Experimental and numerical measurements of the channel packed with disordered cement granules regarding the heat transfer performance

Abstract

The channels packed with disordered granules are common in industry, which permits an improved performance of the facility as well as the energy efficiency. This paper describes the construction of an experimental platform of a packed channel with disordered cement granules. Using the method of dimensionless number correlation, fitting the data of Nusselt and Reynolds numbers provides an experimental correlation. Analysis shows that the Nusselt number in a packed channel is approximately eight times that in a smooth channel. The inner-wall temperature of a channel with smaller granules is lower, implying the heat transfer is stronger. The inverse problem method is adopted to measure the local average velocity and obtain the temperature distribution, permitting then a determination of the Reynold number based on the local average velocity in the channel combined with the fitted experimental correlation and a mathematical model of the experimental section. Comparisons with the Reynold number obtained from the superficial flow velocity shows that the Reynold number obtained from the average local velocity is much smaller and in particular, for the same mass flow rates, the latter Reynold number of the channel packed with smaller granules is larger than that packed with larger granules. It provides useful tools to analysis the local heat transfer performance to improve the energy efficiency in actual applications.