چكيده به لاتين
Topic of phase change heat transfer from liquid to vapor get important more by considering the energy challenges and efficiency improvement, equipment miniaturization and optimized cooling, improvement of insurance and power of nuclear reactor, boiler and exchanger efficiency improvement and etc. More attention is on recent development in fabrication of micro/nanostructured surfaces for phase change enhancement. Effect of different surface parameters on pool boiling enhancement is not clear yet. Recent researches propose the important surface characteristics on pool boiling are porosity, wettability and roughness.
In this thesis, micro/nanostructured surfaces are fabricated on copper substrate according to effective surface parameters in shape of porous, hydrophilic, channel and combination of them to investigate the level of pool boiling enhancement of water in atmospheric pressure. After presenting the concept and advantages of pool boiling enhancement on chapter one and two, new research fields is recognized by literature review. Similar to most other researches in boiling enhancement, our study is based on experiment of new surfaces and explaining the performance. With this regard, design of experiment and experimental setup is explained on chapter three. In chapter four, first the problem of porous surface fabrication by sintering method is presented and then electrodeposition method as an optimized substitution method is used to fabricate different porous structure with changing the parameters of time, current, and temperature of electrolyte. Characteristics which predict is effective on boiling performance, is measured and boiling experiment results show acceptable agreement with predictions. In addition, numerical model with simplification is presented. In chapter five, semi-analytical model for prediction of nucleate pool boiling performance on hydrophilic surfaces by considering the static and dynamic contact angle is presented and prediction results is compared with previous model and experimental data. In chapter six, effect of geometrical characteristic of inclined microchannel which are fabricated with WEDM, is experimented on pool boiling performance. In order to more enhancement, combined surfaces such as porpos layer on microchannel and wettability change on channels is investigated. Results show porosity, channel and hydrophilicity are important parameters for boiling enhancement, respectively. As ecpected combined surfaces enhanced heat transfer coefficient and critical heat flux more than all the simple structured surfaces.
