WO2015129936A1

WO2015129936A1 - Reactor, channel-type stack for heat exchanger, and method for manufacturing same

Info

Publication number: WO2015129936A1
Application number: PCT/KR2014/001564
Authority: WO
Inventors: 정종식; 박성태
Original assignee: 주식회사 포스비
Priority date: 2014-02-26
Filing date: 2014-02-26
Publication date: 2015-09-03
Also published as: KR20160084841A; KR101849540B1

Abstract

The present invention relates to a principle for designing and a method for manufacturing components for fabricating a corrugated plate lamination-type stack that can be used for a reactor, which causes extreme generation and absorption of heat during a reaction, and for a highly-loaded heat exchanger, which has a low coefficient of heat transfer, but which is supposed to have a high heat exchange load between fluids. Corrugated plates, which are fabricated by forming V-shaped corrugations in the vertical direction on thermally-conductive thin flat plates, are laminated at an interval.

Description

Channel type stack for reactor and heat exchanger and manufacturing method thereof

The present invention relates to a channel type stack for a reactor and a heat exchanger and a manufacturing method, and more particularly, from a small high efficiency micro-channel type heat exchanger to a large high efficiency gas-gas heat exchanger and a catalyst filling reactor. A channel stack for a new reactor and a heat exchanger which is possible and easy to manufacture, and a manufacturing method thereof.

Catalytic reactors used for carrying out chemical reactions or heat exchangers for cooling / heating between fluids are generally used in shell-and-tube type. However, reactions involving extreme heat generation or endotherm have a large amount of heat generated or absorbed per reactor volume. Therefore, if the reactor volume is large, heat exchange proportional to the area may not be able to follow. It is necessary to reduce the thickness of the packed bed of the catalyst by using several hundreds and thousands. In addition, even in the case of gas-gas heat exchange, the heat exchange coefficient of the gas is usually low, so that a larger heat exchange area is required, and thus, the volume of the heat exchanger needs to be increased, resulting in a large volume and an increase in manufacturing cost.

Recently, in order to solve these drawbacks, a method of using a channel stack for stacking plates at an interval between odd and even channels by alternately flowing cooling and heating fluids to exchange heat through the plates is used.

The use of channel stacks is lower than that of shell-tubes in which gas flows into laminar flow between plates in a large industrial field, and heat transfer coefficients are in turbulent flow. There is a problem that there is no difference, mainly commercialized only in small micro-channel heat exchanger.

The small microchannel type heat exchanger is used to increase the heat exchange area by engraving or embossing the plate, but it is not suitable for use as a catalytic reactor because it is difficult to fill and discharge the catalyst.

As a result, it has a large heat exchange area, is easy to manufacture, can be used from small reactors to large industries, and a new channel type stack that can be used as a catalytic reactor by filling and discharging catalyst can be used. The demand for channel-type stacks continues.

The problem to be solved in the present invention is a wide heat exchange area, easy to manufacture, can be used from small reactors to large industries, and provides a new channel type stack that can be used as a catalytic reactor by the filling and discharge of the catalyst will be.

Another problem to be solved in the present invention is a new channel type that can control the cooling amount according to the length by arbitrarily adjusting the width and length of the flow of the cooling fluid flows to the turbulent flow so that it can be used even in extreme exothermic reaction To provide a stack.

Another problem to be solved by the present invention is a microchannel type heat exchanger marketed as a conventional high efficiency heat exchanger has a large pressure drop due to the difficulty in parallel flow (parrell flow) in which the flow rate is distributed in each stacking direction due to the complicated flow path, In addition, it is difficult to increase the size of the area to solve the problem that it is impossible to manufacture a large industrial.

Another problem to be solved by the present invention is that the heat exchange area of the conventional flat plate heat exchanger is narrowed slightly compared to the general shell-and-tube type when the spacing between the plates is narrowed, but in this case the catalyst can be filled and removed after use It is to solve the problem that can not be used with the type of catalytic reactor.

In order to solve the above problems, the present invention is a heat exchange device that can be used for heat exchange between the reaction and / or fluid with heat generation or endotherm, the heat conductive metal plate is constantly wrinkles up and down, and in the wrinkle direction A plurality of corrugated plates having flat vertical ends (hereinafter, referred to as 'left and right edges') are stacked at predetermined intervals, and channels through which fluid flows are formed between the stacked corrugated plates.

