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Online calculator for natural convection heat sinks.
NatSink is
a more elaborated code that makes the optimization process
both faster and simpler.
See examples.
Related links
Straight fins are better than pin fins!
Improve natural convection with inclined fins
Improve natural convection with chimneys
Thermal design for electronics
Thermal online tools
Unit conversion
Comments
General
The heat sink tab
Calculates the temperature difference, the thermal
resistance and the volumetric efficiency as function of the heat
load. The bottom plate is assumed to be isothermal. Clicking in
the diagram opens a panel with tabled results that can be copied
and pasted into a spread sheet program.
The heat source tab
Calculates the temperature distribution on the bottom plate as
a function of the heat sources defined. Maximum 5 sources can be
used.
Theory
The equations used can be found in chapter 8 and 10 of the
theory document. The articles
A Volumetric Approach to Natural Convection and
A Fourier Series Solution also covers some
of the matters.
To fully enjoy all the features,look at the
editing options
Options, Heat sink tab
Width.
Is the width of the heat sink.
Height.
Is the height of the heat sink which is assumed to be in
a vertical position.
Cond fins.
Is the thermal conductivity of the fin material.
Some examples are given below.
For other materials see:
Tools from Maya
Extruded aluminium: 210 W/mK.
Cast-aluminium: 150 W/mK.
Copper: 390 W/mK.
Air temp.
Is the inlet air temperature.
Side fins.
This parameter determines how the heat dissipation from
the two outer fin surfaces is calculated.
Insulated: There is no dissipation.
As free surface: The heat transfer coefficient is
calculated as for free surfaces.
As inner surface: The heat transfer coefficient is
calculated as for the inner fin surfaces.
Calculate.
Performs a calculation.
Temp diff.
Displays the temperature difference between the
bottom plate and the incoming air.
Therm res.
Displays the thermal resistance between the
bottom plate and the incoming air.
Vol eff.
Displays the volumetric efficiency. It is a measure on how efficient
the volume is used for cooling. The concept is explained in the
article,
A Volumetric approach to Natural Convection.
If the two extreme fin surfaces dissipate heat, the volumetric
efficiency can for some extreme cases exceed 100%. The same can
happen if radiation is included.
Fin eff.
Displays the fin efficiency. It is defined as the ratio of the
average fin-to-air temperature difference and the virtual
fin-to-air temperature difference had the thermal conductivity of
the fins been infinite.
Equ velo.
Displays the equivalent velocity. It is defined is the approaching
equivalent velocity. It is an approximation. For optimized
fin spacing it typically does not deviate more than 20% from the
physical velocity.
Pressure.
This input mutually depends on the altitude input. On clicking on
one the other one is updated.
Fin count.
Is the number of fins.
Fin height.
Is the distance from the bottom plate to the top
of the fins.
Fin thickness.
Is the thickness of the fins.
Heat diss start/end.
The calculation is made for 30 steps between these
two values.
Include radiation.
If include radiation is selected it is assumed that the
heat sink, (the back side of the bottom plate excluded),
can radiate heat into a large room with walls that have the
same temperature as the inlet air. The emissivity of the
heat sink surface is set to 0.9.
Save last/Delete last.
Saves or deletes the last curve
in the diagram. Maximum capacity is 5 curves.
2D-view/3D-view.
Shows a 2D or a 3D view of the heat sink.
Adjust 3D.
Not significant. Use the left/right mouse on the image to change'
the 3D-view.
Save/read data button.
Opens an panel with an XML text that can be used to save
and read input data.
Altitude.
This input mutually depends on the pressure input. On clicking on
one the other is updated. The allowed altitude
range is 0 - 11000 m.
Options, Heat source tab
X-pos.
Is the X-coordinate position of the heat source.
Y-pos.
Is the Y-coordinate position of the heat source.
Width.
Is the X-width of the heat source.
Height.
Is the Y-height of the heat source.
Heat diss.
Is the heat dissipation of the current heat source. The right
value is the total heat dissiaption
Set source data.
Enters the last heat source defined.
Add source.
This input can only be used in 2D-view mode. It adds an heat
source.
Delete source.
This input can only be used in 2D-view mode. It deletes the
current source marked by a thick frame.
Calculate.
Calculates.
Bottom height.
Is the height of the bottom plate.
Cond plate -X -Y -Z.
Is the thermal 3D-conductivity The values are set to the same as
the fin conductivity unless "Cond=fin" is unchecked.
2D-view.
Shows a 2D image of the heat source side of the bottom plate.
The position of the heat sources can be moved by the mouse.
3D-view.
Shows a 2D image of the heat source side of the bottom plate.
Edit.
The position of the heat sources can be moved by the mouse in
this mode.
Result.
Displays the result in a colored 2D or 3D mode.
Temp diff.
Shows the color scale as temperature difference.
Temperature.
Shows the color scale as temperature.
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