EHD (Electrohydrodynamics) Enhancement of Heat Transfer in Heat Exchangers. Annual Report June 1987-May 1988

摘要

The potential of using an electric field with negligible power consumption (the corona discharge) to enhance corrective heat transfer coefficients for air flow in straight tubes was investigated experimentally. Pressure drop and heat transfer measurements were performed for Reynolds numbers ranging from ReD = 1,000 to ReD = 20,000 and for electrode potentials from 6.5 (the approximate corona threshold) to 7.75 kv (just below the spark over potential). The effects were studied in the presence of both negative and positive corona fields. Based on the results obtained, a maximum of 215 percent enhancement in heat transfer coefficients at Reynolds number of Re subscript D = 2000 and at field potential of 0 = 7.75 kv was obtained. The maximum rise in friction factors was 260 percent and it occurred under the conditions for which heat transfer was maximum (i.e., Re subscript D = 2000, 0 = 7.75 kv). The technique was found most effective at moderate Reynolds numbers and at the highest electrode potential. A heat transfer enhancement for 40 percent with only 12 percent increase in pressure drops was obtained at Te subscript D = 5000 and 0 = 7.75 kv.