WO2002046679A1

WO2002046679A1 - Heat exchanger

Info

Publication number: WO2002046679A1
Application number: PCT/FI2001/001053
Authority: WO
Inventors: Hannu Koponen; Jukka Hyvärinen; Petri Stranden
Original assignee: Oy Lpm Group Ltd
Priority date: 2000-12-04
Filing date: 2001-12-04
Publication date: 2002-06-13
Also published as: EP1346185A1; AU2002216135A1; FI20002648A0; FI20002648A

Abstract

The present invention relates to a heat exchanger, which includes an exchanger part (1), with primary channels (3) and secondary channels (4) in between the heat surface plates 82) in order to circulate media inside the exchanger part and openings (5a-d) with connecting elements (6a-d) to connect the channels (3, 4) of the exchanger part to the rest of the heat exchanger equipment. The heat exchanger in accordance with the invnetion is characterized in that at least to one opening (5d) a mixing element (7) has been attached in order to mix the media heated by the heat exchanger and to equalized the changes in temperature.

Description

HEAT EXCHANGER

The present invention relates to a heat exchanger which includes an exchanger part with primary channels and secondary channels in between heat surface plates to circle the media inside the exchanger and openings with connecting elements to connect the channels in the exchanger part to the rest of the heat exchanger equipment.

Plate heat exchangers are especially used in district heating systems in population centres, but also in other heating and cooling systems as well as in their applications, such as heat utilizing systems of waste heat formed in different kinds of industrial processes. The media in heat exchangers in district heating systems is usually water. In other application also other liquid or gaseous media may be used. In cooling systems, for example, antifreeze such as glycol is often used.

Today recognized plate heat exchangers are divided mainly into two types: heat exchangers possible to be opened and brazed heat exchangers. Heat exchangers possible to be opened are made of two end plates and heat surface plates attached between them. In the biggest exchangers possible to be opened there may be a separate frame construction to support a pack of plates attached between the end plates. A brazed plate heat exchanger is made of heat surface plates pressed into shape and connected to each other by brazing. In both earlier mentioned heat exchangers the quantity of plates of the exchanger part depends, among other things, on the exchanging capacity of the heat exchanger.

Advantage of heat exchangers possible to be opened is, among other things, the possibility to open them for cleaning and for changing plates and gaskets. Advantages of the brazed heat exchangers are good capacity/size relation, leightness, strength as well as ability to be easily mounted and changed. Automatic regulating systems in heating systems and heat distributing centres have recently become more common. Thus heat exchangers are required to posses more stable heat distribution qualities. In present systems the temperature of the media usually equalizes enough while the media draws further from a heat exchanger. In automatic regulating systems the amount of the media to be fed to primary channels of a heat exchanger is regulated owing to the temperature of media coming from secondary channels. In order to make this kind of system to work in real time the temperature of the media in the secondary channels must be measured as early as possible. Therefore it is usually measured at the opening of the outlet of the secondary channels. However, the media has not been mixed enough there and is not homeothermic. Therefore in present automatically regulated heat exchangers the temperature of the preheated media varies excessively because of irregular heating of the media in the heat exchanger. Especially this kind of problem occurs when a heat exchanger is used with small flow volumes in respect to its capacity.

The purpose of the invention is to provide a heat exchanger with which the earlier mentioned problems are prevented. The purpose of the invention is, especially, to provide a heat exchanger in which the temperature of the media coming out of it is uniform. Furthermore, the purpose of the invention is to provide a heat exchanger, which is reliable in function, simple by construction and economical to manufacture.

The object of the invention is accomplished by a heat exchanger, the characteristics of which are presented in the claims.

The heat exchanger according to the invention is charactarized in that at least in one opening there is a mixer adjusted to mix the media heated by the heat exchanger and to equalize the changes in temperature. This way turbulence flows are greated in the media in the heat exchanger according to the invention, which mix the media with different temperatures together before they appear at the opening of the outlet. Therefore problems arising from earlier mentioned changes in temperatures of media are avoided when using this kind of heat exchanger with automatic regulating systems.

