The value of thermal conductivity for most gases and vapors range between 0.01 and 0.03 W/mK at room temperature. Notable exceptions are Helium (0.15) and Hydrogen (0.18). The most common theoretical explanation of heat conduction in gases is provided by the kinetic gas theory, which treats the collisions between the atoms or molecules as the prime mode of transfer of energy. … [Read more...]
Pressure drop coefficients for thin perforated plates
Almost everyone working on pressure drop coefficients of perforated plates encounters the work of I.E. Idelchick {1}. A plethora of graphs or equations - some of which are impossible to evaluate quickly - must then be addressed. To simplify this issue for the reader, this month's Technical Data page has been designed to provide an overview of this information. When focusing on … [Read more...]
Conduction heat transfer in a printed circuit board
In this issue, we examine heat flow in a printed circuit board (PCB), which typically is a layered composite consisting of copper foil and a glass-reinforced polymer (FR-4). A cross-sectional view of such a laminated structure is illustrated in Figure 1. The Figure indicates the numbering system that will be used for indicating the different layers, numbered 1 through to … [Read more...]
The thermal conductivity of silicon
The most important material within the semiconductor industry is Silicon. When dealing with electro-thermal device modelling, or the interpretation of fast transient techniques for the measurement of thermal impedance, thermal conductivity of Silicon is required. For steady state thermal analyses at the board and system level, however, accurate values are not required, because … [Read more...]
Fan selection – quick techniques to compare various tube-axial fan designs
The worldwide market for tube-axial fans is very large and, as a consequence, the number of tube-axial suppliers is significant. This article will focus on the techniques that can be used to quickly compare various tube-axial fan product offerings, in order to provide a quick screen and minimize the number of suppliers that are submitted to a detailed evaluation. Supplier … [Read more...]
