NL2004147C2

NL2004147C2 - Heat exchanger.

Info

Publication number: NL2004147C2
Application number: NL2004147A
Authority: NL
Inventors: Gianluca Vatta
Original assignee: Daalderop Bv
Priority date: 2010-01-26
Filing date: 2010-01-26
Publication date: 2011-07-27
Also published as: EP2354703A2; EP2354703B1; EP2354703A3

Description

Heat exchanger

The invention relates to a heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel. Such a heat exchanger finds application in for instance 5 domestic boilers for central heating.

Often these heaters comprise a casting surrounding the heat source, being thermally connected with the heat source and having the shape of a surface of revolution, wherein a channel for conducting the fluid to be heated is casted into said body.

10

The costs of such a construction a substantial as casting is an expensive process. The aim of the present invention is to provide such a heat exchanger of which the production costs are lower. Another aim of the invention is to provide such a heat exchanger having an improved efficiency. Another aim of the invention is to provide such a heat 15 exchanger having an improved efficiency.

This aim is reached by a heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel, comprising an inner wall made of heat conducting material, surrounding the heat source, being thermally connected with the heat source 20 and having the shape of a surface of revolution, a outer wall concentric to the inner wall, wherein the distance between both walls is substantially constant and a first conduit comprising the first channel, extending between both walls and being in thermal contact with the inner wall.

25 In the heat exchanger according to the invention there is no need to cast in any conduits, so that the production costs thereof are lower. It should however be noted that the inner wall itself may be provided by a casting, although it may also be formed by an extruded element. It is noted that the intimate contact between the heat source and the fluid flowing in the conduits leads to an improved efficiency.

30

Although shapes like frusto-conical shapes may be used, it is advantageous if the inner and the outer wall are both substantially cylindrical and that the first conduit extends helically between the inner and the outer wall. Apart from the ease of locating the helical conduit between the two walls, there is the advantage that the length of the 2 cylindrical heat exchanger is in principle unlimited. Of course there are practical limitations, but the length of the heat exchanger may be adapted to its power, allowing to produce heat exchangers of different powers with the same diameter, leading to simplification of the production facilities.

5

According to a preferred embodiment the first conduit is adjacent to the inner and outer walls and the pitch of the winding of the first conduit is larger than the outer size of the first conduit in axial direction of the heat exchanger to enclose a second helical channel between the windings of the first conduit. This feature provides a second channel which 10 may be operated independently of the first channel without providing a second conduit, leading to substantial savings. Nevertheless two different fluids may be heated independently by the same heat exchanger. An application thereof resides in the so called ‘combi-boiler’ which is adapted to heat both water for central heating and tap water. According to the prior art such a heat exchanger is provided of a casting in which 15 two different channels are incorporated.

It is however also possible to provide a bifilarly wound second conduit extending between and adjacent to the inner and outer walls through which second conduit a second channel extends. This provides the same functionality as the preceding 20 embodiment but at the cost of an extra conduit. There may however be reasons making this embodiment imperative, like the need to heat two separate tap water channels, as tap water may only be contacted by copper in heating appliances. Further the provision of two separate conduits allows the creation of two extra channels enclosed by the conduits if some geometrical conditions are met, resulting in four independent channels, 25 albeit at the cost of complicated headers.

Although varying means of connection between the conduits and the inner and outer walls are possible, like soldering, brazing or welding, it is advantageous when the at least one conduit is formed by a pipe and that the pipe has been clamped between the 30 inner and outer walls as clamping does not require access between the inner and the outer walls to execute an operation.

The clamping is preferably executed by deforming said pipe by subjecting the inner of the pipe to a pressure sufficiently high to cause such a permanent deforming that the 3 pipe is clamped between the inner and outer walls. Again this is an advantageous process of fixing the pipe in its required, hardly accessible location.

Preferably said pipe has been made of copper, as copper is a material which can be 5 deformed permanently by applying a moderate pressure to its inner. Further copper is attractive as it is allowed to be used to heat tap water. However the use of other metals, in particular stainless steel is also anticipated.

