Experimental Investigations of Boiling Heat Transfer in an Evaporator Using Silica Nanoparticle Coatings

• Main Authors: Chun-Hsien Huang, 黃俊賢
• Other Authors: 康尚文
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/72288303003438244606

博士 === 淡江大學 === 機械與機電工程學系博士班 === 102 === This study investigated the effects of silica nanoparticle structures on boiling heat transfer at evaporator. The experiment reveals the effect of thermal performance and bubble growth by nanoparticle structures. The nanoparticle coated structures were used in heating surface of evaporator, and the particles are mesoporous silica nanoparticle (MSM-41), silica nanoparticle (SiO2-S) and silica mircoparticle (SiO2-L), respectively. Comparison of TEOS sol and plat structures are thermal performance with silica particles. The MCM-41 and SiO2-S coated structures contact angle were less than 10 and droplets expanding very fast. The experimental method of using level adjustable thermosyphon (LAT) and two phase loop thermosyphon (TPLT) are researched of boiling heat transfer in atmospheric pressure and sub-atmospheric pressure, respectively. The working fluid is DI water. During a cycle of experiment, the primary heat transfer mechanisms of LAT is sequentially from natural convection, nucleate boiling, thin-film evaporation and dryout in atmospheric pressure, as LAT and TPLT were experimental investigated in pool boiling. The experimental results show that silica nanoparticle structures have a higher heat flux, because they have better surface wettability of hydrophilic. In the atmospheric pressure and surface superheat is 20 oC, the SiO2-S structure heat flux is 677 kW/cm2. SiO2-S structure heat flux is 2.4 times of plat structure. In the sub-atmospheric pressure and surface superheat is 30oC, the SiO2-S structure heat flux is 2391 kW/cm2. SiO2-S structure heat flux is four times of plat structure. The maximum heat flux and minimum thermal resistance in turn were SiO2-S, SiO2-L, MCM-41, TEOS and plat structures. Therefore, nanoparticles coated structures has better thermal performance. The thermal performance of MCM-41 is poor than SiO2-S and SiO2-L, because it is difficult to coated on the heating surface.