The underlying mechanisms controlling heat transfer in the nonboiling gas-liquid, Taylor flow regime were explored by performing systematic adiabatic visualization tests and heat transfer experiments for constant wall heat flux boundary conditions. The system studied was a 2.00 mm vertical tube with fluids flowing in an upward direction. This work extends the study presented in Leung et al. (Leung S. S. Y.; Liu, Y.; Fletcher, D. F.; Haynes, B. S. Chem. Eng.Sci. 2010, 65, 6379-6388) by comparing the results obtained for three different liquids, water, SO wt % ethylene glycol/water mixture, and pure ethylene glycol, which cover a wide range of Capillary numbers (0.001 < Ca < 0.180). The mixture velocity, homogeneous void fraction, and slug length were identified to be important parameters for Taylor flow heat transfer. In addition, the film thickness, size of the recirculation zones in the slug region, and recirculation efficiency, which are strong functions of the Capillary number, were found to have pronounced effects on the heat transfer rate. On the basis of the experimental data, a correlation between the apparent slug Nusselt number (Nu(L).) and the controlling dimensionless groups (L*(s) = L-s/(Re-TP x Pr x d) and Ca) is proposed.