Manufacturing method of heat exchanger, and heat exchanger manufactured by such manufacturing method

#The disclosed method relates to a method of manufacturing a heat exchanger and so forth, used in a heat pump type hot-water supply system, in which a cooling medium is may function as a heat source, and to a heat exchanger manufactured by such a manufacturing method.

#In a heat pump type hot-water supply system in which a CO2 cooling medium subjected to a high temperature and a high pressure is employed as a heat source, heat exchange is carried out between the cooling medium and the water to thereby heat the water, and the hot-water supply system has widely prevailed in recent years. In a heat exchanger used in this known hot-water supply system, in general, a copper alloy tube of heat conductivity and high corrosion resistance is utilized as one of the composition elements. However, for the purpose of improvement in transportability and cost reduction, it has been proposed that an aluminum alloy tube featuring high heat conductivity, lightness and low cost is utilized for a cooling medium passage.

#In a conventional heat exchanger in which copper alloy tubes are utilized for a cooling medium flow-passage and a water flow-passage, respectively, since a joining is made between the copper alloy tubes, a variety of joining methods such as a furnace brazing method, a soldering method and so forth has been put into practice. Nevertheless, it is known that a joining between an aluminum alloy and a copper alloy is very difficult due to the fact that there are many problems such as a difference in temperature of approximately 400° C. between respective melting points of the aluminum alloy and the copper alloy; that a firm oxide film exists on a surface of the aluminum alloy; and so on.

#FIG. 1 (Prior art) is a microscope photograph showing an erosion which occurred when an aluminum alloy material and a copper alloy material were brazed to each other.

#FIG. 2 (Prior art) is a photograph showing a eutectic-melting which occurred when an aluminum alloy material and a copper alloy material were brazed to each other.

#The present invention is explained in detail below.

#(1) Brazing Temperature:

#The brazing temperature, at which an aluminum alloy cooling-medium tube and a copper alloy water tube are brazed to each other, is less than 548° C. This is because a eutectic-melting occurs in the aluminum alloy and the copper alloy at the temperature which is equal to or more than 548° C., so that a member(s) to be joined (i.e., the aluminum alloy cooling-medium tube and/or the copper alloy water tube) is subjected to a deformation and/or a decline in strength. In order that a brazing material can be sufficiently melted, a lower limit of the brazing temperature is preferably equal to or more than 510° C. Thus, preferably, the brazing temperature is within a range from at least 510° C. to less than 548° C.