The construction of the heat exchanger is improved and simplified if at both ends of the 10 heat exchanger a header has been located and when the conduit comprising the first channel extends through both headers to the outside of the heat exchanger and that both headers comprise connection means for the second channel.

To allow an easy assembly at least one of the headers comprises a flange shaped part 15 and a cylindrical part, while the flange shaped part is connected with the inner wall, the cylindrical part is connected with the outer wall and the conduit comprising the first channel extends through the cylindrical part. The separate provision of these parts allow to initially mount the cylindrical part, possibly preceded by the connection of the first and possibly second conduits, followed by the mounting of the flange shaped part, 20 leading to assembly of the header.

Further mounting of and connection of the cylindrical part of the header to the outer cylindrical wall is simplified if the cylindrical part of the header is connected to the outer wall by a U-shaped profile surrounding both the header part and the outer wall and 25 when the U-shaped profile comprises a clamp. Herein the cylindrical part is brought to its location, after which the U shaped profile is applied such that the cylindrical part and the outer wall are connected and subsequently the clamp is tensioned to fix the U-shaped profile and to unite the outer wall and the cylindrical part of the header. The use of a separate header allows an easy removal thereof so that easy access is gained to the 30 heat source, for instance for cleaning purposes during service. Besides it is noted that cleaning is further facilitated by the cylindrical structure of the inner wall.

It will be clear to the skilled man that the heat exchanger comprises two headers and that the above features may apply to one or to both headers. Further it is attractive when 4 the flange shaped part of at least one of the headers comprises a connection face adapted for connection of at least two fittings. Fittings like thermometers, pressure meters and valves may be connected to the heat exchanger. From the preceding feature it appears that it is attractive to connect those fittings to a single face of one or both of the headers. 5 Herein also the fittings required for the heat source, like the supply pipe for gas are also to be regarded as fittings. The use of multiple or all connections in a single face allows the use of a less gaskets or even a single gasket for multiple fittings.

The advantages of the preceding features appear also in a heating boiler, adapted to heat 10 central heating water and tap water and comprising a central heating circuit and a tap water heating circuit, wherein the heating boiler comprises a heat exchanger as claimed in one of the preceding claims and that the first channel of the heat exchanger is connected to the tap water heating circuit and the second channel of the heat exchanger is connected to the central heating circuit.

15

The invention also relates to a method for producing a heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel, comprising the steps of providing an inner wall made of heat conducting material, surrounding the heat source, being thermally connected with the heat source and having the shape of a surface of 20 revolution, providing an outer wall, being concentric to the inner wall, wherein the distance between both walls is substantially constant, providing between both walls at least one helical first conduit through which the first channel extends and permanently deforming said at least one conduit to clamp it between both walls by subjecting the inner of the conduit to a pressure.

25

Preferably the method as referred to above is followed by the steps of connecting a substantial cylindrical part of a header to the outer wall by a surrounding U-shaped profile, guiding the conduit through the substantial cylindrical part of the header and subsequently connecting the flange shaped part of the header to the inner wall and the 30 substantial cylindrical part of the header.

Subsequently the present invention will be elucidated with the help of the following drawings, wherein: 5

Figure 1: depicts the half of a cross section of a heat exchanger according to the present invention;

Figure 2: depicts a diagram for elucidating the invention;

Figure 3: depicts a detailed view of a header, being a part of the heat exchanger 5 depicted in figure 1; and

Figure 4: depicts a detail of the header depicted in figure 3.

The heat exchanger according to the invention is preferably though not exclusively adapted to be mounted in a boiler for a central heating installation for domestic use. The 10 heat exchanger 1 depicted in figure 1 comprises a cylindrical inner wall 2, and which is provided at its inner side with fins 3 to increase the heat transfer surface between a heat source located surrounded by the inner wall 2, like a gas burner not depicted in the drawings. Preferably the inner wall is from cast material like cast aluminium.

Concentric with the inner wall 2 and to the outer side thereof an outer wall 4 is 15 provided. This outer wall may be made of steel sheet, although other materials may be used.

