  We study shear-free spherically symmetric relativistic models with heat flow.
Our analysis is based on Lie's theory of extended groups applied to the
governing field equations. In particular, we generate a five-parameter family
of transformations which enables us to map existing solutions to new solutions.
All known solutions of Einstein equations with heat flow can therefore produce
infinite families of new solutions. In addition, we provide two new classes of
solutions utilising the Lie infinitesimal generators. These solutions generate
an infinite class of solutions given any one of the two unknown metric
functions.