In advantageous application of the invention a mixer is an object attached to the outlet of the secondary channels and which includes a fixing part to be attached to the outlet and a mixing part reaching inside the outlet. By means of the fixing part the mixing part may be attached to the outlet of the secondary side in functional way simply and advantageously as wanted. Because of the mixing part reaching inside the outlet the media may be mixed as mentioned earlier before it appears at the opening of the outlet, where the measuring probe of the automatic regulating system is usually situated.

In the second advantageous application of the invention the mixing part reaches outside the outlet. This way even to a heat exchanger of a small size a relatively big mixer may advantageously be attached, which ensures the mixing of a media before it flows near the probe measuring the temperature.

In the third advantageous application of the invention the mixing part is a cylindrical object mainly of the size of the outlet opening by its outer diameter. This kind of mixing part works in a functional way being simple and advantageous by its manufacturing costs and does not cause pressure losses in the outlet opening having influence on the functioning of the heat exchanging system.

In the fourth advantageous application of the invention the mixing part is a cylindrical part, open in the upper part and formed of the rest of the mixing element, the edges of which reach essentially above the middle of the opening inside the opening. This way a simple but efficiently with turbulence in different direction blending mixing element is created, which does not cause inconvenient pressure losses.

In the fifth advantageous application of the invention the mixing part is penetrated. By penetrating the mixing part the mixing element is made to cause flows that are parallel to the radius of the mixing element and cause turbulence that efficiently blend the media.

In the sixth advantageous application of the invention the mixing part is a part made of netlike material attached to the rest of the mixing element. By means of the netlike construction the earlier mentioned penetrated mixing part may be made without penetration as a separate work phase simply and advantageously.

In the seventh advantageous application of the invention the mixing part is a conical object attached to the rest of the mixing element. This kind of mixing part causes differences in flow speed of the media inside the mixing element, which causes turbulence that blends the media. Furthermore a conical mixing part is easy to manufacture from the same cylindrical object as the rest of the mixing part.

In the eighth advantageous application of the invention the mixing part is a spiral plate object attached to the opening end of the fixing part. This kind of mixing part causes a strong and efficient turbulence that blends the media and it is very simple by construction. Furthermore it is relatively easy to regulate the mixing effect (the spiral shape) of this kind of mixing part, thus the most suitable spiral shape of the mixing part for a certain heat exchanger and the mixing effect owing to it may be relatively simply defined.

In the ninth advantageous application of the invention the mixing element includes an inner flange narrowing the outlet opening. A suitable inner flange in a mixing element may increase the mixing effect of it simply and advantageously without increasing harmful pressure losses in mixing element. Next, the invention will be explained in more detail with reference to the accompanying drawings, in which,

figure 1 illustrates a perspective figure of a heat exchanger and a mixing element according to the invention,

figure 2 illustrates a perspective figure of the second mixing element,

figure 3 illustrates a perspective figure of the third mixing element,

figure 4 illustrates a perspective figure of the fourth mixing element,

figure 5 illustrates a perspective figure of the fifth mixing element, and

figure 6 illustrates a perspective figure of the sixth mixing element.

Figure 1 illustrates a heat exchanger of a brazed type. It includes an exchanger part 1 formed of heat surface plates 2, primary channels 3, secondary channels 4, an inlet opening of primary channels 5a, an outlet opening of primary channels 5b, an inlet opening of secondary channels 5c, an outlet opening of secondary channels 5d and in those in corresponding order attaching flanges 6a - 6d as attaching elements, and fixing bases 13 and 14 and fixing lugsl5 and 16. Furthermore a heat exchanger according to figure 1 includes a mixing element 7 to be attached to the outlet opening 5d of secondary channels with an attaching part 8, a mixing part 9 and a square opening 12 limited to the edges 10 and 11 of the mixing part.

In the application according to figure 1 the exchanger part 1 is a recognized exchanger part of a plate heat exchanger made of stainless steel, in which the heat surface plates 2 are attached on each other by brazing. In an exchanger part primary channels 3 and secondary channels 4 have been formed between the heat surface plates such that every other space is for primary channels 3 and every other for secondary channels 4. Thus heat is conducted by the heat surface plates from the hot media from primary channels to the cold media to be heated in the secondary channels. In the application of the heat exchanger according to figure 1 the media is water, but other suitable media may alternatively be used. The parts of the heat exchanger according to figure 1 are also recognized parts. The supporting bases 13 and 14 in the lower part of the exchanger part are plate constructions with necessary attaching elements to attach heat exchanger to a wanted position on the floor or to other corresponding base. Correspondingly in the upper part of the heat exchanger the fixing lugs 15 and 16 are plate constructions, with which the heat exchanger may be supported from the upper part to constructions around it as wanted to prevent swinging and vibration of the heat exchanger.

