GB2408092A

GB2408092A - A heat exchanger

Info

Publication number: GB2408092A
Application number: GB0326452A
Authority: GB
Inventors: Ahad Ramezanpour
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-13
Filing date: 2003-11-13
Publication date: 2005-05-18
Also published as: GB0326452D0

Abstract

A three-dimensional, staggered, counter flow heat exchanger comprises a series of interconnected heat exchange stages (S1,S2,S3,S4), each stage being formed by four types of cells (1,2,3,4). Each stage comprises at least three, spaced, parallel plates, and at least two further plates at right angles to the three, spaced, parallel plates. One of the further plates is positioned with respect to a first and a second of the spaced, parallel plates at one of the respective side, end portions of the stage, while another of the further plates is positioned between the second and a third of the spaced, parallel plates at the other end of the stage, and on the same respective side of the stage. The heat exchanger comprises a plurality of arrays, each formed of four heat exchange stages, with each stage of an array being turned through 90 degrees clockwise with respective to the next adjacent heat exchange stage. The respective further plates are preferably in the form of solid half-cylinders or the like. The cell constructions generally may be rectangular, trapezium-shaped, or triangular.

Description

A HEAT EXCHANGER

The invention relates to a heat exchanger and in particular to a method and apparatus of exchanging heat between fluids.

Heat exchangers typically operate upon the principle of causing two separate fluids simultaneously to flow across the surfaces of a separated body of the heat exchanger which isolates those fluids and which enables the transfer of heat between the two isolated fluids. In order to increase the heat transfer, generally there are two different strategies: 1) Increasing the heat transfer coefficients in both sides for reducing the thermal resistance and thus more heat transfer and 2) Increasing the surface area of fluid separating portions of the exchanger across which the separated fluids are in contact.

A common design, intended to achieve more heat transfer by increasing the surface area between separated fluids, employs a series of flow tubes arranged in a regular array. However, as a given element of the coolant fluid (or hot fluid) acquires (or loses) heat, the temperature difference between that element and the surface with which it is in contact progressively falls.

This progressively reduces the ability of the fluid element to acquire (or lose) additional heat and therefore reduces the efficiency of the heat exchanger as a whole. The problem is compounded by the tendency of fluids flowing along a surface to form a boundary layer of laminar flow over that surface.

This boundary layer constitutes a thermal boundary which increasingly inhibits heat transfer the thicker it gets. 1 I.

Two alternative concepts for overcoming above deficiency are using impinging flows and staggered tube bundle cross flows. The comprehensive studies into heat transfer characteristics of these concepts show high amount of heat transfer on impinging flow plate and also on the staggered tube cross flow.

Using both these concepts, each as a principle of one side of a heat exchanger is a design proposed in PCT/GB02/02483. In this method, one single stage is formed by impinging of fluid one from number of staggered array jets to a surface and flowing into holes on the surface which are inversely staggered related to impinging jets (stagnation points). The second fluid passes staggered tube bundle which has been made by holes inside the impinging surface. The next stage can be extended when the first fluid impinges a new surface after passing the first stage holes and again moves to inversely staggered holes which build the second staggered tube bundle layer to pass the second fluid.

Although this design overcomes the deficiency of low heat transfer of parallel plate or tube flows, which cause to use a long distance flow inside the tubes to gain a desire heat transfer and deficiency of growing of boundary layer, but it has two main disadvantages in design: 1) The amount of touched surface area between two fluids is not efficient. 2) The distributions of heat transfer coefficient in both sides related together are deficient.

In the above design, in the impinging jet layer in each stage there are only top and bottom surfaces which are touched with both fluids by subtracting the total summation of holes area. Any increase in the holes' circumference for increasing the touched surface area in tube bundle section lead to decreasing the touched surface area in impinging part. The touched body surface area between two fluids related to volume of heat exchanger is low.

The second deficiency of above design is distribution of convection heat transfer coefficients in both sides of shared surface of fluids (body surface).

The total thermal resistance in common heat exchangers is a summation of two convection resistances from flow in both sides and one conduction resistance of wall between two fluids. Generally, the conduction resistance related to other convection resistances is small enough to be vanished. By assuming the constant convection heat transfer coefficient in a differential small part of touched surface between two fluids, the thermal resistance in this differential area is summation of inverse convection heat transfer coefficients in both sides. However, the convection coefficient varies in both sides of touched wall in different positions related to flow characteristic.

