The heat transfer in a rotary kiln is unique compared to other geometries because it transfers the heat under the load as well as on the top. The heat is transferred to the solid bed in two paths: across the exposed surface of the solid bed (direct heat flow) and the covered surface of the bed (regenerative heat flow). Some studies about the latter heat transfer mechanism have been cited in the literature. However, the works have to be solved numerically because of the 2-dimensional problem which considers the thermal conduction in radial and circumference direction. Therefore, this study has established an analytical solution in a simple manner to accomplish the task in directly and indirectly heated rotary kilns. In directly heated rotary kilns the hot gas introduced into the kiln is transferred directly to the exposed kiln wall surface and to the exposed bed surface. As the kiln rotates the heat, which is stored in the kiln wall, is transferred again to the solid bed. In indirectly heated rotary kilns the heat source is from the hot gas or the steam. The heat is given to the outer shell of the kiln wall and that this heat is distributed over the circumference of the kiln. The heat transfer mechanism to the solid bed is divided into two parts: the radiation heat flow from the exposed wall surface to the exposed bed surface and the conduction heat flow from the covered wall to the solid bed.