This is Hsink

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this is Introduction

Hsink is a heat sink design program that is particularly targeted for front-end design and optimization purposes.

The idea is to provide a tool that takes the user from an idea to an actual design in the smallest time possible.

Options are added almost ceaselessly. The ambition is to keep keep up with the rapid development of electronics.

The calculation procedure uses a step variable principle. The diagram above was created by 4 calculations with the pitch as step parameter. Total creation time ~ 15 min,

The integrated diagram option makes it simple to create intuitively understandable diagrams.

A large variety of problems can be addressed. Examples.


Program structure



The heat sink is defined in a set up window with several tabs. Which of these that are visible or active depends on the problem definition. The set up tab handles this functionality. There is also an image that symbolically shows the options selected


The program performs calculations for a range of values of a step parameter which could be either of: the pitch, the fin count, the velocity or the fan speed.

The result is presented in a list that has as many rows as defined by the count variable. It can be presented in a large selection of pre-defined diagrams. The entire list can also be copied to the clip board.



Set up options


Calculation step
Defines the step variable.

Calculation task
Can be either given temperature difference or given heat dissipation.

Fin calculation
Defines if the fin thickness takes the given value or if it optimized for each calculation step.

Defines if heat transfer by radiation should be considered or not.

Flow condition
Defines how the air flow is calculated. The fan option is associated with a fan curve. The velocity and pressure drop options are associated with single value inputs.

Bottom plate
Defines if the bottom plate is isothermal or if there are one or several discrete sources.

Defines the bypass type. The heat sink bypass option is associated with an area ratio. The duct bypass option is associated with a pressure drop coefficient in a off-branching duct.

Side fin cooling
Defines if the cooling of two extreme side is double sided or not.

The input window automatically out-selects combinations that not are allowed.



The measures tab handles the physical dimensions of the heat sink. The image makes it easy to check that the values are reasonable set. One or several inputs can be inactive depending on how the problem is defined.

Heat load


The heat load tab handles the heat load. If the bottom plate is isothermal it only has a single input line. If there are discrete sources it is more detailed.

The heat sources are defined as rectangles. They are specified in a table and can also be moved with the mouse. Overlapping is allowed.

Temperature difference

This tab is only visible if the given temperature difference option has been selected. It is a simple input.



This tab is only visible if the fan option has been selected as flow condition. The fan curve is a line train defined by an arbitrary number of points. The curve can be saved, various units can be used and the fan count can be controlled.


This tab is only visible if velocity has been selected as flow condition. It is a single value input.

Pressure drop

This tab is only visible if pressure drop has been selected as flow condition. It is a single value input.


This tab is only active if the include radiation option has been selected. The inputs are the emissivity of the heat sink and the radiation environment temperature.

Air duct

This tab defines the pressure loss coefficient for in the air duct and the area ratio at bypass flow and the properties for the bypass flow channel. Which one of these inputs that are active depends on the problem definition.


Defines the properties for the fluid.


The result list


Hsink presents the calculation result in a list with 15 columns which enables a very rich result presentation. The list can be copied to a spread sheet program which further expands the presentation possibilities.


Result diagrams


Hsink can show and save the values generated by a calculation in a rich collection of pre-defined diagrams.

The diagrams have a large number of appearance options. The font, the background color, the margins and the scales can all be controlled. An image of the heat sink, curve labels and set up data can be included. The diagrams can be saved as GIF-files and copied to the clip board. An exact width and height control makes it simple to fit the diagram into a given space.


Calculation principle


Hsink is based on analytical correlations for the heat transfer coefficient and the pressure drop in rectangular flow channels. Although this method has its constrains, it has the advantage of being fast. The unique possibility to cover a range of cases in each calculation would not have been possible without it.

There is also has a unique ability to calculate heat sinks in bypass flow. The theory for this procedure was developed as a result of a cooperation with the Applied Thermodynamics and Refrigeration department at KTH in Stockholm.

Bottom plates with discrete heat sources are calculated by an analytical three dimensional solution to the conduction equation.




Hsink creates intuitively understandable overviews in a matter of a few minutes. To do anything corresponding with programs that only calculate single cases takes hours. The code is a great time saver.


User support

Hsink comes with a 37 pages long manual and there are quite detailed help files. To learn to run it only takes a few of hours.