Pool boiling heat transfer intensification by electro-stimulation

Abstract

In this investigation, a novel technique for intensification of pool boiling heat transfer coefficient has been proposed. This method is applicable to electrolyte aqueous solutions at the isolated bubble regime. This approach is based on stimulating heating surface by DC electricity. In this condition, boiling and electrolysis phenomena performs simultaneously. Decomposed hydrogen and oxygen blends to vaporized water during boiling and provides extra bubble volume; moreover, active nucleation sites increase on the heating surface. Consequently, bubble dynamics including frequency, diameter and active nucleation site density are significantly affected. In this investigation, two opposing consequence from modified bubble dynamics have been observed: (1) enhanced heat transfer up to 40% as a result of increased active nucleation site density, bubble diameter and frequency at some low voltages of electrolysis, and (2) reduced heat transfer down to 70% because of an interconnected clusters of hydrogen/water vapor mixture which are attached on the heating surface at some high voltages of electrolysis. The experimental data were analyzed by artificial neural network and sensitivity analysis have been performed. The impact of bulk and wall temperatures, also electrolysis and heat power flux on heat transfer rate have been determined by sensitivity analysis. Results present that maximum enhancement of heat transfer coefficient is observed at about 1 kW m−2 electrolysis power flux. At wall temperatures above 290 K, no enhancement is observed by increasing bulk temperatures. Enhancement requires minimum boiling heat flux of 45 kW m−2.