plates defining at least two fluid circuits, at least some the plates each comprising fluid circulation channels each delimited at least in part by a groove, the channels of at least one of the two circuits, termed the first circuit, including: a zone (Z1), termed the feeding zone, of feeding the fluid from the exterior of the stack, in which the channels are parallel to one another and extend along a secant axis (X′) intersecting the longitudinal axis (X) and in which two adjacent channels communicate with one another via at least one notch formed in a rib separating their respective grooves; a zone (Z3) termed the bifurcation zone in which each channel is divided into at least two straight channels parallel to one another and parallel to the longitudinal axis (X), being separated from one another by a rib; a zone (Z2) termed the connection zone between the feeding zone and the bifurcation zone, in which each channel has a straight profile that extends along the secant axis (X′) and a curved profile continuous with the straight profile in order to connect the channel with a straight channel of the bifurcation zone; a zone (Z4) of continuous exchange with the bifurcation zone in which the parallel straight channels separated from one another by ribs extend parallel to the longitudinal axis (X); wherein the channels of each plate of the first circuit communicate with those of the other plates of the first circuit in their respective feed zone (Z1), via openings, made in each channel of the feeding zone, passing through the stack but not communicating with the channels of the second circuit, the notches and the openings forming a jet-break grille for rebalancing the flows of the fluid between the channels of the first circuit when said fluid is circulating in said channels.

2. The heat exchanger module as claimed in claim 1, wherein the curved profile of each channel of the first circuit comprises two curves to connect the straight profile of the connection zone to the straight channel of the bifurcation zone.

3. The heat exchanger module as claimed in claim 1, wherein each straight channel is divided into four channels in the bifurcation zone (Z3).

4. The heat exchanger module as claimed in claim 1, wherein the angle between the secant axis (X′) and the longitudinal axis (X) of the module is between 0 and 45° inclusive.

5. The exchanger module as claimed in claim 1, wherein a plate of the first circuit is inserted between two plates of the other of the two circuits, termed the second circuit, at least in the central part of the stack.

6. The exchanger module as claimed in claim 1, wherein the channels of the first circuit have an oval, circular, rectangular or square section.

7. A method of producing a heat exchanger module as claimed in claim 1, comprising the following steps: machining grooves in first metal plates in order to constitute the channels of the first circuit configured with the feed, connection, bifurcation and exchange zones; machining grooves in second metal plates in order to constitute the channels of other of the two circuits, termed the second circuit; stacking in an alternating manner the first plates and the second plates so as to have the through-openings that enable communication between channels of the plates of the first circuit but not with those of the plates of the second circuit; assembling the first and second metal plates to one another, either by hot isostatic compression (HIC), or by a process termed a hot uniaxial diffusion welding process, so as to obtain welding by diffusion between them, or by brazing.

8. The use of a heat exchanger comprising a plurality of heat exchanger modules as claimed in claim 1, wherein the fluid of the first circuit, by way of primary fluid is a liquid metal and the fluid of a second circuit, by way of a secondary fluid, being a gas or a gas mixture.

9. The use as claimed in claim 8, wherein the fluid of the second circuit comprises mainly nitrogen and the fluid of the first circuit being liquid sodium.

10. The use as claimed in claim 8, wherein the fluid of the first or second circuit comes from a nuclear reactor.

11. A nuclear installation comprising a fast neutral nuclear reactor cooled with liquid metal, notably a liquid sodium cooled fast reactor (SFR) and a heat exchanger comprising a plurality of exchanger modules as claimed in claim 1.

Description

DETAILED DESCRIPTION

(1) Other advantages and features of the invention will emerge more clearly on reading the detailed description of embodiments of the invention given by way of nonlimiting illustration with reference to the following figures, in which:

(2) FIG. 1 is a diagrammatic perspective view of a plate heat exchanger module plate according to one example of the prior art, with a single channel at the inlet and at the outlet and bifurcations ahead of the exchange zone;

(3) FIG. 2 is a diagrammatic perspective view of a plate heat exchanger module plate according to another example of the prior art with only one channel at the inlet and at the outlet and bifurcations ahead of the exchange zone;

(4) FIG. 3 is a diagrammatic perspective view of a plate heat exchanger module plate according to a further example of the prior art with a single channel at the inlet and at the outlet and bifurcations ahead of the exchange zone;

(5) FIG. 4 is a top view of a plate heat exchanger module plate according to a first variant of the invention with a feed zone with a plurality of inlet channels forming a feed grille and a zone with bifurcations ahead of the exchange zone;