Mathematically, it can be proved that maximum amount of heat transfer happens when in both sides the distributions of convection heat transfer coefficient are homogenous related to each other (same phase distribution) .

In other words, the maximum convection coefficient happens in same location and its falling trend also happens in same locations in both sides of 1 1 heat exchanger. According to investigations, in impinging jet the maximum convection happens in stagnation point and after a small pick near the stagnation point, reduces with moving from stagnation point in every direction. In tube bundle side of PCT/GB02/02483, the maximum convection heat transfer happens in front of tubes (the flow in front of tubes is like impinging jet to curved surface). In above design, the regions with large heat transfer are not in same location in both sides of touched wall with fluids. Generally, the high convection heat transfer coefficient is obtained with a pressure loss in fluid flow (heat transfer amount is increases with momentum of flow on the surface, like impinging jets, which cause to pressure loss). In fact by the design which distribution of convection heat transfer in both sides of body shared surface between fluids are in same phase, in the same amount of convection coefficient in both sides (same pressure loss) the total amount of heat transfer is increased.

It is the aim of present invention to overcome above deficiencies in previous design. The convection heat transfer amount is in direct relation with amount of flow momentum on the wall. This is the reason that the maximum heat transfer happens in stagnation point of impinging jet or in front of tubes in staggered bundle. Considering these principles, at its most general, the present invention proposes an arrangement which fluids in both sides of a heat exchanger are impinging to same plate. In the present design, the flow and thus the heat transfer characteristics in both sides of heat exchangers are same in every location and therefore the performance of heat exchanger is in optimum point. Such design is possible by a counter flow three dimensional impinging Jet heat exchanger.

The fluids from counter sides flow inside the array of cells which in a regular form isolate two fluids from each other while impinging happens in both sides of some cells continuously and regularly. The fluids flow directions in both sides are three dimensional staggered which have been designed inversely related to each other. The nature of impingement and staggered fluid flow in both sides keep the flow always turbulence and prevent increasing the boundary layer thickness.

According to above aspects of this invention in its general design may be provided a heat exchanger comprising: Means for forming some arrays of preferably cubic cells which each array has a desire numbers and sizes of rows and columns and also a desire size in deep, each cubic cell has a six surrounded square wall which each can be open or close related to present invention; The desire numbers of arrays are stick together from deep side by sharing one surface of cubic shape of each array perpendicular to deep, The number of arrays stick together is the number of stages which fluids should pass in a counter side flow form; is The fluids in each stage alternately flow in columns or in rows, thus the sides walls (parallel to flows) in every array at each stage, are all horizontal or vertical alternately.

If one doesn't consider the share surface (perpendicular to flows) between stages stick together, each stage has one surface perpendicular to flows which includes an array of component surfaces of each cell, these array of surfaces in each stage are open in staggered form which next stage the surfaces are open in inverse staggered of previous stage alternately.

From fluids flowing view, one cycle is completed to four stages and after that fluids flow to the entrance of a next cycle. For tracing the flow in one side, the stages may be designed as: Stage 1: Consider in stage one, the fluid flow in one side is in all columns with odd numbers (thus the side plates all are vertical in the array of stage and parallel to flow). In deep of stage the plates perpendicular to flow are close in the cells which the summation of row and column numbers become an even number (when the both row and column number of cell are odd or even). Thus the incoming flow inside odd columns impinges to deep surface of odd row cells and because the side plates are vertical the only way to flow are odd columns with even rows which are open.

Stage 2: In stage two, the fluids are isolated from each other by horizontal plates parallel to flow in the array of stage. The fluid in stage one flows inside the even row numbers which is in the order with previous stage (The flow from all odd columns in stage one is transferred to all even rows in stage two). The deep array of cells surface in stage two is in inverse staggered to stage one i.e. the surface of cells which summation of rows and columns become an odd number are closed (the cells with one odd and one even column and row numbers are closed). Thus the incoming flow inside even rows impinges to deep surface of odd columns and because the side plates are horizontal the only way to flow are even rows and even columns which are open.

Stage 3: In stage three side plates are all vertical and deep surfaces perpendicular to flow are close when the both row and columns number of cells are odd or even (same as stage one). The incoming flow from even row and columns from stage two, impinges to perpendicular plates in deep of stage three and only way to flow is even columns and odd rows.

Stage 4: Same as stage two, in stage four the side plates are horizontal and deep perpendicular plates are closed when the summation of row and column numbers are odd. According to the flow from stage three, the impinging happens in odd rows and even columns and the way to flow through are odd rows and odd columns which will continue impinging in the next stage like stage one in odd rows and columns.