In the present invention, the corrugated plates in the heat exchanger are provided with a flat spacer (flat bar) inserted into the left and right edges and a corrugated spacer (pleated bar) inserted into both end portions of the corrugation direction (hereinafter referred to as 'upper and lower edges'). Spaced apart by

In the practice of the present invention, in order to use the heat exchanger as a reactive heat exchanger with heat generation or endotherm, wrinkle bars are inserted into the upper and lower edges of odd-numbered channels, and flat bars are inserted into left and right edges of even-numbered channels. The even-numbered channels are filled with a catalyst with endothermic or exothermic heat, and the odd-numbered channels have fluid flowing perpendicular to the corrugation direction to supply heat for endothermic or to remove the exothermic heat.

In another embodiment of the present invention, in order to use the heat exchanger with high efficiency, a corrugated bar is inserted into the upper and lower edges, and the heat exchanger is heat-exchanged with each other while the fluid flows perpendicularly to the corrugation direction in odd-numbered channels and even-numbered channels. .

In the present invention, the term "pleat plate" is understood to mean a plate corrugated side by side in a wave shape.

In the present invention, the corrugated plate is preferably formed so that the valley of the upper corrugated plate is lower than the floor of the lower corrugated plate, preferably the valley of the upper corrugated plate overlaps with the valley of the lower corrugated plate 50% or more. . It is preferable to use the corrugated plate in which the V-shaped corrugations are regularly held up and down so that the upper corrugated board and the lower corrugated board overlap a lot.

In the practice of the present invention, the thermally conductive corrugated plate may typically have a thickness of 0.1-3 mm, and a corrugated plate may be manufactured in which V-shaped straight corrugations are formed up and down using grooved rollers.

The width of the corrugation in the corrugated board (the gap between the floor and the floor) can be from several mm to several tens of mm, and the length between the vertices of the corrugation is larger than the width of the corrugation. This is possible. When the corrugation is formed at right angles in the longitudinal direction of the metal plate, it is advantageous to manufacture a long heat exchanger, and when formed in parallel to the longitudinal direction, it is advantageous to manufacture a long reactor in which a catalyst is filled. The left and right edges of the corrugated plate are made to be horizontally stretched after being wrinkled for later sealing, or not to form wrinkles during fabrication. The corrugated plates thus manufactured are stacked in the vertical direction at regular intervals, wherein the intervals are maintained by inserting flat flat bars of thickness corresponding to the distance between the vertices of the two corrugated plates at the left and right edges, and the width of the flat bars is later. It should be thick enough for welding, usually about 3-10 mm. The corrugated bar (pleated bar) of about 3-10mm in width is made in the cross-section between the two corrugated boards. The corrugated bar is impossible to produce a corrugated plate by using a roller using a flat bar, it is important to make a gap between the corrugated plate by making a pattern shape given between the corrugated plate by a wire cutting method.

When the corrugated bar and the flat bar are placed on the upper, lower, left and right edges of the corrugated board except for the fluid entrance, and the stack is repeated to form a stack having a predetermined height, the four sides of the stack stacked up, down, left, and right Filled with plates and bars, the outside of the corrugated plate and the bar can be easily welded and sealed from the outside.

Two methods are provided to further provide inlets and outlets for cooling and heating fluids (or reactants) in the stack.

To be used as a catalyst filling reactor, the reactants should flow up and down the corrugated plate, and the cooling or heating fluid for controlling the reaction temperature should flow left and right in the direction perpendicular to the corrugated plate. Accordingly, it is preferable to insert the corrugated bar only at odd times of the upper and lower edges for the inflow and discharge of the reactants, and to insert the flat bar only at the even times of the left and right edges for the inlet and discharge of the cooling or heating fluid. The reactor can be filled with catalyst in the up-and-down corrugation direction and discarded after use.

