When making temperature measurements with infrared cameras and point detectors, we are always facing the question of the emissivity of our sample. In practice we would like to have a single number set in the IR device. To approach the question, let's first recall some fundamental definitions. Planck's radiation law gives the energy density emitted by a blackbody as a function … [Read more...]
Hot Spots in Data Centers
Heat loads of data processing equipment continue to increase at a rapid rate. This increasing heat load has been documented by a Thermal Management Consortium of 17 companies [1] as shown in Figure 1. Also shown in this figure are measured heat fluxes (based on product footprint) of some recent product announcements. The most recent shows a rack dissipating 28,500 watts, … [Read more...]
Recognizing the Limits of Conventional Axial Hub-Motor AHS Devices
Conventional axial hub-motor AHS (Active Heatsink) devices (Figure 1) have reached their functional and cost limits and may not be improved significantly. These devices have a number of inherent, severe contradictions (design limitations) that determine the "evolutionary maturity" of this concept. Figure 1. Conventional axial hub-motor AHS. Let us look at different … [Read more...]
How Much Heat can be Extracted from a Heat Sink?
Thermal transport from a heat sink creates a unique condition in heat transfer and fluid flow once it is placed on a PCB in an unducted fluid flow delivery system. Although a heat sink may appear structurally simple, the fluid flow through its fin field and thermal coupling between it and the surrounding create a rather complex problem. As a result, heat sinks are often … [Read more...]
The Weakest Link in Air Cooling
So far, this 21st Century has been a big disappointment. I grew up on the science fiction of the 1950's and 60's. Plus I knew that the stories of Jules Verne and H. G. Wells had turned out to be amazingly accurate predictions of real technological advances. So I was expecting that, if I lived long enough to see the 21st Century (no way - I'll be in my 40's!), I'd be … [Read more...]
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