Experimental study on thermal performances of ultra-thin flattened heat pipes

Abstract

With the fast development of microelectronic devices, high-efficient heat dissipation in narrow spaces faces significant challenges. Ultra-thin flattened heat pipe (UTHP) technology is proposed as a breakthrough in this field; however, some improvement, especially in optimizing the capillary wick, is required before UTHPs can be further applied. In the present study, the thermal performance of UTHPs (thickness of 1 mm) with mesh wicks in various mesh structure have been investigated. Results demonstrate that a higher mesh number of the mesh wick can not only accelerate the start-up response but also reduce the thermal resistance in steady-state operation. However, too high mesh number has disadvantages. The corresponding permeability will decrease as the mesh number increasing, resulting in a large working fluid flow resistance. The mesh structure should be optimized for sufficient capillary pumping power and high permeability to insure the best thermal performance of the UTHP. Within the mesh number range of 120 in−1 to 220 in−1, the 180 in−1 mesh wick should be a better choice to achieve the optimum performance for the UTHP. Moreover, through multi-orientations tests, it is revealed that the gravity plays an important role in the thermal performance of the UTHP. The mesh wick with 200 in−1 mesh number can effectively help the UTHP to maintain good anti-gravity stability.