The Application of Self-Rewetting Fluids on Loop Heat Pipe
| Autor: | Wei-Jhih Lin, 林威志 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 The objective of this study is the application of self-rewetting fluid as the working fluid on loop heat pipe (LHP), with sintered copper as the chosen capillary structure material; this study also investigates the effect of using different components and concentrations of self-rewetting fluid as well as compares their heat transfer performances with that of water. Previous studies have show that using self-rewetting fluid as working fluid can enhance the heat transfer mechanisms of pool boiling,traditional heat pipe, and wickless heat pipe. Compared with using pure substance as working fluid, where the surface tension decreases linearly with increasing temperature, self-rewetting fluid’s surface tension has a non-linear relationship with temperature changes; therefore, at a certain temperature, the self-rewetting fluid’s surface tension increases with increasing temperature, resulting in the Marangoni effect, and the condensed liquid can be transported to the heating surface, delaying the occurrence of dryout and thus increasing the critical heat load. Concerning the effect of varying the concentration of butanol aqueous solution on heat transfer performance of LHP, concentrations ranging from 2% to 8% is investigated. Experimental results show that 6% butanol aqueous solution results in the the best heat transfer performance of LHP; compared with that of water, the critical heat load is increased by 130% and the total thermal resistance is decreased on average by 50%. Concerning the effect of changing the components of self-rewetting working fluid, the fluids considered are butanol, pentanol, hexanol, and heptanol, with the concentration of each as the maximum solubility concentration in water under standard conditions. Experimental results show that, compared with using water as working fluid, using self-rewetting fluid can allow the total thermal resistance of LHP system to decrease, increasing the critical heat load. Concerning the heat transfer performance of different self-rewetting fluids, under operating temperature of 90°C or lower, hexanol aqueous solution achieves the largest heat load of 250W and lowest total thermal resistance of 0.33°C/W; at operating temperatures higher than 90°C, hexanol aqueous solution has already reach the critical heat load, causing the system to be unstable, but butanol aqueous solution achieves the best results, with maximum critical heat load of 350W and minimum total thermal resistance of 0.32°C/W. Therefore, after analysis of the heat transfer performance of various self-rewetting fluids, butanol water solution has the largest operating temperature range, highest critical heat load, and lowest total thermal resistance, indicating that butanol water solution is most effective on heat transfer performance of LHP. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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