Abstract
Effects of applied EHD1 on in-tube condensation of R-134a refrigerant in a double pipe heat exchanger are experimentally investigated to present applicability of the EHD technique in vertical position. The refrigerant's vapor was flowed inside of the inner tube and cooling water was counter currently flowed in annulus section. Tests were performed at different mass flow rates 35-65 kg/m(2) s of refrigerant and different electrical field strengths (0-8 kV), under their identified breakdown strengths for two various electrode diameter sizes (4 and 6 mm), while the average saturation temperature was 43 and 33 degrees C respectively. Experimental results demonstrate a remarkable potential in utilizing EHD to enhance condensation heat transfer. It is concluded that the enhancement is driven by the effective removal of the condensate through EHD induced liquid extraction and dispersion phenomena. For the presence of the electrodes, the experimental results indicate that the maximum heat transfer ER2 is around 14% and 31% respectively for electrodes with diameter of 4 mm (10.7 mm electrode gap) and 6 mm (9.7 mm electrode gap), while power expenditure was negligible. (C) 2014 Elsevier Inc. All rights reserved.