Experimental and Modeling Study on Void Fraction Using Thermal Distribution Sensor in Horizontal Annular Flow

The void fraction is an important parameter to characterize the characteristics of annular flow, which is an important precondition for calculating the flow velocity, average density, pressure gradient, and analyzing the flow status. Based on the principle of convective heat transfer, the effects of the void fraction <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and the liquid Froude number Frl on the heat transfer coefficient h of annular flow are analyzed. The thermal distribution sensor of constant power type is designed in this article. Air-water annular flow experiments have been conducted in a stainless-steel tubular test section having an inside diameter of 17.0 mm on the high-precision small-diameter two-phase flow experimental device of Hebei University. The 75 sets of temperature T at four angles (0°, 90°, 180°, and 270°) of pipe circumference and entrainment E under different flow conditions were collected. Utilizing the S. L. Smith correlation, the void fraction is calculated. By introducing dimensionless heat transfer coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${h} ^{+}$ </tex-math></inline-formula>, the prediction correlation of void fraction <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>, which could acceptably handle the data, is proposed. Laboratory results indicate that the relative error of 99% of the data is within the ±3% error band, the mean absolute percentage error (MAPE) of the correlation is 0.63%, and the root-mean-square error (RMSE) is 0.76%.