When used exclusively for heat exchangers, the top and bottom edges seal the laminated surfaces by sandwiching the corrugated bars with layers, and the left and right edges are further divided into left and right sides for odd numbers in the left half and even numbers in the right half. The bars are inserted and stacked to form four inlets and outlets for cooling and heating fluids. The heat exchanger manufactured in this way increases the heat transfer efficiency due to the turbulent effect as the fluid flows into the zig zag. At this time, it is preferable to insert the cut pleated bar cut off one end of the pleated bar at regular intervals between the pleated plate of the inner space, and thus to support the pleated plate mechanically between the pleated plate and It prevents crushing, improves fluid distribution, and can also control flow rate. In addition, the inserted cut bar can be arranged on the same side of the inlet and the outlet of the odd open side, even if the even number can be arranged in the opposite direction of the diagonal to facilitate the piping design of the final heat exchanger. The stack formed with the inlet and the outlet is welded between the bars closely adhered to the end of the corrugated plate of the four sides of the stack to complete the final stack, and the manifold is attached to the stack including the same inlet or outlet array. Welding to complete the inlet and outlet of the fluid (or reactant) completes the final reactor or heat exchanger.

The design principle of the heat exchange stack produced by the principle of close-insertion of the corrugated plate proposed by the present invention, in particular, the corrugated plate formed by forming the V-shaped corrugate up and down by inserting the corrugated bar and the flat bar is easy and easy to manufacture It is easy to seal and can adjust the contact gap between the corrugated sheets regardless of the size of the corrugation. It has the advantage that it can be applied to various ranges from the small microchannel type heat exchanger to the large industrial catalytic reactor. The heat transfer efficiency is increased by flowing to the zig zag up and down of the plate and back to the zig zag to the left and right of the stack. High efficiency heat exchanger for gas-gas heat exchange with low heat transfer efficiency There is an advantage that can be effectively used in the manufacture of the machine.

1 is a thermally conductive corrugated plate in which the V-shaped folds are held up and down constantly according to the proposal of the present invention.

FIG. 2 is a view showing a plane and a cross section of a corrugated bar inserted into and sealed at both ends of a longitudinal direction of a channel formed between laminated corrugated plates according to the proposal of the present invention.

FIG. 3 is a view showing a plane and a cross section of a corrugated bar inserted into a channel formed between a top and bottom plate and a corrugated plate according to the proposal of the present invention and used as a support.

Figure 4 is a cutting wrinkle bar for inserting inside the channel to change the channel in the channel in accordance with the proposal of the present invention.

5 is a bottom and top cover plate of the stack produced in accordance with the proposal of the present invention.

6 is a plan view of the half pleated bar and the heat insulating material placed on the bottom plate.

FIG. 7 is a cross-sectional view of line segments F1-F1 'and F2-F2' in FIG.

FIG. 8 is a plan view of an odd number of corrugated plates, corrugated bars, cut corrugated bars, and flat bars stacked on the plane shown in FIG.

FIG. 9 is a cross-sectional view taken along line G1-G1 ', G2-G2', and G3-G3 'in FIG.

FIG. 10 is a plan view of a state in which a flat bar is placed on an even number of corrugated plates and left and right edges on the plane illustrated in FIG. 8.

FIG. 11 is a cross-sectional view taken along line H1-H1 ', H2-H2', and H3-H3 'in FIG.

12 is a plan view of a state in which an odd number of corrugated plates and an even number of corrugated plates are alternately stacked to a predetermined thickness, and then a cover plate is covered on the top.

13 to 17 are cross-sectional views taken along the lines J1-J1 ', J2-J2', J3-J3 ', L1-L1', and L2-L2 'of FIG.

18 is a plan view of the stacking of the stack for the non-isothermal reactor and the manifold is attached to the outlet and the inlet.

19 is a plan view of a high-efficiency heat exchanger in which odd-numbered corrugated plates and even-numbered corrugated plates are alternately stacked to a predetermined thickness, and then a cover plate is covered on the top.

20 to 24 are cross-sectional views taken along the line K1-K1 ', K2-K2', K3-K3 ', M1-M1', and M2-M2 'of FIG.

25 is a plan view of the state in which the lamination of the high efficiency heat exchanger is completed and the manifold is attached to the outlet and the inlet.

26 and 27 are cross-sectional views taken along line N1-N1 'and N2-N2' of FIG. 25, respectively.

Explanation of Reference Numbers

1. heat conductive corrugated plate

2. Corrugation bar for sealing the upper and lower edges of the channel between laminated corrugated boards.

3. Corrugated bar for supporting between the bottom plate or top plate in the stack

4. Corrugated bar for changing channel inside channel

5.Flat plate used as bottom or top plate of stack

7. Flat bar for sealing edges at both ends of the stack between the bottom plate or the top plate and the corrugated plate.

