  We argue that outward transport of energy by convection and photon diffusion
in a common envelope evolution (CEE) of giant stars substantially reduces the
fraction of the recombination energy of hydrogen and helium that is available
for envelope removal. We base our estimate on the properties of an unperturbed
asymptotic giant branch (AGB) spherical model, and on some simple arguments.
Since during the CEE the envelope expands and energy removal by photon
diffusion becomes more efficient, our arguments underestimate the escape of
recombination energy. We hence strengthen earlier claims that recombination
energy does not contribute much to common envelope removal. A large fraction of
the energy that jets deposit to the envelope, on the other hand, might be in
the form of kinetic energy of the expanding and buoyantly rising hot bubbles.
These rapidly rising bubbles remove mass from the envelope. We demonstrate this
process by conducting a three-dimensional hydrodynamical simulation where we
deposit hot gas in the location of a secondary star that orbits inside the
envelope of a giant star. Despite the fact that we do not include the large
amount of gravitational energy that is released by the in-spiraling secondary
star, the hot bubbles alone remove mass at a rate of about 0.1 Mo/yr, which is
much above the regular mass loss rate.
