平行板间自然散热计算

Bar-Cohen and Rohsennow Solution Finned surfaces of various shapes, called heat sinks, are frequently used in the cooling of electronic devices. Energy dissipated by these devices is transferred to the heat sinks by conduction and from the heat sinks to the ambient air by natural or forced convection, depending on the power dissipation requirements. Natural convection is the preferred mode of heat transfer since it involves no moving parts, like the electronic components themselves. However, in the natural convection mode, the components are more likely to run at a higher temperature and thus undermine reliability. A properly selected heat sink may considerably lower the operation temperature of the components and thus reduce the risk of failure. Natural convection from vertical finned s...

NATURAL CONVECTION:NATURAL CONVECTION FROM FINNED SURFACES AND PCBs

Natural convection flow through a channel formed by two parallel plates as shown in Fig. 20–16 is commonly encountered in practice. When the plates are hot (Ts> Too), the ambient fluid atToo enters the channel from the lower end, rises as it is heated under the effect of buoyancy, and the heated fluid leaves the channel from the upper end. The plates could be the fins of a finned heat sink, or the PCBs (printed circuit boards) of an electronic device. The plates can be approximated as being isothermal (Ts= constant) in the first case, and isoflux ( · = constant) in the second case. Boundary layers start to develop at the lower ends of opposing surfaces, and eventually merge at the midplane if the plates are vertical and sufficiently long. In this case, we will have fully developed chann...

Thermal Resistance Comparison Of Graphite Foam, Aluminum, And Copper Heat Sinks

Introduction With thermal solutions becoming more challenging, there is a push for novel cooling ideas or materials to further mitigate thermal issues facing today’s electronics. In these design situations, the proven method of analytical calculations, modeling, and laboratory testing is sometimes bypassed in the search for a quick “cure-all” solution. Evolutionary progress is needed in the thermal industry of course. However, in a rush to implement new ideas/materials thorough testing should not be overlooked in determining thermal performance of a solution before implementation. Table 1. Heatsink GeometryThe stated thermal properties of engineered graphite foams have been a motivator for their consideration as heat sink materials. Yet, the literature is void of true compariso...