Frequently Asked Questions
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No special training is needed to use the HeatSinkCalculator. You just need to know the physical dimensions, material and flow conditions of the heat sink. No advanced thermal analysis knowledge is required.
The thermal resistance value provided by the manufacturer is only valid for the heat source size used by the manufacturer to determine the thermal resistance. As the heat source dimensions are varied the thermal resistance will change. Also in the case of natural convection cooled heat sinks the manufacturer's thermal resistance value is again only valid for the heat source size and power dissipation used by the manufacturer when calculating this value. The natural convection thermal resistance is highly dependent on the temperature of the heat sink and hence the power dissipation of the heat source. If your design has a different heat source size and/or power dissipation the natural convection thermal resistance can be significantly different from the manufacturer's stated value.
CFD analysis is an excellent tool that can be used to accurately analyse heat sinks in various flow conditions. However its main drawback is that it can be very time consuming especially if you are analysing several design options or trying to figure out which design best meets your thermal requirement. The HeatSinkCalculator allows the user to set up and analyse a heat sink within minutes. Changes can be made to the design parameters quickly and the analysis re-run in seconds unlike CFD analysis that may take several minutes or even hours to conduct one analysis.
The best use of the HeatSinkCalculator if you have CFD software at your disposal is to use it to narrow down your design options. Once you have selected one or two options for further investigation, CFD analysis can be used to refine your design by analysing the options in the environment in which it will operate such as an enclosure with other components.
The HeatSinkCalculator uses a combination of analytical and empirically derived equations to calculate the thermal resistance, temperature and pressure drop across the heat sink.
The results of the HeatSinkCalculator have been compared against experimental data and are found to be in good agreement with these data. Below are links to two blog posts that provide a detailed explanation of the comparisons done.
Validation of the Calculator Results (Forced Convection)
Validation of the Calculator Results (Natural Convection)
Yes, the calculation takes into account the differences between laminar and turbulent flow.
If you wish to compare multiple designs at once then open several instances of the calculator in different browser windows or tabs.
When the approach velocity or volumetric flow rate option is selected the flow rate through the heat sink is fixed. The velocity of air flowing between the fins is determined by the space between the fins. The smaller the fin spacing the higher the velocity of air flowing between the fins. The higher the air velocity the more effective the cooling of the fins. If you were to try to optimize the heat sink dimensions the spacing between the fins would be a very small value since the air velocity and hence rate of cooling increases with decreasing fin spacing. In real world applications the flow is supplied by a fan or blower. The flow rate would not be fixed, it would be limited by the increase in pressure drop across the heat sink that would occur as the spacing between the fins decreases.