The present invention concerns a plate heat exchanger for at least two heat exchanging fluids which heat exchanger is permanently joined and comprises at least one core of plates with a plurality of heat exchanging plates and at least two end plates, the heat exchanging plates creating plate interspaces between each other as defined in the preamble of claim 1.

EP, A2, 0 905 453 shows such a water heater which above a primary heat exchanger heated by a heat source also comprises a secondary heat exchanger and a hot water storage. The hot water storage is in close thermal contact with heat exchanging plates in the secondary heat exchanger and is built together with this one. The described modes of execution of the hot water storage are however not at optimum when it comes to heat transfer, strength, material consumption etc.

The purpose of the invention is to create a plate heat exchanger for heating of water, the plate heat exchanger being of such of kind that the hot water may be obtained directly at tapping even after a longer period of standstill without the need for hot water. The purpose of the invention is also, as a consequence of the just said, to create a plate heat exchanger for heating or cooling of any convenient fluid so that the fluid handled in such of way may be obtained directly even after a longer period without the need for such a handled fluid. At the same time the heat transfer between the working fluids in the core of plates shall be good under all service conditions, the properties of strength be good for single plates as well as the core of plates and the material consumption be small.

The invention thus comprises a plate heat exchanger for at least two heat exchanging fluids which heat exchanger is permanently joined and comprises at least one core of plates with a plurality of heat exchanging plates and at least two end plates. The heat exchanging plates create plate inter spaces between each other.

Each one of the heat exchanging plates is provided with one or several corrugations vertically extending within an area bounded by two at a distance from each other situated parallel first and second planes respectively and which both are mainly in parallel with all the heat exchanging plates as well as with the end plates of the plate heat exchanger. Each one of the heat exchanging plates is provided with at least four port holes being parts of an inlet channel and an outlet channel through the core of plates for each one of the fluids.

At least one of the end plates has a plurality of port holes each one communicating with one of the inlet channels or one of the outlet channels and the inlet channels and outlet channels for a first and a second fluid respectively are in fluid communication with a first and a second set of plate interspaces respectively.

At least two of the said and next to each other in the present core of plates situated heat exchanging plates (2a, 2b) is each one provided with at least one trough-shaped section (19) which each one in cooperation with the respective adjacent heat exchanging plate (2a, 2b) creates a towards all the fluids except the said second fluid sealed space and each one constitutes a part of the respective heat exchanging plate (2a, 2b) in such a way that the said part lacks port holes (9, 10, 13, 14) and each one is created with a flange like edge (22) extending around the hole periphery of the trough-shaped section (19) which edge makes an angle with the different main planes of extension of the section (19) and the heat exchanging plate (2a, 2b) and which along at least the main part of its length is in contact with the present corresponding edges (22) on the adjacent heat exchanging plates (2a, 2b).

Each one of a plurality of said heat exchanging plates may be provided with at least one trough-shaped section which in cooperation with the respective adjacent heat exchanging plate creates a towards all fluids except the said second fluid sealed space.

The characteristics in other respects of the present invention are clear from the following patent claims.

The plate heat exchanger will now be closer described in connection with forms of execution of the invention and with reference to the accompanying drawings.

Figure 1 shows in a respective view a plate heat exchanger according to the invention.

Figure 2 shows a cross section through the plate heat exchanger along the line A-A in figure 1.

Figure 3 shows a cross section through the plate heat exchanger along the line B-B in figure 1.

Figure 4 shows in a perspective view a first type of heat exchanging plate being part of the plate heat exchanger in figure 1.

Figure 5 shows in a perspective view a second type of heat exchanging plate being part of the plate heat exchanger in figure 1.

Figure 6 shows a cross section through a part of the plate exchanger in figure 1, the cut following the line C-C in the figures 4 and 5.

The plate heat exchanger in figure 1 comprises a core of heat exchanging plates 2a, 2b, whereby only the common denotation 2 is given in the figure, and end plates 3, 4. Connections 5, 6, 7, 8 for two heat exchanging fluids are present. In the mode of execution shown here the connections 5 and 6 constitutes inlet for a first and a second heat exchanging fluid respectively while the connections 7 and 8 constitutes outlet for the said first and second heat exchanging fluids respectively.

