JP2010540882A - Heat exchanger material coating - Google Patents

Abstract

A heat exchanger composite that can withstand corrosion and / or erosion phenomena regardless of heat conduction / heating fluid flow rate conditions, and that can reduce the thickness of the coating layer and has high mechanical strength. A coating layer for the material is provided.
In a composite material for a heat exchanger consisting of two or three layers that can contact a heat generating fluid, the core (3) covered with a brazing coating layer (2) that can directly contact the fluid. And the coating layer (2) comprises 1.2 to 1.8% by weight of zinc, 0.9 to 1.8% by weight of manganese and / or 0.05 to 0.25% by weight of zirconium. % Of silicon, 0.3 to 1% by weight of silicon and / or 0.3 to 0.9% by weight of iron and / or 0.1 to 0.4% by weight of copper and / or 0 of magnesium A composite material comprising less than 0.05% by weight and / or 0.05 to 0.25% by weight of titanium.
[Selection] Figure 1

Description

  The present invention relates to the field of heat exchangers, and in particular to heat exchangers of the type through which fluid passes.

  Currently, tubes for heat exchangers are known in which the ends are conventionally attached to two water distribution tanks, respectively. These tubes constitute a heat exchange bundle of the heat exchanger. A heat transfer / heating fluid, typically a coolant type liquid, flows through the tube and exchanges heat with another fluid, usually air, that flows outside the tube.

  When the fluid needs to be a liquid, it is generally corrosive to the metal that makes up the tube in an automobile. Conventionally, the core of the tube wall, i.e. the core of the tube, is coated with a coating layer that is in contact with the fluid and serves in particular as a sacrificial protective layer against chloride. Therefore, the tube wall core is not eroded and the coating layer is eroded. This coating layer contains about 1% by weight of zinc.

  The function of this sacrificial layer is that of the coating layer of the heat exchanger tube.

  However, it was observed that the corrosion of the metal wall was not uniform and this corrosion was caused by pitting and a local alteration of the coating layer was formed.

  The tube pitching phenomenon is a combination of corrosion and erosion phenomena. In fact, the coating layer proximate to the pitching zone is not stable, so corrosion products ride on the flow and enter the circuit, and a new chemical equilibrium occurs. This is a dynamic thermochemical phenomenon.

  However, when the flow rate of the fluid circulating in the tube is high, the mechanical strength of the coating layer is weak and significantly lower than the mechanical strength of the core, so that corrosion due to pitting is accelerated. This causes rapid corrosion of the heat exchanger tubes when the fluid velocity is as high as, for example, about 60-20 L / min, resulting in rapid wear and leakage of the tubes.

  The only solution currently conceivable is to increase the thickness of the coating layer so that the coating layer can withstand such accelerated corrosion phenomena over time if the fluid flow rate is high. Conceivable.

  However, this solution only improves the tube service life temporarily and is not satisfactory. Furthermore, increasing the thickness of the coating layer not only increases the tube thickness and hence the size of the heat exchanger, but also increases the thickness of the material (resistance to heat conduction), resulting in improved heat exchange performance. It will decline. Therefore, for a similar heat exchanger capability, a large size and heavy mass heat exchanger must be provided. Finally, the addition of this material thickness is obviously costly because the coating layer has a specific structure depending on its chemical function.

  These findings are for heat exchanger composites consisting of tubes, but any type of heat exchange with similar properties, i.e. the properties required for a coating layer that chemically protects the core of the composite wall. It should be noted that the composite material of the vessel is the object of the present invention and has drawbacks and problems similar to those of the prior art tubes described above in current heat exchangers.

  The present invention has been made to solve the above-mentioned drawbacks and problems. In particular, the present invention can withstand corrosion and / or erosion phenomena regardless of the heat conduction / heating fluid flow rate conditions, and the thickness of the coating layer. It is an object of the present invention to provide a coating layer for a composite material of a heat exchanger having a high mechanical strength that makes it possible to reduce the thickness.

