Patent Publication Number: US-2012031594-A1

Title: Heat Exchanger and Fin Suitable for Use in a Heat Exchanger

Description:
The present invention relates to heat exchanger for use in a heating appliance. The invention further relates to a fin for use in such a heat exchanger. 
     Usually, a heating appliance or, in other words, a central-heating boiler is used for heating a house. In addition to heating the house, such a boiler frequently also supplies hot tap water. In addition to that, there are heating appliances which only provide hot tap water. Heating appliances generally use gas for heating the water for the heating system or tap water. Air is heated by a gas burner, and the heated gas is passed through a heat exchanger for heating the liquid that is also being passed through the heat exchanger. 
     The object of the present invention is to provide an efficient, versatile, compact and/or easy to produce heat exchanger for use in a hot water and/or heating appliance. 
     According to the invention, in order to accomplish that object, there is provided a heating appliance comprising a channel for conveying a heated gas in a longitudinal direction of said channel and a multitude of fins for conveying a liquid, said fins being provided with an inlet and an outlet, which open in a common plane, wherein the fins are provided on a wall of the channel, extending into said channel, wherein the inlets and outlets of the fins open in the plane of the wall and wherein the heat exchanger further comprises connecting elements for connecting at least one outlet to at least one inlet of separate fins. In this way a very efficient heat exchanger is provided, which, in addition, is easy to adapt and to manufacture. The fins, which form the channel or a flow path for the liquid to be heated, open in the wall of the channel with their inlets and outlets, so that the fins are very easy to connect in series using the connecting elements. The wall of the channel is to that end provided with suitable passages, which connect to the inlets and outlets of the fins. The connecting elements are preferably provided on the wall of the channel and extend over at least one outlet and at least one inlet of separate fins. 
     The use of several fins extending into the channel, through which hot gas is passed, obviates the need to use relatively large channels for realising an efficient heat transmission between the gas and the liquid. By connecting several fins in series by means of the connecting elements, an efficient heat exchange is realised in a compact manner. 
     It is advantageous if the connecting elements are designed for interconnecting inlets and outlets of at least two separate fins. Two fins are connected in parallel in that case. If a flow channel in a fin should become obstructed, the other fin will be able yet to provide a continued flow of the liquid. The two parallel-connected fins can subsequently be connected in series with yet further fins, which are also connected in parallel. 
     In a preferred embodiment of a heat exchanger according to the invention, a connecting element is made of a plate-shaped element provided with upright edges, said connecting element being designed to form a watertight enclosure around at least one inlet and at least one or outlet extending in the plane of the wall. Since the inlets and outlets of the fins open in the plane of the wall of the channel, an efficient connection can be realised by realising a watertight enclosure of the inlets and outlets to be interconnected. The connection between an inlet and an by realising a watertight enclosure of the inlets and outlets to be interconnected. The connection between an inlet and an outlet is in that case made up of the wall of the channel and the plate-shaped connecting element provided with the edges. 
     In another preferred embodiment of a heat exchanger according to the invention, a fin is plate-shaped, with the plane of the thin extending in the longitudinal direction of the channel. The fin functions as a guide for the liquid, at least substantially in a plane oriented transversely to the flow direction of the gas. This results in a very efficient heat exchange between the heated gas and the liquid in the fins. 
     In another preferred embodiment of a heat exchanger according to the invention, a fin comprises an at least substantially U-shaped flow path. The inlet and the outlet extend at the ends of the legs of the U-shaped flow path in this embodiment. In this way a simple and efficient fin is provided. 
