Patent Application
20200408466
The present invention relates to a heat exchanger comprising series of passages for each of the fluids to be placed in a heat-exchange relationship, the exchanger comprising at least one mixer device for distributing at least one two-phase liquid/gas mixture into one of the series of passages.
In particular, the present invention may apply to a heat exchanger which vaporizes at least one flow of liquid-gas mixture, particularly a flow of multi-constituent mixture, for example a mixture of hydrocarbons, through exchange of heat with at least one other fluid, for example natural gas.
The technology commonly used for an exchanger is that of aluminum brazed plate and fin exchangers, which make it possible to obtain devices that are very compact and afford a large heat-exchange surface area.
These exchangers comprise plates between which are inserted heat-exchange corrugations, formed of a succession of fins or corrugation legs, thus constituting a stack of vaporization passages and of condensation passages, the former intended to vaporize refrigerant liquid and the latter intended to condense a calorigenic gas. The exchanges of heat between the fluids may take place with or without phase change.
In order to ensure correct operation of an exchanger employing a liquid-gas mixture, the proportion of liquid phase and of gas phase needs to be the same in all of the passages and needs to be uniform within one and the same passage.
The dimensions of the exchanger are calculated on the assumption of a uniform distribution of the phases, and therefore of a single temperature at the end of vaporization of the liquid phase, equal to the dew point of the mixture.
In the case of a multi-constituent mixture, the temperature at the end of vaporization is going to depend on the proportion of liquid phase and of gas phase in the passages.
In the event of an unequal distribution of the two phases, the temperature profile of the first fluid is then going to vary from passage to passage, or even vary within one and the same passage. Because of this non-uniform distribution, there is then the possibility that the fluid(s) in a heat-exchange relationship with the two-phase mixture may have an exchanger outlet temperature that is higher than intended, and this consequently degrades the performance of the heat exchanger.
One solution for distributing the liquid and gas phases of the mixture as uniformly as possible is to introduce them into the exchanger separately, then mix them together only once they are inside the exchanger.
Document FR-A-2563620 describes such an exchanger in which a grooved bar is inserted into the series of passages which is intended to channel the two-phase mixture. This mixer device comprises separate channels for a liquid phase and for a gas phase, and an outlet for distributing the liquid-gas mixture to the heat-exchange zone.
A problem which arises with this type of mixer device concerns the distribution of the liquid-gas mixture in the width of the passage containing the mixer device. In order to mix the two phases, the mixer device generally comprises a first channel for the flow of one phase. This channel is equipped with a series of orifices arranged along the channel, each orifice being in fluidic communication with the second channel for the flow of the other phase. When the inlet to the first channel is supplied with fluid, the flow rate of the fluid will tend to diminish as the fluid flows along the channel. This is because the flow of fluid reduces as the orifices are supplied.
Now, the orifices are generally machined perpendicularly to the direction of flow of the fluid, and are therefore less well supplied when the fluid speed is higher. The orifices arranged on the channel inlet side therefore have a tendency to be under-supplied, whereas the orifices situated on the bottom of the channel are over-supplied. The result is an uneven introduction of the respective phase into the channel for the other phase, and hence an uneven distribution of the liquid-gas mixture in the width of the exchanger passage.
In order to minimize this phenomenon, one solution is to supply the channel concerned via two opposite inlets of the channel. However, this results in a complication of the exchanger, and the problem of uneven distribution remains at least in the central part of the channel.
Increasing the number of channels is also not an ideal solution in view of the mechanical strength and brazing of the device.
Another known solution is to arrange orifices of cylindrical form with different diameters along the channel. However, this solution may prove insufficient for certain processes.
It is an object of certain embodiments of the present invention to fully or partially solve the above-mentioned problems, notably by proposing a heat exchanger in which the distribution of the liquid and gas phases of a mixture is as uniform as possible, and to do so without excessively adding to the complexity of the structure of the exchanger, or increasing the size thereof.
The solution according to the invention is therefore a heat exchanger comprising several plates arranged parallel to one another and to a longitudinal direction so as to define a plurality of passages for channeling at least one fluid which is to be brought into a heat-exchange relationship with at least one other fluid, a mixer device being arranged in at least one passage and comprising:
Depending on the case, the exchanger of the invention may comprise one or more of the following technical features:
Furthermore, the invention relates to a method for distributing a two-phase liquid/gas mixture in an exchanger according to the invention, said method comprising the following steps:
According to another aspect, the invention relates to a method for adjusting the positions of the orifices of a mixer device which is arranged in an exchanger according to the invention, said method comprising the following steps:
The present invention may apply to a heat exchanger which vaporizes at least one flow of liquid-gas mixture, particularly a flow of multi-constituent mixture, for example a mixture of hydrocarbons, through exchange of heat with at least one other fluid, for example natural gas.
