EP2457054A1

EP2457054A1 - Heat exchanger in particular for solar applications, with improved design

Info

Publication number: EP2457054A1
Application number: EP10802502A
Authority: EP
Inventors: John Mills; Kevin Hartley; Peter Kerr
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 2009-07-22
Filing date: 2010-06-30
Publication date: 2012-05-30
Also published as: EP2457054A4; WO2011010931A1

Abstract

Heat exchanger in particular for solar heat applications. The heat exchanger is composed of one or more, preferably plate-like, flat elements (2) each with one or more integrated tubes (3) with channels (13) for a heat exchanging fluid. The elements (2) are each at their respective ends interconnected by means of inlet, respectively outlet manifolds, or manifold tubes (4). Each of the ends of the plate-like element (2) with the integral tube (3) is formed by cutting alongside the integral tube (3) making recesses (6) on each side of the tube (3) and notches (7) forming two or more tabs (8, 9) stretching beyond the tube (3) and which are bent and formed such that the resulting, projecting shape (10), conform closely to the outside profile of the manifold tube (4) making the solution self-jigging, easy to assemble and with accuracy and high performance.

Description

Heat exchanger in particular for solar applications, with improved design

The present invention relates to a heat exchanger, in particular for solar heat applications, composed of one or more heat absorbing (collecting) elements, preferably flat elements, each with one or more integrated tubes with one or more channels for a heat exchanging fluid.

Solar heating harnesses the power of the sun to provide solar thermal energy for different purposes such as solar hot water, solar space heating/cooling and solar pool heaters. A solar heating system saves energy, reduces utility costs, and produces clean energy.

The efficiency and reliability of solar heating systems have increased dramatically, making them attractive options in connection with energy supply to private houses as well as in stores, office spaces, industrial plants and process heating.

Most solar water-heating systems for buildings have two main parts, namely a solar collector and a storage tank. Solar water heaters use the sun to heat either water or a heat-transfer fluid in the collector. Heated water is then held in the storage tank ready for use, with a conventional system providing additional heating as necessary. The tank can be a modified standard water heater, but it is usually larger and very well insulated. The most known collector used in solar hot water systems is the flat plate collector. But other types of collectors are known as well such as the individual element based solution composed of a number of flat elements each with one or more integrated tubes. The present invention is, as stated above, related in particular to solar thermal type heat exchanger, but the principle of the invention may as well be used in any heat exchanging situation where there is a transfer of heat from a component including a channel circulating a fluid to another component or vice versa.

From the applicant's (patentee's) own Norwegian patent application No.

20091877 is known a process for making a heat exchanger unit comprising a number of parallel tubes with channels for a heat exchanging fluid and a heat conductive plate, the tubes being integrated in the plate. The process comprises the extrusion of a suitable metal, preferably aluminium, whereby the plate and the tubes are formed in one step. Preferably the plate is extruded in a nearly circular fashion, and after extrusion, the plate is reshaped into the required or wanted shape.

There is a gap between the plate-like part of the collector and the manifold into which it is connected. This raises several concerns about ease of manufacture and product efficiency.

When inserting the tube part of the plate into holes made to receive this into the manifold tube, there is possibility for over or under inserting into the manifold and also maintaining the plate-like part and the manifold in the same plane. This will create difficulties in joining the parts together, whether by brazing, welding, gluing or other method of fixturing.

Obviously, over-insertion of the tube into the manifold tube will result in restriction to fluid flow in the manifold tube and could affect the efficiency of the assembled part in its function to circulate the heat transfer fluid in the heat exchanger /solar collector.

Likewise, under-insertion of the tube into the manifold will result in potential leakage of the heat transfer fluid from the assembly. Furthermore, if the plate- like parts are not in the same plane as the manifold tube, then their orientation towards the sun will not be optimised and will affect the performance of the heat absorber. A further imperfection in the efficiency of the performance of the solar absorber lies in the gap between the manifold and the plate-like part of the absorber tube. When the efficiency of such an absorber is measured, the total dimension of the unit, including the manifold tube is taken into account.

Clearly, the aforementioned gap in the assembly has a negative impact on overall thermal performance and efficiency.

To overcome these drawbacks to the current solution known from the applicant's abovementioned application, the heat exchanger is modified as defined in the attached independent claim 1.

The independent claims 2 - 4 define preferred embodiments of the invention.

The present invention will be further described in the following by means of examples and with reference to the drawings where:

Fig. 1 shows an example of a partly assembled heat exchanger of the known type mentioned above, seen in perspective view,

Fig. 2 a) shows in larger scale a top view of a end part of a flat element of the type shown in Fig.1 , but with the modifications according to the present invention, b) shows a cross sectional view of the same element,

Fig. 3 shows a side view of the flat element shown in Fig. 2, but with the end tabs being bent to a semi circular shape, Fig. 4 a) shows a manifold tube and bent element with semi circular shape as shown in Fig. 3, prior to assembly and b) after assembly,

Fig. 5 shows an example of a partly assembled heat exchanger according to the present invention, in perspective view.

