Flow boiling critical heat flux experiments for a microchannel at high mass velocities

Abstract Many flow boiling applications require high critical heat flux (CHF) levels, which can be obtained with high mass velocities and microchannel flow. At the same time, some situations require non-electrical conductive refrigerants as halogenated fluids with boiling points distinct from water. Most of the CHF experiments available in the literature for halogenated fluids are available at low mass velocities, G &lt; 2000 kg/m $$^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>2</mml:mn> </mml:mmultiscripts> </mml:math> s, and therefore, correlations used to predict CHF should be validated at high mass flow conditions. In this work, CHF experimental data were obtained at high mass velocity for R134a at microscale conditions. The data were obtained in horizontal 1.0 and 1.1 mm inside diameter stainless-steel single tubes with 100 and 46 mm heating lengths and mass velocities from 3000 to 26426 kg/m $$^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>2</mml:mn> </mml:mmultiscripts> </mml:math> s. CHF of up to 2212 kW/m $$^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>2</mml:mn> </mml:mmultiscripts> </mml:math> was measured; the highest CHF value reported in the literature for a single uniformly heated tube with R134a. The parametric trends of CHF were ascertained relative to important flow and geometrical parameters, and the experimental data were compared against 10 CHF predictive methods. The results of the comparisons showed agreements with correlations in the order of 35% mean absolute error. A new correlation is developed, achieving a prediction error of 11.6%.