  As such, the present invention is a composite material for a heat exchanger that includes at least one wall that can contact an exothermic fluid, the wall comprising a core covered with a brazed coating layer that is in direct contact with the fluid. The coating layer contains 1.2 to 1.8 wt% zinc and 0.9 to 1.8 wt% manganese and / or 0.05 to 0.25 wt% zirconium. The proposed composite material is proposed.

  Note that the composite material according to the invention comprises two or three layers: the core and its coating, and an optional outer layer.

  It is to be understood that the term “core” means the part of the wall, ie the part provided in the core.

  Percentages herein are by weight. That is, the ratio of the target component in the layer or part is determined by the weight of the target component with respect to the total weight of the layer or part.

Other features of the heat exchanger of the present invention are as follows.
-According to one embodiment, the composite material comprises a tube and a coating layer is provided on the inner surface of the tube.
The composite material / tube can be secured by brazing at least one attachment member, not shown in the attached drawings, for example an intermediate layer / turbulator / fin, located on the opposite side of the coating layer It has an outer layer.
According to a preferred embodiment of the invention, the coating layer comprises 0.3 to 1% by weight of silicon and / or 0.3 to 0.9% by weight of iron and / or 0.1 to 0.1% of copper. It contains 0.4% by weight and / or less than 0.05% by weight of magnesium and / or 0.05 to 0.25% by weight of titanium.
According to one preferred embodiment of the invention, the core is 0.1-0.65% by weight silicon and / or 0.2-0.7% by weight iron and / or 0.2% copper. -1.1 wt%, and / or manganese 0.6-2 wt%, and / or magnesium less than 0.05 wt%, and / or zinc 0.1 wt% or less, and / or zirconium 0 .2% by weight or less is contained.
-The core is basically made of aluminum.
According to one feature of the invention, the thickness of the coating layer is 10-30% of the total thickness of the composite material, preferably 10-15% of the total thickness of the composite material, It consists only of the core and outer layers.
-Preferably, the coating layer contains 1.4 to 1.8 weight% of manganese. This manganese percentage is similar or close to the core manganese concentration.
-Preferably, the coating layer contains 0.1 to 0.2 weight% of zirconium.
-Preferably, the coating layer contains 1.4 to 1.8 weight% of zinc.

  In summary, the present invention is a heat exchanger composite material that can contact a heat generating fluid, comprising a core covered with a brazed coating layer that directly contacts the heat generating fluid, the coating layer being sacrificial protected The present invention relates to a composite material that is a layer and has a yield strength Rp 0.2 of greater than 45 MPa and a tensile strength of greater than 125 MPa.

  The present invention also relates to a heat exchanger mainly for automobiles, in which a heat exchange bundle is provided between at least two kinds of fluids, and one of the fluids circulates in the above-described composite material.

  In the following description, examples are given only and reference is made to the accompanying drawings.

It is a schematic diagram of the wall of the composite material of a heat exchanger provided with three structure layers.

  In the following description, the present invention is illustrated using a composite material consisting of a tube, precisely a flat tube, attached to a heat exchanger to form a bundle of heat exchangers. However, the composite material can also be used to form plates or other walls that are used to form heat exchanger conduits.

  FIG. 1 schematically shows a wall 1 of a composite material according to the invention. Three layers, a coating layer 2, a core 3 and an outer layer 4, are present, similar to a conventional composite wall.

  The present invention relates to the coating layer 2 and also to the core 3 bonded to the coating layer 2.

  The coating layer 2 and the outer layer 4 are attached to the composite material / tube wall core 3 in a completely conventional manner without any modification or specific processing or treatment. Since this technique is known to those skilled in the art, the procedure / method for attaching / fixing these layers to the metal core will not be described further.

