Study of Physical Characteristics of a Bi-porous Composite Capillary Wick for a Flat Miniature Loop Heat Pipe

Miniature loop heat pipe (mLHP) can meet the demand of high heat flux dissipation, arising out of miniaturization of modern electronic devices. Capillary wick is an essential component of mLHP because it serves as a thermal and hydraulic locking in the device, and also provides capillary pumping that renders the device passive. In the current study, a bi-porous composite capillary wick made of copper and aluminium powder was fabricated for flat mLHP, with a diameter of 50 mm and a thickness of 4 mm. Capillary performance index of the wick such as capillary rise, wettability, porosity, permeability, and pore size were studied. The process of the capillary rise was observed using an infrared camera. The capillary rise height was determined to be 9.5 mm, utilizing the mass conservation method. Static contact angles (CA) on aluminium and Copper surfaces were observed for acetone and methanol fluids by sessile drop method. Acetone was found to be a better choice as it has low CA, hence higher wettability. The wick was found to have a porosity of 42% and permeability of 0.031 µm2. The average pore diameter of the aluminium and the copper wick is found 6.82 µm and 0.38 µm, respectively.