With the ever-increasing global energy demand, more environmentally sustainable energy resources will be required to diminish the world’s dependency on traditional fossil fuels. Microalgae is a promising biofuel solution that has the benefit of not utilizing agricultural land to grow. Microalgae is grown in photobioreactors, which are large bodies of recirculating water used to cultivate algae populations. The growth of microalgae is strongly dependent on the temperature of the reactor medium. Large temperature fluctuations exert stress on algae thus, affecting their growth. Furthermore, the reactor temperature exceeds a certain threshold could be fatal to algae. Since sunlight is the primary ingredient for the algae growth, depending on the reactor design, there is a possibility that the reactor temperature may reach this threshold. Similarly, the day and night cycle may also introduce large temperature variations, affecting the growth rate. In order to use microalgae as a reliable and consistent source for biofuels, the optimization of their growth rate is vital, which can be achieved through the thermal regulation of the reactor. &nbsp;The current work is part of a larger project to develop an innovative reactor design to regulate the reactor temperature by using phase change material (PCM) as the thermal regulating medium. PCMs are materials that store excess heat by phase transition from solid to liquid and release it back by phase transition from liquid to solid. &nbsp;The specific focus of the current work is to investigate the influence of PCM insert shapes on the mean and turbulent flow behavior inside the reactor channel. The inserts were wall-confined, offset columns. Two cross-sectional geometries square and circular, were considered. Particle Image Velocimetry (PIV) technique was used to measure the two-dimensional velocity fields. Experiments were performed for each of the two column cross-section configurations as well as the no column configuration as the reference case. For each configuration, measurements were conducted in the mid-horizontal plane as well as mid-vertical plane of the channel, under identical conditions. Results show that the column inserts have a significant impact on both mean and turbulent velocity fields inside the channel. Detailed results will be presented.

Multiplane Characterization of Mean and Turbulent Fields in a Channel Flow With Wall-Confined, Offset Columns

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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