内置十字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 Cross Twisted Spiral Component

针对换热设备传热效率低等问题,研究开发出一种十字形截面传热强化螺旋元件.提出十字形螺旋元件4种强化传热机理,包括轴向流速增大效应强化、螺旋流流速增大效应强化、二次流流速增大效应强化及边界层减薄效应强化.采用理论推导的方法,建立Nu数预测关联式和压力降预测关联式.研究结果表明:传热强化评价值PEC随着心轴直径比的增大而增大,但增加的幅度很小;传热强化评价值PEC在y<4时,随着叶片宽度直径比的增加而增大,在y>4后,随着叶片宽度直径比的增加而减小;传热强化评价值PEC随着y的减小而增加,在y<2时增加明显.强化传热机理的理论分析结果与数值模拟结果吻合良好,具有相同的趋势.

A kind of cross twisted spiral heat transfer enhancement component is developed in order to solve the problem of the low efficiency for heat exchangers.Some heat transfer enhancement mechanisms of cross twisted spiral component are proposed,which involve the strengthening effect of the increasing axial velocity,the strengthening effect of the increasing spiral velocity,the strengthening effect of the increasing secondary flow velocity and the strengthening effect of the thinning thermal boundary layer.Through the theoretic analysis of these mechanisms,using the method of derivation,the prediction correlation of Nussle number and pressure-drop is established in the condition of turbulent flow.The research show that,the value of PEC increase with mandrel-diameter rate increase,but rate of increase is tiny;when the torsion y4 the value of PEC increase with the blade width-diameter rate increase,when the torsion y4 the value of PEC decrease with the blade width-diameter rate increase;the value of PEC increase with the torsion y decrease,torsion y2 rate of increase is obvious.The theoretic analysis of heat transfer enhanced agrees with the numerical simulation and have the same trend.