Flat extruded aluminum multi-port tube whose inner surface is highly corrosion-resistant and an aluminum heat exchanger using the tube
In this flat extruded aluminum multi-port tube, the corrosion-resistance, at inner surfaces of a plurality of flow passages independently and parallelly extending in the tube axial direction, is effectively enhanced. In a flat extruded aluminum multi-port tube 10 formed by an extrusion by employing an aluminum tube material and an aluminum sacrificial anode material having an electrochemically lower potential than the aluminum tube material, the aluminum sacrificial anode material is exposed to form a sacrificial anode portion 18 at least in a part of an inner circumferential portion in each of the plurality of flow passages 12.
1. An aluminum multi-port tube with a flat cross sectional shape obtained by extruding an aluminum material, the aluminum multi-port tube being an extruded tube which has a plurality of flow passages extending independently of each other in an axial direction of the tube, the flow passages being arranged in a longitudinal direction of the flat cross sectional shape via internal partition wall portions extending in the axial direction of the tube in a peripheral wall portion of the tube, wherein:
the aluminum multi-port tube is formed by extrusion wherein an aluminum tube material and an aluminum sacrificial anode material having an electrochemically lower potential than the aluminum tube material are employed as said aluminum material, a difference of the potential between the aluminum tube material and the aluminum sacrificial anode material being in a range from 100 mV to 300 mV, and
the aluminum sacrificial anode material is exposed to form a sacrificial anode portion at least in a part of an inner circumferential portion in cross section of each of the plurality of flow passages,
whereby the aluminum multi-port tube has an internal corrosion-resistance, and
the internal partition wall portions positioned at opposite end portions in the longitudinal direction of the flat cross sectional shape, among the internal partition wall portions existing between adjacent ones of the plurality of flow passages, have a larger thickness than that of the other internal partition wall portions.
2. The aluminum multi-port tube according to claim 1 , wherein the internal partition wall portions are formed of the sacrificial anode portion.
3. The aluminum multi-port tube according to claim 1 , wherein, in the inner circumferential portion in the cross section of each of the plurality of flow passages, the aluminum sacrificial anode material is exposed to form the sacrificial anode portion in the internal partition wall portions, while the aluminum tube material is exposed in the peripheral wall portion of the tube other than the internal partition wall portions.
4. The aluminum multi-port tube according to claim 1 , wherein the sacrificial anode portion exists at the internal partition wall portion positioned between adjacent ones of the plurality of flow passages, in a ratio not higher than 100% of a thickness of the internal partition wall portion.
5. The aluminum multi-port tube according to claim 1 , wherein the sacrificial anode portion exists at the peripheral wall portion other than the internal partition wall portions, in a ratio not higher than 90% of a thickness of the peripheral wall portion.
6. The aluminum multi-port tube according to claim 1 , wherein the sacrificial anode portion is formed along at least 10% of a peripheral length of each flow passage in cross section of the tube, and exposed to an inner surface of the flow passage.
7. The aluminum multi-port tube according to claim 1 , wherein the internal partition wall portion positioned between adjacent ones of the plurality of flow passages extends with a thickness increasing continuously or stepwise from the thinnest part of the internal partition wall portion toward opposite sides of the peripheral wall portion which are joined by the internal partition wall portion, and are joined to said opposite sides of the peripheral wall portion by connecting parts having a thickness larger than that of the thinnest part of the internal partition wall portion.
8. An aluminum heat exchanger comprising the aluminum multi-port tube according to claim 1 and aluminum outer fins brazed on an outer surface of the aluminum multi-port tube.