Two-phase flow in small channels has become another effective means for dissipating heat. Flow boiling, for instance, involves very high heat transfer rate but backflow and instabilities, which are considered as drawbacks [9], have to be carefully controlled.According to the open literature, two-phase heat transfer in micro-channels have been mainly reported for flow boiling studies.The effects of such parameters as mass flux and heat flux on flow boiling phenomena have been reported in several publications [10–12]. Moreover, the up-to-date comprehensive discussions on flow boiling in micro-scale channels were given by Ribatski [13] and Tibirica and Ribatski [14]. In contrast, the data corresponding to heat transfer characteristics during non-boiling two-phase flow in micro-channels is still limited.