8. Insulation filled in channel interior between stack base or top plate and corrugated plate

9. Flat bar for right and left edge sealing between stacked channels in stack

11. Inlets to channels in the stack of fluid (or reactants) to be cooled (or heated)

12. Outlet from the stack channel of the cooled (or heated) fluid (or reactant)

13. Channel space through which the fluid (or reactant) to be cooled (or heated) flows

15. Inlet of the fluid (or reactant) to be heated (or cooled) into the channel in the stack

16. Outlet from stack channel of heated (or cooled) fluid (or reactant)

17. Channel space through which a heated (or cooled) fluid (or reactant) flows

21. Manifold including inlets of fluid to be attached to the stack and cooled (or heated)

22. Manifold including outlets of fluid attached to the stack and cooled (or heated)

23. An integrated manifold comprising an outlet of fluid to be cooled (or heated) in the first stack and an inlet of fluid to be cooled (or heated) in the second stack.

25. Manifold including inlets of fluid attached to the stack and heated (or cooled)

26. Manifold including outlets of fluid attached to the stack and heated (or cooled)

31. Piping for manifold 21

32. Piping for No. 22 Manifold

35. Piping for No. 25 Manifold

36. Piping for manifold 26

41.Pitch-top of wrinkles in corrugated plate

51. Edge area of the lower end of the corrugation direction in the corrugation plate

52. Edge area of the upper end of the corrugation direction in the corrugation plate

Hereinafter, the present invention will be described in detail through examples. It should be noted that the following examples are illustrative of the invention and are not intended to limit the scope of the invention. In addition, additional aspects, features, and advantages of the invention include the following description of representative embodiments, which description should be understood in conjunction with the accompanying drawings. In order to facilitate a clear understanding of the present invention, some elements in each drawing may be exaggerated, omitted, or schematically illustrated. In addition, the size of each component does not entirely reflect the actual size.

In the drawings shows a process of manufacturing the reactor using the components and components for the production of the reactor for heat exchange.

Figure 1 shows a corrugated plate (1) that is pleated up and down and the left and right edges are flat. As shown here, in order to increase the overlap ratio between the two plates when laminating the corrugated plates (reducing the gap between the corrugated plates), the corrugations should be formed in a straight line in a V shape except for the curved portion of the corrugated vertex 41.

Figure 2 is a picture of the corrugated plate sealing corrugated bar (2) is inserted into the upper and lower edges (51, 52) between the two plates when the corrugated plate (1) laminated, the width of the bar shown in the overview is later welded It is enough to protect the end of the corrugated plate sandwiched between the hour bars, and usually about 3-10mm is appropriate. The shape of the cross-sectional area of the corrugated bar (2) is manufactured so that it can be perfectly inserted when inserted between the gap of the laminated corrugated plate (1), as shown in the following figure, can be produced by the wire cutting method have.

FIG. 3 is a view of a half corrugated bar 3 inserted to fit tightly in the upper and lower edges between the flat plate 5 and the corrugated plate 1, which are finally placed on top and top for lamination.

4 is a design drawing of a cutting corrugation bar 4 for an inner channel which is inserted into a zig zag for improving mechanical stability between corrugated plates inside the channel and changing the flow path of the fluid flowing therein. It can be easily made by cutting off a bit.

5 shows a flat plate placed on the bottom and top of the stacked stack.

In order to fabricate the stacked stacks using the above components, in Figs. 6 and 7, the bottom plate (5) is placed, on top of which two half corrugated bars (3) are placed, and three half corrugations in the middle. After the bar 3 is placed, the insulation 8 is filled in between. Next, the flat bar 7 of the corresponding length is sandwiched between the half corrugated bars of the left and

right edges

53 and 54, and the corrugated plate 1 can be stacked.

8 and 9 show a case in which the first odd number of corrugated plates 1 are stacked, two corrugated bars 2 on the upper and lower edges and three corrugated cutting lines 4 for changing the inside of the channel after the lamination are zig. The flat bar (9) is placed in the empty place of the left and right edges by zag. At this time, the cooling fluid (or heating) fluid is introduced into and discharged from the right edge so as not to install the flat bar 4 to secure the inlet 11 and the outlet 12 of the fluid.

