Introduction of a new crossover radius for the guaranteed heat transfer reduction in radial thermal insulation systems

The use of the critical radius for radial heat conduction in thermal insulation systems has been widely reported in the literature. When it is desirable to increase heat dissipation, this critical radius can be used in a definitive manner to maximize the heat dissipation. However, if it is desirable to decrease heat gain or heat loss, the critical radius only serves as a necessary condition and is not sufficient. To address the design of such thermal systems, a new crossover radius is introduced. A crossover radius is a radius greater than the critical radius and is defined such that the heat transfer with the corresponding amount of insulating material is equal to that of the bare thermal system. Both cylindrical and spherical systems are considered.