This thesis presents an analytical treatment of some gradually evolving coherent problems of thermodynamic optimization with engineering importance to propose some physical theories. The first problem is related to the characteristics of macroscopic organization in a class of fluid flow systems. With the findings of the first problem, the second addresses the heat transfer issues of insulation design for nonconjugate heat transfer systems. The third problem is extended to a class of conductive-convective type conjugate heat transfer systems, as a successor of the second. Based on the concepts build in the first problem, the fourth discusses the thermodynamic issues of heat flow with reference to a thermoelectric generator which is a natural heat engine as well as a category of insulating system. The fifth and final problem inculcates the issues of real heat engine as a consequence of fourth. The abstract of each problem follows in order. In analyses of engineering systems, fundamental quest remains the distribution of certain entities (matter, energy) into the space. Thus certain definite forms are generated to serve a specific purpose. Bejan’s constructal theory specifically deals with such optimal geometrical constructions. In the first problem, equipartition theory is revisited from macroscopic standpoint with reference to some fluid flow systems. It is noted that equipartition principle is a corollary of a more generalized formulation―the constructal theory. It is seen that equipartition principle leads to certain power laws with which certain entities are distributed. This constitutes a deterministic law of nature in some finite length and time scale. Thus equipartition principle is to be recognized as an authentic basis of design for most efficient systems, which in turn obeys constructal principle of organization in nature.