Experimental and modelling results on critical heat flux in upward flow in round tubes are presented. The data were collected at a high pressure boiling facility using single component hydrocarbons (pentane and iso-octane), binary and ternary hydrocarbon mixtures (pentane/iso-octane and pentane/hexane/iso-octane). The system pressure ranged from 2 to 11 bar, the total mass fluxes from 100 to 550 kg/m2s and the wall heat flux from 30 to 100 kW/m2. The 8.68 m long vertical test section is made of 321 stainless steel. The inner and outer diameters are 25.4 and 38.0 mm, respectively. When the results are compared with predictions from an annular flow modelling code, an over-prediction (i.e., non-conservative) of the dryout quality for both single component and multicomponent cases is observed. Reasons for such discrepancies are explored and corrections to the calculation methodology are proposed in the context of droplet entrainment and deposition calculations.