In the Tech Data series on thermal conductivity, gases - especially air - have been the subject of a few contributions. So far, the influence of two important parameters has been covered: temperature and pressure. However, people regularly ask: "What exactly is the influence of humidity?" And my standard answer has always been: "Nothing to worry about." Some time ago, one of … [Read more...]
E missivity in Practical Temperature Measurements
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...]
Estimating Parallel Plate-fin Heat Sink Pressure Drop
In the last issue of ElectronicsCooling a methodology was presented for estimating parallel plate-fin heat sink thermal resistance [1]. The method presented assumes that the air flow rate is given, either in terms of the average velocity, V, between the fins or a volumetric flow rate, G. Although this methodology was shown to be useful in examining the effects of heat sink … [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...]
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