Between the inner 2 and the outer walls 4 a cylindrical gap 5 is located. According to the invention in the gap 5 a helical wound copper pipe 6 has been provided. Instead of 20 copper other materials can be used. The copper pipe 6 is clamped between the inner and outer walls 2, 4. The copper pipe 6 has been fixed by the following process. Initially the copper pipe 6 is helically wound on a mandrel to obtain its helical shape, although other methods to obtain a helical shape are not excluded. After removal from the mandrel the helical pipe 6 is inserted into the gap between the inner and outer walls. It is noted that 25 the pipe 6 can easily be inserted into the gap 5 and be positioned to obtain its proper position. A first channel 8 extend through the pipe 6. When the correct position between the inner 2 and the outer 4 walls have been reached one of the ends of the pipe 6 is closed, for instance by applying a stopper, after which a substantial pressure through a fluid like a gas or a liquid is applied to the internal side op the pipe, and indeed so much 30 pressure that the pipe expands. This in continued to a pressure wherein the expansion of the pipe 6 is such that it is clamped between the inner 2 and outer walls 4. Care must be taken that the deforming of the pipe 6 is permanent so that the pipe remains in shape when the pressure is taken away. Although in the preceding lines the use of a round pipe is assumed, other cross sections are not excluded.

6

The winding of the pipe 6 on the mandrel takes place such that the pitch of the winding is larger than the size of the pipe in the axial direction of the helical winding. Expressed otherwise the pitch is such that there is space between adjacent turns of the winding so 5 that enclosed between the inner and outer walls of the heat exchanger and adjacent turns of the pipe 6 a second channel 7 is formed, which channel 7 also has a helical shape.

The second channel 7 can be used for conducting a second fluid circuit. This offers the possibility to provide a heat exchanger 1 with two independent channels 7, 8 through 10 which fluid for heating may flow. When the heat exchanger is used as a domestic boiler, one of the channels 7, 8 can be used as a channel for heating tap water while the other channel 8, 7 can be used for heating central heating water. The tap water is then preferably conducted through the channel 8 extending through the copper pipe 6.

15 For feeding and draining the fluids to and from the channel in the pipe 5 and the channel 7 enclosed by the pipe 5, the heat exchanger comprises a first header 10 located at the top of the walls 2, 4 and a second header 11 located at the bottom of the walls 2, 4.

The upper header 10 is depicted in figure 3 in more detail. The header 10 is composed 20 of a flange shaped part 11 and a cylindrical part 12. The flange shaped part 11 is located on top of and in contact with the inner wall 2, and it comprises a skirt 13 extending in the downward direction, which extends adjacent to the inner wall 2. A groove 14 has been provided in the inner side of the skirt 13 and an O-ring has been located in the groove 13 to obtain a proper sealing. The cylindrical part 12 is located 25 adjacent to the top of the outer wall 4. The top of the outer wall 4 is fold over to the outside to form a nose 16. At its lower side the cylindrical part comprises a nose 17. A U-shaped profile 20 extends around both noses 16, 17 and it connects the cylindrical part 12 of the header 10 to the outer wall 4. The U-shaped profile 20 is tensioned by a clamp not depicted in the drawings. At the lower side of the nose 17 of the cylindrical 30 part 12 a groove 18 has been provided in which an O-ring 19 is located for sealing. The flange shaped part 11 and the cylindrical part 12 of the header 10 are mutually connected by a bolt connection. Also here a groove 21 and an 0-ring 22 have been provided in the flange shaped part 11 to provide sealing.

7

The headers serve to provide connections between the channels 7, 8 and the conduits outside. Therefore the upper header 10 comprises an aperture 23 with a connection for an external conduit which connects said conduit to the inside 24 of the upper header 10. The pipe 6 is guided to a connection piece integrated in the header 10, but which is not 5 depicted in the drawing. A similar construction is present in the lower header 11, which will be described with the help of figure 4. The lower header 11 comprises, just as the upper header 10 both a flange shaped part 31 and a cylindrical part 32. The construction thereof is substantially similar to that of the upper header 11. In the cylindrical part 32 of the lower header 11a connection socket 33 has been provided which is connected 10 with the pipe 6. the socket 33 further leads to a connection for an external conduit. It will be clear that the lower header is further provided of a connection for the second channel 7 on a similar way as is present in the upper header 10.

