Creating a composite wick from a variety of wick types can maximize performance by using the unique benefits of each individual wick structure to overcome the weaknesses of a single wick type. The main drawback of composite wicks is higher cost and more complex manufacturing techniques. However, the thermal performance gains can be anywhere from 20% to 50% over single-wick-type heat pipes.
Some common configurations for composite wicks are:
This is created by using two screens of different pore sizes; the smaller pore size is next to the vapor space, and the larger pore size is next to the pipe wall. This difference in pore size creates higher capillary pressure than a single screen would alone.
This is created by a screen layer placed over grooves in the heat pipe wall. This allows the heat pipe to function at angles that would strain a grooved wick by itself, due to the increased capillary head.
This is created by placing a slab of porous material in the center of the vapor space, with grooves in the pipe wall that distribute the condensate all along the pipe wall from the slab wick. This is used in low-vapor velocity applications where the heat pipe length is short.