Experimental and Numerical Investigations of Subcooled Boiling Heat Transfer in a Small-Diameter Tube

The boiling heat transfer for subcooled water flowing in a small-diameter tube was investigated experimentally and numerically. In the experiment, a platinum tube was used as an experimental tube (d = 1.0-2.0 mm) to conduct joule heating by direct current. The heat generation rate of the tube was controlled with an exponential function. The numerical simulation of boiling heat transfer for subcooled water flowing in the small-diameter tube was conducted using the commercial computational fluid dynamics (CFD) code, phoenics ver. 2013. The small-diameter tube was modeled in the simulation. As the boundary condition, the measured heat flux was given at the inner wall. The inlet temperature ranged from 302 to 312 K. The flow velocities of d = 1.0 mm and d = 2.0 mm were 9.29 m/s and 2.34 m/s, respectively. The three-dimensional analysis was carried out from non-boiling to the critical heat flux (CHF). Governing equations were discretized using the finite volume method in the phoenics. The semi-implicit method for pressure linked equation (SIMPLE) method was applied in the numerical simulation. For modeling boiling phenomena in the tube, the Eulerian-Eulerian two-fluid model was adopted using the interphase slip algorithm of phoenics. The surface temperature difference increased as the heat flux increased in the experiment. The numerical simulation predicted the experimental data well. When the heat flux of the experiment reached the CHF point, the predicted value of the heat transfer coefficient was approximately 3.5% lower than that of the experiment.