A thermochemical approach for the determination of convection heat transfer coefficients in a gun barrel

A finite element thermo-mechanical analysis of firing through a gun barrel requires the convection heat transfer coefficient values under high temperature and pressure among input parameters. A thermochemical approach has been formulated in order to obtain these coefficients. Considering a variable burning speed for a typical gunpowder configuration, the variation of pressure wave speed, density, and heat conduction of the burning gas mixture is used to evaluate the Reynolds and Prandtl numbers along the barrel axis. These two numbers are then used to calculate the Nusselt numbers from which the continuously changing convection heat transfer coefficients are determined. It is confirmed from an experimental firing process and its corresponding thermo-mechanical finite element analysis that the calculated coefficients present a good estimate of the real coefficients.

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► Surface temperatures were measured after 10 shots using a bolt action sniper rifle.
► A thermochemical method is built to obtain convection coefficients in this rifle.
► A finite element analysis was performed for temperatures using these coefficients.
► Comparison of theoretical and experimental surface temperatures shows 8% variance.
► This reasonable variance demonstrates the effectiveness of the developed method.