石墨膜表面临界热流密度实验研究

Experimental Study of Critical Heat Flux on a Graphite Film

本文以光滑石墨膜作为加热表面,在标准大气压下以去离子水为工质进行了饱和池式沸腾实验。实验研究表明,在热流密度达到1.83 MW/m^2时,石墨膜发生膨胀并使其表面局部破裂,随着热流密度的进一步升高,破裂的面积逐渐扩大,石墨膜的电阻呈现阶跃式升高。在2.40 MW/m^2的热流密度下,石墨膜表面全部破裂,此后随着热流密度增加,电阻上升幅度变小,最终,在热流密度达到3.17 MW/m^2时,石墨膜发生烧毁。可见,石墨膜通过膨胀破裂的方式能自适应地强化沸腾传热临界热流密度,强化比例达到73%。同时,通过高速摄像机的观察发现,在相同热流密度条件下,与光滑表面相比,膨胀表面的气化核心数增多,气泡脱离直径变小,气泡脱离频率变大。

Saturated pool boiling experiment with heater surfaces of smooth graphite films was conducted under atmospheric pressure,and the deionized water was used as working fluid.The test results showed that the graphite film began to expand and fracture in some parts of the surface as the heat flux reached 1.83 MW/m^2.Then the expanded area enlarged and the resistance of the graphite film rapidly increased with the increase of the heat flux,until the whole film was expanded and the surface was ruptured uniformly under a heat flux of 2.40 MW/m^2,while the resistance increased slowly during this process.Ultimately,the graphite film was burned out at a heat flux of 3.17 MW/m2.Consequently,the critical heat flux of the graphite film could be enhanced by an adaptively expanding processing with an enhancement ratio of 73%.The visualization results through a high-speed camera showed that compared with the smooth surface,the quantity of nucleation was greater,the bubble departure diameter was smaller,and the bubble departure frequency was higher on an expanded graphite surface under the same heat flux condition.