Enhancement in heat transfer using two phase slug flow in microtubes and microchannels has encouraged researchers to focus on this topic as one of the potential methods for miniaturizing heat sinks and exchangers. Numerical simulation of two phase slug flow is time consuming, so some researchers conduct their numerical studies using the moving frame of reference technique for a unit cell consisting of only one slug, i.e. a single phase study, in order to accelerate the simulation process. Both single phase and two phase simulation methods have been performed in the present study and results have been compared. This shows to what extent the moving frame of reference assumption is valid in the case of two phase flow in hydrophilic microtubes when a thin liquid film exists around moving gas bubbles. The present comparison has been conducted for pressure drop and heat transfer for two thermal boundary conditions i.e. constant wall temperature and constant wall heat flux. It has been shown that the moving frame of reference method overpredicts pressure drop and heat transfer and possible reasons have been discussed. This also shows that in a slug flow with no film around bubbles more heat transfer could be achieved. (C) 2012 Elsevier Ltd. All rights reserved.