10 and 11 show a case in which even-numbered corrugated plates 1 are stacked therein, in which a flat bar 9 is placed only on the left and right edges, and an inlet and an outlet 16 for inlet and outlet of reactants in the up and down direction are provided. The reactant enters the lower inlet 15 and flows in parallel with the corrugation direction and is finally discharged to the upper outlet 16. Therefore, it is possible to charge the catalyst in even-numbered whole channel spaces in this area, and to keep the thickness of the catalyst packed layer thinner than in the tubular reactor having a general tube-and-shell structure by narrowing the channel spacing if necessary. And even in the case of a reaction that is difficult to control the temperature accompanied by the endotherm provides an advantage that the internal temperature of the catalyst packed bed more uniformly maintained.

12 to 17 show a plan view and cross-sectional views of the final stacked stack, wherein the stack repeats the process of laminating odd-numbered corrugated plates and even-numbered corrugated plates as desired (repeated five times here). After the mold is laminated once more, the flat plate 5 and the attached bar are symmetrically completed on the top of the mold as in the case of the bottom flat plate.

As shown in FIG. 13, the completed stack is opened with even-numbered channels 17 through which reactants are introduced or discharged in the longitudinal direction of the corrugated plate, as shown in cross-sectional views J1-J1 'of the upper and lower edge portions. 13) is blocked by the corrugated bar (2) and the sealing between the corrugated plate (1) and the corrugated bar (2) and the half corrugated bar (3) and flat bar (9) can be sealed by welding. On the other hand, as shown in FIG. 14, the inflow or outflow of the cooling (or heating) fluid is introduced into the odd-numbered channel 13 through the inlet 11 of the lower right side as shown in the cross-sectional view J2-J2 '. The inside of the channel flows into the zig zag and exits the outlet 12 on the upper right. As shown in FIG. 15, cross-sectional view J3-J3 'is a view of three pay alternating cutting pleated bar positions where the reactant flows in the even direction of the even channel 17 and the cooling (or heating) fluid is odd. At the end of the channel 13, the flow path direction is changed to the left or right at the end of the pay change cutting wrinkle bar (4) to flow to the zig zag in the direction perpendicular to the wrinkle. In addition, in the cross-sectional view L1-L1 'of FIG. 16, it can be seen that the cooling fluid (or the heating fluid) flows into the left inlet 11 of the odd stage and is discharged into the right outlet 12 of the same stage at the right side of the stack. As shown in the cross-sectional view L2-L2 'of FIG. 17, the left side part of the stack is completely blocked by the stacking flat bar 9 and the channel change cutting wrinkle bar 4.

As described above, the four side surfaces of the stack are stacked without gaps except for inlets and outlets of reactants and fluids, so that the end of the corrugated plate and the stacking bars can be easily sealed by welding. The stack thus manufactured is finally attached to each inlet and outlet, and the manifold is finally attached and connected to the pipe to complete the final reactor. As shown in FIG. 18, when the length of the stack is short, the plurality of stacks are connected in series and externally. It can also be used as a reactor by welding, and the cooling (or heating) fluid on the right side is also provided with a plurality of inlets and outlets by installing a plurality of different ways to adjust the degree of cooling in the longitudinal direction of the reactor.

As another example for explaining the principle of the present invention, a fabrication of a high efficiency channel type heat exchanger stack using the above components is shown in FIG. 19. Here, unlike in the case of reactor stack fabrication, not only the cooling (or heating) fluid but also the non-reactant heating (or cooling) fluid flows in the right direction of the corrugated channel to increase the heat transfer efficiency, thereby increasing the heat transfer efficiency. It is characterized by maximizing. To this end, as shown in cross-section K1-K1 ', the upper and lower edge portions of the longitudinal end of the stacked stack corrugated plate 1 are sealed by welding by blocking all the channels between the channels using the corrugated bar 2. Instead, the inlet and outlet of the cooling and heating fluid are formed together at the left and right sides of the stack. For this purpose, when laminating an odd number of corrugated plates (1), a corrugated bar (2) is inserted and placed at the upper and lower edges. On the left half, the flat bar (9) is emptied and piled up.In the same way, when the even-numbered corrugated plate (1) is stacked, the pleated bar (2) is inserted and stacked on the upper and lower edges, but the right half of the left and right edges is flat bar (9). Complete the stack by emptying and stacking). In this case, when the channel change cutting crease bar 4 placed inside the channel is evenly stacked with zig zag, the inlet and outlet of the fluid are diagonally opposite to each other. FIG. 25 shows a final heat exchanger manufactured by attaching a manifold to an inlet and an outlet of a fluid in the heat exchanger stack thus manufactured, and for example, a cooling fluid is introduced into a manifold 21 through an inlet pipe 31 and is excited Flows into the zig zag up and down in the perpendicular direction of the pleats, and flows in the zig zag back to the left and right sides of the stack by the cutting pleat bar 4 for changing the flow path. The fluid flows into the discharge manifold 22 in the diagonally opposite direction and is finally heated up and discharged through the discharge pipe 32, and the heating fluid is also attached to the left side right side of the stack. 25) through the corrugated plate (1) to distribute evenly into the even-numbered channel, likewise through the up-down and left-right flow changes, and finally through the right manifold (26) on the right side of the stack. The temperature sensing provides the method of manufacturing the principle being discharged.

