石墨纳米溶液的沸腾传热特性研究

Study of the Boiling Heat Transfer Characteristics of a Graphite Nano Solution

为研究强化沸腾传热系数和临界热流密度的方法,本文采用石墨纳米溶液作为沸腾工质,分析了不同质量浓度的石墨纳米溶液对沸腾传热系数和CHF(临界热流密度)的影响。实验结果表明:相比去离子水,石墨纳米溶液能够强化沸腾传热系数,在测试工况下,传热系数最大可增加30%。当石墨的浓度从0.05 g/L增大到2.5 g/L时,沸腾传热系数的强化效果先增大后减小。同时,纳米溶液使CHF得到增强,随着浓度的增大,CHF的强化效果也是先增大后减小。在实验测试的工况中,1 g/L石墨纳米溶液强化沸腾传热的能力最强,此时的CHF值也最大。石墨纳米溶液沸腾后,加热表面亲水性增强,静态接触角变小,这是CHF提高的一个重要因素。

To investigate the enhanced boiling heat transfer coefficient and the critical heat flux method,with a graphite nano solution serving as the boiling working medium,analyzed was the influence of the graphite nano solution at various mass concentrations on the boiling heat transfer coefficient and critical heat flux density. The test results show that compared with deionized water,the graphite nano solution can enhance the boiling heat transfer coefficient. Under the test conditions,the heat transfer coefficient can maximally increase by 30%. When the concentration of graphite increases from 0. 05 g / L to 2. 5 g / L,the enhanced boiling heat transfer coefficient will first increase and then decrease. In the meantime,the nano solution will enhance the critical heat flux. With an increase of the concentration,the enhanced critical heat flux will first increase and then decrease. Among all the test conditions,the graphite nano solution at a concentration of 1 g / L will have a strongest ability in enhancing the boiling heat transfer and at such a time,the critical heat flux will be maximal. After the graphite nano solution had been boiled,the hydrophilicity of the heating surface will be enhanced and the static contact angle will become smaller,which is an important factor to enhance the critical heat flux.