This paper is concerned with the modelling and analysis of the interaction between particles and fluids with particular regarding to fragmentation processes. We simplify the model by assuming that the particles are constituted by spheres jointed by springs. Then the aim is to deduce the terms appearing in the Navier-Stokes-type equations for the fluid and the counterpart influence in the Boltznmann system for the particles. The resulting coupled system is analysed by means of a refined averaging lemma.