窄环隙内水流动沸腾时阻力特性的实验研究

鉴于流体在小尺度流道内流动时所表现出的特殊性和换热设备小型化的需要,在水加热条件下,对水在竖直环隙内流动沸腾时的摩擦压降特性进行了实验研究.环隙的宽度为0.9、1.4和2.4mm,实验压强为0.1 MPa.实验结果表明,窄环隙内的摩擦阻力压降高于普通圆管,环隙宽度越小,摩擦压降越大;随着含气率的增加,摩擦压降先缓慢降低,然后开始逐渐增加,环隙越宽,压降由降低到升高的转变点的含气率的值越高;可以用奇母霍斯关系式来计算窄环隙内的两相摩擦压降,式中的常数可由含气率计算.

Frictional pressure drop characteristics of boiling water flowing through narrow annulus

Considering the special characteristics of fluids flowing through ducts with small gap sizes and the need of miniaturization of the heat exchanger, experiments were performed to investigate the frictional pressure drop characteristics of boiling water flowing through vertical narrow annuli heated by water. The widths of the annuli are 0. 9, 1. 4 and 2. 4 mm,and the pressure in the annuli is 0. 1 MPa. The results show that the frictional pressure drop of narrow annuli is higher than that in common ducts. The frictional pressure drop decreases slowly with the increase of the quality and begins to increase gradually when the quality exceeds a certain value. The quality value at turning point increases with the increase of the width of the annuli. The frictional pressure drop can be calculated by Chisholm equation, and the constant C in the equation depended on the quality.