Heat transfer enhancement in medium temperature thermal energy storage system using a multitube heat transfer array

An experimental energy storage system has been designed using an horizontal shell and tube heat exchanger incorporating a medium temperature phase change material (PCM) with a melting point of 117.7 °C. Two experimental configurations consisting of a control unit with one heat transfer tube and a multitube unit with four heat transfer tubes were studied. The thermal characteristics in the systems have been analysed using isothermal contour plots and temperature time curves. Temperature gradients along the three directions of the shell and tube systems; axial, radial and angular directions have been analysed and compared. The phase change in the multitube system was dominated by the effect of convective heat transfer compared to conductive heat transfer in the control system. The temperature gradient in the PCM during phase change was greatest in the radial direction for both the control and multitube systems. The temperature gradients recorded in the axial direction for the control and multitube systems during the change of phase were respectively 2.5 and 3.5% that of the radial direction, indicating essentially a two-dimensional heat transfer in the PCM. The onset of natural convection through the formation of multiple convective cells in the multitube system significantly altered the shape of the solid liquid interface fluid flow and indicates the requirement for an in-depth study of multitube arrangements.     

制导系统启控时刻对火箭弹初始扰动的影响研究

借助ADAMS和MATLAB／SimuLink的接口环境建立了带制导系统的发射动力学模型。模型可综合考虑弹管间隙以及系统时变参数特性；进行有无制导系统的模拟对比发现，火箭弹离轨前启制导系统可以适当减小火箭弹的扰动角速度，而且启控时刻越早，对火箭弹的出口姿态越有利；研究了制导系统启控时刻随机性对火箭弹出口角速度散布的影响，结果发现其影响不容忽视。