The lattice Boltzmann method is applied to computationally investigate the laminar flow and heat transfer of an incompressible fluid with constant material properties in a 2-D channel with a built-in bluff body. In this study, a triangular prism is taken as the bluff body. Not only the momentum transport, but also the energy transport is modeled by the lattice Boltzmann method. A uniform lattice structure with a single time relaxation rule is used. For obtaining a higher flexibility on the computational grid, interpolation methods are applied, where the information is transferred from the lattice structure to the computational grid by Lagrange interpolation. The flow is investigated for different Reynolds numbers, while keeping the Prandtl number at the constant value of 0.7. The results show how the presence of a triangular prism effects the flow and heat transfer patterns for the steady-state and unsteady-periodic flow regimes. As an assessment of the accuracy of the developed lattice Boltzmann code, the results are compared with those obtained by a commercial computational fluid dynamics code. It is observed that the present lattice Boltzmann code delivers results that are of similar accuracy to the well-established computational fluid dynamics code, with much smaller computational time for the prediction of the unsteady phenomena.