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沸沸腾傳热有核状沸腾与膜状沸腾之分。在核状沸腾时给热系数很大,而且随着热负荷升高,给热系数a也不断地增加。但是热负荷超过某一临界值q_(kp)时,给热系数a剧烈下降而发生膜状沸腾。如果热负荷不变,即与膜状沸腾发生的同时壁温剧烈升高,出现“烧毁”现象。所以临界热负荷乃是一切存在沸腾傳热的设备的实际操作极限。因此,近年来临界热负荷的研究引起了广泛的注意,出现了一些理论分析和实验数据。但现有的一些计算公式,不是过分简化不能全面反映各种物性因素的影响,就是缺乏明确物理意义而不便于计算。本文乃是在研究沸腾傳热之临界负荷与流化床临界气速类似的概念基础上,提出一个准数方程式,以全面综合过去和新近各种条件下各种物料的沸腾临界热负荷数据。
Boiling heat transfer nucleate boiling and film boiling points. In the nucleate boiling heat coefficient is great, and as the heat load increases, the heat coefficient a also continue to increase. However, when the thermal load exceeds a certain critical value q_ (kp), the heating coefficient a drastically drops and membrane boiling occurs. If the heat load is constant, that is, with the film boiling occurs at the same time the wall temperature increased dramatically, there “burn” phenomenon. Therefore, the critical heat load is the actual operating limit of all devices that have boiling heat transfer. Therefore, in recent years, the study of critical heat load has attracted wide attention, and some theoretical analysis and experimental data have appeared. However, some existing calculation formulas are not over simplistic and can not fully reflect the influence of various physical factors, that is, they lack physical meaning and are not easy to be calculated. Based on the concept that the critical load of boiling heat transfer is similar to the critical fluidized bed velocity, a quasi-equation is proposed to comprehensively synthesize the critical boiling heat load data of various materials under various past and recent conditions.