This paper illustrates numerical simulations of heat transfer and fluid flow in triangular section and unit cell section of fuel blocks of High Temperature Gas-cooled Reactor (HTGR). The thermal hydraulic simulations have been performed in a minimalistic computational resource environment and their viabilities have been studied. General Atomics Modular High Temperature Gas-cooled Reactor (MHTGR) has been considered in this work as a reference design. In this paper, 3-D models of triangular section and unit cell section of fuel blocks similar to the MHTGR design have been developed for single phase helium flow using COMSOL Multiphysics software. In these models, velocity profiles, temperature profiles, pressure profiles, Reynolds number profiles and Nusselt number profiles have been studied. Algebraic y+ turbulence model has been used in this work. Finally, the simulation results have been compared with General Atomics provided MHTGR design parameters and theoretically obtained results to check for their accuracy and viability.