| 摘要 |
A double wall heat exchanger for use in solar heaters and the like. An outer drawn copper tube of predetermined thickness and inside diameter is slid over a second drawn copper tube also of a predetermined thickness and outside diameter. The tubes are then placed in a furnace and annealed for a specified time and temperature. The double wall tubes are placed in a finning machine. Under a specified pressure and at a specified feed rate, integral fins are formed on the outside tube. While the fins are being formed on the outside tube, internal pressure is being applied forcing the inner tube to expand and conform to the inside diameter of the outer tube. The mating surfaces form a helical passageway which serves as the path of leakage. The double wall heat exchanger has good surface contact between the tubes, has a path of leakage between the tubes at a pressure differential of 10 psig, and has good heat transfer. The production process provides reduced cost of manufacture, improved heat transfer and the safety feature required by the various state and local codes.
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