Abstract:

Heat transfer performance of pulsating heat pipe (PHP) could be affected by adding surfactant, and its mechanism was complicated. In this study, the effects of cetyltrimethyl ammonium bromide (CTAB) solution and heating power on the heat transfer performance of PHP were investigated experimentally. The liquid filling rate of 50% was fixed, and the mass fraction of 0—0.288% (0—8.0CMC)and heating power range of 10—105W were adjusted, respectively. The results showed that when heating power ranged from 20W to 90W and concentration ranged from 0.5CMC to 8.0CMC, the addition of CTAB could improve the heat transfer performance of PHP, which was reflected in the decrease of amplitude and increase of frequency of evaporation and condensation temperature fluctuation, and the decrease of thermal resistance of PHP. Among them, the strengthening rate of 4.0CMC was higher up to 11.0%—37.3%. At higher heating power, the strengthening effect of CTAB on heat transfer weakened or even deteriorated, such as the "drying" trend in PHP at 105W and 8.0CMC. For CTAB solution, the optimal concentration was about 4.0CMC, which was much higher than the critical micelle concentration (CMC). For these results, we should not only analyze the influence of static surface tension and viscosity, but also introduce the influence of dynamic surface tension.

Key words: surfactant, pulsating heat pipe, concentration, heat transfer performance, surface tension, viscosity

摘要：

添加表面活性剂会影响脉动热管（pulsating heat pipe，PHP）的传热性能，其机理较为复杂。本文以十六烷基三甲基溴化铵（CTAB）溶液为工质，实验研究浓度及加热功率对PHP传热性能的影响。固定充液率约50%，调节质量分数及加热功率范围分别为0~0.288%（0~8.0CMC）、10~105W。结果表明：加热功率20~90W、浓度0.5~8.0CMC范围内，添加CTAB可改善PHP的传热性能，体现为蒸发及冷凝温度波动幅度减小、频率增加，PHP热阻降低；其中，4.0CMC的强化作用率较高，为11.0%~37.3%。在较高加热功率时，CTAB对传热的强化作用减弱甚至恶化，如105W、8.0CMC时PHP内会出现“烧干”趋势。对于CTAB溶液，其最优浓度约为4.0CMC，远大于临界胶束浓度。对此结果，不能仅用静态表面张力及黏度的影响去分析，还需引入动态表面张力的影响。

关键词: 表面活性剂, 脉动热管, 浓度, 传热性能, 表面张力, 黏度