(6) FIG. 5 is a plan view of a plate heat exchanger module plate according to a second variant of the invention with a feed zone with a plurality of inlet channels forming a grille and a zone with bifurcations ahead of the exchange zone;

(7) FIG. 6 is a detail view in perspective showing the stack of plates of a module according to the invention, at the level of the feed zone with a grille in accordance with a first variant;

(8) FIG. 7 is a detail view in perspective showing the stack of plates of a module according to the invention, at the level of the feed zone with a grille in accordance with a second variant;

(9) FIG. 8 is a detail view conforming to the second variant from FIG. 7, FIG. 8 showing an example of dimensions;

(10) FIG. 9 is a detail view of a part of a bifurcation zone according to the invention, FIG. 9 showing an example of dimensions.

(11) For clarity, the same elements in accordance with the prior art and in accordance with the invention are designated by the same reference numbers.

(12) In the whole application, the terms “inlet”, “outlet”, “upstream”, “downstream” are to be understood in relation to the direction of circulation of the fluid concerned in a heat exchange module according to the invention.

(13) FIGS. 1 to 3 relating to the prior art have already been commented on in the preamble. They are therefore not described hereinafter.

(14) There has been shown in FIGS. 4 to 7 a plate 1 of one of the two fluid circuits, termed the first circuit, of a heat exchanger module according to the invention, which extends along a longitudinal axis X. This first circuit is preferably intended to circulate a liquid metal, such as liquid sodium.

(15) This plate 1 is grooved with channels 10, 11, 12, 13 with zones Z1, Z2, Z3, Z4 produced and shaped differently.

(16) In the feed zone Z1 for feeding fluid from outside the stack, the channels 10 are parallel to one another and extend along a secant axis X′ intersecting the longitudinal axis X and two adjacent channels 10 communicate with one another via at least one notch 16 formed in the rib 15 separating their respective grooves.

(17) As can be seen in FIG. 6, through-openings 17 are made in each channel 10 to enable communication between all the plates 1 of the first circuit through the stack. To this end, other through-openings not shown are also made through the plates 2 of the second circuit. These other through-openings do not enable communication between the channels of the first circuit and those of the second circuit.

(18) Accordingly, the channels 10 with the notches 16 between channels and the openings 17 through the plates 1 form a communication grille between channels of the same plate 1 and between the plates 1.

(19) In continuity with the feed zone Z1, the channels are extended in a connection zone Z2. In this zone Z2, each channel has a straight profile 11 that extends along the secant axis X′ and a curved profile 12 continuous with the straight profile to connect the channel 11 with a straight channel of a bifurcation zone Z3 in continuity with and downstream of the connection zone Z2.

(20) FIG. 5 is a variant of FIG. 4 in which the curved profiles are shorter in order to have all of the channels 13 in the bifurcation zone aligned transversely with the longitudinal axis X.

(21) As can be seen in FIGS. 4 and 5, the connection zone Z2 has a relatively large area, which enables sufficient physical separation between the feed zone Z1 and the downstream bifurcation zone Z3. This physical separation enables sufficient space to be provided in the plates 2 of the second circuit so that there is no communication between the channels of the first circuit with those of the second circuit.

(22) In the bifurcation zone Z3, each channel 13 is divided into four channels 13.1, 13.2, 13.3, 13.4 that are straight, parallel to one another and extend parallel to the longitudinal axis X, being separated from one another by a rib.

(23) Finally, in continuity with the bifurcation zone Z3, the thermal exchange zone Z4 integrates the straight, parallel channels 13.1, 13.2, 13.3, 13.4 separated from one another by the ribs extending parallel to the longitudinal axis X.

(24) There has been represented in FIG. 7 a variant embodiment of the feed zone Z1 in which the rib portions 18 that separate the openings 16 between channels 10 are all identical and aligned, likewise the through-openings 17.

(25) There has been represented in FIG. 8 an example of the dimensions of the plate 1 in the feed zone Z1 in the variant from FIG. 7.

(26) For example, the numerical values are as follows: R1=1.5 mm, e1=42.5 mm, e2=32.5 mm, e3=3 mm, e4=7 mm.

(27) In an analogous manner, FIG. 9 shows an example of the dimensions of a channel 13 with four bifurcations 13.1 to 13.4 based on the curved profile 12 of the connection zone Z2.

