Principles and Application

Heat-conducting pipes can conduct very large amounts of heat. The conduction of heat within the pipes is due to the processes of evaporation and condensation. The heat is conducted by the vapour. Following evaporation of the liquid in the hot zone of the heat-conducting pipe, the vapour then condenses in the cold dissipation zone. The condensation returns to the evaporation zone through gravity and the capillary effect.

Fig. 1. Heat-conducting pipe

Diameter selection

Heat-conducting pipes should be installed as closely as possible to the die contours. The diameter of the heat-conducting pipe should be as large as possible. Heat-conducting pipes with a diameter half that of the core are ideal.

Fig. 2: Selection of diameter for heat-conducting pipes in rectangular and cylindrical cores

Length selection

Conditions are ideal when the heat absorbing, conducting and dissipating zones each amount to one third of the total length of the heat-conducting pipe. As the thermal expansion of the heat-conducting pipes is greater than that of tooling steels, it is advisable to allow for an axial clearance of 0.3% of the length of the pipe:

Fig 3: Selecting the length of heat-conducting pipes

Tempering with heat-conducting pipes

Heat-conducting pipes withdraw heat from hot areas of a die and conduct it to cooler areas. Depending on application, heat-conducting pipes can be used to dissipate heat or to conduct heat into the contour areas during the warm-up phase. As heat-conducting pipes can be installed much closer to the die contours than water-cooling passages, the heat transfer is much higher.
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Recommendation for installation

The diameter of bore should be approx. 0.05 ot 0.1 mm greater than that of the heat-conducting pipe. The pipe should be installed without using force. The pipe should be installed using heat-conducting paste. Do not heat the heat-conducting pipe beyond the recommended operating temperature e.g. with a welding torch.