Heat-Transfer Systems for Submerged Oceanographic Equipment
by Glenn McDonald and Matt Naiman
Performance requirements for submerged oceanographic systems demand timely,
cost-effective solutions of heat transfer problems. This effort investigated
various heat transfer methods utilizing modern fabrication techniques in conjunction
with computer modeling to provide low-risk alternatives for thermal management.
Traditional dry contact methods, liquid cooling, and heat pipes along with improved
geometry were subject to investigation.
The rationale for this effort was multifaceted; excessive heat is the enemy of solid-state electronics. It reduces component longevity and efficiency in addition to introducing undesired drift in instrumentation. Increased component density is creating more heat per volume. Additionally, power conversion modules and improved motor drives are decreasing in form factor, thus providing less volume for heat dissipation.
Materials such as titanium, which are gaining greater use because of their structural properties and corrosion resistance, limit heat transfer. The same is true for plastics/composites, ceramics and glass. Trends in electronic components and material selection can continue to improve system design without compromising overall heat transfer.
With more complicated electronic systems being utilized for oceanographic research, the cooling and heat transfer requirements have grown considerably with little change in design other than making heat sinks larger. This growth in the size of heat dissipation systems is done often at expense of weight and volume of the effective payloads. The increased component density of electronics is impacting this trend as well. Improved computer modeling techniques combined with modern machine and fabrication techniques has potential for design and production of more volumetric and weight efficient heat transfer structures for the benefit of the AUV, ROV, manned submersible and remote submerged observatory communities.
Heat sinking and heat transfer technology used in present oceanographic systems, whether vehicles or static instrumentation, is not keeping pace with the trend described above. Currently, thermal interfaces are based on dry contact area methods. With systems at greater depths the effectiveness of this method is often impacted by the use of titanium and distortion of the pressure housing itself. Utilizing a “package” designed for depth in a shallow deployment is not only affected by the higher water temperature but again by the titanium material and the thicker walls for a “deep” pressure vessel. Heat transfer designs using liquid cooling, heat pipes, and fabrication techniques such as electroplating, electro-dynamic machining (EDM) or vacuum brazing combined with computer modeling and analysis show great gains over conventional methods.
Methods under consideration:
Traditional dry contact
Heat pipe
Liquid, closed and open loop cooling
Increased effective area structures (brazed and plated assemblies)
The techniques outlined above allow for larger more complicated
sub sea systems with greater science payloads. It is often cost that thwarts implementing “new
and improved” technologies and methods over the “tried and true.”
However in this instance, finite element modeling combined with limited prototype
and testing reduces the cost of developing expertise in thermal
management of oceanographic packages. Additionally, coupling of computer
modeling with limited testing reduces the risk associated with fielding
gear that departs from present practices.
Page designed and maintained by gmcdonald@whoi.edu
The funds to support continued efforts in heat transfer system design have been provided by The Alfred H. Zeien Endowed Fund for Innovative Ocean Research and an endowment from The Cecil H. and Ida M. Green Technology Innovation Awards.