  The core accretion model of giant planet formation has been challenged by the
discovery of recycling flows between the planetary envelope and the disc that
can slow or stall envelope accretion. We carry out 3D radiation hydrodynamic
simulations with an updated opacity compilation to model the proto-Jupiter's
envelope. To isolate the 3D effects of convection and recycling, we simulate
both isolated spherical envelopes and envelopes embedded in discs. The
envelopes are heated at given rates to achieve steady states, enabling
comparisons with 1D models. We vary envelope properties to obtain both
radiative and convective solutions. Using a passive scalar, we observe
significant mass recycling on the orbital timescale. For a radiative envelope,
recycling can only penetrate from the disc surface until $\sim$0.1-0.2
planetary Hill radii, while for a convective envelope, the convective motion
can "dredge up" the deeper part of the envelope so that the entire convective
envelope is recycled efficiently. This recycling, however, has only limited
effects on the envelopes' thermal structure. The radiative envelope embedded in
the disc has identical structure as the isolated envelope. The convective
envelope has a slightly higher density when it is embedded in the disc. We
introduce a modified 1D approach which can fully reproduce our 3D simulations.
With our updated opacity and 1D model, we recompute Jupiter's envelope
accretion with a 10 $M_{\oplus}$ core, and the timescale to runaway accretion
is shorter than the disc lifetime as in prior studies. Finally, we discuss the
implications of the efficient recycling on the observed chemical abundances of
the planetary atmosphere (especially for super-Earths and mini-Neptunes).
