Characterization

The Competence Center Heat Pipes has developed a test bench for the characterization of cylindrical heat pipes which is characterized, among other things, by its high angle of inclination precision. We can use it to flexibly and precisely measure heat pipes in terms of their function from vertical to horizontal, depending on the respective requirements. At the measuring station, we vary the power applied as well as the temperature of the cooling water and determine the thermal resistance and heat transfer limits depending on different operating conditions.

Specification of the measuring station:

• Size: 200 – 2000 mm length, 8 mm – 12 mm diameter
• Temperature range: 10 – 90 °C in the cooling water, up to 200 °C at the heat pipe
• Power range: 10 – 1000 W
• Orientation: -5 – 90° (negative angles: condenser below evaporator)
• Customized variations

A measuring station has been specially developed for characterizing planar heat pipes (e.g. heat spreaders/vapor chambers, pulsating heat pipes). This allows heat pipes to be investigated with regard to their thermal resistance, temperature operating range, and startup behavior. In addition, the test objects can be measured in different orientations in order to investigate the influence of gravity on their performance.

Currently, the measuring station has the following specifications, which, however, can be adapted to customer-specific requirements or extended beyond the specified dimensions, performance, etc., if required:

• Size: base area up to approx. 13 x 13 cm²
• Temperature range: approx. 20 – 200 °C
• Power range: up to kW range, depending on dimensions of test object
• Orientation: horizontal, vertical, and with tilt angle of 45 °C
• Heat source (ceramic heater) and heat sink can be placed in different locations
• Air or water cooling as heat sink possible

In addition to contact-based thermal measurement technology (thermocouples and resistance temperature sensors), the Competence Center Heat Pipes disposes of the equipment and practical experience to characterize heat pipes using infrared thermography. It allows fast two-dimensional quantitative visualization and evaluation of the temperature distribution on the heat pipe, both in still image and time-dependent. Various high-resolution infrared cameras with high frame rates are available for this purpose. Hereby, many practical relevant questions for heat pipes can be answered quickly and easily.

A 3D computer tomograph enables three-dimensional imaging of the internal structure of a heat pipe. Due to the powerful 300 kV X-ray tube used, parts made of heavy elements that are otherwise difficult to ray, such as copper, can also be examined. This also allows leaks or other defects to be detected and thus heat pipes to be analyzed for damage if necessary. For certain fluids (e.g. water), the fluid distribution in a heat pipe can even be examined »live« and with several images per second under suitable conditions.  

A quick test is available to check heat pipes with regard to their general functionality as well as manufacturing defects, e.g. an excessively high inert gas content.

Development of individual test setups

The Competence Center Heat pipes develops individual test setups according to the customer's requirements. For example, the measurement method, the measurement infrastructure, or the safety requirements can be adapted to the customer's specific wishes to enable the best possible characterization of the heat pipes.