Hydrodynamics and particle motion in upward flowing dense particle suspensions: Application in solar receivers. (2nd June 2016)

• Record Type: Journal Article
• Authors: García-Triñanes, Pablo; Seville, Jonathan; Boissière, Benjamin; Ansart, Renaud; Leadbeater, Thomas; Parker, David
• Is Part Of: Chemical engineering science. Volume 146(2016)
• Page Start: 346
• Page End: 356
• Publication Date: 2016-06-02
• Subjects: Fluidisation -- Fine particles (A/B-type) -- Dense particle suspension -- Upward flow -- Heat transfer media -- Solar energy -- Positron Emission Particle Tracking; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2016.03.006
• Languages: English
• ISSNs: 0009-2509

Abstract

Abstract: Dense gas–solid suspensions have the potential to be applied as heat transfer fluids (HTF) for energy collection and storage in concentrated solar power plants. At the heart of these systems is the solar receiver, composed of a bundle of tubes which contain the solid suspension used as the thermal energy carrier. In the design investigated here, the particles form a dense upward-flowing suspension. Both density of the suspension of these particles and their movement have a strong influence on the heat transfer. An apparatus was designed to replicate the hydrodynamic and particle motion in the real solar energy plant at ambient temperature. The governing parameters of the flow were established as the solid feeding flow rate, the fluidisation velocity, the solids holdup, the freeboard pressure and the secondary air injection (aeration) velocity. In the case studied, aeration was applied with air introduced into the uplift transport tube some way up its length. This study finds that the amount of this secondary air injection is the most important parameter for the stability and the uniform distribution of the solids flow in the tubes. Solids motion was measured using the non-invasive positron emission particle tracking (PEPT) technique to follow the movement of a 60 µm tracer particle, onto which was adsorbed the positron emitting 18 F radioisotope. Analysis of the resulting three-dimensional trajectories provides information on solids flow pattern and solids velocity. Results show the overall behaviour of the bulk material in detail: small step-wise movements associated with bubble motion superimposed on a general trend of upward flow in the centre and downward flow close to the walls. These findings suggest that this particular type of flow is ideal for transporting energy from the walls of the solar receiver tubes. Graphical abstract: Highlights: An experimental apparatus for the investigation of hydrodynamics of upward-flowing dense phase particle suspensions. The effect of fluidisation and aeration flow rate on solid flow stability is presented. PEPT was used to visualise particle trajectories and velocity profiles. A novel procedure was used to obtain vertical solid flux.