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 percent to 80 percent. Zero degree (axial grooving) and 18 degree helix microfin tube configurations have been examined in both condensation and evaporation. Four tubes were examined (7.3mm and 8.9mm 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.
Citation: Hvac&R Research
Pub Type: Journals
condensation, evaporation, microfin tube, microgroove tube, refrigerant, two-phase flow, void fraction