The second fluid's flow (from counter side of first fluid) is a same as first fluid but in inverse staggered locations. This inverse location become possible with three dimensionally geometry of this design, in any surface which impinging happens from one fluid flow if flow continues in rows, in the other side of surface second fluid impinges to same plate and continues in columns in counter side.

Above structure produces following results: This Gains the possible large amount of convection heat transfer by using the impinging jet technique which percent of impinging plates area to total heat exchanger area can be vary related to the length of stages.

The distributions of convection heat transfer coefficients in both sides always are in optimum point. Generally, there are three different sections from heat transfer behaviour point of view in this invention: 1) the shared impinging body plates which both fluids have maximum convection heat transfer coefficients in both sides of these plates and thus maximum heat transfer happens in this area. 2) The counter flow plates which in sides of each plate fluids are in counter flow parallel to plate. 3) The minimum convection happens in separator plates. These plates are perpendicular to flow (like share impinging flow plates) and separate fluids between stages.

The convection heat transfer of this area is like behind the flat plate perpendicular to a flow.

The larger touched surface area in above design compare with same category of heat exchangers is other advantages of present invention. The total touched surface area of present heat exchanger in same volume varies with the length of rows, columns, and stages. In a constant volume, the area of shared impinging and separator plates will be increased with increasing the number of stages (reducing the distance between stages) and the area of counter flow plates will be increased with increasing the number of rows and columns (reducing the length and width of each cell).

Because in every impinging the direction of flow is changed, the total amount of flow in each stage impinges to shared surfaces. This keeps the efficiency of impinging jets always in highest level.

Because the flow in impinging and separator plates is not parallel, the boundary layer thickness stays always low. Also in parallel flow plates the turbulence produces from mixing effect of flow between impinging plates in passing to next stage, increases the convection heat transfer in parallel flow plates.

The description so far was about general aspects of present invention and more about heat transfer improvements. Using the impinging flow obviously improves the heat transfer but it also causes to a high pressure loss. In most application pressure loss at least in one side of heat exchanger is an important parameter. The present invention depending on the application and parameters suggests using the flow impinging on the curve surface instead of flat plate in one side or both sides of shared impinging surfaces in above heat exchanger. The slope of curves leads the flow to both sides of impinging surface and reduces pressure loss. This may be possible by putting a half cylinder solid shape on the impinging surfaces (in the case which in one side impinging happens on circular curve and in other side impinging happens on a flat plate) which the curve of cylinder may be half circle (the chord equal to circle diameter) or any other chord size of a circle and also any curve of an ellipse.

The amount of pressure loss by using the half cylinder curves in this design in impinging surface may be two dimensionally approximated as a staggered tube bundle cross flow in a duct when the half behind of tubes have been substituted with a cubic shape (like a bullet). The difference in simulating the three-dimensional staggered impingement to half cylinder in present invention and two-dimensional staggered bullet cross flow tube bundle is that in present design, because of three- dimensionally effect, change of the flow direction, prevents pressure loss because of bullet shape behind edges.

In other words, the edges of substitution of a cubic shape as a half behind the impinging surfaces (half cylinders) will not be against the flow, as it is in two-dimensional similar flow, and doesn't increase the pressure loss.

However the wake flow is formed in different direction behind the separator plates. The total pressure loss may be approximated in this patent by using the half cylinder volume (half circle curve in front of flow) as staggered tube bundle cross flow inside a duct.

Instead of curved solid also it is possible to use a triangle cross section which one side of it is stick to impinging surface and two other sides lead the flow to sides. In this case the impinging is called inclined. The angle of triangle may different for different applications. Also it may be used other curve solid surfaces like trapezium etc. In addition to solving the pressure loss by adding above designed volumes, the other two advantages of curved or inclined impinging flow are: Additional surface area in impinging surfaces; In fact by adding the curved surface volume stick to impinging plate, the total sides touched surface reduces and the total impinging surface increases. Knowing that the area of impinging plates in general design (impinging to plate) by having the one sixth of total touched area, transfers about half of total heat in present design, clarifies that how much increasing in impinging surfaces can be caused to increase of heat transfer and the percent of this additional heat transfer depends to curve or inclined surface which is used. Simply by using the half a cylinder, the impinging surface increases more than fifty percent. Using other curves or inclined surface can increase impinging surface more than hundred percent of its initial design (flat plate).