From the cross section in figure 2 is evident how portholes 9, 10 in every heat exchanging plate 2a, 2b, create two port channels 11, 12 through the core of plates in one of its ends. In the form of execution shown here the port channel 11 constitutes the inlet channel for the first heat exchanging fluid while the port channel 12 constitutes the outlet channel for the second heat exchanging fluid. In a corresponding way supplementing port holes 13, 14 are present in the second end of the core of plates (the nearer end of the core of plates in figure 1) in every heat exchanging plate 2a, 2b which port holes create an inlet channel for the second heat exchanging fluid and an outlet channel for the first heat exchanging fluid respectively. The inlet channel and the outlet channel for the first heat exchanging fluid are in fluid communication with a first set of plate interspaces 17 while the inlet channel and the outlet channel for the second heat exchanging fluid are in fluid communication with a second set of plate interspaces 18.

From the cross section in figure 3 is evident how each one of the heat exchanging plates 2a, 2b is provided with a trough-shaped section 19. (It is for the inventive idea enough with two trough-shaped sections 19 in the core of plates.) The trough-shaped section 19 shows corrugations 20 vertically extending within an area delimited by two at a distance to each other situated parallel third and fourth planes respectively and which both are mainly in parallel with all the trough-shaped sections 19 and the heat exchanging plates 2a, 2b as well as with the end plates 3, 4 of the plate heat exchanger. The corrugations 20 are not to be mistaken for those corrugations which are present on the rest of the parts of the respective heat exchanging plate 2a, 2b and which are vertically extending within an area delimited by two at a distance to each other situated parallel first and second planes respectively.

The trough-shaped section 19 further shows several through holes 21 (not plate 2a, 2b situated next to an end plate 3, 4 or by itself constitutes such an end plate - also a plate 2a may thus be situated next to an end plate or itself constitute such an end plate, not only a plate (2b)) which is not to be mistaken for port holes 9, 10, 13, 14 which port holes each one is part of and inlet channel 11 or an outlet channel 12 through the core of plates for anyone of the fluids. The trough-shaped section 19 is created with a flange like edge 22 extending around the whole periphery of the section 19, which edge makes an angle with the main planes of extension of the section 19 and the plate 2a, 2b and which bears on the corresponding edges 22 on the adjacent heat exchanging plates 2a, 2b in the core of plates.

In a corresponding way each one of the heat exchanging plates 2a, 2b is made with a flange like edge 23 running along the whole outer circumference of the plate which edge makes an angle with the main plane of extension of the plate 2a, 2b and which bears on the corresponding edges 23 on the adjacent heat exchanging plates 2a, 2b in the core of plates.

On each other bearing heat exchanging plates 2a, 2b are joined along the said edges 23, around at least two of the said port holes 9, 10, 13, 14, around the trough-shaped sections 19 along said edges 22 along at least the main part of the length of the edges 22 as well as in a large number of those points upon the heat exchanging plates 2a, 2b where the respective corrugations bear on each other, within as well as outside the trough-shaped sections 19. The core of plates is normally permanently joined by soldering or brazing but any other known method for permanent joining, such us welding or gluing, is thinkable.

Every other heat exchanging plate 2a in the core of plates is of a first kind, see figure 4, and the remaining heat exchanging plates 2b in the core of plates are of a second kind, see figure 5. The heat exchanging plates 2a, 2b are placed next to each other as they appear in the figures 4 and 5 without any mutual turning or overturning.

The way of the heat exchanging fluids through the heat exchanger will now be more closely described. The said first fluid, in the present case hot water, enters through the said connection/inlet 5 and flows through said port hole 9 and port channel 11 further out into the said first set of plate interspaces 17. On its way in each one of the plate interspaces 17 the first fluid passes on both sides of the said trough-shaped section 19 without being able to enter and fill up the space between adjacent trough-shaped sections 19 since each one of the trough-shaped sections 19 is made with the said flangelike edge 22 bearing on and being fluidum tightly joined with the corresponding edge 22 on the adjacent plate 2 in the plate interspace along the hole length of the edges 22. The first fluid leaves each one of the plate interspaces 17 through the said porthole 14, the said port channel and the said connection/outlet 7.

The said second fluid, in the present case tap water to be heated, enters through the said connection/inlet 6 and flows through the said port hole 13 and port channel further on out into the said second set of plate interspaces 18. On its way in each one of the plate interspaces 18 the second fluid flows first in a first passage situated alongside with and between the said trough-shaped section 19 on one hand and the said outer edge 23 on a first long side of the plates 2a, 2b on the other hand whereafter the second fluid due to first irregularities 24a, 24b present in the pressing patterns of the plates 2a, 2b in a first end of the trough-shaped section 19, is allowed to enter and flow through the space between adjacent trough-shaped sections 19 and after that, due to in the same way in the pressing patterns of the plates 2a, 2b present second irregularities 25a, 25b in a second end of the trough-shaped section 19, once again leave the space between adjacent trough-shaped sections 19 and continue in a second passage situated alongside with and between the said trough-shaped section 19 on one hand and the said outer edge 23 on a second long side of the plates 2a, 2b on the other hand. The second fluid leaves each one of the plate interspaces 18 through the said port hole 10, said port channel 12 and said connection/outlet 8.