     According to the invention, a fin comprises a double-walled element, with the flow path being formed by interconnecting the walls along the circumferential edge, except along a connecting edge for forming the inlet and the outlet, with the walls furthermore being interconnected from the connecting edge between the inlet and the outlet in a direction transverse to the connecting edge along a predetermined length so as to form the flow path, preferably a U-shaped flow path. If, for example, a rectangular double-walled element is used as the starting material, walls of three of the four edges are connected to each other, forming an envelope, as it were, with the connecting edge forming the opening. Said connecting of the walls to each other can be done by welding, for example. By providing a connection between the walls, preferably from the centre of the connecting edge, which connection extends up to a location spaced some distance from the opposite wall, a flow path is provided which extends in a U-shape between an inlet and an outlet. This connection divides the connecting edge into an inlet and an outlet. 
     It is also possible to provide several connections between the walls besides the connection from the connecting edge. In this way it is possible to create a flow path in the fin which follows a more meandering route through the fin. It is furthermore possible to provide a connection provided with corners for that purpose, in which two parts of the connection extend at an angle to each other. 
     The fin is preferably made of metal plate material having a thickness of between 0.4 and 1.5 mm, more preferably between 0.5 and 1.0 mm, even more preferably a thickness of about 0.6 mm. This provides sufficient rigidity, whilst also an adequate heat exchange is provided. The fin is preferably made of (stainless) steel or aluminium. 
     The surface of the channel to which the fins are connected is preferably made of plate material, for example steel or aluminium, having a thickness of between 0.8 and 2.5 mm so as to provide additional rigidity. 
     In another preferred embodiment of a heat exchanger according to the invention, a multitude of fins extend in a transverse direction perpendicular to the longitudinal direction of the channel, parallel to the plane of the wall. In this embodiment the fins are arranged in a row, which extends transversely to the longitudinal direction, and thus to the flow direction of the gas. Since the fins are preferably plate-shaped, a large area is provided for heat exchange between the gas and the liquid. Preferably, such a row consists of a multiple of at least two fins, making it possible to provide the parallel connection as already mentioned before. It is moreover advantageous if a multitude of fins extend in the longitudinal direction of the channel. In this way the heat of the gas flowing past is optimally utilised. 
     The connecting elements are in that case preferably designed for first connecting the fins that extend in the transverse direction in series with each other and subsequently connecting the rows of fins thus formed in series in longitudinal direction. When different fins are being connected in series, the fins are first connected in transverse direction, and subsequently the rows thus formed are connected in longitudinal direction. Preferably, the connecting elements are designed for guiding the liquid first through the row downstream of the heated gas and subsequently through the row of fins upstream of the heated gas. Thus the liquid first flows through the row located furthest away from the heat source, for example the burner. Subsequently, the liquid flows through the row on the side of the burner. It has been found that this results in a very efficient heat exchange. 
     In another preferred embodiment of a heat exchanger according to the invention, the channel comprises guide means for guiding the heated air in longitudinally undulating fashion through the channel. By passing the gas in undulating fashion through the channel, an enlarged contact area between the fins and the heated gas flow is provided. The guide means preferably comprise at least one baffle, which extends in the transverse direction of the channel on a wall of said channel. The baffle, and preferably several baffles, in that case function to guide the gas. The baffles are preferably arranged in spaced-apart relationship on opposite walls of the channel. The heated gas flow will thus zigzag between the baffles. Preferably, the baffles are provided on the walls to which the fins are connected and on the wall that extends parallel thereto. 
     More preferably, at least one baffle is comb-shaped and extends between the fins extending in the transverse direction. By designing a baffle to have a comb-shaped configuration, i.e. provided with recesses for accommodating a fin, the baffle can be placed at the location of a row of fins. As a result, the location of the guide means is not limited to the space between rows of fins. 
     The invention further relates to a fin and to a connecting element for use in a heat exchanger according to the invention. 
    