The second advantage to use the curve volume on the impinging plates happens only when the slope of edge in sides reaches to infinite value (like exact half circle or ellipse). This prevents separation of flow after impinging in next channel and thus will increase the total heat transfer in parallel flow plates. Using the flat plate impinging creates a huge separation flow after passing flow from impinging surface and there were be a wake flow layer in channel walls (parallel flow plates) which cause to reducing the convection heat transfer value.

By using the solid half cylinder stick to one or both sides of impinging surface, the design might become heavy. In some applications, if the weight is a critical parameter, it may be preferable in this design to use the curves with a size less than half circle. It is predictable that by reducing the half circle angle until a point, the pressure loss won't have a sensitive change but the weight reduces by power of two. In some aerospace industries which weight may be more important and the cost parameter is not critical, instead of solid, the curves in both sides may be built by plates. But for a conducting heat between two impingement surfaces, both sides should be connected together by some designed fines in inside.

The thickness of solid and its conduction thermal resistance by adding the curve volumes in its worst condition (having curve in both sides and using half circle curve) for a common size of row and columns and common material (Aluminium) still is less than three percent of convection heat transfer resistance in each of both side.

The finalized design of present invention depends to application and the critical parameters which the designer should consider. The amount of heat transfer, pressure loss, compactness, weight, and cost are common parameters for designing of a heat exchanger. Decreasing the size of rows and columns for more compactness increases the counter flow touched surfaces but doesn't affect impinging or fluids separator surfaces. Decreasing the stage sizes increases the impinging and separators but doesn't have effect on counter flow surfaces. Both of above compactness methods increase the heat transfer and also pressure loss but effect of reducing the stage sizes is more. Using the curve surface (preferable by having a half cylindrical solid volume) on impinging surfaces reduces pressure loss in one side and increases heat transfer but it may increase the weight. Amount of this increased weight generally doesn't matter in many applications. Using a plate to build the volume and fin to conduct heat from both sides reduces the weight and may cause to increase the manufacturing cost.

In final design, the above designed rows and columns are closed and general form of heat exchanger is like a cubic rectangular which stages are in height direction of this cubic. By adding curve surfaces to let the flow to sides of curve, by closing the heat exchanger, some half circle solid curves in the sides, lead the flow to the side walls and it causes to have a choked flow in sides of heat exchanger which increases of pressure loss and reducing of the heat transfer. To prevent this deficiency, one may use a quarter-circle-curve to lead the flow only in one side. This may be possible by using bigger curve diameter to fill the impinging surface or by using the same size curve and reducing the size of sides' rows or columns to half (reducing the impinging surface area to half in sides' rows and columns).

The general type of present heat exchanger is counter flow, thus the inlet of first fluid and outlet of second fluid are in one side and outlet of first fluid and inlet of second fluid are in other side. Capturing the outlet flow and the inlet flow may be designed based on this fact that in every stage both fluids are in columns or rows but alternately. For capturing the each fluid in outlet, by closing all rows or columns which that fluid flows, by adding a collector in one side (one may also add two collectors in both sides) the outlet flow is captured from one side. The flow enters to the heat exchanger from that side directly flows into heat exchanger from other rows or columns which are open and a part of flow after impinging to closed surfaces of other side flow flows into heat exchanger. This impinging surfaces transfer final heat between two fluids. The edge of these impinging surfaces may be curve to reduce the pressure loss. Also using a half cylinder curve along the impinging rows or columns in inlet (as the impinging plates inside the heat exchanger) is possible. Also in outlet side where the flow is led to collector on one side a low slope to collector side reduces the pressure loss by inclined impinging.

Also by reducing the number of rows and columns stage by stage and leading the outlet flow to one direction until reduction of number of rows and columns to one, the outlet flow may be collected without using a collector in sides. In this type of design the length of heat exchanger increases and the shape of the heat exchanger parallel to stages from a rectangular changes to a parallelogram.

In both cases of outlet design (lead the flow to a collector or collect the flow stage by stage to one cell outlet), in inlet side a diffuser leads the flow to impinge to closed rows or columns or flow through the open cells inside the heat exchanger. The diffuser prevents pressure loss of sudden expansion of fluid in inlet and also distributes the inlet flow in all cells.

Also present heat exchanger may be designed for open conditions fluid flow.

In such design, using the diffuser in open side is ignored and free flow as one side fluid flows into the heat exchanger. This design may be interested in vehicles when by moving the vehicle, air flows inside the heat exchanger.