Fig. 1 shows as stated above a perspective view of an example of a heat exchanger 1 according the present invention which is especially designed to be used for solar heat collection (solar heat absorption). The heat exchanger 1 may be composed of one or more plate-like, flat elements 2, each element being provided with one or more integrated tubes 3 with channels 13 capable of carrying a fluid absorbing and transporting the heat generated in the flat element 2 to the desired destination, a heat storage, hot water tank etc.. Each element 2 of the heat exchanger 1 is treated and/or coated such that the surface has high solar absorbance and low thermal emissivity and at the same time high corrosion resistance. The heat exchanger may be made of any suitable material, but preferably a metal with good thermal conductance such as aluminium or copper or a combination of these, such as a flat element 2 made of aluminium and a tube made of copper braced to it (see later section).

Fig. 1 shows an example with two elements 2 with integrated tubes 3 where the elements are interconnected by means of inlet, respectively outlet manifolds 4 (here in the form of tubes), the manifolds in turn being provided with connectors to be connected to the required piping (not further shown). As stated above and as can be visualized from Figure 1 , there is a gap 5 between the plate-like part of the collector and the manifold into which it is connected.

When inserting the tube 3 of the plate-like element into holes made to receive this into the manifold tube 4, there is a possibility for over or under inserting into the manifold and also maintaining the plate-like element and the manifold in the same plane. This will create difficulties in joining the parts together, whether by brazing, welding, clueing or other method of fixturing.

As stated above, Fig. 2 a) and b) shows an end part of a flat element 2 with the modifications according to the present invention. The integral tube 3 and each of the ends of the plate-like element 2 is formed by cutting of the profile alongside the integral tube making recesses 6 on each side of the tube 3 and by notching 7 of the plate-like element to form tabs 8, 9 stretching beyond the tube 3.

Figure 3 shows how the notched tab parts 8, 9 of the profile shown in Fig. 2 are bent and formed (fabricated) such that the resulting semi circular form of the projections 10 conform closely to the outside profile of the manifold tube 4. Furthermore, it is shown that these projections 8, 9 (10) are preferably formed in pairs where each tab 8, 9 in a pair is formed as a mirror image of the other. Preferably there are two such tab projections 8, 9 on each side of the fluid carrying integral tube but more are possible.

Fig. 4 a) and b) shows how the semi circular shaped ends 10 of the plate-like element 2 can then be assembled with the manifold tube. The formed tabs 8,9 shown in Fig. 3 clip onto the manifold tube and the tube 4 of the plate-like element 2 is inserted into holes 12 (see Fig. 4 a) prepared in the manifold tube at predetermined intervals such that a collector can be made utilizing several such plate-like elements. Fig. 5 shows an example of a partly assembled heat exchanger according to the present invention, in perspective view.

By reference to Figs. 4 and 5 it can be seen that the profile and manifold become self-jigging and will not twist from the intended plane. Furthermore, it becomes possible to ensure that the insertion depth of the tube part of the plate-like profile can be inserted into the manifold to optimum depth by trimming the length of its projection to suit the dimensions.

The self-jigging feature renders the assembly ready for fixturing by glueing, welding or brazing.

Furthermore, it can be seen that the connection of the tab parts of the wings to the manifold tube will enhance heat transfer and thereby improve efficiency of performance over the design shown in figure 1.

The invention as defied in the claims is not restricted to the example shown in the drawings and explained above. Thus, for instance the manifolds may have a shape departing from the circular, pipe shape. Further, the flat plate like element with the integral pipe may be manufactured from separate

components (pipe and sheet material), being welded, braced or glued together rather than being made from an extruded profile.

Claims

1. Heat exchanger, in particular for solar heat applications, composed of one or more, preferably plate-like, flat elements (2) each with one or more integrated tubes (3) with channels (13) for a heat exchanging fluid, where the elements are each at their respective ends

interconnected by means of inlet, respectively outlet manifolds, or manifold tubes (4)

characterised in that

each of the ends of the plate-like element (2) with the integral tube (3) is formed by cutting alongside the integral tube (3) making recesses (6) on each side of the tube (3) and notches (7) forming two or tabs (8, 9) stretching beyond the tube (3) and which are bent and formed such that the resulting, projecting shape (10), conform closely to the outside profile of the manifold tube (4).

2. Heat exchanger according to claim 1 ,

characterised in that

the projecting shape (10) is semi circular corresponding to a manifold tube (4) with circular shape.

3. Heat exchanger according to claim 1 ,

characterised in that

the insertion depth (11 ) of part of the tube (3) of the plate-like profile entering into the hole (12) of the manifold (4) is adjusted to optimum lenght by trimming the depth of the recesses (6) and the bending of the projection.

4. Heat exchanger according to claim 1 ,

characterised in that

the plate-like elements (2) are attached to the manifolds by gluing, welding or brazing.