Experimental and Numerical Investigation of a Latent Heat Thermal Energy Storage Unit with Ellipsoidal Macro-encapsulation

Experimental and Numerical Investigation of a Latent Heat Thermal Energy Storage Unit with Ellipsoidal Macro-encapsulationTianhao Xu, Emma Nyholm Humire, Silvia Trevisan, Monika Ignatowicz, Samer Sawalha, Justin NW Chiu*Department of Energy Technology, KTH Royal Institute of Technology, 100 44, Stockholm, SwedenAbstractIn this paper, a novel type of macro-encapsulated phase change material (PCM)shaped in ellipsoidis investigated on a component scale.The encapsulated PCM is a paraffin-based commercial material (ATP60); differential scanning calorimetry and transient plane source method are used to measure the thermo-physical properties of the PCM. A numerical model and a 0.382 m3latent heat thermal energy storage (LHTES) prototype have been built and experimentally characterized. The temperature measurements indicate that thermocline is retainedin the packed bed region. The charge/discharge can be accelerated by65% with20 K increase intemperature difference between the phase-change temperature and heat transfer fluid (HTF)inlet temperature. Increasing HTF inlet flowrate from 0.15 m3/h (Re=77) to 0.5 m3/h (Re=256) shortenscompletion time of charge by51%. Furthermore, a one-dimensional packed bed using source based enthalpy method was constructed and validatedwithin6.6% errorfor aReynolds numberof 90 to 922. Compared with a conventional cylindrical PCM capsule, the ellipsoidal encapsulation shows60% increase in discharge speed but 23%lower storage capacity. This work demonstrates a combined experimental and numerical characterization approach for a novel ellipsoidal PCM encapsulationgeometry.
The manuscript has been submitted to the journal of Energy. On the date when this manuscript is uploaded in Diva (2021-04-30), the manuscript is still under reviewing process.QC 20210506