内置Y形螺旋元件换热管的强化传热研究

Research on Heat Transfer Enhancement of Heat Exchanger Tubes Containing A Y-Shaped Spiral Component

针对换热设备传热效率低等问题,研究开发出一种Y形截面传热强化螺旋元件,该元件由三个沿圆周均布的螺旋叶片及连接固定叶片的中心圆柱组成。提出了Y形螺旋元件四种强化传热机理:轴向流速增大效应强化、螺旋流速增大效应强化、二次流速增大效应强化及热边界层减薄效应强化。通过对这些强化机理的理论分析,建立了湍流工况下强化传热的努赛尔准数预测关联式。研究结果表明:当螺旋叶片扭率较小时,螺旋流速增大效应和热边界层减薄效应是传热强化的主要控制机制;当螺旋叶片扭率较大时,轴向流速增大效应成为强化传热的主要控制机制;强化传热机理的理论分析结果与数值模拟结果吻合良好,且变化发展趋势相同。

A kind of Y-shaped spiral heat transfer enhancement component is developed in order to solve the problem of the low efficiency for heat exchangers.The component consists of three spiral blades u- niformly distributed along the circumference and a central spindle connecting and fixing these blades. Some heat transfer enhancement mechanisms of Y-shaped spiral component are proposed,which involve the strengthening effect of the increasing axial velocity,the strengthening effect of the increasing spiral veloci- ty,the strengthening effect of the increasing secondary flow velocity and the strengthening effect of the thin- ning thermal boundary layer.Through the theoretic analysis of these mechanisms ,the prediction correlation of nusselt number is established in the condition of turbulent fow.The results show that：when the spiral blade twist rate is small,the spiral velocity increasing effect and the thermal boundary layer thinning effect is the main control mechanism of heat transfer enhancement;when the spiral blade twist rate is large ,the strengthening effect of the increasing axial velocity becomes the leading control mechanism.The theoretic analysis of heat transfer enhanced agrees with the numerical simulation and has the same trend.