This paper presents a three-dimensional thermal Lattice Boltzmann model to simulate the interaction of suspended solid particles with the flow field and their effects on hydrodynamic and thermal performance of microchannels. A 19-bit single-relaxation-time Lattice Boltzmann method (D3Q19) is used to perform thermal fluid flow, while the Newtonian dynamic equations are solved to investigate the transport of the suspended solid particles. The needed forces in equations of the particle motion are evaluated by the momentum exchange method. The effects of solid spherical particles with various diameters on the fluid flow and heat transfer enhancement in a rectangular microchannel, at different Reynolds numbers, are investigated and discussed. Three cases of stationary, constant velocity and freely moving single particle are investigated which the results show the latter case has the highest heat transfer enhancement and the lowest pressure drop. The particulate flows in the microchannel for both cases of 15 stationary and freely moving particles are also studied and the hydraulic and thermal performances are compared. (C) 2013 Elsevier Ltd. All rights reserved.