Pool boiling heat transfer on the microheater surface with and without nanoparticles by pulse heating |
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| Authors: | Li Xu Jinliang Xu Bin Wang Wei Zhang |
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| Affiliation: | 1. College of Chemistry and Molecular engineering, Zhengzhou University, Zhengzhou 450001, PR China;2. Department of Environmental Engineering and Chemistry, Luoyang Institute of Science and Technology, Luoyang 471023, PR China;3. National Engineering Laboratory for Wheat & Corn Further Processing, Henan University of Technology, Zhengzhou 450001, PR China;4. Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Clippinger Laboratories, OHIO University, Athens, OH 45701-2979 USA;1. Institute of Science and Technology in Art, Academy of Fine Arts, Schillerplatz 3, A-1010 Vienna, Austria;2. Institute of Chemical Technologies and Analytics, Analytical Chemistry Division, Vienna University of Technology, Getreidemarkt 9/161, Vienna, Austria;1. School of Human Settlement and Civil Engineering, Xi’an Jiaotong University, Xi’an, China;2. Key Laboratory of Renewable Energy Utilization Technologies in Building of the National Education Ministry, Jinan, Shandong, China;1. Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China;2. Department of New Energy Vehicle and Technique, SAIC Motor Corporation, Shanghai 201805, PR China |
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| Abstract: | We study the pool boiling heat transfer on the microheater surface with and without nanoparticles by pulse heating. Nanofluids are the mixture of de-ionized water and Al2O3 particles with 0.1%, 0.2%, 0.5% and 1.0% weight concentrations. The microheater is a platinum surface by 50 × 20 μm. Three types of bubble dynamics were identified. The first type of bubble dynamics is for the boiling in pure water, referring to a sharp microheater temperature increase once a new pulse cycle begins, followed by a continuous temperature increase during the pulse duration stage. Large bubble is observed on the microheater surface and it does not disappear during the pulse off stage. The second type of bubble dynamics is for the nanofluids with 0.1% and 0.2% weight concentrations. The microheater surface temperature has a sharp increase at the start of a new pulse cycle, followed by a slight decrease during the pulse duration stage. Miniature bubble has oscillation movement along the microheater length direction, and it disappears during the pulse off stage. The third type of bubble dynamics occurs at the nanofluid weight concentration of 0.5% and 1.0%. The bubble behavior is similar to that in pure water, but the microheater temperatures are much lower than that in pure water. A structural disjoining pressure causes the smaller contact area between the dry vapor and the heater surface, decreasing the surface tension effect and resulting in the easy departure of miniature bubbles for the 0.1% and 0.2% nanofluid weight concentrations. For the 0.5% weight concentration of nanofluids, coalescence of nanoparticles to form larger particles is responsible for the large bubble formation on the heater surface. The microlayer evaporation heat transfer and the heat transfer mechanisms during the bubble departure process account for the higher heat transfer coefficients for the 0.1% and 0.2% nanofluid weight concentrations. The shortened dry area between the bubble and the heater surface, and the additional thin nanofluid liquid film evaporation heat transfer, account for the higher heat transfer coefficient for the 0.5% nanofluid weight concentration, compared with the pure water runs. |
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