An investigation of refrigerant void fraction in horizontal, microfin tubes

A series of experiments to determine void fraction in both condensation and evaporation have been performed in horizontal microfin tubes with refriger ants R134a and R410A. Mass flux varied from 75 kg/m(2).s to 700 kg/m(2).s a nd average rest section quality varied from 5% to 80%. Zero degree (axial g rooving) and 18 degree helix microfin tube configurations have been examine d in both condensation and evaporation. Four tubes were examined (7.3 mm an d 8.9 mm diameters with axial and 18 degree helix angle microfins). Evapora tion and adiabatic conditions in microfin tubes generally show similar void fraction trends found in smooth tubes. Condensation results for microfin t ubes show a lower void fraction than smooth tubes.