As seen above, in the manufacture of the reactor and the heat exchanger container stack by laminating at intervals using a corrugated plate formed by forming the V-shaped corrugations up and down on the flat plate proposed in the present invention, the upper and lower edge sealing corrugated bars, left and right The design principle of the heat exchanger, which is manufactured by inserting the edge sealing flat bar and the cutting pleated bar for changing the inner channel flow path, and tightly stacking them without any gaps between them, is easy to manufacture and the welding for sealing between channels is performed on the outside of the stack side. It is easy to make and can be applied to various ranges from small micro-channel type heat exchanger to large industrial catalytic reactor, regardless of the size of wrinkles. There is, in particular, the flow path into the zig zag up and down of the corrugated plate and back zig zag from side to side of the stack The heat transfer efficiency is increased, so it can be designed to easily meet the requirement of thin catalyst layer thickness and high efficiency heat exchange load for effective temperature control of reactor with extreme exothermic or endothermic reaction. There is an advantage that can be effectively used in the production of high efficiency heat exchanger for.

Claims

In a heat exchange apparatus that can be used for reactions involving exothermic or endothermic heat and / or fluid-to-fluid heat exchange, a plurality of corrugated plates having regular wrinkles up and down and flat left and right edges are laminated at predetermined intervals on the thermally conductive metal plate, and laminated. And a stack formed with channels through which fluid flows between the corrugated plates.
The heat exchange apparatus according to claim 1, wherein the corrugated plates in the stack are stacked such that the valley of the upper corrugated plate is lower than the floor of the lower corrugated plate.
The heat exchange apparatus according to claim 1, wherein the corrugated plate is a straight corrugated line which is laterally displaced by vertically displacing the V letter.
According to claim 3, wherein the size of the corrugation is a range between the vertex width is 4-100mm range and the length between the vertices is 1.5-2.0 times the width between the vertices, the spacing between the corrugated plate in the stacked stack is based on the spacing between the vertices Heat exchanger, characterized in that laminated in the range of 1-40mm.
The heat exchange apparatus according to any one of claims 1 to 4, wherein the stack is spaced apart by a flat bar inserted into the left and right edges and a corrugated bar inserted into the upper and lower edges.
The heat exchange apparatus according to claim 5, wherein a cutting crimp bar is inserted between the corrugation bars in a channel provided with corrugation bars between upper and lower edges so that a flow path is formed as a zigzag.
The corrugated bar according to any one of claims 1 to 5, wherein a corrugated bar is inserted between the upper and lower edges of the odd-numbered channels and used for the use in a reactive heat exchanger with heat generation or endotherm. Bar is inserted, the heat exchange apparatus characterized in that the even-numbered channel is filled with a catalyst with endothermic or exothermic.
The method according to any one of claims 1 to 5, wherein for use as a high-efficiency heat exchanger, a pleat bar is inserted between the odd and even channels between the upper and lower edges, and is different from the odd and even channels. Heat exchanger, characterized in that the heat-exchanging heat through the corrugated plate while the fluid having heat.
8. The heat exchanger of claim 7, wherein a removable manifold is attached to the even-numbered channels so that the catalyst can be filled and disposed of after use.
9. The heat exchanger according to claim 8, wherein a manifold for outlet and discharge is attached to the stack by inlet and outlet of each fluid.