Laminar Heat Transfer Data with a Step-Varying Wall Heat Flux

In 1958 Siegel et al. derived a thermal-entry-length integral solution for laminar flow in circular tubes with an arbitrary wall heat flux. From this we derived a solution for a step-varying flux. The objective of this research was to obtain experimental data to verify the accuracy of the above solution. The steps used were a good approximation of the sinusoidal heat flux, which exists along the cooling tube in nuclear reactors. The experimental results fell above the theoretical solution, the average difference being 10.9%. Thus, the step-varying wall heat flux solution may be used for the design of cooling systems within that uncertainty.