By the acknowledge of high heat transfer in an impinging jet plate or in front surface of tubes in staggered tube bundle flow and also by using this principle that optimum design of a heat exchanger (without fin) happens when there is a same distribution of convection coefficient in each point in both sides of a shared wall between two fluids inside the heat exchanger, and by considering efficient surface area between two fluids in a constant volume, present design (preferably by using curve volume on impinging plates) is a optimum design for a compact heat exchanger (however all the design parameters in any special application should be considered).

Although the cells in each stage preferably is square (equal rows and columns size), but the shape of cells may be rectangular, lozenge, parallelogram (and in particular condition any regular shape which may be closed like triangle, pentagonal, etc or the combination of curved geometries). The size of rows, columns, and stages may be varied in different directions which cause to have flexible complete heat exchanger volume. This may be useful when the place of heat exchanger is not a regular volume in particular application which placing the equipment is critical.

The curved volume instead of impinging plate for reducing the pressure loss and also impinging surface may be circle arc in different angles, arc of an ellipse, and also triangle and trapezium in different angles.

A non-limiting example of the present invention shall now be described with reference to the following drawings in which: Figure la illustrates a front plan of first stage of the heat exchanger with flat plate impinging in one side and half-cylinder impinging in other side. The plan includes two section view from left (section A-A) and a view from bottom (section B-B).

Figure lb illustrates the perspective of first stage of the non-limiting heat exchanger (figure la).

Figures lo and id illustrate the plan and perspective of second stage of the non-limiting heat exchanger, respectively, as described in figure la and lb. Figures le and if illustrate third stage and figures lg and lh illustrate fourth stage of plan and perspective of non-limiting heat exchanger, respectively.

Figures 2a and 2b illustrate the plan and perspective of the four stages of figure 1 in a complete cycle of non-limiting present heat exchanger, respectively.

Figure 3a illustrates the plan of a 2 rows in 2 columns heat exchanger in one of stages which by closing the heat exchanger the flow in one side of curve chokes.

Figure 3b illustrates the suggested options for changing the curve in situations of figure 3a to avoid choking the flow.

Figure 3c illustrates the modified perspective of figure 3a by using the triangle instead of half cylinder in figure 3a.

Figure 4 illustrates one method of separating of inlet and outlet flow in present heat exchanger. In this method the coming flow is guided to a collector and exits from side of heat exchanger and inlet flow enters the heat exchanger after expanding in a diffuser.

Figures 5a, 5b, 5c, and 5d illustrate the alternative method to collecting the outlet flow by reducing the number of rows and columns in different stages.

Figure 6 illustrates the different curves which may be substituted instead of half cylinder in figure 1.

Figure 7 illustrates some different array of cells in each stage of the present heat exchanger in different geometries.

Referring to figures 1 and 2 a non-limiting complete cycle section for 5 rows in 8 columns and by using half cylinder impinging in one side and flat plate impinging in other side is described.

Figures la and lb show the first stage of a non-limiting heat exchanger. The parallel plates to flow, as a sample plate 5, in this stage are all vertical. The first fluid flows into the heat exchanger from odd columns (cl,c3,cS,c7) and second fluid flows outside in even columns (c2,c4,c6,c8) , so the heat exchanger is a counter-flow type.

There are four types of cells on every stage of heat exchanger (as sample cells 1, 2, 3, and 4). The share impinging plates (a half cylinder solid which impinging happens in one side in half cylinder curve plate and other side to flat plate) which in the figure la are perpendicular to the flow in intersections of odd rows and odd columns as a sample plate 1. The fluid one by impinging to half-cylinder curve of the share impinging solid plates, in odd columns enters the next stage from open cells in sides of shared impinging plates. These open cells are in odd columns and even rows in figure la and as a sample cell number 4 has been shown. The second fluid impinges to share impinging plates in the other side of these plates and moves horizontally (because in the next stage the parallel flow plates are horizontal) and comes out through the odd rows and even columns as a sample cell 2 and flows inside the all even columns. The fourth types of cells are the flat plates which separate the fluid one and two in the heat exchanger.

These cells in figure la are in the intersection of even columns and even rows (as a sample plate 3). Figure la also shows two sections of stage one by view from bottom (section B-B) and left (section A-A). The parameter "r" in section B-B shows the radius of half-cylinder shared impinging solid (number 1 as a sample). Also in section B-B, the parameter "w" shows the thickness of separator plates and also the parallel flow plates. A section of half-cylinders, separator plates, and the parallel flow plates have been shown in the section A-A.

