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Additive Manufacturing
Embedded fiber optic sensor .
by adding copper onto the entire face of the panel , the heat was spread across the part evenly , resulting in improved heat radiation effects of the part . The last key requirement of this fully integrated heat exchanger that had to be met was hermeticity . These parts needed to be 100 % leak free , as they would be flying on satellites . The final parts met all hermeticity and cleanliness specs from NASA , as they were measured to be hermetic beyond 1x10^-8 std cc / sec of helium .
Improved measurements in in-situ applications As previously mentioned , UAM enables the embedding of sensors for collecting real-time , in-situ data . This can be important to understand the performance of a cold plate in a heat exchanger system , particularly when cold plates are buried inside of a larger system and are hard to access , or when cold plates are installed in systems such as satellites , UAVs , electric vehicles , or eVTOLs . Having the sensors embedded into the cold plate allows for the collection of data much closer to the location of performance , and also protects the sensor ( s ) from environmental effects external to the cold plate . For example , UAM has been utilized not only on parts flying in space but also on critical ground components of rocket systems . Fabrisonic teamed up with Luna Innovations and NASA to create a pipeline device called the Smart Pipe that measured stressed , strain , pressure , and temperature of the pipe . This device was to be used in rocket liquid hydrogen fuel lines to monitor the conditions of the fluid as it pumped into the rocket . Because the fuel
was liquid hydrogen , the Smart Pipe had to be able to withstand cryogenic temperatures and pressures up to 6000 psi . To achieve the accuracy , sensitivity , and repeatability necessary to measure small changes in the fluid ’ s parameters , fiber optic sensors were fully embedded into the outside wall of a stainless steel 304 pipe . To embed a fiber using UAM , a channel that matches the fiber ’ s diameter is milled into the pipe . The sensor is placed in the channel , and a metal foil is vacuumed down over top of the device . Since metal flows under an ultrasonic field , the fiber optic sensor is completely surrounded in the metal matrix – see the cross section on the right as an example . As the pipe expands and contracts due to pressure and temperature changes , that fiber optic sensor reads a corresponding strain value . This strain value can then be mapped to read numerous different parameters depending on the user ’ s interests . The pipe was successfully cycled at 6000 psi and was taken down to < -240 degrees Fahrenheit while maintaining repeatable and accurate measurements . Similar performance can be seen in cold plates embedded with sensors . For example , a popular measurement device used with heat exchangers is thermocouples . Traditionally , a thermocouple is adhered to the outside of the part or inserted into a drilled hole to take measurements at an area of interest inside the part . The problem with these approaches is that the measurements are limited to either the outside of the part or are restricted by the geometry of a drilled hole . With UAM , complex thermocouple routing can be designed to get measurements from as close to the area of interest as possible . The thermocouple is also bonded or coupled to the surrounding metal , resulting in faster and more accurate readings . Based on the manufacturing advantages of UAM , engineers and designers can envision a cold plate that is made from different metals to take advantage of thermal properties of one metal and the light-weight properties of another . They can also incorporate embedded sensors to get real-time , in-situ data on the health and performance of the heat exchanger system at the point of cold plate integration . The benefits of UAM enable new ways of designing and making cold plates .
About the author
Dan King is a mechanical engineer who has been with Fabrisonic for around 5 years . Here , Dan has lead work in various areas including but not limited to machine design and build , machine training , fiber optic sensor embedding , heat exchanger manufacturing , and cylindrical printing development .
The smart pipe undergoing pressure testing . Cryogenic testing .
40 Heat Exchanger World April 2024 www . heat-exchanger-world . com