Thermocouples are widely used for temperature measurements. They are particularly useful in lab testing, due to their relatively low cost and the ability to easily fabricate thermocouples of specific lengths for a given test. This Tech Brief discusses issues related to the size of a thermocouple that may be considered when using them. A thermocouple consists of two wires made … [Read more...]
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Calculation Corner: Properties of Humid Air
INTRODUCTION Long time readers may recall that one answer to the question of how humidity changes the thermal conductivity of air is “Nothing to worry about” [1]. Generally, the effect of humidity on air properties is small enough that it can be neglected. However, at high ambient temperatures and low pressure, humidity effects may need to be addressed in applications such as … [Read more...]
Calculation Corner: A Simple Method for Estimating Radiation Heat Transfer
This article describes a semi-empirical equation that can be used to assess radiation heat transfer in terms of an effective convection coefficient. The effective convection coefficient due to radiation is shown to be: Where temperatures are in °C and ε is the emissivity of the radiating surface. This equation is accurate to within ~10% over a temperature range of 0 - … [Read more...]
Electronics Cooling Sanity Check
Introduction A number of years ago I attended a meeting at Purdue University to discuss future challenges and goals for electronics cooling research. One topic that generated a significant amount of interest was, what magnitude of heat flux represented a substantial challenge that the electronics cooling community should be striving to meet with new developments. The closest … [Read more...]
Rank Sum Tests
Introduction The previous column in this series described methods for assessing whether a set of data was normally distributed [1]. In the event that data is shown to not have a normal distribution, one might ask how to conduct a statistical analysis on it given that many statistical tests are developed on the assumption that the data are normal. For example, how can two … [Read more...]