Figures to and Id are shown the plan and perspective of the second stage of a non-limiting section of heat exchanger respectively. The parallel flow plates in this stage are inverse related to previous stage and so horizontal (the plate 10 is a sample of parallel flow plates). In this stage the shared impinging jet plates are in intersection of even rows (r2, r4) and odd columns (cl, c3, cS, and c7) where the first fluid enters the stage 2 from stage 1 (plate 9 is a sample of shared impinging plates)and impinges to these plates and flows to the next stage from intersection of even rows (r2, r4) and even columns (c2, c4, c6, and c8) which cell 8 has been shown as a sample of the open cells for first fluid flowing. The second fluid impinges to the shared impinging plates in other direction and comes out from cells in intersection of odd rows (rl, r3, and rS) and odd columns (cl, c3, cS, and c7), where the cell 6 is a sample cell of this type, because the parallel flow plates in the next stage are vertical and lead the flow in vertical direction. The separator plates in this stage are in the intersection of odd rows (rl, r3, and rS) and even columns (c2, c4, c6, and c8) where the plate 7 is a sample of separator plates.

Figures le and if show the third stage of heat exchanger cycle. The first fluid flows in all even columns (c2, c4, c6, and c8) and enters and then impinges in even rows (r2, r4) and flows to the next stage in odd rows (rl, r3 and rS). The second fluid impinges to shared impinging plates (intersection of even rows and even columns) in other side and flows out from cells in intersections of even rows and odd columns. The separator plates are in intersections of odd rows and odd columns where as a sample plate 11 has been shown. The other general descriptions are same as previous stages.

In stage four (Figures lg and lie), the first fluid flows in all odd rows (rl, r3, and rS) where enters and then impinges to curve surfaces in even columns (c2, c4, c6, and c8) and flows to the next stage in odd columns (cl, c3, cS, and c7). The second fluid impinges to other side of shared impinging plates (half cylinders in intersections of odd rows and even columns) and enters to stage four from open cells in intersections of odd rows and even columns.

The separator plates in stage four are in intersections of even rows (r2, r4) and odd columns (cl, c3, cS, and c7).

The next stage of above non-limiting section of heat exchanger is same as stage 1 which was described before. Note that if the both fluids had impinged to flat plate, the number of stages for a complete cycle geometrically would have been reduced to two stages (although from fluid flowing view still the flow cycle was completed in four stages).

By considering the rows 1 and 2 and also columns 1 and 2 in the first stage (Figure la and lb), cells which have been shown by numbers 1,2,3, and 4 are impinging shared plate, open cell for coming flow, separator plate, and open cell for entering flow respectively. In the second stage the position of these four cells changes and rotates 90 degree in clockwise (9,6,7, and 8). In third (13,14,11, and 12) and fourth (17,18,19, and 16) stage also this rotation is done and the fifth condition is same as first stage. In other word, if in two dimensional staggered array the positions change only in one direction, in this invention which positions change in two directions, we may call it threedimensional staggered array. Thus by above explanation, the present invention may be called three-dimensional staggered counter-flow heat exchanger.

Figures 2a and 2b show the plan and perspective of the non-liming complete cycle of heat exchanger which has been made by sticking the four stages (S 1, S2, S3, and S4) of Figure 1 together. This complete example which includes rows and 8 columns may be extended in same arrangement to more rows or more columns. Also the number of stages to build the heat exchanger depends to design and is desirable.

The other step to complete the heat exchanger is closing the heat exchanger from sides. As an example in the heat exchanger of Figure 2, there must be added two parallel flow plates in each four sides of heat exchanger (top, bottom, left and right) to close the heat exchanger completely from sides. For a 2 rows in 2 columns heat exchanger the plan of one stage by closing the heat exchanger from sides has been shown in Figure 3a. The problem which arises by these plates is that in some situations the flow chokes between closing wall and curve. In the section A-A of Figure 2a the flow in direction of vector 22 flows as usual design while closing the side causes to choking the flow in direction of vector 21. For improving the performance of the heat exchanger in this situation, the designer may change the curves in sides of the heat exchanger which cause to the choke to lead the flow to one side only.