The expression “natural gas” relates to any composition containing hydrocarbons, including at least methane. This comprises a “crude” composition (prior to any treatment or scrubbing) and also any composition which has been partially, substantially or completely treated for the reduction and/or removal of one or more compounds, including, but without being limited thereto, sulfur, carbon dioxide, water, mercury and certain heavy and aromatic hydrocarbons.
Further features, advantages and possible applications of the invention are apparent from the following description of working and numerical examples and from the drawings. All described and/or depicted features on their own or in any desired combination form the subject matter of the invention, irrespective of the way in which they are combined in the claims or the way in which said claims refer back to one another.
The present invention will now be better understood by virtue of the following description, given solely by way of nonlimiting example and made with reference to the attached drawings, among which:
For preference, each passage has a flat and parallelepipedal shape. The separation between two successive plates is small in comparison with the length, measured in the lateral direction y, and the width, measured in the longitudinal direction z, of each passage.
The exchanger 1 may comprise a number of plates in excess of 20, or even in excess of 100, between them defining a first series of passages 10 for channeling at least one first fluid F1, and a second series of passages 20 (not visible in
In a way known per se, the exchanger 1 comprises distribution and discharge means 40, 52, 45, 54, 55 configured to distribute the various fluids selectively into the passages 10, 20 and to discharge said fluids from said passages 10, 20.
The sealing of the passages 10, 20 along the edges of the plates 2 is generally afforded by lateral and longitudinal sealing strips 4 attached to the plates 2. The lateral sealing strips 4 do not completely block the passages 10, 20 but advantageously leave fluid inlet and outlet openings situated in the diagonally opposite corners of the passages.
The openings of the passages 10 of the first series are arranged in coincidence one above the other, whereas the openings of the passages 20 of the second series are arranged in the opposite corners. The openings placed one above the other are respectively united with one another in manifolds 40, 45, 50, 55 of semi-tubular shape via which the fluids are distributed and discharged.
In the depiction of
In this variant embodiment, the manifold supplying one of the fluids and the manifold discharging the other fluid are situated at one and the same end of the exchanger, the fluids F1, F2 thus flowing counter-currently through the exchanger 1.
According to another variant embodiment, the first and second fluids may equally circulate co-currently, the means supplying one of the fluids and the means discharging the other fluid then being situated at opposite ends of the exchanger 1.
For preference, the direction y is oriented vertically when the exchanger 1 is in operation. The first fluid F1 flows generally vertically and in the upward sense of that direction. Other directions and senses for the flow of the fluids F1, F2 are of course conceivable, without departing from the scope of the present invention.
It should be noted that, in the context of the invention, one or more first fluids F1 and one or more second fluids F2 of different natures may flow within the passages 10, 20 of the first and second series of one and the same exchanger.
As a preference, the first fluid F1 is a refrigerant fluid and the second fluid F2 is a calorigenic fluid.
The distribution and discharge means of the exchanger advantageously comprise distribution corrugations 51, 54, arranged between two successive plates 2 in the form of corrugated sheets, which extend from the inlet and outlet openings. The distribution corrugations 51, 54 ensure the uniform distribution and recovery of the fluids across the entire width of the passages 10, 20.
Furthermore, the passages 10, 20 advantageously comprise heat-exchange structures arranged between the plates 2. The purpose of these structures is to increase the heat-exchange surface area of the exchanger and to increase the coefficient of exchange between the fluids by making the flows more turbulent. Specifically, the heat-exchange structures are in contact with the fluids circulating in the passages and transfer thermal flux by conduction to the adjacent plates 2, to which they may be attached by brazing, thereby increasing the mechanical strength of the exchanger.
The heat-exchange structures also act as spacers between the plates 2, notably while the exchanger is being assembled by brazing, and in order to avoid any deformation of the plates during use of pressurized fluids. They also provide guidance for the flows of fluid in the passages of the exchanger.
For preference, these structures comprise heat-exchange corrugations 11 which advantageously extend across the width and the length of the passages 10, 20, parallel to the plates 2, in the prolongation of the distribution corrugations along the length of the passages 10, 20. The passages 10, 20 of the exchanger thus exhibit a main part of their length, constituting the heat-exchange part proper, which is covered with a heat-exchange structure, said main part being flanked by distribution parts covered with the distribution corrugations 51, 54.
