Two-phase microchannel cooling is a promising high-performance cooling t echnique to cool next-generation electronic devices. The design of such a cooling system is nontrivial. To facilitate this design process, a dyn amic system model of a two-phase microchannel cooling system is construc ted in this work. In addition, an easy-to-use steady-state heat sink mod el is elaborated to obtain operational envelopes of two-phase microchann el heat sinks. Furthermore, figures of merit that aid in the choice of c oolants are derived and an overview is given on the performance of large sets of coolants. Moreover, the system model is used to investigate the size effects of small, portable cooling systems on their performance. A lso analytical models of the size effects and design equations are obtai ned to incorporate these effects early in the design process. Finally, i nitial experimental validation of the numerical model and the size effec ts is performed with two separate test facilities focused on steady-stat e results. The models agree well with the experimental results.