Over the past two decades our understanding of the charge and heat transport properties of graphene has evolved progressively as the quality of graphene devices improved. In this talk, I shall present some new experimental result on the electrical and thermal transport measurements in graphene devices of unprecedented electrical mobility (> 1 million cm2/V.s). We show that the transport in such graphene devices is limited by intrinsic acoustic phonons and their scattering with electrons, rather than charged impurities – which is the case in conventional disordered graphene devices. This manifests in a rather striking violation of the Wiedemann-Franz law and density-dependent variation of the effective Lorenz number over six orders of magnitude. We find that the transport properties of ultra-clean graphene are quantitatively consistent with that of a hydrodynamic Dirac fluid.