A new mathematical model for the calculation of the radiation field in heterogeneous photocatalytic reactors using the new concept of "effective radiation field model" or ERFM is proposed. In this concept, the incident radiation associated to the photons flow is an energy cloud. The generated space-phase and the properties of the cloud are considered isotropic and independent of the propagation angle and photon frequency. The isotropic nature of the ERFM concept provides a simple estimation of the radiation field of a catalyst in suspension (particles and fluid) for polychromatic radiation and the solar spectrum. The ERFM is an alternative model for the calculus of the radiant energy distribution in heterogeneous photocatalytic reactors as an extension of concept to the overall volumetric rate photon absorption - OVRPA. The local volumetric rate of photon absorption (LVRPA) predicted by the ERFM were compared with the Six Flux Model (SFM) and the rigorous solution using Discrete Ordinate Method (DOM) for the radiative transfer equation (RTE). The calculated LVRPA with the ERFM was found to be closer to the solution of the RTE-DOM. These results were attributed to the performance of the phase function in both models. (C) 2015 Elsevier B.V. All rights reserved.