Pool Boiling Heat Transfer Performance of Micro-Thick Copper Foam with Porosity

As electronic equipment’s overheating issues become more serious, heat transfer through latent heat, especially by utilizing boiling, is gaining more attention compared to sensible heat. Surface modification, including the use of metal foams, can be employed to enhance boiling and thus improve heat transfer performance. Metal foams, being easily obtainable and possessing a micro-porous structure, have been used in several studies for promoting boiling. However, most of these studies used metal foams with a thickness greater than 1 mm and did not consider an important factor: porosity. Therefore, this study analyzed the change in pool boiling heat transfer performance with varying porosities of micro-thick copper foam through experimentation and visualization. Experiments were conducted with copper foams of thickness 200 μm and porosities of 54 %, 68 %, and 85 %. Regarding the heat transfer coefficient, the 68 % porosity copper foam showed the highest value at 273.7 kW/㎡ ⋅K, while the 85 % porosity foam showed the lowest at 144.2 kW/㎡ ⋅K. T he C ritical H eat F lux(CH F) w as h ighest for the 8 5 % porosity foam at 237.5W/㎠, and lowest for the 54 % porosity foam at 174.7W/㎠. Visualization analysis indicated that the heat transfer coefficient decreases with increasing porosity due to reduced conductive effects at low heat flux. At high heat flux, where bubble escape resistance is also a crucial factor, the 54 % porosity copper foam exhibited the highest heat transfer coefficient. At very high heat flux, where the effect of bubble escape resistance is dominant, the 85 % porosity foam achieved the highest CHF. These results provide guidance in selecting the appropriate porosity for copper foams used in boiling enhancement, based on the desired superheat and CHF.