变风量空调末端单元中均速管流量计的布设方法及优化

Layout method and optimization of averaging Pitot tube in VAV terminal unit

为提升变风量空调末端单元风量调控的有效性,针对末端单元的气流入口至后部风道的空气流场进行数值模拟,结合风道不同截面上的速度分布,提出基于均速管流量计的测量值与理论值平均相对误差最小的判据.比较100~300 m^(3)·h^(-1)的风量下(不同风阀开度),风道截面上速度分布曲线与理论值的交点数目及位置,得出流量计的安装位置与测孔尺寸.结果表明:均速管流量计位于风道的X=306 mm(沿程方向)、Y=21.0 mm(高度方向)处截面上,测孔坐标依次为Z=116、188、264、330 mm的布设方案,其风速测量值与理论值的一致性较好,最小相对误差仅为2.25%(50%的风阀开度),最大相对误差为9.04%(30%的风阀开度).

To improve the effectiveness of air volume control,the airflow field from the inlet to the rear duct in VAV terminal unit was numerically simulated.Combined with the velocity distribution at different cross section in the air duct,the reasonable method for the layout of the averaging Pitot tube was proposed by minimizing the mean relative error of air volume between the measured value and the theoretical value.Comparing the number and position of intersection points of the velocity distribution curves and the theoretical values on the cross section of the air duct under the conditions of air volume of 100-300 m^(3)·h^(-1)with different opening degrees of damper,the installation position of the averaging Pitot tube and the location of the measuring holes were determined.The results show that the optimal averaging Pitot tube is located on the section with X of 306 mm along the flow direction and with Y of 21.0 mm along the height direction of air duct,and the measuring hole coordinates are at Z of 116 mm,188 mm,264 mm and 330 mm,respectively.The measured value of the air velocity is well consistent with the theoretical value.The minimum relative error is only 2.25%at the opening degree of damper with 50%,and the maximum relative error is 9.04%at that with 30%.