JPH02290669A - Heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a heat exchanger used in water heaters, radiators, hot air heaters, and the like.

In this specification, the term aluminum is used to include its alloys.

Conventional technology For example, a heat exchanger for a water heater generally has a configuration in which a plurality of plate-like fins are arranged in parallel in the length direction of a tube, and the heat imparted to the surface of the fins by combustion gas is transferred into the tube. It is designed to heat the circulating water by transmitting it to the circulating water.

Conventionally, the constituent materials of such heat exchangers include tubes,
All fins were made of steel. The tube is made of steel because it has good corrosion resistance against water, and the fins are also made of steel because it has excellent thermal conductivity and can maintain sufficient bonding with tubes made of the same material. .

Problems to be Solved by the Invention However, such a heat exchanger in which both the tubes and fins are made of steel has the following drawbacks.

That is, in a heat exchanger for a water heater, the part where the fins are present is exposed to the combustion gas, but in city gas with a high S content, the combustion cycle conditions cool the combustion gas to below the dew point, and the water vapor in the gas condenses. There was a drawback in that corrosion due to the drain (so-called low-temperature corrosion) was likely to occur. Moreover, this low-temperature corrosion produces CuSO4 ・5H20,
This clogs the fins, causing a decline in the performance, durability, and safety of the heat exchanger. In recent years, as heat exchangers have become smaller and more efficient, these drawbacks have tended to occur more prominently. Furthermore, since the entire structure was made of copper, it had the drawbacks of increased duplication and increased cost. However, PB dipping is sometimes performed as a preventive measure against low-temperature corrosion, but this leads to other problems in terms of cost, safety, environmental pollution, etc.

This invention was made in view of this technical background, and when used in a heat exchanger for hot water supply, etc., low temperature corrosion caused by drains formed by condensation of S-containing combustion gas, and eventually fin blockage. The purpose of the present invention is to provide a heat exchanger that can prevent the occurrence of heat exchangers, and can also be made lighter and lower in cost.

Means for Solving the Problem In order to achieve the above objective, it may be possible to construct the tubes and fins from aluminum, which is relatively strong against low-temperature corrosion and lightweight in terms of weight. From this point of view, using aluminum for the tube is problematic. Furthermore, when only the fins are made of aluminum, there is a problem in joining the copper tube and the fins. That is, when mechanically joining a copper tube and an aluminum fin by expanding the tube or the like, the thermal resistance becomes large and heat conductivity decreases, and the joint becomes loose due to repeated use. Also, direct brazing of copper and aluminum causes erosion.

Therefore, in this invention, the fins are made of aluminum, the tube is made of stainless steel which has relatively good corrosion resistance against flowing water, and also has good low temperature corrosion resistance, and the stainless steel tube and the aluminum fin are combined. It is intended to be joined by brazing, and measures have been taken to ensure sufficient joint strength between the two.

That is, as shown with reference to the reference numerals in the drawings, the present invention provides a heat exchanger in which a tube (1) is covered with plate-like fins (2) in parallel in the longitudinal direction and joined to the tube. 1) is made of stainless steel, and its outer surface is provided with a plurality of narrow grooves (3) extending in the axial direction at the joint portion with the plate-shaped fin (2), while the plate-shaped fin (2) It is characterized by being made of aluminum and having a tube (1) and a plate-shaped fin (2) joined by brazing.

Function Aluminum and stainless steel have good brazing properties, and the plate-shaped fin (2) and tube (1) can be easily joined together by brazing under the same conditions as those for aluminum materials. In this case, the narrow grooves provided on the outer surface of the tube increase the bonding area at the interface between the brazing material layer and the tube, ensuring stronger bonding. Moreover, since the narrow grooves are provided along the axial direction of the tube, even if an undesired impact rotational force is applied to the fins in the direction of the outer circumference of the tube, a resistance force is generated in the narrow grooves, and the brazing material layer and tube are The risk of peeling at the interface is reduced, and the bonding strength is further increased. Furthermore, since the fins are made of aluminum, they are more resistant to low-temperature corrosion than steel materials, and the heat exchanger as a whole can be made lighter. Furthermore, since the tube is made of stainless steel, it has good corrosion resistance against circulating water.

Embodiment FIGS. 1 to 3 show a heat exchanger for a water heater as an embodiment of the present invention. In these figures, (1
) is a tube, and (2) is a plate-like fin.

The tube (1) is made of stainless steel and has three straight pipe sections (lla) arranged in parallel in the vertical direction.
(llb) (llc), and one end of the tube is connected to the water supply port (12).
and the other end serves as a hot water supply port (13). Furthermore, on the outer surface of the straight tube portion (lI.a) (llb) (lie), as shown in detail in Fig. 4, there are narrow grooves (3) extending in the axial direction at eight equal parts of the tube outer circumference. It is provided in parallel over the joining range with the fin (2). The narrow grooves (3) are provided in order to increase the joint area with the fins (2) by increasing the surface area of the tube, thereby improving the joint strength.