(28) For example, the numerical values are as follows: R2=20 mm, R3=26 mm, e5=25 mm, e6=5.2 mm, e7=25 mm, e8=5.2 mm, e9=25 mm and e10=6 mm.

(29) The following procedure is used to produce an exchanger module according to the invention.

(30) There are respectively machined in identical metal plates 1 of rectangular shape grooves with the feed zone Z1, connection zone Z2, bifurcation zone Z3 and exchange zone Z4 as described in detail above. The plates 1 are then machined in the zones Z1 so as to have the notches 16 between the channels 10 and the openings 17 through each plate 1.

(31) Grooves 20 defining the channels of the second circuit are machined in metal plates 2 of identical shape and size to the plates 1.

(32) An alternating stack is produced of the plates 1 of the first circuit with the plates 2 of the second circuit so as to have the through-openings 17 that enable communication between channels of the plates 1 of the first circuit but not with those of the plates of the second circuit.

(33) The metal plates 1, 2 are then assembled together, either by hot isostatic compression (HIC), or by a hot uniaxial diffusion welding process so as to obtain diffusion welding between them.

(34) Comparative CFD calculations have been carried out by the inventors, in order to verify the best fluid distribution performance in the first circuit of the module according to the invention.

(35) The calculations have been done with the hypothesis of circulation of liquid sodium at a temperature of 545° C. at the inlet of the first circuit.

(36) It is specified here that a channel in accordance with the comparative examples 1 and 2 has the same dimensions, i.e. length, width and height, as a channel in accordance with example 3 in accordance with the invention.

(37) All the comparative calculations are summarized in the table below.

(38) Comparative example 1 relates to a prior art module in which the channels of the zone Z4 of the Na circuit are straight and all discharge into the manifold.

(39) Comparative example 2 relates to a module comprising channels in the plates 1 only between the fluid inlet and the exchange zone Z4, a zone Z3 with the bifurcations as shown in FIGS. 4 and 5 and sized like those of the invention in FIG. 9.

(40) Example 3 conforms to the invention, with a module comprising channels in the plates 1 with all the zones Z1 to Z4, the zone Z1 being sized as in FIG. 8 and the zone Z3 with the bifurcations sized like those of the invention in FIG. 9.

(41) In all the examples the other shapes and dimensions of the plates 1 and 2 are identical.

(42) There has further been indicated in the table an ideal case of exchange between liquid sodium that leaves the exchanger at 345° C. and nitrogen that enters at 310° C.

(43) TABLE-US-00001 TABLE Total Flow head dispersion Liquid sodium temperature losses per at outlet of module Thermal ΔP channel (° C.) efficiency (Pa) (%) minimum mean maximum (ε) Ideal case 0 345 345 345 0.93 Example 1 6000 25 315 349 438 0.91 Example 2 50000 8 330 343 384 0.92 Example 3 60000 <2 −345 345 −345 0.93 (according to the invention)

(44) In this table, it is seen that thanks to the invention the dispersion of the flows per channel is much lower, the head losses much higher but acceptable, with a thermal efficiency equal to the ideal case.

(45) Moreover compared to example 2, it is seen that the zones Z1 with notches 16 and the through-openings between plates 1 enable a reduction of the dispersion of the flows by a factor of 4.

(46) It may therefore be concluded from this that the system enables improvement of the distribution of liquid sodium.

(47) Other variants and improvements may be provided without this departing from the scope of the invention.

(48) For example, in an exchanger module using a liquid metal, such as liquid sodium, and a gas, such as nitrogen, it is therefore possible and advantageous to envisage the gas circuit with straight channels and a liquid metal circuit with channels having the various zones Z1, Z2, Z3, Z4, and preferably of larger sections than those of the gas circuit channels.

(49) It goes without saying that a liquid metal/gas exchanger is one application example, and that it is entirely possible to envisage having the same zones Z1 to Z4 according to the invention for both the fluid circuits in the same exchanger.

(50) The second circuit being for preference more dedicated to the circulation of gas, not too much head loss must be introduced, and it is therefore preferable not to provide the bifurcation zone for the plates of this second circuit. On the other hand, it is advantageous to integrate a jet-breaker grille in each plate of the second circuit, in order to perfect the distribution.

(51) It goes without saying that the number of stages, that is to say of plates for the first circuit and/or for the second circuit, is to be adapted according to the operating conditions and that it is entirely feasible to envisage a number different from that in the embodiments shown.