During the past two decades, thermal microfluidic chips have significantly been investigated. Due to their high capacity of heat transport, an increasing number of studies on different aspects of thermal microfluidic chips have been conducted. However, a comprehensive investigation on the geometry of microfluidic chips using, state of the art finite element software is absent from the literature. In this thesis, geometric parameters of thermal microfluidic chips have been optimized, using finite element software. Consequently, micro and macro phenomena were investigated in different models. The micro modelling approach investigated single microchannels and optimized the microchannel cross-section. Furthermore, two-phase flows in the microchannel were modelled, using finite element software ANSYS CFX. Liquid accumulation in the sharp corners of the microchannel was captured in the model and the phase change phenomenon was observed. The results of the finite element analysis were compared to the literature and a good correlation was observed. The configuration of microchannels in a microfluidic chip was studied through the macro modelling approach. Dimensionless design charts were presented in this section to be employed for all kinds of thermal microfluidic chips with different boundary conditions. Based on the validity of the finite element software, two-phase flows in the optimized three-dimensional network of microchannels were modelled. The results showed the circulation of the two phases in the microchannels and demonstrated the proper operation of the thermal microfluidic chip.
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