Experimental investigation of a novel asymmetric heat spreader with nanostructure surfaces

• We developed an asymmetric heat spreader with nanostructured hydrophobic condenser.
• We examine changes in the level of initial pressure with the heat transfer coefficient.
• The asymmetric vapor chamber can greatly reduce the heater temperature.
• The novel vapor chamber can transfer heat upwards more effectively.
• The aspect ratio is crucial to the horizontal effective thermal conductivity.

A novel asymmetric vapor chamber is developed in this study. In this vapor chamber, nanostructure is patterned on the inner top surface of condensing wall and this condensing wall is made to be super-hydrophobic to replace the conventional porous wick. This improvement not only results in drop-wise condensation which has a much higher heat transfer coefficient compared with film condensation, but also provides a shortcut for the condensed water to drop back directly to the center wick. Thus, a smaller liquid flow resistance and higher anti-dryout capability are achieved. The evaporator wick is made of sintered multi-layer copper powder. The dimensions of the vapor chamber are 70 × 70 × 3 mm3. The test module includes an aluminum block with recirculated cooling water going through it and a heater with an area of 1.5 × 1.5 cm2. The optimum working pressure is determined by testing the performance of the vapor chamber under different initial pressures. Heater temperature, horizontal resistance and vertical resistance are identified as key parameters to evaluate the performance of heat spreader. It is found that heater temperature increases with increasing heat flux. However, the vertical resistance shows the opposite tendency with increasing heat flux. The performance of the novel vapor chamber is compared with that of a conventional vapor chamber and copper plate. The newly developed vapor chamber can greatly reduce the heater temperature. Furthermore, better temperature uniformity and a lower vertical resistance can be achieved for the newly developed vapor chamber which is promising for the thermal management of high power electronic devices.