    
     
       The invention will now be explained in more detail with reference to figures illustrated in a drawing of a preferred embodiment of the invention, in which: 
         FIG. 1  is a schematic, perspective view of the heat exchanger; 
         FIG. 2  is a schematic, cross-sectional view of the heat exchanger; 
         FIGS. 3 and 4  are schematic, cutaway views of the heat exchanger; 
         FIGS. 5   a  and  5   b  are schematic views of fins; and 
         FIG. 6  is a schematic view of a baffle 
     
    
    
     In  FIG. 1  a heat exchanger a  1  for use in a heating appliance, such as a central heating boiler, is schematically shown. The heat exchanger  1  has an inlet  3  for introducing liquid to be heated and an outlet  2 , from which the heated liquid flows. A burner is provided for heating the liquid, a holder  4   a  of which burner is shown in the figure. An exhaust  5  is provided for discharging the flue gases from the burner after said gases have given off heat to the liquid. 
     In  FIG. 2  the heat exchanger  1  is shown in cross-sectional view. The heat exchanger  1  comprises a channel  10  for guiding a heated gas (schematically indicated at  41 ) in a longitudinal direction I. A burner  4  is provided for heating the gas. Disposed in the channel  10  are a multitude of fins  6 , which fins extend into the channel  10 . The water to be heated is passed through the fins  6 . The flow direction of the water is schematically indicated at  42 . The flow direction  42  of the water is opposite to the flow direction  41  of the gas. As shown, the fins  6  have a U-shaped flow path. 
     The fins  6  are arranged on a wall  11  of the channel  10 , such that the inlets and outlets of the fins open into said wall  11 . To interconnect the fins, connecting elements  7  are provided, as will be discussed in more detail hereinafter. 
     Guide means in the form of baffles  8   a  and  8   b  extend into the channel  10  as well. Said guide means are mounted to the walls  11  and  12  of the channel  10  and provide an undulating flow of the gas  41  through the channel  10 . The zigzag movement of the gas leads to a very efficient heat transmission between the gas and the liquid in the fins. The baffles  8   a  and  8   b  extend over the entire width of the channel  11 . In order to make it possible to place baffles  8   a  at the location of the fins  6  as well, the baffles are comb-shaped, as is shown in  FIG. 6 . The baffles  8   a  are provided with recesses  81 , in which the fins  6  are accommodated with a close fit. 
     As  FIG. 3  clearly shows, a multitude of fins  6  are present in the channel  10 . The fins  6  are arranged in two rows  101  and  102 . In this embodiment, each row comprises twenty-one fins  6 , seen in the transverse direction II. The fins  6  are configured and provided on the wall  11  of the channel  10  in such a manner that the inlets  61  and the outlets  62  of the fins  6  open and extend in the plane of the wall  11 . The fins  6  are welded to the wall  11 . 
     A connecting element  71  is provided for connecting the outlets  62   a  of a fin  6   a  to the inlets  61   b  of a fin  6   b . Said connecting element  71  is formed by a plate-shaped element provided with upright edges, which forms a watertight enclosure of the three outlets  62   a  and the three inlets  61   b . The fins  6  are connected in parallel in clusters  103  of three fins each so as to prevent any clogging problems. The connecting element  71  is provided for interconnecting the two rows  101  and  102 . A connecting element  72  is for example provided for interconnecting fins in a single row  101 . The connecting elements  7  are welded to the wall  11 , so that a watertight connection is provided. 
     It will be understood that a configuration as shown in  FIG. 3  makes it possible to realise a very efficient interconnection of the fins by selectively connecting the inlets to the outlets. Using the connecting system, it is furthermore very easy to use several rows of fins  6 , or to connect more or fewer fins  6  in parallel. Thus it is advantageous, for example in the case of more compact appliances, to connect two fins in parallel. 
     In  FIG. 4  a preferred embodiment of such a connection is shown, in which the flow of the liquid through the connecting elements  7  is indicated by a line  42 . The gas flows in the longitudinal direction I, so that the liquid first flows through the row  102  and subsequently through the row  101 , after which it is discharged from the outlet  2 . 
     In  FIG. 5   a  a first fin  6  according to the invention is shown. A fin  6  is a double-walled plate-shaped element, as is clearly shown in  FIG. 3 , for example. The walls of the double-walled element are connected at the circumferential edges  63 , with the exception of a connecting edge  66 . A connection  64  is provided at the centre of the connecting edge  66 , which divides the connecting edge  66  into an inlet  61  and an outlet  62 . The connection  64  extends as far as a location spaced from the upright edge  63  by a distance III, so that a U-shaped flow path is formed. A stiffening rib  65  is provided so as to impart additional rigidity. The walls of the thin  6  are made of steel plate having a thickness of 0.6 mm. 
       FIG. 5   b  shows a variant in which the U-shaped flow path comprises an additional bend. To that end a further connection  64  is provided between the walls of the plate-shaped element. In addition, an edge  63   a  is additionally connected in comparison with the embodiment shown in  FIG. 5   a . The connection  64  divides the connecting edge  66  into an inlet  61  and an outlet  62 , and in this embodiment the connection  64  has corners. The additional connection  64  thus provides an additionally meandering flow path. 
     It is noted that the invention is not limited to the embodiments shown herein, but that it also extends to other preferred variants that fall within the scope of the appended claims.