Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Room: Exhibit Hall A
Carlos D Espino-Mendez - Garden City Community College
Co-Author(s): Jordan Morrow, Kansas State, KS; Melanie Derby, Kansas State, KS
Heat exchangers and heat pipes are used to transport heat from one fluid to another. Heat pipes currently use sintered particles, screen meshes, and rectangular grooves to flow water from the condenser to the evaporator side. In recent years, capillary wicking structures have been proposed to improve heat pipe performance. Research is now being done to understand the fundamentals of capillary driven motion . This research?using lightweight polymers instead of metals?could reduce the weight of future heat pipes and create better performing heat exchangers. For our research, we studied three geometry wicks. Conical, two cylindrical (1.22 mm and 1.86 mm diameter), and pyramidal micropillars were 3D-printed on a small base. We also printed particles with diameters of 1.0 mm, 1.5 mm, and 1.75mm in a cubic structure and one with 1.0 mm diameter particles in a pyramidal structure. The diameter and spacing of the micropillars were adjusted so the porosities were similar, from 0.640 to 0.755. For the experimental process we used the rate-of-raise test, where we visually see a liquid rise vertically through the pores of the wicks. First, we place a wick in a stand above a dish of water (surface tension: 72 mN/m) or a low-surface-tension liquid, i.e. FC-40 (surface tension: 16 mN/m ). We raised the dish until the liquid touches the bottom surface of the micropillars and capillary force raises the liquid through the pores, opposing gravity. All of this was recorded with a high-speed camera. The videos were analyzed to calculate rate of raise, permeability, and effective pore radius. Our hypothesis was that the pyramidal and conical micropillars would outperform the cylindrical wick. Since they take more space and with their peaks, they can hold more liquid. Once we tested all eight wicks, the 1.22 mm cylindrical wick had the highest permeability. With FC-40, all the wicks performed almost the same. We also learned that the particle wicks were more effective than the micropillars. The micropillars have potential but need to be studied more to make them useful. References:  Ranjan, R., Patel, A., Garimella, S. V., & Murthy, J. Y. (2012). Wicking and thermal characteristics of micropillared structures for use in passive heat spreaders. International Journal of Heat and Mass Transfer, 55(4), 586-596.  Heat transfer applications using 3M Fluorinert Electronic Fluids(Tech.). (2016, July). Retrieved July 12, 2019, from 3M website: https://multimedia.3m.com/mws/media/1091998O/3m-fluorinert-electronic-liquids-for-heat-transfer-line-card.pdf
Funder Acknowledgement(s): Funder Acknowledgement(s): To Kansas Louis Stokes Alliances for Minority Participation supported by the National Science Foundation under Grant Number 1305059 and NASA Cooperative Agreement Notice Grant Number 80NSSC18M0030.
Faculty Advisor: Melanie Derby, email@example.com
Role: I designed the geometrical wick designs and adjusted particle designs that the lab had previously worked on. After calculating the porosities I hypothesized that the pyramidal and conical wicks would outperform the cylindrical wick because the peaks would help hold more liquid. And through the rate-of-rise test I determined that the hypothesis was false.