| Abstract: | A mixed lumped-differential formulation for double-pipe heat exchangers is presented that radially lumps the temperature distribution in the outer channel, providing a differential problem for the inner channel that involves a more general type of boundary condition for the wall temperature. The generalized integral transform technique is extended to allow for the analytical solution of this class of problems. Applicability limits for the simplified model are then established in terms of related parameters, based on numerical results obtained for bulk temperatures and Nusselt numbers, as compared to more involved approaches for the complete differential model. |
