A series of experiments to determine void fraction in both condensation and evaporation have been performed in horizontal microfin tubes with refrigerants R134a and R410A. Mass flux varied from 75 kg/m²-s to 700 kg/m²-s and average test section quality varied from 5% to 80%. Zero degree (axial grooving) and 18 degree helix microfin tube configurations have been examined in both condensation and evaporation. Four tubes were examined (7.3 mm and 8.9 mm diameters with axial and 18 degree helix angle microfins). Evaporation and adiabatic conditions in microfin tubes generally show similar void fraction trends found in smooth tubes. Condensation results for microfin tubes show a lower void fraction than smooth tubes.

Reprinted from the International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research, Vol. 7, No. 1, January 2001, pp. 67-82.

Units: SI