•Object of analysis: minichannels 5.5, 6.0 and 10 mm deep and 0.5 1.2 mm wide.•Boiling curves for ethanol, FC-72 and Novec-649.•Visualization studies: growing bubble diameter changes and bubble departure diameter.•Determining the bubble departure diameter with static and dynamic methods. Pool boiling heat transfer experiments were conducted with ethanol, Novec-649 and FC-72 at atmospheric pressure on surfaces with deep minichannels. The minichannels 5.5, 6.0 and 10 mm deep and 0.5–1.2 mm wide were uniformly spaced with a pitch of 2.0 mm on the base surfaces. Heat transfer coefficients obtained with ethanol were similar for all surfaces tested. Novec-649 and FC-72 produced the highest coefficients at heat fluxes above 100 kW/m2 in 1 mm wide minichannels. All the working fluids provided a significant increase in the maximum (critical) heat flux. The images were recorded using high speed imaging techniques across the entire surface of the samples. Boiling visualization aimed to study vapor bubble diameter changes during the growth period and measure the bubble departure diameter. The bubble diameter at departure was also determined analytically according to force balance static and dynamic variants. The dynamic variant provided a high consistency between the theoretical and experimental data for bubble departure diameter with FC-72 and Novec-649.