It is noted that the headers are only described in so far as relating to the invention. It 15 will be clear that there are other differences between the upper and lower headers in relation to the heat source, like a gas burner present within the cylindrical wall 4.

20 25 30

Claims

What is claimed is: 1. A heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel, comprising an internal wall of thermally good conductive material which extends around the heat source and is made of thermally conductive material. surface of rotation, an external wall concentrically arranged around the inner wall, the distance between the first and second wall being substantially constant, and a first pipe extending between the two walls through which the first channel extends and wherein the first pipe is in thermal contact with at least the internal wall is placed.

2. A heat exchanger as claimed in claim 1, characterized in that the internal and the external wall are both cylindrical and the first conduit extends helically between the internal and the external wall.

3. A heat exchanger according to claim 1 or 2, characterized in that the first conduit is placed contiguous to the internal and the external wall, that the pitch of the winding of the first conduit is greater than the dimension in axial direction of the cross-section. of the first conduit so that a helical second channel is enclosed between the turns of the first conduit.

4. A heat exchanger as claimed in claim 1 or 2, characterized in that a second pipe wound bifillarly with the first pipe extends between the inner and the outer wall, in which second pipe a channel extends and that the second pipe adjoins extends the internal and external wall.

5. A heat exchanger according to any one of the preceding claims, characterized in that the at least one pipe is clamped between the inner and the outer wall by deformation of the at least one pipe.

A heat exchanger according to claim 5, characterized in that the at least one conduit is deformed by subjecting the interior of the conduit to pressure, which pressure is sufficiently large to permanently deform the conduit such that it is located between the internal and external wall is clamped.

A heat exchanger according to claim 6, characterized in that the pipe is made of copper or stainless steel.

8. A heat exchanger according to any one of claims 3-7, characterized in that a connecting head is placed at both ends of the heat exchanger and in that the conduit through which the first channel extends extends through both connecting heads to outside the heat exchanger and that both connecting heads are provided with connecting means for the second channel.

9. A heat exchanger according to claim 8, characterized in that at least one of the connecting heads comprises a substantially flange-like first part and a substantially cylindrical second part, the flange-like part being connected to the inner wall, the substantially cylindrical part being connected to the outer wall and that the conduit through which the first channel extends extends through the substantially cylindrical portion.

A heat exchanger according to claim 9, characterized in that the substantially cylindrical part of the connecting head is connected to the external wall by means of an all-round U-shaped profile and that the U-shaped profile is provided with a clamping clamp.

A heat exchanger according to claim 10, characterized in that the substantially flange-shaped part is provided with a connecting surface for connecting at least two appendages.

12. Heating boiler for heating water for space heating and tap water, which is provided with a space heating water circuit and a tap water circuit, characterized in that the heating boiler is provided with a heat exchanger according to one of the preceding claims, wherein the first channel of the heat exchanger is connected to the DHW circuit and the second channel of the heat exchanger is connected to the space heating water circuit.

13. A method for manufacturing a heat exchanger for transferring heat from a heat source to a fluid flowing in a first channel, comprising the following steps: 5. applying a comprising a thermal source with the heat source extending around the heat source connected internal wall made of thermally conductive material; - arranging an external wall extending around the inner wall; 10. arranging at least one helically extending first conduit between the two walls through which the first channel extends; and - permanently deforming the at least one conduit until it is clamped between the interior and exterior walls by applying pressure to the interior of the at least one conduit. 15

14. Method as claimed in claim 13, characterized in that subsequently a substantially cylindrical part of a connecting head is connected to the external structure by means of an all-round U-shaped profile, the pipe being arranged in the substantially cylindrical part of the connecting head 20, the flange-shaped part of the connecting head is then connected to the internal wall and to the substantially cylindrical part of the connecting head.