The mixer device 3 preferably extends in the section of the passage 10 over almost all of the, or even the entire, height of the passage 10, such that the mixer device is in contact with each plate 2 that forms the passage 10.
The mixer device 3 is advantageously fixed to the plates 2 by brazing.
The mixer device 3 is advantageously of generally parallelepipedal shape.
As a preference, the mixer device 3 is a monolithic component, namely formed as a block or as a single piece. The mixer device 3 may have, parallel to the lateral direction y, a first dimension of between 20 and 200 mm and, parallel to the longitudinal direction z, a second dimension of between 100 and 1400 mm.
As a preference, the first channel 31 extends over the entirety of the second dimension and/or the second channel extends over the entirety of the first dimension.
The mixer device 3 comprises at least a first channel 31 for the flow of the first phase 61 parallel to the longitudinal direction z, and at least a second channel 32 for the flow of the second phase 62. Said first channel 31 extends parallel to the longitudinal direction z. As a preference, the first channel 31 and/or the second channel are rectilinear in shape. As a preference, the second channel 32 extends parallel to the lateral direction y which is orthogonal to the longitudinal direction z and parallel to the plates 2.
A plurality of orifices 34i, 34i+1, . . . are distributed over the mixer device 3 so as to fluidically connect at least a first channel 31 with at least a second channel 32 designed for the flow of the second phase 62. The mixer device 3 is configured so that when the first phase 61 is flowing along the first channel 31 and the second phase 62 is flowing along the second channel 32, a two-phase liquid/gas mixture F1 is distributed at outlet from the mixer device 3.
As a preference, the mixer device 3 comprises at least one first inlet 311 in fluidic communication with the first manifold 30, and a second inlet 321, separated from the first inlet 311, in fluidic communication with the second manifold 50. The first manifold 30 is fluidically connected to a source of first phase 61, and the second manifold 50 is fluidically connected to another source of second phase 62. Said at least one first inlet 311 and said at least one second inlet 321 are placed in fluidic communication via the orifices 34i, 34i+1, . . .
As a preference, the mixer device 3 comprises a mixing volume situated in the second channel 32, downstream of the orifice 34i, when following the direction of flow of the first phase 61 through the orifice 34i. The two-phase liquid/gas mixture is distributed via a second outlet 322 of the second channel 32.
The first and second channels 31, 32 advantageously take the form of longitudinal recesses formed in the mixer device 3.
The orifices 34 are advantageously bores 34 made in the material of the device 3 and extending between the first channel 31 and the second channel 32, preferably in the vertical direction x. As a preference, the orifices 34 exhibit cylindrical symmetry.
As a preference, said at least one first channel 31 comprises a bottom wall 3c and said at least one second channel comprises a top wall 3d which faces the bottom wall 3c, the orifices 34 being pierced in the bottom wall of the first channel 31 and opening into the top wall of the second channel 32.
As can be seen in
In the devices according to the prior art, the orifices occupy successive positions zi, zi+1, . . . that are situated at equal distances from one another. Now, the first phase 61 flows along the first channel 31 at different speeds along the length of the longitudinal direction z, and the flow of first phase 61 flowing through each orifice varies according to the speed of flow of the first phase 61 at the position zi of the orifice concerned.
In order to solve this problem, what is proposed is a mixer device 3 in which the distances between two successive positions zi, zi+1, . . . are variable. In other words, the distances between the successive positions zi, zi+1, . . . are not all identical. At least one pair of successive orifices exhibits a distance between two successive positions that differs from that of another pair of successive orifices.
By varying the distances between orifices in the longitudinal direction z, it is possible to compensate for nonuniformities of flow rates per unit length in the longitudinal direction z or, to put it another way, per unit width of exchanger passage, distributed by the orifices 34 by adapting the distribution of the orifices 34 across the width of the mixer device 3. “Flow rate per unit length” typically means a flow distributed by an orifice, divided by the distance between this orifice and the next one. For example, greater distances may be left between orifices which have a tendency to be oversupplied with a flow of fluid in the first phase 61, and this will have the effect of locally reducing the flow rate per unit width distributed by the orifices. In fact, the aim is not to make the flow of fluid passing through each of the orifices 34i, 34i+1, . . . uniform by adjusting the configuration of the orifices 34 or of the first channel 31, but rather to adapt the distribution of the points via which fluid is distributed by the orifices 34 in such a way as to render the flow rate of first phase 61 per unit length uniform in the longitudinal direction z.
