RESUMO

A miniature loop heat pipe (mLHP) with heat transfer enhancement in the evaporator and condenser is a reliable alternative for thermal management of high-power electronic components. Experiments are conducted to investigate the heat transfer performance of an mLHP which uses Cu-water nanofluid with different concentrations as the working material. The boiling heat transfer coefficient of the evaporator is largest when nanoparticle concentration is 1.5%. Experiments are also conducted to understand the repeatability of the mLHP with different mass concentrations of nanoparticles and heat transfer characteristics of the mLHP with different wick materials. At steady state, temperature differences of the evaporator between the first operation and the fourth are small. It takes even less time for the mLHP to reach steady state at the fourth operation. It is also found that the mLHP with a wick of sintered copper fiber presents a smaller boiling heat transfer resistance and condensation heat transfer resistance. Based on diffusion theory, the heat flux is classified as heat transfer resulting from the assumed single-phase fluid plus heat diffusion produced by Brownian movement of the nanoparticles. A Cu-water nanofluid with a moderate concentration of 1.5 wt % presents the best heat diffusion effect.