Metallic porous body incorporated by casting into a heat exchanger

Abstract

The present invention relates to a co-cast heat exchanger element intended for a central heating boiler, which heat exchanger element is made from substantially aluminum, the heat exchanger element being provided with walls which enclose a water carrying channel, and with at least one wall which encloses at least one flue gas draft to which a burner can be connected, at least one wall which encloses the at least one flue gas draft being water-cooled in that it also forms a boundary of the water-carrying channel, while one of the water-cooled walls is provided with heat exchanging surface enlarging pins and / or fins which extend in the respective flue gas draft and is also provided with other heat exchanging surface enlarging metallic porous structures.

Description

TECHNICAL FIELD[0001]The present invention relates to a co-cast heat exchanger element intended for a central heating boiler, which heat exchanger element is made from substantially aluminum, the heat exchanger element being provided with walls which enclose a water carrying channel, and with at least one wall which encloses at least one flue gas draft to which a burner can be connected, at least one wall which encloses the at least one flue gas draft being water-cooled in that it also forms a boundary of the water-carrying channel, while at least one of the water-cooled walls is provided with heat exchanging surface enlarging pins and / or fins which extend in the respective flue gas draft and is also provided with other heat exchange surface enlarging metallic porous structures.[0002]The present invention also relates to a method for obtaining such a co-cast heat exchanger element and its use in a central heating boiler.BACKGROUND ART[0003]A heat exchanger according to above describ...

AI Technical Summary

Benefits of technology

The invention provides a heat exchanger element for a central heating boiler that is compact and has low weight. The heat exchanger element is made from aluminum and has a flat design with wide flue gas draft. It uses shorter and smaller pins and fins as heat exchange surface enlarging structures, which allows for efficient cooling and transfer of heat to the water-cooled walls. The heat exchanger element has a one-piece water channel core, which simplifies the manufacturing process. The metallic porous body incorporated in the heat exchanger element provides a good metallic bond and is surrounded by the melt, creating a big contact surface that enhances heat transfer and extracts even more heat from the flue gases. The heat exchanger element can be manufactured quickly and efficiently. Additionally, the invention suggests using flue gas draft with two opposite walls having pins with a cross sectional surface smaller than 25 mm2 to increase the efficiency of the central heating boiler.

Problems solved by technology

The use of such a heat exchanger element on its own in a boiler is not possible as the metallic foam would melt by the heat of the flue gases.

On the other hand, casting of complex structures together with the already complex open cell foam body (as an example of a metallic porous structure) is a rather difficult job, resulting in a lot of scrap and waste.

But the effective quality of these bonds is not always satisfactory.

One can achieve a proper mechanical bond between a porous aluminium body and a solid metal carrier, by, for example soldering, but as this method uses an extra material, heat dissipation from carrier to porous structure, or the other way around can be distorted and the extra material, e.g. Zn, can give corrosion problems at the bonding place and even have the effect of a thermal insulating layer.

It also gives an end product which is limited in use for heat applications, i.e. limited by the melting temperature of Zn in the solder.

When these aluminium-oxides are not sufficiently removed, no good heat conduction bond can be obtained.

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