Transient Conjugate Heat-Transfer Model for Circular Tubes Inside a Rectangular Substrate

The transient heat transfer for laminar flow inside a circular microtube, embedded in a rectangular substrate, during power startup has been numerically investigated using the finite element method. Silicon and silicon carbide were the substrates used, and water and FC-72 were the working fluids. Equations governing the conservation of mass, momentum, and energy were solved in the fluid region. Within the solid wafer, the heat-conduction equation was solved. A thorough investigation for velocity and temperature distributions for different substrates and coolants was performed by varying geometrical dimensions. The Prandtl number, thermal conductivity ratio, and diameter ranges were 6.78-12.68, 27-2658, and 300-1000 pm, respectively