HEAT EXCHANGER

PROBLEM TO BE SOLVED: To provide a light-weight and compact heat exchanger, improving a heat transferring performance of the heat exchanger even under use configuration where a flow rate of the water is small such as a storage type heat pump water heater. SOLUTION: This heat exchanger includes: an inner pipe 2 in which a refrigerant passes; and an outer pipe 3 disposed outside of the inner pipe 2 to pass the water between the inner pipe 2 and the outer pipe 3. The outer pipe 3 has a spiral corrugated groove 4 formed by a corrugating processing, and the heat exchanger satisfies Pc/De≤560×(Hc/De)2-70×(Hc/De)+2.5, and Hc/De≥0.09 when a depth of the corrugated groove 4 is Hc, a clearance between the corrugated grooves 4 adjacent to each other in the pipe shaft direction is Pc, and the difference between the maximum inner diameter of the outer pipe 3 and an outer diameter of the inner pipe 2 is De. COPYRIGHT: (C)2010,JPO&INPIT