Operating characteristics and fabrication of a uniquely compact helical heat exchanger

A two-fluid heat exchanger of unusual compactness and high thermal performance is set forth in this paper. The underlying principle of the exchanger is a very tight helical intertwining of two small-diameter tubes (e.g., hypodermic tubes) such that tubes mutually envelope each other. A high-conductivity thermal bridge between the tubes is assured by the use of a braze material insinuated into interstices created by the helical windings. Heat transfer and pressure drop experiments carried out to validate the operational performance of the device are described. The uniqueness of the device has motivated a description of both the underlying design issues and fabrication processes. It is shown that the device can be manufactured by means of remarkably simple operations and machine tools.