JPH02101179A - Heat exchanger - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger made of a metal heat transfer member used in instantaneous water heaters, water heaters, heating equipment, and the like.

BACKGROUND OF THE INVENTION The figure shows a heat exchanger used in a conventional instantaneous water heater. It consists of a heat exchanger tube 2 passing through and a heat transfer member of fins 3 provided on the upper part of the drum 1.

In this configuration, on the side in contact with the combustion exhaust gas, especially in low-temperature areas such as the contact area between the drum 1 and the heat exchange tube 2, or the contact area between the endothermic fins 3 and the heat exchange tube 2, NOXSOX and CO contained in the combustion exhaust gas are , Co, , water vapor, etc. condense and become an acid. In order to prevent this acid from corroding the copper and aluminum metals that make up the heat transfer member, copper is coated with lead-based hot-dip metal plating, and aluminum is coated with hot-dip metal plating containing lead as the main component. are coated with silicone curvature epoxy paint.

Problems to be Solved by the Invention When trying to make hot water heaters more efficient and more compact, the combustion exhaust gas temperature decreases, the amount of dew condensation inside the heat exchanger increases, and the load on the combustion chamber increases. By converting to NOx, oxidation of condensed water progresses. The results of this, et al.
Condensation corrosion tends to occur, and conventional surface treatment methods cannot prevent corrosion.
Furthermore, high-temperature baking requires a type of paint or high-temperature molten metal, but due to this high-temperature baking, the inner surface of the heat exchange tube 2 is oxidized to form an oxide film. This oxide film peels off, causing circuit troubles from the heat exchange tube 2 onwards.

Another way to solve the problem: When coating the surface of the heat exchanger with a high-temperature firing or melting surface treatment material, the inner surface of the passage through which liquid or gas flows inside the heat exchanger is coated with a type of nickel or chromium. It is coated with a surface treatment material containing the above elements.

Function: As mentioned above, corrosion on the surface of the heat exchanger can be suppressed, and
Oxidation of the inner surface of the heat exchange tube can be prevented.

Example An embodiment of the present invention will be described below.

<Example 1> Polyphenylene was applied to the outer surface of a copper heat exchanger consisting of a heat exchange tube 2 through which water or gas heat-exchanged with the drum L provided inside the combustion chamber passes, and fins 3 provided at the top of the drum 1. A high-temperature baking type heat-resistant paint composed of a fluororesin polymer containing at least one type of sulfide or polyether sulfone resin as a main component and a pigment filler having heat resistance and acid resistance. In addition to coating the heat exchange tubes, electroless nickel plating was applied to the heat exchange tubes to prevent them from oxidizing.

This electroless nickel-plated heat exchange tube showed no discoloration up to 350°C.

Furthermore, no corrosion due to condensed components of combustion exhaust gas was observed.

At 370°C, slight discoloration was observed, but no oxidized scale formation was observed.

On the other hand, when the heat exchange tube was not subjected to electroless nickel plating, formation of an oxide film was observed on the surface at 250°C, and slight peeling of the oxide film was observed.

As described above, by applying electroless nickel plating that can withstand high temperature baking, oxidation of the heat exchange tube can be prevented.

〈Example 2〉 Heat exchange tubes were treated with Dacrotized treatment (coating treated by immersing metal zinc flakes in an aqueous dispersion solution of chromic anhydride, glycol, etc., and forming a film that did not seize at 300 to 350°C) manufactured by Kansai Dacro ■. Even when applied, 370°C
In the following cases, no changes such as peeling of the oxide film were observed, and the same results as in Example 1 were obtained.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention prevents oxidation of the inner surface of the heat exchanger tube, so that baking of the surface coating material for improving the corrosion resistance of the heat exchanger occurs at a temperature of 35%.
It is now possible to use heat-resistant paints or molten metals at temperatures above 0°C.

In addition, since the product of the oxide film does not peel off, it has the effect of preventing problems with parts such as solenoid valves and filters installed in the rear circuit of the heat exchange tube, and has practical value. is extremely high.

[Brief explanation of drawings]

The figure is an external perspective view showing an instantaneous water heater. 1...Drum, 2...Heat exchange tube, 3...Fin. Name of agent: Patent attorney Shigetaka Awano Haka 1 - Drum 2 - Kuma 2 Sho + Yup 3 - Finn

Claims (1)

[Claims] When the surface of the heat exchanger is coated with a fusion type surface treatment material, the inner surface of the passage through which liquid or gas flows inside the heat exchanger is coated with at least one element of nickel or chromium. A heat exchanger equipped with a surface treatment material containing