Convective heat transfer of longitudinal laminar droplet flow in the thermal entrance region of tube bundles is analyzed for constant wall temperature and constant heat flux conditions, respectively. The tube bundle geometry is taken into consideration based on the free-surface model. The saturated droplets in the superheated vapor stream are considered as distributed heat sinks. Calculations are performed for the variations of droplet size, vapor velocity, droplet number density and the local Nusselt number in the streamwise direction until the single-phase fully-developed condition is reached. The effects of different governing parameters on the heat transfer results are studied.