Some sample curves to change the common half-cylinder curve in sides of the heat exchanger have been shown in Figure 3b. The elliptic and circle quarter curves, the right triangular, the half trapezium, the combination of line and quarter circle, and the combination of two quarter circle are the suggestion curves to prevent flow choking in sides of impinging plates by closing the heat exchanger. Any of suggested sections in Figure 3b may be replaced by section A-A of Figure 3a. By changing the circle curve in Figure 3a (23) to triangle curve (24) a perspective of the Figure 3a has been shown in Figure 3c where the flow is guided in one direction near the wall. For the heat exchanger with any number of rows, columns, or stages in similar manner preventing the choking of flow in some curves in sides of the heat exchanger, will increase the performance of the heat exchanger by increasing the heat transfer and also reducing the pressure loss.

Consider Figure if and lg as a first stage of heat exchanger. In that case the first fluid enters the heat exchanger in odd rows (rl, r3, and rS) and second fluid which comes from inside the heat exchanger, exits from even rows (r2 and r4). Figure 4 as an example suggests a method to collect outflow and also enter inlet flow in such a situation of Figure if and lg. The outlet flow in rows 2 and 4 by closing these rows is guided to one side to a collector (25) designed in side of the heat exchanger. For reducing the pressure loss the closing of the rows 2 and 4 has been done by a slope to collector side. The amount of this slop is desirable related to design parameters. The fluid after collector is guided to an outlet tube to exit the heat exchanger. For any number of rows in same manner outlet flow can be collected. An alternative is also to collect outlet flow by having a collector in each two sides of rows in a heat exchanger. For inlet flow a diffuser (26) has been suggested (Figure 4) where leads the flow from a tube to odd rows (rl, r3, and rS). The closing the outlet flow in rows 2 and 4 causes that all the surface of closing surface acts as shared impinging surface (impinging happens in both sides of these surfaces by two fluids) and it increases the heat transfer rate in last stage of touched surface between two fluids. Although the closing surfaces in Figure 4 has been done by simple flat plate, but for reducing the pressure loss in inlet flow a half cylinder may be added instead of flat plate. In this case inlet flow from diffuser impinges to half circle curves on rows 2 and 4 which lead the inlet flow to sides to rows 1, 3, and S to enter inside the heat exchanger.

Figures Sa, Sb, Sc, and Sd show another alternative method to managing inlet and outlet flows. In this method the outlet flow from rows or columns step by step is guided to a one desirable point in side of the heat exchanger and then exits from this point. By this arrangement inlet flow, enters the inside the heat exchanger in different level of stages. As an example consider a sample stage of the heat exchanger with 4 rows and 4 columns in Figure Sa which outlet flow leaves the heat exchanger in columns 1 and 3. By adding the next stage as has been shown in Figure Sb, the outlet flow in this stage is led totally to row 2 which only exists in three columns (cl, c2, c3). In Figure Sc, the outlet flow has been led to column 2 which only exists for two rows (rl and r2). In the final step (Figure Sd) the outlet flow is led to row 1 in columns 1 and 2 and exits the heat exchanger from the side which the exit tube has been placed. By reducing the rows and columns in these stages, some cells are closed step by step which for reducing the pressure loss a half cylinder volume in the middle or a combination of the line and quarter circle volume in sides are added on the closed cells to lead the inlet flow inside the heat exchanger. By putting the different stages in Figures Sa, Sb, Sc, and Sd together, inlet flow enters the heat exchanger cells in different stages (in Figure S. inlet flow enters the heat exchanger first in rows 1,2 and columns 1,2 and in fourth stage the inlet fluid flows inside of all cells.

Instead of half cylinder solid in Figure 1 which was used to reduce the pressure loss and increase the heat transfer in one side of the heat exchanger, some other curves may be used in the design. Figure 6 shows some alternative curves which may be used instead of half circle. These curves include isosceles triangle, ellipse with different skewness, and trapezium shape for an optimum design (other curves may be considered but they may not have a suitable performance). The theoretical analysis and some numerical simulations show that half cylinder solid (half circle curve) is optimum design for the present heat exchanger but the other options of Figure 6 should be studied extensively to estimate more optimum performance of the present invention.

Although the cells in rows and columns of the heat exchanger in Figure 1 are all square but the array of cells in the design of this heat exchanger may also be rectangular, lozenge, parallelogram, trapezium, triangle, pentagonal, and etc. Some of these forms of arrays have been shown in Figure 7. The principal of shared impinging plates is same in all the arrays but the fluid flow is a little different in some arrays which the cells' geometry is not quadrangular. Because the optimum performance point of the present invention is when the geometry of cells is quadrangular, this description doesn't discuss the details of such triangle array counter flow shared impinging jet heat exchanger. But the general principles of all arrays are same. The cells in an array may also be combination of some basic geometry 2s with and without curve. Also the size of cells may vary in an array and in different arrays (different stages). These parameters make the present invention flexible and suitable to use in limitation of space and size in any application.

