Experimental study on electrochemical etching for titanium printed circuit heat exchanger channels

Printed circuit heat exchangers (PCHEs) have attracted wide attention in the nuclear energy field owing to their high compactness, strong pressure endurance, and high heat transfer capacity. In situations where corrosion resistance or light weight is required, PCHEs made of titanium exhibit obvious advantages. However, the corrosion resistance of titanium is so high that it is hard to machining titanium using common chemical etching method. Also, etching methods to fabricate fluid channels on titanium plates for microchannel plate heat exchangers such as PCHEs have not been reported in the open literature, therefore the research of producing fluid channels on titanium plates using etching method for PCHEs is demanded. In this work, an electrochemical etching experimental system was established, and the electrolytic machining process using NaCl-containing ethylene glycol as an electrolyte for preparing PCHE fluid channels on titanium plates was studied. To improve the corrosion rate, ultrasonic transducers were added to the experimental system. The influences of the etching temperature and ultrasonic exposure were examined with respect to the etching rate and surface topography. The results showed that ultrasonic transducers with a rated power of 120 W and a frequency of 50 kHz can enhance the corrosion rate by a factor of 4–5 and that the growth trend of the etching rate can be improved with increasing etching temperature. An etching temperature of 45 °C leads to the best comprehensive performance under ultrasonic exposure in terms of etching rate, roughness, and etching factor. Two improved methods including secondary polishing method and pulsed electrode method are proposed to maintain the quality of the surface profile when the etching rate is enhanced.