On the other hand, the plate-shaped fin (2) is made of aluminum. As shown in Figures 7 and 8, this plate-like fin (2) has a tube (1) in its center.
Three tube insertion holes (21) having a diameter slightly larger than the outer diameter of the tubes are arranged in parallel, and cylindrical fin collars (22) are erected around the peripheries of the various through holes (21).

Then, by inserting a plurality of plate-like fins (2) into each straight tube part (lla) (llb) (lie) of the tube (1) in each tube insertion hole (21), the fin collar (22) ) is arranged parallel to the length direction of the straight pipe section in such a manner that it seamlessly covers the outer surface of the straight pipe section. In this way, the fin collar (22)
The reason why the outer surface of the straight pipe part is covered with aluminum material is to provide even better low-temperature corrosion resistance. This is also to secure as large a bonding area between the fin (2) and tube (1) as possible to further increase the bonding strength. The fin (2) consists of a single-sided aluminum brazing seam with a core +4' (23) coated with a brazing material (24), and the inner surface of the fin collar (22) is the brazing material layer side. It is formed by the direction. The fin collar (22) and the stainless steel tube (16) are brazed together via a brazing material (24).

Here, brazing between an aluminum material and stainless steel is possible under almost the same conditions as brazing between aluminum materials, and either vacuum brazing or flux brazing can be used. Therefore, in the brazed state, the brazing material (
24) has a fin collar (
22) and the outer circumferential surface of the tube (1) without any gaps, and therefore the narrow grooves (3) on the outer surface of the tube (1) are also densely filled.

Due to the presence of this narrow groove (3), the bonding area at the interface between the brazing filler metal (24) and the tube (1) increases compared to the case where the narrow groove does not exist, and the brazing filler metal (24) and the tube (1), which easily peel off, increase. 1) to ensure the bonding strength at the interface.

In addition, (4) shown in FIGS. 1 and 2 is a straight pipe part (lla) (llb) in the manufacturing process of a heat exchanger.
This is a brazed part when a U-shaped connecting part (5) or an L-shaped water supply part (6) is connected to (llc) by brazing.

In the illustrated heat exchanger for hot water supply, water flowing in from the water supply port (l2) flows along the tube (1), but during this time it is heated by the combustion gas applied to the part where the plate-shaped fins (2) are present. , the water becomes hot water and flows out from the hot water supply port (13).

Effects of the Invention As described above, the tube is made of stainless steel which is excellent in both water corrosion resistance and low temperature corrosion resistance, while the plate-shaped fins are also excellent in low temperature corrosion resistance. It is made of aluminum and has a tube and plate-like fins joined by brazing. Therefore, when used as a heat exchanger for water heaters, the low-temperature corrosion resistance of the entire heat exchanger can be improved compared to conventional products made entirely of copper, and the fear of fin clogging can be eliminated. .

In addition, the fins, which account for most of the product's weight, are made of lightweight and inexpensive aluminum, reducing the weight of the heat exchanger.
Cost reduction can be achieved. In addition, since the fins are joined through stainless steel, they can be easily joined together by brazing, and the thin grooves provided on the outer surface of the tube increase the joint area at the interface between the brazing metal layer and the tube. Sufficient bonding strength can be achieved. Moreover, since the narrow grooves are provided in the axial direction of the tube, even if an undesired impact rotational force is applied to the fins in the direction of the outer circumference of the tube during handling of the heat exchanger, a resistance force will be generated in the narrow groove portion. The risk of peeling at the interface between the brazing material layer and the tube can be reduced, and the joint strength can be further increased.

[Brief explanation of the drawing]

Fig. 1 is a front view of a heat exchanger for a water heater according to an embodiment of the present invention, Fig. 2 is a bottom view, Fig. 3 is a side view, Fig. 4 is a cross-sectional perspective view of a single tube, and Fig. 5 is a cross-sectional view showing the state of connection between the fin and the tube, and FIG.
7 is a front view of the plate-like fin alone, and FIG. 8 is a sectional view taken along the line ■--■ in FIG. 7. (1)...Tube, (2)...Plate-shaped fin, (3)...Small groove. that's all

Claims (1)

[Claims] Plate-shaped fins (2) along the length of the tube (1)
In the heat exchanger, the tubes (1) are made of stainless steel, and the tubes (1) are made of stainless steel, and the outer surface thereof extends in the axial direction at the joint part with the plate-like fins (2). A plurality of narrow grooves (3) are provided, while the plate-like fins (2) are made of aluminum, and the tube (1) and the plate-like fins (
2) A heat exchanger characterized in that the points are joined by brazing.