This then results in a more uniform distribution of the liquid-gas mixture across the width of the passage 10. This solution offers the advantages of being simple to implement, of not altering the size of the exchanger, and of not making its structure more complex.
According to one embodiment, the distances between the successive positions zi, zi+1, . . . vary monotonically or near-monotonically in the longitudinal direction z. In other words, the direction of variation of the successive positions is constant or generally constant along the length of the longitudinal direction z.
According to one embodiment, the mixer device 3 exhibits, in the longitudinal direction z, an increase in the distances between two successive positions zi, zi+1, . . . . Such a configuration is implemented when the mixer device 3 is supplied with first phase 61 via a first inlet 311, the first phase flowing in the longitudinal direction z, as illustrated in the example of
According to an embodiment variant (not illustrated), the mixer device 3 exhibits, in the longitudinal direction z, a reduction in the distances between two successive positions zi, zi+1, . . . Such a configuration is implemented when the mixer device 3 is supplied with first phase 61 via an additional first inlet 312 arranged in such a way that the first phase 61 flows parallel but in the opposite sense to the longitudinal direction z.
This embodiment allows the flow of first phase 61 distributed downstream of the orifices 34 to be made even more uniform along the length of the longitudinal direction z.
As a preference, the first inlet and the additional first inlet 311, 312 are arranged at two opposite ends of the mixer device 3. A first flow of first phase 61 is distributed by the first inlet 311 and flows in the direction of flow z, and a second flow of first phase 61 is distributed by the additional first inlet 312 and flows parallel, but in the opposite sense, to the longitudinal direction z.
Advantageously, the first portion 301 is situated on the side of the first inlet 311 and the second portion 302 is situated on the side of the additional first inlet 312.
As a preference, the first and second portions 301, 302 are arranged symmetrically relative to the center of the mixer device 3. However, said portions could be arranged in different numbers and exhibit different amplitudes of variations in distances between successive orifices on either side of the center of the mixer device 3.
Advantageously, a mixer device 3 according to the invention may be configured by adjusting the position of the orifices 34 according to the steps described hereinafter. Note that all or some of these steps may be performed by numerical simulation, for example using Computational Fluid Dynamics (CFD), or by correlating pressure drops along the first channel 31 and orifices 34, or by actual measurements, etc.
An initial state of the mixer device 3 is defined in which the orifices 34i, 34i+1, . . . are arranged in successive positions zi, zi+1, . . . that are separated by predetermined distances di, di+1, . . . As a preference, in the initial state, the predetermined distances di, di+1, . . . are identical.
The first channel 31 is supplied in such a way that the first phase 61 flows in the longitudinal direction z. The mass flow rates Qi, Qi+1, . . . of the first phase 61 flowing through each orifice 34i, 34i+1, . . . of the mixer device 3 are determined and the orifices are repositioned in such a way that, for each orifice 34i, the next orifice 34i+1 is situated away from the previous orifice 34i by a modified distance di that is expressed:
d
i
=F
i
×d
m
where dm is the mean of the predetermined distances di, di+1, . . . and Fi is a correction factor determined for each orifice as being a function of the flow rate Qi flowing through the orifice 34i.
It should be noted that, for preference, in the initial state, the mean distance between orifices corresponds to the identical distance separating all the orifices 34i, 34i+1, . . . .
Advantageously, the correction factor Fi is a function of the ratio Qi/Qm between the mass flow rate Qi flowing through the orifice 34i and the mass flow rate Qm averaged over all the orifices.
As a preference, this function is a polynomial function of the ratio Qi/Qm, more preferably an affine function of the ratio Qi/Qm, expressed:
where Qi is the mass flow rate flowing through the orifice 34i, Qm is the mass flow rate averaged over all the orifices, A and B are predetermined constants dependent on the characteristics of the mixer device 3. According to one particular embodiment, A=1 and/or B=0.
It being emphasized that the adjustment method described can be applied whatever the configuration of supply with first phase 61 of the first channel 31 since it is in the determination of the flow rates Qi, Qi+1, . . . that the configuration of supply of the first channel 31 is involved.
According to the exchange method considered and its sensitivity to the uneven distribution of the phases of the first fluid F1, one single step of repositioning the orifices 34i, 34i+1, . . . may suffice to even out the distribution of the first phase across the width of the mixer device 3.
