Flow boiling of ethanol/water mixture in a square mini-channel

Abstract

Two-phase flow heat transfer was examined in a single 5 mm inner hydraulic diameter square channel in a vertical orientation. The channel uses a resistive coating to allow for transparent heating of the walls. Transparency of the heating enabled high speed visualization of the boiling phenomena at various heat and mass fluxes. The pressure is monitored at the inlet and outlet of the channel. Infra-red thermography is used to map the external wall temperature of the channel and the local heat transfer coefficient is estimated from the local wall temperature and the saturation temperature of the liquid. Ethanol, deionized water and a 5% v/v ethanol/water mixture were used as working fluids. Three mass fluxes (0.33, 0.66 and 1.00 kg/m2s) were tested as well as three heat fluxes (2.8, 4.2 and 6.1 kW/m2). Experiments were conducted in a controlled temperature environment (40oC). The addition of ethanol into water (5% v/v ethanol/water mixture) was found to enhance heat transfer resulting in higher heat transfer coefficients than for either of its pure components.