The paper analyses a novel model of unsteady convective heat transfer in a nanofluid layer on a flat vertical surface subject to instantaneous (abrupt) onset of film boiling. It occurs if heat flux suddenly switched on exceeds the critical heat flux necessary to bring a nanofluid to film boiling regime. The usual system of equations of fluid flow and convective heat transfer is supplemented by an equation for the concentration of nanoparticles. To complement the problem statement, two sets of the boundary and initial conditions were used. The first condition corresponds to problem of film boiling derived by Bromley, whereas the second was suggested by Ellion for a stationary liquid at the vapor-liquid interface. The solution of the problem enabled predicting variation of temperature distributions, Nusselt numbers, velocity profiles and friction coefficients in time. Computations were performed numerically based on the self-similar equations derived using the Lie group transformations. Results of unsteady simulations of convective heat transfer during instantaneous onset of film boiling of a nanofluid with different concentrations of nanoparticles demonstrated qualitative agreement with experiments.

本文分析了一个新的非稳态对流传热模型，该模型在平坦的垂直表面上的纳米流体层中，会瞬时（突然）发生薄膜沸腾。如果突然打开的热通量超过了将纳米流体带入薄膜沸腾状态所需的临界热通量，就会发生这种情况。通常的流体流动和对流传热方程组由纳米颗粒浓度方程组补充。为了补充问题陈述，使用了两组边界和初始条件。第一个条件对应于Bromley提出的薄膜沸腾问题，而第二个条件由Ellion建议用于气液界面处的固定液体。该问题的解决方案可以预测温度分布，努塞尔数，速度曲线和及时的摩擦系数。基于使用李群变换导出的自相似方程，以数值方式进行计算。具有不同浓度的纳米颗粒的纳米流体的薄膜沸腾瞬间开始时对流传热的非稳态模拟结果表明，该定性与实验吻合。