CATHARE is a 2-fluid thermal-hydraulic system code, capable of simulating phenomena occurring in the primary and secondary circuits of a PWR (Pressurized Water Reactor) under a wide variety of accidental situations. The latest version CATHARE-3 uses a 3D modeling of a PWR core at the assembly scale to simulate various accidental situations such as the loss of coolant accident (LOCA) or the steam line break accident. This requires that the one-phase and two-phase mixing models are adapted to the assembly scale and that every closure law is validated in a separate way. The code models for the 3D turbulent diffusion and dispersion of momentum and energy have been validated at sub-channel scale against experimental data. In this work, the energy and momentum mixing models are validated at assembly scale with the PNNL and the Weiss tests experimental results, respectively.