New experimental data of CO2 flow boiling in mini tube with micro fins of zero helix angle

Heat transfer and pressure drop characteristics of CO2 flow boiling in mini tube with micro fins of zero helix anglewere experimentally investigated. Theworking conditions cover mass flux from 100 to 600 kg m(-2) s(-1), heat flux from 1.67 to 8.33 kWm(-2), vapor quality from 0 to 0.9 and saturation temperature from 1 to 15 degrees C. The results show that the heat transfer coefficient increases with increasing vapor quality, but sharply decreases at vapor quality around 0.2 similar to 0.4 under most conditions, and the dryout vapor quality decreases with the increasing heat flux and saturation temperature. Pressure drop increases with increasing mass flux and heat flux, or decreasing saturation temperature, and mass flux is the major influence factors. The enhancement ratio of heat transfer coefficient is higher than that of pressure drop, which shows potentials of using such kind tubes to enhance the overall heat transfer performance. A heat transfer coefficient correlation and a pressure drop correlation for 0 degrees helix angle micro-fin tube were developed, and they agree well with the experimental data. (C) 2015 Elsevier Ltd and International Institute of Refrigeration. All rights reserved.