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This paper investigates the effect of silver nanofluid on a flat-plate pulsating heat pipe (FP-PHP). The simulation was performed using FLUENT 15.0 software, for which a three-dimensional model having a microchannel structure in the condensation section was developed. The developed model adopted the volume of fluid (VOF) method to track the internal vapor-liquid interface of the FP-PHP and to observe the state of the two-phase flow. The result revealed the evident presence of various types of bubble flows, including dispersed bubble flows, slug flows, annular flows, and column flows in the evaporation section. Trends in thermal resistance variation during simulation were studied by changing the volume fraction, liquid filling rate, and heating power. The thermal resistance of the FP-PHP containing silver nanofluid was lower and the FP-PHP exhibited stable state when the heating power reached 120 W. The optimal volume fraction of silver nanofluid was 1%, and the FP-PHP containing sliver nanofluid exhibited increased heat transfer efficiency.

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The extremely hot environment attributed to the combustion and aerodynamic heating exposes the scramjets to intense thermal-structural loads. The scramjet life is limited due to the wall cracks caused by the large temperature difference. The focus of this study was on performing coupled 3D fluid-thermal-structural analysis of the cooling jacket for scramjet engines. Firstly, the mathematical models and simulation method were established. The three-dimension CFD numerical simulations were based on the conservation equations of mass, momentum, and energy. Strain compatibility, equilibrium equations, and constitutive law of elastic solids were applied for the 3D static thermal-structural analysis. Secondly, the fluid-thermal-structural analysis was performed. Results show that both large temperature difference and structure geometry have obvious impact on the deformation of the cooling channel. Highest deformation (2.1%) of the straight square channel occurs at the middle of the hot side ligament. Compared with the straight square channel, the maximum temperature of the triangular channel and the spiral square channel is reduced by 7.3% and 26.1%, and the total deformation is increased by 5.0% and reduced by 28.3%, respectively.