The development of an inexpensive and easy natural convection experiment

With a simple, inexpensive apparatus natural convective heat transfer is determined experimentally and compared to theoretical values as part of an undergraduate laboratory. A cylindrical heating cartridge is placed horizontally through the wall of a clear plastic tank. The tank contains water. Surface temperature is measured along the axis of the heating cartridge, and bulk water temperature is determined. Power input to the cartridge heater is known, and no losses are assumed. Theoretical convective heat transfer from the cartridge heaters is determined by finding the Nusselt number using conventional relationships in the literature, calculating the convective heat transfer coefficient, and solving for heat transfer. Agreement between experimental and theoretical heat transfer values is good, and a basic concept in heat transfer is thus demonstrated in the classroom. Comparisons are made between different Nusselt correlations, students gain an appreciation for the range of acceptable answers, and a simple, calculus-based analytical correction is applied to the result.