Optionally, the step of repositioning the orifices 34i, 34i+1, . . . may be reiterated at least once, preferably between 1 and 5 times, more preferably twice at most. The adjustment method then comprises a step of defining the distances di, di+1, . . . modified previously as predetermined distances. The new mass flow rates Qi, Qi+1, . . . of the first phase 61 flowing through each repositioned orifice 34i, 34i+1, . . . are determined. The mean distance dm between the orifices and the mean flow rate Qm flowing through the orifices are calculated and new modified distances di, di+1, . . . are determined, using the expressions given hereinabove.
In the case of a mixer device 3 having several first channels 31, the adjustment method may be performed generally on all of the first channels 31 together, by considering the distances di, di+1, . . . between two successive orifices, whether these orifices be arranged in one and the same first channel 31 or in different first channels 31.
Alternatively, the method may be performed by considering each first channel 31 individually. In order to do that, the method may optionally comprise, prior to step a), at least one step of selecting a subset of orifices 34i, 34i+1, . . . which are arranged in one and the same first channel 31, steps a) to e) being executed for said subset. At least one other subset of orifices 34i, 34i+1, . . . arranged in another first channel 31 may then be selected and steps a) to e) executed for this other subset.
In order to demonstrate the effectiveness of the invention, CFD simulations have been run with a mixer device 3 as illustrated in
The results of these simulations are given in
Within the context of the invention, the evolution of the distances between two successive positions zi, zi+1, . . . can be assessed in the light of an evolution of actual, measured or simulated values, or of a so-called “fitted” or “smooth” evolution constructed from a mathematical fitting of the actual evolution in the distances between two successive positions zi, zi+1, . . . .
Thus, the terms “increase” or “decrease” cover monotonic variations, like those illustrated in
The device 3 may comprise several first channels 31 arranged successively within the device 3, and/or several second channels 32, the first and/or the second channels 31, 32 being preferably parallel to each other.
As a preference, the first channels 31 and the second channels 32 extend parallel to the plates 2. According to the embodiment illustrated in
It being emphasized that the channels 31 and 32 may have the same or different shapes and quantities. The distances between the successive first channels 31 and the distances between the successive second channels 32 may also vary. As a preference, the distances between the channels 32, measured in the direction of the longitudinal direction z, are adjusted according to the position of the orifices 34.
In this embodiment, the mixer device 3 as a whole forms a parallelepiped, delimited in particular by a first surface 3a intended to be arranged facing one plate 2 of the exchanger, and a second surface 3b arranged facing another plate 2. The first and second surfaces 3a, 3b preferably extend generally parallel to the plates 2. The mixer device 3 is preferably arranged in the passage 10 such that the first and second surfaces 3a, 3b are in contact with the plates 2.
The channels 31, 32 advantageously take the form of recesses provided within the mixer device 3. They may or may not open onto the surfaces 3a and/or 3b.
The orifices 34 are advantageously bores 34 made in the material of the device 3 and extending between the first channel 31 and the second channel 32, preferably in the vertical direction x. As a preference, the orifices 34 exhibit cylindrical symmetry.
It should be noted that the orifices 34i, 34i+1, . . . do not necessarily have the same shape or the same dimensions. The number of different shapes, the dimensioning and the distribution of the orifices, in one and the same first channel 31 or between several first channels 31, might vary according to the desired distribution of liquid-gas mixture, so as to achieve even finer adjustment of the flow rate of fluid through the orifices 34. In particular, in the case of a first channel having an inlet 311, orifices of larger cross sections may be arranged upstream in the first channel 31, where the speed of the first phase 61 is greater, and orifices of smaller inlet cross section may be arranged downstream in the first channel 31. The shape and the dimensions of the first and/or second channels 31, 32 may also vary along the directions y and/or z, and from one channel 31, 32 to another.
Of course, the invention is not limited to the particular examples described and illustrated in the present application. Other alternative forms or embodiments within the competence of a person skilled in the art may also be considered without departing from the scope of the invention.
For example, the exchanger according to the invention is chiefly described for the case in which the passages 10, 20 extend in the lateral direction y, the first longitudinal channel 31 extending in the flow direction z, and the lateral channel 32 extending in the lateral direction y orthogonal to the direction z. The reverse is also conceivable, for example a first longitudinal channel 31 extending in the lateral direction y, and a lateral channel 32 extending in the flow direction z. The directions y and z may also not be mutually orthogonal.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.
“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited
| Number | Date | Country | Kind |
|---|---|---|---|
| 1852469 | Mar 2018 | FR | national |
This application is a § 371 of International PCT Application PCT/FR2019/050642, filed Mar. 21, 2019, which claims the benefit of FR1852469, filed Mar. 22, 2018, both of which are herein incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2019/050642 | 3/21/2019 | WO | 00 |
