DE9420878U1 - Gas condensing boiler - Google Patents

Description

Steffen Möller, Mühlenbeker Str. 9, 25548 Kellinghusen

Gas condensing boiler

The invention relates to a gas condensing boiler with an aluminum heat exchanger through which heating water flows and arranged in the exhaust gas flow of the gas burner.

Gas condensing boilers, especially their heat exchangers, are increasingly made of aluminum, which achieves better heat transfer than, for example, gray cast iron. The heat transfer is approximately four times higher than with gray cast iron. Furthermore, the heat exchangers are relatively light, making them easy to transport and are more economical than conventional metals .

1966

Bremen: Berlin: Munich: Leipzig: Dusseldorf: Kiel: Hollerallee 32, D-28209 Bremen Uhlandstrasse 173/174 Franz Joseph Street 38 Philipp-Rosenthal-Street 21 Nelilerstrasse 5 Niemannsweg 133 Posti. 10 71 27. D-28071 Bremen D-10719 Berlin .. . PiSOSOLMfinchejj _{#### #} D-04103 Leipzig D-40593 Dusseldorf D-24105 Kiel Telephone (04 21) 3 40 90 Telephone (0 5O)3i iS3 5o#>6» *TeI(J)IJm ((J ⁸ ^i*0 SO.* '.Ji-Iephon (03 41)960 29 77 Telephone iO2 Hl 71 S9 83 Telephone (04 31) 8 40 75 Fax (04 2!) 3 49 17 68 Fax (0 501 !&Lgr;&Bgr; JTCW J' &bull; TeWa.* (»8») 34<F0 1«
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BOEHMERT & BOEHMEIfI^ NÖRjDBMA^J jjnd PARTNER

They are corrosion-resistant because a passivating oxide layer forms on the aluminum.

However, in some heating systems where the heating water has a higher pH value, additives must be added to reduce the pH value to below 8.5. However, these additives wear out over time, with the old iron radiators in some heating circuits in particular having a negative effect on the pH value of the water.

The invention was therefore based on the object of creating a heat exchanger for a gas burner that has a longer service life because it is better protected against aggressive media influences.

According to the invention, the object is achieved by a gas condensing boiler with the features listed in the main claim.

What is particularly advantageous here is that the chemical nickel layer applied means that the previously existing voltage series between the exposed iron surface of a radiator and the aluminum and aluminum-silicon surface of a heat exchanger is no longer shifted to the detriment of the thin-walled heat exchanger with the less noble material. In fact, the nickel coating has significantly reduced an electrochemical voltage, since both iron and nickel are cation formers at the assumed temperatures.

Despite opposing thermoelectric voltages (iron 1.8 mV, nickel -1.5 mV), the property of both metals as cation formers results in corrosion.

BOEHMERT & BOEHMERT, NCRDEMABTN: 4th PARTNER

resistance of the heat exchanger surfaces, which is significantly increased.

In particular, if there are additional plastic pipes in the heating circuit, e.g. underfloor heating, through which oxygen can get into the heating water, a decisive improvement in corrosion resistance is achieved, as is the avoidance of a thick oxide layer of heat transfer values in the heat exchanger.

Because a smoother surface is achieved, less lime and oxide deposits will settle at the point of heating in the heat exchanger and the heating pump will be protected. All areas of the heat exchanger will be evenly supplied with water.

The application of nickel to the outside of the heat exchanger is also particularly recommended in the event that the intake of combustion air is sucked in as secondary air in a chimney through which a flue gas discharge pipe is led. Such chimneys have so far mostly been used by oil heating systems and contain a large amount of sulphurous residues, which, particularly in damp weather, form sulphurous, acidic compounds that enter the combustion chamber as intake air.

Sulphurous compounds will therefore form in the exhaust gases, which, particularly at low heating water temperatures, will lead to condensate containing sulphuric acid settling on the outside of the heat exchanger. This condensate is so chemically aggressive that it attacks the passivating aluminium oxide layer. A galvanic coating with chemical nickel

BOEHMERT &

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On the one hand, the smoother surface will lead to a faster drainage of the condensate, dripping downwards, and on the other hand, it will increase the corrosion resistance.

Due to the improved corrosion resistance against aggressive heating water, it is also possible, in the event that an additive is added to the heating water with water hardness >18°dH, the heat exchanger is no longer exposed to the risk of damage as before.

The nickel coating is preferably carried out by galvanic application of chemical nickel, in which several acids are first pumped through the heat exchanger to prepare the inner surfaces of the heat exchanger, then a galvanizing solution from which the nickel is evenly deposited on the inner surface of the heat exchanger, whereby at the same time a smoothing of the pores in the aluminum is possible.

A layer of at least about 0.3 μια is advantageously proposed. With regard to passivation of the outsides by galvanization with nickel, it is proposed that this should also be applied to the premix burner and that it should be provided in particular in cases where chimneys can be used to draw in combustion air, into which oil heating systems previously emitted sulphurous exhaust gases. In particular in the case of oil heating systems that have been in existence for a very long time, in addition to the problem of long storage times, there is also the problem that previous heating oil qualities contained significantly more sulphur.

Claims (3)

BOEHMERT & BOEHMERT, NORDEMANN and PARTNER ·· ·· · ·· ·· · M 5082 CLAIMS 1. Gas condensing boiler with a heat exchanger made of aluminum or aluminum-silicon through which heating water flows and arranged in the exhaust gas flow of the gas burner, characterized by a galvanic nickel coating on the inside and/or outside of the heat exchanger. 2. Gas condensing boiler according to claim 1, characterized in that a nickel coating consists of chemical nickel electroplated onto the finished heat exchanger by means of pumping. 3. Gas condensing boiler according to one of the preceding claims, characterized in that the thickness of the nickel layer is greater than approximately 0.3 µm. 0 ·