Experimental evaluation of a paraffin as phase change material for thermal energy storage in laboratory equipment and in a shell-and-tube heat exchanger

Abstract

The thermal behavior of a commercial paraffin with a melting temperature of 58 ºC is analyzed as a phase change material (PCM) candidate for industrial waste heat recovery and domestic hot water applications. A full and complete characterization of this PCM is performed based on two different approaches: a laboratory characterization (mass range of milligrams) and an analysis in a pilot plant (mass range of kilograms). In the laboratory characterization, its thermal and cycling stability, its health hazard as well as its phase change thermal range, enthalpy and specific heat are analyzed using a differential scanning calorimeter, thermogravimetric analysis, thermocycling and infrared spectroscopy. Laboratory analyses showed its suitability up to 80 ºC and for 1200 cycles. In the pilot plant analysis, its thermal behavior was analyzed in a shell-and-tube heat exchanger under different heat transfer fluid mass flow rates in terms of temperature, power and energy rates. Results from the pilot plant analysis allowed understanding the different methods of heat transfer in real charging and discharging processes as well as the influence of the geometry of the tank on the energy transferred and required time for charging and discharging processes. ; The work is partially funded by the Spanish government (ULLE10-4E-1305, ENE2015- 64117-C5-1-R and ENE2015-64117-C5-3-R). This project has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under Grant agreement N PIRSES-GA-2013-610692 (INNOSTORAGE) and No ENER/FP7/295983 (MERITS), and from the European Union's Horizon 2020 Research and Innovation Programme under Grant agreement No 657466 (INPATH-TES). The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543). Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2016FI_B 00047). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Alvaro de Gracia and Camila Barreneche would like to thank the Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940 and FJCI-2014-22886, respectively.