IN-TUBE BOILING HEAT-TRANSFER COEFFICIENTS OF R-123 AND THEIR ENHANCEMENT USING THE EHD TECHNIQUE

The applicability of the Electrohydrodynamic (EHD) technique for boili ng heat transfer enhancement of R-123 was investigated experimentally. The test rig consisted of a tube-in-tube heat exchanger with hot wate r flowing in the outer tube and the test refrigerant flowing in the in ner tube. The experiment utilized a stainless steel cylindrical electr ode of 3 mm (0.118 in) outside diameter placed coaxially in the test s ection which was a smooth, stainless steel tube of 9.4 mm (0.37 in) in side diameter and 1.22 m (4 ft) long. The experiments were performed a s a function of parametric values of inlet quality, heat flux and mass flux. It was found that R-123 exhibits excellent response to the EHD effect. As high as 550% increase in the heat transfer coefficient was obtained, when compared to the base case (absence of EHD effect). In t he worst case the electrical power consumption penalty was found to be less than 0.27% of the corresponding test section heat transfer rate.