Characterization of flow-pattern and heat transfer of micro flat heat pipes

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.In this study, thermal performance and flow visualization of a double layer flat micro vapor chamber are carried out. Two micro vapor chambers having pin fin and pin fin array support structure were fabricated and tested. The micro vapor chambers were composed of silicon and glass wafers having an overall size of 35 mm × 40 mm × 1.525 mm. Test results show that both the pin fin and pin fin array vapor chambers show appreciably lower thermal resistance as compared to the solid silicon counterpart, the thermal resistance of the pin fin vapor chamber is about 52-60% of the solid silicon whereas the corresponding thermal resistance of pin fin array is only 17-20 % of the solid silicon. The thermal resistance of the pin fin vapor chamber is moderately increased with the increase of supplied power whereas opposite trend is encountered for the pin fin array. The phenomenon is associated with the influence of dry-out phenomenon. It is found that the pin fin array vapor chamber is still in function even for an upside-down arrangement. The thermal resistance, however, is reduced with the rise of tilt angle, and the vertical arrangement gives the lowest thermal resistance. However, the thermal resistance is considerably increased if the heat source is placed upwards, and the corresponding thermal resistance for an upside-down heat source can be threefold higher than that of the vertical arrangement.