The mixing element 7 in the heat exchanger in the application according to figure 1 is made of a tube with round cross section and suitable wall thickness or of a piece of plate with suitable thickness that has been bend to be like one. The outer diameter of it is as the inner diameter of the outlet opening 5d of the secondary side such that it may be adjusted tightly inside the outlet. It includes a fixing part 8 and a mixing part 9 with diameters alike in this case. The meaning of the fixing part 8 is to fix the mixing element 7 to the outlet. In this application the fixing part does not include separate fixing elements but it has been attached to the outlet by welding permanently. Alternatively the fixing part or the outlet opening may include fixing elements to be opened with which the mixing element may be attached to the outlet opening removable. This kind of fixing elements may be, for example, bolts or eccentric fixing elements to be locked by turning.

In the application according to figure 1 there is a square opening 12 longitudinal to the mixing element 7 and reaching to the end with the opening of the mixing element in the mixing part 9. Thus the mixing part is, as a matter of fact, an open cylindrical object, the longitudinal sides 10 and 11 of which reach remarkable above the middle of the opening horizontally inside the opening. The purpose of the longitudinal opening 12 such formed is to provide turbulence flowing into different directions in the media flowing to the outlet opening, to mix the media and equalized the temperature differences as much as possible before media flows to the measuring probe placed at the opening of the outlet. The opening 12 reaches in this application in longitudinal direction of the mixing element near the outlet opening 5d. The size and the length/width ratio of the opening 12 in different heat exchangers may vary. The opening may also vary from the shape in the application according to figure 1. Then the edges 10 and 11 may be inclined or curved in respect to longitudinal direction of the mixing element and/or there may be conical or triangular teeth to increase the forming of turbulence into different directions.

In the second application according to figure 2 the mixing part 9 in the mixing element 7 corresponds to the mixing part in the application according to figure 1 except by cross section round openings at short distance to each other. The purpose of the penetration is to provide flows radial to the mixing element, which cause turbulence that mixes the media. The density of the openings and the distance between each other as well as the size of the area of penetration may vary. This way different kinds of mixing effects are created, for example, for different media and different volume flows used with them.

In the third application of the mixing element according to figure 3 the mixing part 9 is a cylindrical object, by diameter the same size as the rest of the mixing element and has been made of a netlike material. In the application in figure 3 a mixing part 9 made of netlike material has been attached as an extension to fixing part 8. The opening in the net is, in this application, conical but they may be in this kind of applications of some other shape, for example, round or of shape of a parallelogram. When wanted the inner end of the exchanger part 1 of a mixing element may be closed with a netlike material, which is a part of the rest of the mixing part or attached to it. Furthermore, the mixing part made of netlike material may be designed to be inclined, conical or ball-shaped in some applications.

In the fourth application of the mixing element according to figure 4 the mixing part 9 is a conical object reaching inside the exchanger part. In the application in figure 4 it is a separate object attached to the fixing part, but in other applications alike it may also be a part of a mixing element made of the same object as the mixing part. The conicality of the conical part may be chosen suitable in respect to the heat exchanger and the media used in it. In this application the size of the cone opening is about half diameter of the fixing part of the heat exchanger. A conical mixing part may also include penetration or it may be made of netlike material as earlier mentioned.

In the fifth application of the mixing element according to figure 5 the mixing element is one uniform round by cross section tubular object with outer diameter suitable to the outlet opening. In this application it has been made long enough for media to flow longer than earlier and to go round the sides of the cylindrical tube inside it thus creating turbulence due to which the media is mixed before flowing to the outlet opening. In some other application alike the inner end of the mixing part may be shaped to be inclined to wanted direction, curved inside and/or outside and so on.

