This paper shows the study of a computational fluid dynamics approach through the investigation and evaluation of the intrinsic characteristics of the optimization associated with the variational principle method when applied to a multiphase fluidized bed reactor modelling and simulation operating in a-slurry bubble column mode. The optimization criterion associated in the method is based on the minimization of the amount of energy. The variational method has advantages in modelling and fitting parameters (constants) of equations in the critical regions of the flow, where other methods may not give good results, and regions under the influence of the equipment wall or other disturbences. The disadvantage of this method is that there is no general method applicable in all processes, just for particular cases. The type of reactor evaluated is employed in hydroconversion and hydrotreatment processes. There are few experimental results available in the literature for real situations. The simulated computational results are compared with the experimental results from the literature of an fluidized system formed by water-ah-glass spheres. Also, computational results are compared with the result obtained for a hydroconversion reactor solved by means of the finite volume method. The results obtained show that the variational method is capable of simulating a multiphase fluidized bed reactor as well as other methods, This show that it is possible to explore the optimization characteristics of the variational principles.