Electrohydrodynamically (EHD) Augmented External Condensation for R-134a in a Tube Bundle Heat Exchanger

Electro-hydrodynamic (EHD) enhancement of external condensation of refrigerant R-134a for a seven-tube bundle heat exchanger was studied experimentally. The tubes used in the bundle were commercially available, state of the art enhanced tubes provided by a heat transfer tube manufacturer. Both horizontal and vertical bundle configurations were tested at different heat flux levels, ranging from 10 to 30 kW/m². The saturation temperature was 30 °C and the applied electric field voltage ranged from 0 to 20 kV. The results obtained indicated that the external heat transfer coefficients increased with increase in the applied electric field, and that EHD had a more significant influence for the vertical bundle orientation. A maximum of nearly fourfold enhancement was achieved for the vertical configuration, compared to a maximum enhancement of 38% for the horizontal configuration. The EHD technique is accordingly more efficient for heat transfer augmentation in vertical condenser orientations where the base line (non EHD enhanced) heat transfer are rather poor.