Experimental validation of a continuum model for local heat transfer in shell-and-tube moving-bed heat exchangers

Kurzfassung

Moving-bed heat exchangers with a horizontal tube arrangement offer a promising solution to exchange high-temperature heat with a particle stream. However, in order to guide the design of such heat exchangers, accurate and time-efficient simulation tools capable of capturing the complex heat transfer characteristics still need to be improved. In this article we present experimental results of the local heat transfer coefficients around the tube circumference of a heat exchanger mockup. To this end, specially prepared measuring probes were developed and a test campaign was conducted. A comprehensive thermal model was applied to the setup under consideration. This model takes into account the temperature-dependent thermophysical properties of the bulk, variable temperature boundary conditions, and the increased thermal resistance caused by the stagnation and void zones. To validate the model, calculated and experimental results were compared. It turns out that the predicted heat transfer coefficients well match the experimental data, albeit with slight deviations at the stagnation and void zones of the tubes. The prediction of a tube’s area-weighted heat transfer coefficient, which constitutes the most important factor for design purposes, yields results with errors of less than 3%. Therefore, it is concluded that the proposed thermal model is able to well predicts the heat transfer in shell-and-tube moving-bed heat exchangers.