Claims

1. A counter-flow heat exchanger comprising: An array of volume cells (at least two rows and two columns in rectangular array) in each stage and a desire number of stages which two fluids, flow in counter direction along the stages by impinging to same plates as a counter flow impinging flow surfaces in the heat exchanger; The alternately parallel flow plates in each stage which separate the fluids in each stage and are as parallel counter flow surfaces area between fluids in the heat exchanger; The vertical plates between stages as separator which wake flow happens in both sides of these plates; The parallel and vertical flow plates in array of each stage and between each stage are close or open to make a three dimensional staggered counter flow from both sides of the heat exchanger. The definition of staggered arrangement may be different for non quadrangular cells like triangular by the principle of impingement to same plate in each stage by two fluids in both sides.

2. A heat exchanger according to claim 1, comprising of three dimensional array (rows, columns, stages in rectangular array) which the plates in each direction are close or open in the manner that fluids from counter sides impinge to same plate and flow in different direction to next stage as a three dimensional staggered arrangement inversely from each sides of heat exchanger.

3. A heat exchanger according to claim 1, wherein the three spaced, preferably parallel, preferably horizontal or vertical plates may not be parallel, horizontal or vertical in which each stage, In repeatable heat exchange stages, may be formed by turning of the three spaced plates In different degrees of angles and shape of the further plates may become different.

3. A mixed fluids heat exchanger according to claim 1, wherein at least two complete mixed heat exchangers are stick together from at least one side and build an unmixed heat exchanger.

4. A heat exchanger according to claim 1, wherein the array in each stage may be rectangular by the geometrical base of square, rectangular, lozenge, parallelogram, and trapezium or polar array with base geometry of triangular, pentagon etc or any rectangular or polar array with combined geometry bases (like rectangular array of circle and hyperbolic geometries) which may be used for a counter flow three dimensional staggered flow in both sides of the heat exchanger.

5. A heat exchanger according to claim 1, wherein the impinging plate in each stage, may be replaced with a volume which has a curve or slope in order to flow direction in one or both sides. This curve in one or both sides may be a desire part of a circle, ellipse, or other type of curves or a triangle, trapezium etc with desire amount of slopes in sides (or with different combination of curves or slopes).

6. A heat exchanger according to claim 1, which may be used in a open flow condition or as a closed heat exchanger by using a diffuser in entrance of each fluid in both sides.

Amendments to the claims have been filed as follows

1. A three dimensional staggered counter flow heat exchanger comprising: A serious of interconnected heat exchange stages, each stage being formed by four types of cells; Each stage being comprises al least three spaced, preferable paralici, preferable horizontal or vertical plates, wherein fluid one flows in the heat exchanger with respect to a first and a second of the spaced, preferable parallel, preferable horizontal or vertical plates and fluid two flows out the heat exchanger between the second and a third of the spaced, preferable parallel, preferable horizontal or vertical plates, and at least two spaced, preferably para]] el, preferably horizontal or vertical plates at two ends and while right angles of three spaced, preferably parallel, preferably horizontal or vertical plates to close the stage, and at least two further plates at right angles to the three and at the same time to the two spaced, preferable parallel, preferable horizontal or vertical plates; One of the further plates is positioned with respect to the first and the second of the three spaced, preferable parallel, preferable horizontal or vertical plates at one of the respective side, end portions of the stage, wherein fluid one Impinges to the further plate (cell type one) and flows in the heat exchanger from other end of stage (cell type two), while another of the further plates is positioned between the second and the third of the three spaced, preferable para]]el, preferable horizontal or vertical plates at apposite side of first further p]atc and end of the stage. and on the same respective side of the stage, wherein further plate is separated fluid one and fluid two in the heat exchanger (cell type four) and fluid two flows out the heat exchanger from other end of stage (eel] type three); The heat exchanger comprises a plurality of stages in four repeatable heat exchange stages, with each stage bemg turned through preferably 90 degrees clockwise with respective to the next adjacent heat exchange stage.

2 A heat exchanger according to claim 1, wherein the further plate between the first and the second of the spaced, preferable parallel, preferable horizontal or vertical plates (cell type one) may be a flat or curve plate, or a volume formed by combination of flat or curved plates in which the volume may be an empty space, a solid, or a spaced with fins, or the like.