Publisher Summary Thermal control of electronic components has one principal objective, to maintain relatively constant component temperature equal to or below the manufacturer's maximum specified service temperature, typically between 85 and 100°C. It is noted that even a single component operating 10°C beyond this temperature can reduce the reliability of certain systems by as much as 50%. Therefore, it is important for the new thermal control schemes to be capable of eliminating hot spots within the electronic devices, removing heat from these devices and dissipating this heat to the surrounding environment. Several strategies have developed over the years for controlling and removing the heat generated in multichip modules, which include advanced air-cooling schemes, direct cooling, and miniature thermosyphons or free-falling liquid films. The chapter summarizes analytical, numerical, and experimental work in literature, in order to facilitate the improvement of existing schemes and provide a basis for the development of new ones. The chapter focuses on investigations performed over the past decade and includes information on the thermal control of semiconductor devices, modules, and total systems.

Thermal Control of Electronic Equipment and Devices

Many of the candidate fluids for immersion cooling of microelectronic components possess both low surface tension and high gas solubility. As a consequence, ebullient heat transfer with such fluids is accompanied by nucleation anomalies and a frequently observed wall temperature overshoot. The difficulty in preventing this thermal excursion and in predicting its magnitude constrains the development of immersion cooling systems. This paper begins with a brief review of the mechanisms that may be responsible for delayed nucleation and examines the limited literature on incipience superheat excursions.

wall Superheat Excursions in the Boiling incipience of Dielectric Fluids

An Hand der variablen geometrischen Grosen Richtungsanderung ω, Wellenberglange S1 und “Formparameter” ξ lassen sich alle technisch sinnvollen Profile feingewellter Kondensatoberflachen erfassen. Aus diesem Katalog konnen die fur den Kondensationsvorgang optimalen Konturen einfach abgeleitet werden. Dabei sind schlanke Formen gunstiger als die bisher ublichen runden Formen. Die optimalen Konturen der schlanken Formen liegen in der Grosenordnung der Rippenprofile, die momentan auf dem Markt sind, wahrend das Optimum der runden Wellen um den Faktor 2 feiner ist (0.6–1.0 mm bzw. 0.3–0.5 mm).

Bestimmung der Kondensationsgrößen auf feingewellten Oberflächen zur Auslegung optimaler Wandprofile

This paper deals with certain aspects of convective condensation phenomena and condenser behaviour in capillary-driven cooling loops (CPL or LHP) studied in the LAPLACE laboratory, Toulouse. The effects of phase distribution, in the condenser, on the stability and the reliability of the whole system were studied. A model is proposed for convective condensation at low mass fluxes in a microgravity-like situation. The numerical results are in good agreement with experimental data. On increasing the mass flux, both numerical and experimental results suggest that the stationary state no longer exists, and intrinsic instabilities occur and develop in the condenser. The effects of such instabilities, as well as flow regime transitions, on loop behaviour remain an open question.

Condensation in capillary-driven two-phase loops

Flow and Heat Transfer Characteristics of a Natural Circulation Evaporative Cooling System for Electronic Components

Condensation on a Downward-facing Horizontal Rippled Surface

The operating characteristics of an experimental submerged condenser system are described and related to specific operational modes. The relevant thermal transport mechanism are examined and shown to accurately define the upper and lower bounds of system operation. A non-dimensional vapor bubble collapse length is shown to govern the rate and mechanism of heat transfer at the submerged condenser surface.

Avram Markowitz

Papers

Condensation on a Downward-facing Horizontal Rippled Surface

Operational limits of a submerged condenser