HEAT EXCHANGER

PROBLEM TO BE SOLVED: To realize high heat exchanging efficiency with a simple structure, to inhibit breakdown of a heat exchanger by deposition of mineral components such as calcium (Ca) in service water only at a high temperature side, and to prevent impairing of heat exchanging performance. SOLUTION: High heat exchanging efficiency is achieved by allowing the water to flow inside of an inner pipe 2, allowing carbon dioxide to flow in a annular portion 6 between the inner pipe 2 and an outer pipe 4 in opposition to the water, comprising a complete double wall 3 and securing a sufficient contact area. As a cross-sectional area of a flow channel at an outflow side 2b of the inner pipe 2 in which the water flows, is enlarged in comparison with a cross-sectional area of a flow channel at an inflow side 2a, the flow of water is not sealed and the stop of heat exchange can be inhibited even when calcium in the water is deposited and attached to a pipe wall 2b of the inner pipe 2 at the outflow side 2b. Further as a temperature of the water is lowered at the inflow side 2a, the attachment of scale is not found even when an inner diameter of the inner pipe 2 is comparatively small, a heat transfer area is enlarged by a spiral fin 7, and the heat transfer rate is improved by stirring the water, the impairing of heat exchanging performance can be prevented in the whole heat exchanger 1. COPYRIGHT: (C)2006,JPO&NCIPI