Experimental dataset of fluid flow and heat transfer in a shallow packed bed at low Reynolds numbers

Abstract

This article presents an experimental campaign on the transient behaviour of a packed bed, which is filled with spherical particles and is subjected to heating and cooling with air as the heat transfer fluid. The investigation focuses on a shallow bed with a diameter twice its height, a geometry alike to cost effective thermal energy storage systems, where the bed-to-particle diameter ratio is typically also large. The packed bed is heated from ambient temperature to temperatures up to using hot air from an air heater. Then, when a specified shutdown criterion is reached, the heater is turned off and the bed is cooled by air with nearly ambient temperature. Following this procedure, 9 experiments have been conducted. The fluid velocity into the packed bed was conditioned to be almost homogeneous, which is achieved by wire screens and checked for in detailed flow pretests. For each of the 9 experiments, the generated data consists of measurements of various temperatures, pressures, ambient conditions and air mass flow, all collected about 60 times per second during the whole experiment, i.e. from the beginning of heating to the end of cooling, which takes up to 300 minutes. Operational data of heater and blower are saved as well. Data is presented in form of tables (CSV,ASCII). To collect the data, extensive instrumentation is employed, including more than 40 thermocouples, which are placed within the packed bed at multiple circumferential, radial, and axial positions and within the insulation, as well as above and below the bed. Pressure transducers are installed up- and downstream of the packed bed. A long-range infrared camera has an unobstructed view to the bed surface, enabling the investigation of average bed surface temperature, and thus, adding value to the point measurement data of the thermocouples. Additionally, the publication includes data on material properties of insulation and particles. For example, bulk density was measured by pouring particles in a defined volume and measuring their mass. Particle size distribution and sphericity is evaluated based on image analysis and 3614 random selected particles. Here, raw data of the evaluation as well as the respective images can be found in the accompanying data set. Regarding other data such as specific heat capacity and thermal conductivity, relevant information is presented in form of equations and values. Particle emissivity is measured in-house with a simplified experimental setup, that is adaptable to other materials. The detailed presentation of experimental methodology, material properties, flow pretests with and without fluid homogenization screens installed, and exemplary result description, ensures the results are suitable for validating advanced models such as detailed simulations based on Computational Fluid Dynamics (CFD) coupled with the Discrete Element Method (DEM) of shallow packed bed systems. Additionally, information about fluid homogenization with metal screens has the potential to support researchers in the design of similar test rigs.