As discussed previously in this section, the measurement of the thermal conductivity is notoriously difficult. The consequence is that, while the measurement accuracy by individual researchers is claimed to be of the order of 2%, laboratories participating in round-robin tests produce results differing from each other by 15% or more [1]. Even the measurement of pure metals is … [Read more...]
Use of junction-to-board thermal resistance in predictive engineering
The readers of "Electronics Cooling" are familiar with the reasons why the junction to ambient thermal resistance [1], JA or RJA, is an inadequate description of the thermal performance of an integrated circuit. Likewise, you realize that vendors cannot continue to state the integrated circuit will work at a specified ambient temperature (55°C, 70°C, 85°C, or 125°C) as device … [Read more...]
Acoustic noise emission and communication systems in the next century
Acoustic noise emission is one of several physical design issues addressed during the design of telecommunications and information technology equipment. In most systems, noise is a by-product of the air-movers used for system cooling. The amount of heat dissipated in electronic systems cooled by forced convection is directly proportional to volumetric flow rate. The flow rate, … [Read more...]
Beyond the arrow plot – New methods for flow visualization
Within the realm of CFD-based flow analysis, the presentation of data is a vital issue. Researchers and developers need to gain insight, and non-technical managers and commercial staff have a critical need to understand the true ramifications of the data. Unfortunately, current methods for visualizing flow have limitations that make it difficult to interpret vast quantities of … [Read more...]
Convection and radiation heat loss from a printed circuit board
In last issue's column, a method for calculating the thermal conductivity of a printed circuit board (PCB) was described. Now, we look at a more complicated heat transfer process, namely the loss of heat from the surface of a PCB to the ambient air. This situation is more challenging to describe mathematically since it involves the simultaneous processes of heat spreading by … [Read more...]
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