UC San Diego

Heat pipe is widely use in electronic system cooling, benefit from it’s simple structure and high cooling efficiency. With the emergence of new-generation computers generating heat fluxes of up to thousands of watts per square centimeter, there is a need to explore innovative heat transfer solutions to meet these higher thermal demands. One promising approach is to improve the fluid transport performance of the wick structure. However, there is a trade off between high capillary pressure and high permeability in wick structure. Here, a low cost glass fiber based wicking structure was presented to enable liquid film evaporation for enhancing both heat transfer coefficient (HTC) and critical heat flux(CHF). The membrane utilized in our study features a biopores structure created by randomly pressing glass fibers together. This specific structure was chosen due to its simple but advantageous characteristics, allowing for enhanced performance in our capillary-driven wicking structure. A study on the dependence of heat transfer performance on the pore size of glass fiber membrane was conducted. Remarkably, a high CHF of 600W/cm2 was observed under atmosphere pressure when the heater area and evaporation area were equal (0.5cm2). This indicates the wicking structure's exceptional ability to handle high heat fluxes. Additionally, the study revealed that the highest HTC reached an impressive value of 5.5W/cm2 K, demonstrating the efficient heat transfer capability of the glass fiber-based wicking structure.Another possible to solve the trade off between high capillary pressure and high permeability is to change capillary pressure to osmotic pressure using hydrogel. To revel the feasibility of osmotic driven wick, we made two kind of hydrogel: PSA [poly(sodium acrylate)] and PEGDA[poly(ethylene glycol) diacrylate], then tested the permeability. Based on the obtained results, we proceeded to calculate the evaporation heat flux theoretically, considering the hydrogel thickness as a variable. Through this analysis, we were able to demonstrate the feasibility of the osmotic pumping wick concept. We also attempt to make some hydrogel coated sample for evaporation test.