Gravitational Collapse of Self-Similar and Shear-free Fluid with Heat   Flow
  A class of solutions to Einstein field equations is studied, which represents gravitational collapse of thick spherical shells made of self-similar and shear-free fluid with heat flow. It is shown that such shells satisfy all the energy conditions, and the corresponding collapse always forms naked singularities. 
R. Chan, M. F. A. da Silva, Jaime F. Villas da Rocha