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

Natural convection flows in a vertical, open tube resulting from combined buoyancy effects of thermal and mass diffusion

Heat transfer enhancement by the chimney effect in a vertical isoflux channel

Laminar mixed convection in a partially blocked, vertical channel

Laminar natural convection in a vertical isothermal channel with symmetric surface-mounted rectangular ribs

A few numerical analyses of the free convection between two heated parallel plates have been carried out without using the boundary-layer approximation. In this paper, an approach that can determine the flow rate with consideration of the pressure drop is proposed. As an example of the calculation, the method is applied to Kettleborough's model. In addition, a comparison is made with Kettleborough's and Aihara's results.

Heat transfer by free convection between two parallel flat plates

Natural convection is often a convenient and inexpensive mode of heat transfer. It is commonly employed in the cooling of electronic equipment and many other applications. Since the initial work by Bodoia and Osterle (1962) on finite difference solutions of natural convection between vertical isothermal plates, many other researchers have studied natural convection in vertical channels. Specifically Davis and Perona (1971) studied natural convection in vertical heated tubes. A thermally insulated chimney attached to a vertical heated channel induces an increase in the natural convection in the channel and leads to a higher heat transfer rate. This is the well-known chimney effect discussed in the paper by Haaland and Sparrow (1983). If the chimney diameter is larger than the heated tube diameter, the friction loss in the chimney region decreases with increasing chimney diameter. This induces an increase in the mass flow rate and leads to a higher heat transfer rate than the case for a chimney of the same diameter. However, from a geometric consideration it is evident that the chimney effect diminishes in the limiting case of an extremely large chimney diameter compared with its height. Therefore, there exists an optimum diameter where the heat transfer is maximum.more » To investigate the chimney effect computations are carried out for a Rayleigh number of 12.5, based on the heated tube radius, and for a Prandtl number of 0.7. The numerical results are based on a control volume finite difference method. The average Nusselt number results are compared with the numerical results obtained for a chimney attached to a tube of the same diameter.« less

Natural convection in a vertical heated tube attached to a thermally insulated Chimney of a different diameter

Three-dimensional natural convection in a vertical porous layer with hexagonal honeycomb core of negligible thickness

Numerical solutions are obtained for a three-dimensional natural convection heat transfer problem in an inclined air slot with a hexagonal honeycomb core. The air slot is assumed to be long and wide such that the velocity and temperature fields repeat themselves in successive enclosures. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the complex cross section onto a rectangle, coupled with a calculation procedure for fully elliptic three-dimensional flows. The calculations are performed for Rayleigh numbers in the range of 10{sup 3} to 10{sup 5}, inclination angles in the range of {minus}90 to 80 deg, Prandtl number of 0.7, and for five values of the aspect ratio. Three types of thermal boundary condition for the honeycomb side walls are considered. The average Nusselt number results are compared with those for a rectangular two-dimensional enclosure.

Three-Dimensional Laminar Natural Convection in an Inclined Air Slot With Hexagonal Honeycomb Core

A solution methodology is developed to obtain three-dimensional natural convection in a honeycomb enclosure with hexagonal end walls. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the complex cross section onto a rectangle, coupled with a calculation procedure for fully elliptic three-dimensional flows. To the authors' knowledge this is the first three-dimensional numerical study of the problem. The results are obtained for laminar flow and for both conduction and adiabatic side wall thermal boundary conditions. The calculations are performed for Rayleigh numbers in the range of 103 to 105, for a Prandtl number of 0.7, and for five values of the aspect ratio of the honeycomb enclosure. The average Nusselt number results are compared with the corresponding values for two-dimensional rectangular enclosures.

Hiroshi Nakamura

Papers

Heat transfer by free convection between two parallel flat plates

Natural convection in a vertical heated tube attached to a thermally insulated Chimney of a different diameter

Three-dimensional natural convection in a vertical porous layer with hexagonal honeycomb core of negligible thickness

Three-Dimensional Laminar Natural Convection in an Inclined Air Slot With Hexagonal Honeycomb Core

Three-dimensional laminar natural convection in a honeycomb enclosure with hexagonal end walls