Thermal performance evaluation of subsea enclosure geometries

Abstract Passive cooling systems have emerged as a solution to ensure proper thermal management, electrical insulation, and reliability in subsea equipment. Geometry design is crucial, as natural convection is the primary heat transfer mechanism. Therefore, this study combines computational fluid dynamics (CFD) and equivalent thermal network (ETN) analyses to assess the performance of a novel subsea frequency inverter enclosure geometry when compared to reference and variant geometries. They were optimized using a genetic algorithm coupled to the ETN model using the specifications of a three-phase inverter and synthetic ester oil as dielectric fluid. The heat sink temperatures, volumetric Nusselt number and volumetric thermal conductance (a figure of merit) obtained by the ETN models were compared with numerical data obtained through CFD simulations of the design circuitry at various power dissipation values and for different circuit-heat sink aspect ratios at a given power dissipation rate. The results for the design circuitry showed an average deviation between the results for heat sink temperatures of 2.4 $$^\circ$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:mmultiscripts> </mml:math> C, and the figures of merit for the annular geometries were more than 66% superior than the cylindrical (reference) geometry. Furthermore, the circuitry aspect ratio assessment pointed out that the annular geometry with rounded end caps had a thermal performance 190% superior to the cylindrical geometry, and up to 52% higher than the annular variant with flat end caps, making it the most suitable option for a compact and efficient passive cooling system.