DAU - A Miba Group Company

Basic Design Concepts in the use of Super
Thermal Conductors

When deciding upon the appropriate solution for any thermal applications, it becomes immediately important to the maximum amount of heat energy to be transmitted or dissipated in terms of Watt.

On having quantified this, it is then necessary to determine what are the thermal performance requirements of systems in term of W/°C to effectively manage the energy transfer with an acceptable temperature differential T.

In virtually all thermal applications, including those utilising Super Thermal Conductors, a minimum number good thermal interface is essential to minimise the overall system Rth (thermal resistance).

The following tables provide the design engineers with information about the thermal performance of DAU Super Thermal Conductors.

Table 1 needs to be read in conjunction with table 2 and 3 and shows STC and STX Series thermal power transmission capabilities.

Power rating of DAU Heatpipes is generally tested and rated at horizontal working position.

Table 1 shows the typical power transmission in Watts as a function of the diameter and the temperature differential T between hot and cold side of the heatpipe.

Table 1 - Thermal Power transmission of STC and STX Series Heatpipes

Super Thermal Conductors (Heatpipes) rely upon an effective capillary action between the working fluid and the internal porous lining (wick structure).

Gravity has a very important influence on the thermal performance.

As can be seen in tables 2, gravitational effect can increase the thermal transmission capabilities of an STC or STX Heatpipe to 2 times that of its maximum thermal transmission capability when operating in a vertical plane; i.e. with Evaporator section lower than Condenser section.

In this orientation gravity assists the return fluid flow.

In the opposing mode, i.e. Evaporator section high, and driving heat downwards, the capillary action must work against gravitational force.

Table 3 shows the influence in this case, which is entirely dependent upon the static height difference between the Condenser and Evaporator section.

For certain applications, where this effect would cause an unacceptable constraint on a system, DAU can offer also special antigravity Heatpipes (Series SSC and SSX) with special capillary wick structures, which have a much reduced sensitivity to effects of gravity.

Table 2

Table 3