According to the present invention, it is possible to provide a particularly strong wall in both the core 3 and the coating layer 2. Conventionally, the core 3 has been strengthened, but neither the core 3 nor the coating layer 2 has almost the same high mechanical properties. However, the core 3 and the coating layer 2 of the present invention have the following mechanical properties.
Yield strength Rp 0.2 is greater than 45 MPa Tensile strength is greater than 125 MPa

  It should be noted that the yield strength Rp 0.2 of the core 3 and the coating layer 2 is generally in the range of 45 to 65 MPa.

  In the coating layer 2 according to the invention, the proportion of zinc contributes to corrosion resistance and manganese and / or zirconium are essential for improving the mechanical properties. Zirconium has in particular the property of limiting the recrystallization (to smaller crystals) of the alloy.

  In order to obtain excellent protection against corrosion, the corrosion potential difference between the coating layer 2 and the core 3 must be at least 120 mV / SCE (saturated calomel electrode as measured by ASTM G69-1997 standard). The difference in corrosion potential between the core 3 of the present invention and the coating layer is higher than this value of 120 mV / SCE, usually higher than 150 mV / SCE.

  The present invention is particularly advantageous when the fluid circulating in the composite / tube according to the present invention is a liquid type corrosive fluid, such as that used in engine coolants. It can be used for all types of composites / tubes in heat exchangers to reduce coating thickness and to impart high mechanical properties.

1 Wall 2 Coating layer 3 Core 4 Outer layer

Claims (11)

A composite material for a heat exchanger consisting of two or three layers and in contact with a heating fluid,
Comprising a core (3) covered with a brazed coating layer (2) capable of direct contact with said fluid;
The coating layer (2) contains 1.2 to 1.8 wt% zinc, 0.9 to 1.8 wt% manganese, and / or 0.05 to 0.25 wt% zirconium, and 0.3-1 wt% silicon and / or 0.3-0.9 wt% iron and / or 0.1-0.4 wt% copper and / or 0.05 wt% magnesium And / or 0.05 to 0.25% by weight of titanium.   The composite material according to claim 1, characterized in that the composite material constitutes a tube and the coating layer (2) is provided on the inner surface of the tube.   The composite / tube has an outer layer (4) on the opposite side of the coating layer (2), to which at least one attachment member, for example an intermediate layer / turbulator / fin, can be fixed by brazing. The composite material according to claim 1, wherein:   The core (3) comprises 0.1 to 0.65% by weight of silicon and / or 0.2 to 0.7% by weight of iron and / or 0.2 to 1.1% by weight of copper and / or Or containing 0.6 to 2% by weight of manganese, and / or less than 0.05% by weight of magnesium, and / or 0.1% by weight or less of zinc and / or 0.2% by weight or less of zirconium. Features. The composite material according to any one of claims 1 to 3.   The composite material according to any one of claims 1 to 4, characterized in that the core (3) consists essentially of aluminum.   The thickness of the coating layer (2) is 10-30% of the total thickness of the composite material, preferably 10-15% of the total thickness of the composite material, the composite material comprising the coating layer (2), the core (3 ) And only the outer layer (4).   The composite material according to claim 1, wherein the coating layer (2) contains 1.4 to 1.8% by weight of manganese.   The composite material according to claim 1, wherein the coating layer (2) contains 0.1 to 0.2% by weight of zirconium.   The composite material according to claim 1, wherein the coating layer (2) contains 1.4 to 1.8% by weight of zinc. In composite materials for heat exchangers that can contact the exothermic fluid,
A core (3) covered with a brazed coating layer (2) in direct contact with the fluid;
The coating layer (2) is a sacrificial protective layer containing zinc and manganese and / or zirconium, and has a yield strength Rp 0.2 of greater than 45 MPa and a tensile strength of greater than 125 MPa. And composite materials.   A heat exchange bundle between at least two fluids, one of the fluids being adapted to circulate in the composite material according to any one of claims 1 to 9, mainly for automobiles Heat exchanger.

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