The present paper presents an investigation of the effects of the refrigerant type on the heat transfer coefficient during flow boiling inside micro-scale channels. Experimental results for R134a, R1234ze(E), R1234yf and R600a for flow boiling in a circular channel with internal diameter of 1.1 mm are presented. The experimental database comprises 3409 data points covering mass velocities ranging from 200 to 800 kg/m(2) s, heat fluxes from 15 to 145 kW/m(2), saturation temperatures of 31 and 41 degrees C, and vapor qualities from 0.05 to 0.95. The experimental data were parametrically analysed and the effects of the experimental parameters (heat flux, mass velocity, saturation temperature and working fluid) identified. Subsequently, the experimental data were compared against the most quoted predictive methods from literature, including macro and micro-scale methods. Based on the broad database obtained in the present study, an updated version of the predictive method of Kanizawa et al. (2016) was proposed. The updated version provided accurate predictions of the present experimental database, predicting more than 97% and 86% of the results within error bands of 30 and 20%, respectively. (C) 2017 Elsevier Ltd. All rights reserved.