The liquid flow and conjugated heat transfer performance of single phase laminar flow in rectangular microchannels equipped with longitudinal vortex generators (LVGs) are numerically investigated. Deionized-water with temperature-dependent thermo-physical properties is employed to conduct the simulations. Three dimensional simulations are performed using an open-source flow solver based on finite volume approach and SIMPLEC algorithm. Five different configurations of the microchannel with different angles of attack of the LVGs are considered. Simulation results are compared with available experimental data and a deviation below 10% is achieved. The results show that for Reynolds number ranged from 100 to 1100, there is a 2-25% increase in the Nusselt number for microchannels with LVGs, while the friction factor increased by 4-30%. Except one at Re = 100, the overall performance of the all configurations of microchannels with LVGs is higher than ones without LVG's.