The said irregularities 24a, 25a on each one of the said heat exchanging plates 2a of the first kind as well as the said irregularities 24b, 25b on each one of the said heat exchanging plates 2b of the second kind have such a form that, for each one the said heat exchanging plates 2a of the first kind, the said edge 22 around the said trough-shaped section 19 in the said second plate interspace 18 cannot bear on and thus after joining cannot seal against the corresponding edge 22 around the hole circumference of the said trough-shaped section 19 on the adjacent plate 2b, see figure 6 where only eight plates 2a, 2b are shown, but just along two continuous parts of the circumference which parts however together constitute the main part of the circumference, i.e. more than half the circumference. Two local passages are thus present for the said second fluid to and from a second trough space respectively which trough space is limited by the said trough-shaped sections 19 with the said intermediate edges 22 for adjacent heat exchanging plates 2a, 2b in each one of the said second plate interspaces 18.

Each one the said local passages has a certain extension along the respective said edge 22 whereby a first passage by the said first irregularities 24a, 24b extends from a fold 27 to a fold 28 in the edge 22 and a second passage by the said second irregularities 25a, 25b extends from a fold 29 to a fold 30 in the edge 22, see figure 4. The passages are distinguished by a more flattened flank angel than the rest of the said edge 22, i.e. the said edge 22 outside the passages on each one of the plates 2a, 2b makes a larger angle with the plane of the plate than the corresponding section edge does in the area for any one of the said local passages.

When the said second fluid flows in the mentioned second trough space the flow is in a direction which is mainly contrary to the flow direction outside the mentioned second trough space in the same plate interspace. The said trough hole 21 means that the mentioned second trough space is also in fluid communication with a first trough space which is delimited by the said trough-shaped sections 19 with the said intermediate edges 22 for adjacent heat exchanging plates 2a, 2b in each one of the said first plate interspaces 17 in the core of plates. Since all the trough-shaped sections 19 in the core of plates, except those that are present on plates 2a, 2b which are closest to end plates or which constitute end plates themselves in the core of plates, show the said through holes 21, all the trough spaces between plates 2a, 2b are in fluid communication with each other.

The heat exchanger described here functions in a relatively normal way in continuous operation. The advantages appear when after an interruption in the need for hot water there is again a need for hot tap water. If, during the standstill period, i.e. when no tapping of hot water occurs, hot water is still intermittently provided to the primary side the water volume which is housed within the mentioned trough spaces is held warm. This heated water volume will almost instantly come out from the heat exchanger when tapping is again started and the volume is so adapted that the heat exchanger reaches continuous operational performance before the water which is stored in advance is used up.

Compared to prior art the construction shows the definitive advantaged that the present trough-shaped sections 19, in spite of the holes 21, are continuous, i.e. the sections may be said to be equipped with bottoms of a certain form which to a high degree contributes to the strength of the plates and the core of plates. For this reason a thinner material may be used in the plates with the same demand for strength and stability than had otherwise been the case. The bottoms also contribute to an excellent heat transfer into or out from the mentioned trough spaces, which are sealed off against all fluids except, in the present case, tap water to be heated.

The plates are often made of steel plate with a thickness of 0,20-0,35 mm but also other materials may be used such as for example titanium. The heat exchanger plates 2a, 2b are often thin and the end plates 3, 4 are thick but also other modes of execution may exist. For example it is possible to think of the end plates 3, 4 not being thick and not looking like those in the figures but instead being of an appearance totally or partly in accordance with the present heat exchanging plates 2a, 2b but with the difference that port holes only are present where the mounting of connections are desired. It is also possible to use end plates 3, 4 of different designs in different ends of the present core of plates or even several end plates 3, 4 of the same appearance or different appearances in each one of the ends of the present core of plates. In an alternative mode of execution at least one end plate may be planar and totally without connections in order to make connections via O-rings possible to a finished collection of coupling components or alike, a so called block.

The corrugations 20 and the holes 21 may be varied in number as well as in size and form. When brazing the core of plates together copper braze, nickel braze or any other known brazes may be used. When using the plate heat exchanger one or several of the fluids may be another fluid than water. For example it is possible to think of heat exchange between oil and water.

The invention is not restricted to the forms of execution shown here but may be varied in accordance with the following patent claims.