In the sixth application of the mixing element according to figure 6 the mixing part 9 is a spiral plate object, attached to the fixing part 8 according to figure 6 on the outlet opening 5d side. In this case it has been made originally of a square plate that has been bent spiral according to figure 6. The purpose of this kind of spiral shape of the mixing part is to create gyratory motion in the direction of the perimeter of the outlet opening in the media to mix the media in a suitable way. In this application the amount of spirality is chosen such that there will not be too much pressure loss, but media flows in gyratory motion suitably in respect to the longitudinal axis of the mixing element. Furthermore the purpose of the spiral mixing element is to pass the media inside the exchanger part 1 in different places and thus with different temperatures variably near the measuring probe at the outlet opening.

The mixing element included to the heat exchanger according to the invention may also differ from the earlier mentioned example applications or some of their combination may also be by shape of other kind than a tubular object round by cross section. It may be situated to the primary side or to the secondary side in the exchanger part or next to the exchanger part. In principle, it may be by construction and by shape any separate object to be attached to the heat exchanger mixing media as earlier mentioned without too much pressure loss or it may be a part of an object being a part of other parts of the heat exchanger such as an outlet opening in the heat surface plate by shape different from recognised round opening or a shoulder in it.

Also other recognized parts of the heat exchanger according to the invention may be by other way realized. The exchanger part may be made of whatever material suitable to material of an exchanger part such as different kinds of metals or some suitable ceramic material. It may also be of whatever size and shaped to wanted shape. The exchanger part may also be unlike in application in figure 1 of type to be opened, and in that case the heat surface plate are been attached to each other to be opened. The exchanger part may also be unlike the application mentioned earlier so called parallel-flow type with more than two inlet openings and two outlet openings. In this case also the other outlet opening includes a mixing element, which may be like earlier mentioned. Naturally, the size and the shape of the openings of the exchanger part may vary. The attaching part used with them may also differ from the fixing flanges according to figures 1 - 6. Alternatively other fixing elements such as spiral attachment or sleeve attachment which are usually used in this kind of situations may be used. Furthermore, supporting bases and fixing lugs of the heat exchanger, among other things, may differ in many ways from the figure 1. Besides, also other recognized parts of the heat exchanger may vary depending on the construction of the heat exchanger and its parts.

The invention is not limited to the presented advantageous application but it can vary within the frames of the idea of the invention formed in the claims.

Claims

1. A heat exchanger which includes an exchanger part (1), in which between heat surface plates primary channels (3) and secondary channels (4) have been made in order to circulate media inside the exchanger part and openings (5 a - d) which include fixing elements (6a - d) to connect the channels (3, 4) of the exchanger part to the rest of the heat exchanger equipment, c haracterize d in that at least to one opening (5d) a mixing element (7) has been attached in order to mix the media heated by the heat exchanger and to equalize the changes in temperature.

2. A heat exchanger in accordance with claim 1, characteri ze d in that the mixing element (7) is an object attached to the outlet opening (5d) of secondary channels (4), and the mixing element (7) includes a fixing part (8) to be attached to the outlet opening (5d) and the mixing part (9) reaching inside the outlet opening.

3. A heat exchanger in accordance with claim lor2,characte riz e d in that the mixing part (7) reaches outside the outlet opening (5d).

4. A heat exchanger in accordance with any of claims 1-3, ch ara c t eriz e d in that the mixing element (7) is a cylindrical object with the outer diameter mainly of the outlet opening (5d).

5. A heat exchanger in accordance with any of claims 2-4, ch ara c t eri z ed in that the mixing part (9) is a cylindrical part open in the upper part and formed from the rest of the mixing element (7), the edges of which (10, 11) reach essentially the upper part of the middle of the opening inside the opening (5d).

6. A heat exchanger in accordance with any of claims 2-4, ch ara c t eriz ed in that the mixing part (9) is penetrated.

7. A heat exchanger in accordance with any of claims 2-4, ch ara cteriz e d in that the mixing part (9) is a part made of netlike material and attached to the rest of the mixing element (7).

8. A heat exchanger in accordance with any of claims 2-4, ch ara c t eriz e d in that the mixing part (9) is a conical object attached to the mixing element (7).

9. A heat exchanger in accordance with any of claims 2-4, chara c t eriz ed in that the mixing part (9) is a spiral plate object attached to end with the opening (5d) of the fixing part (8).

10. A heat exchanger in accordance with any of claims 1-9, ch ara c t eri z e d in that the mixing element (7) includes an inner flange narrowing the outlet opening (5d).