Optimization of Radiator Design for Immersion Cooling of a Powerful Thyristor

Numerical modeling of the thermal state of the T283-1600 thyristor with various radiators, on the surface of which boiling of the 3M Novec 649 liquid dielectric occurs, was carried out. Calculations were performed in the “in-house” CFD code ANES. Heat-transfer coefficients for nucleate and transition boiling, as well as critical heat flux, were calculated using the formulas of  V.V. Yagov. The change in boiling mode from nucleate to transition was carried out with equal heat flux calculated using the corresponding formulas: approximately 110 kW/m², which is 17% lower than the critical heat flux predicted by Yagov’s formula for technically smooth surfaces. This led to slightly higher calculated temperatures of radiators on surface fragments with a transient boiling regime compared to temperatures during nucleate boiling over the entire cooling surface. The proportion of the surface area covered by the transition boiling regime did not exceed 3.2% of the total radiator area. Various forms of radiators were studied: in the form of fins from several disks and rectangular parallelepipeds with vertical slotted channels. At the same time, the geometric parameters of the fins and channels and their number and dimensions of the radiators were varied. As a result of numerical optimization, a radiator design was determined that meets the required conditions for the maximum temperature of the thyristor on the surface of contact with the radiator. To validate the results of numerical modeling, an experimental setup was created containing an assembly of thyristors with radiators immersed in a 3M Novec 649 dielectric. In normal operation, measuring the temperature of one of the radiators near the contact with the thyristor showed good agreement with the results of numerical simulation.