1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Solar Energy Research Institute / Institut Penyelidikan Tenaga Suria (SERI)

Title:	Performance enhancement of triplex tube thermal energy storage system using fins-nano-phase change material
Authors:	Ammar Mohammed Abdulateef (P73163)
Supervisor:	Sohif Mat, Prof. Dr.
Keywords:	Thermal energy storage Solar thermal systems Heat storage
Issue Date:	30-Jul-2018
Description:	Enhancement in thermal energy storage (TES) reduces the mismatch between energy supply and energy demand. This will ensure reliability and increase the efficiency of many energy technologies such as solar thermal systems. Major problem is that most phase-change materials (PCMs) are used in these applications have low thermal conductivity (𝑘 ≤ 0.2 W/m K), resulting in an incomplete melting and solidification processes. A significant temperature difference within these materials can also cause failure and system overheating. The main objective of this research work is to evaluate the latent heat thermal energy storage (LHTES) system using fins-nano-PCM in a triplex-tube heat exchanger (TTHX) during charging and discharging processes. A new finnanoparticle in various configurations has effectively contributed to enhance heat-transfer rate to a large PCM-TTHX and to achieve the melting and solidification processes in a shorter time period. Using the software Ansys Fluent 15 and the software Gambit 2.4.6 via the enthalpyporosity and the finite-volume methods, two physical configurations of TTHX model were simulated (1) TTHX with longitudinal fins and (2) TTHX with triangular fins with PCM and alumina (Al2O3) as a nanoparticle, respectively. The TTHX with fins model consists of an inner tube, middle tube, and outer tube with 76.2 mm, 381 mm, and 500 mm, respectively, in diameter and 3 mm thick, with eight fins each 121 mm long. The dimensions of the TTHX with longitudinal fins were the same for the TTHX with triangular fins, but the difference was in the base (thickness) of the longitudinal and triangular fin was at 2 mm and 25 mm, respectively. This study also designed, tested, and evaluated a horizontal TTHX with internal longitudinal fins incorporating PCM then nano-PCM during charging and discharging processes. The same dimensions that mentioned above are designed with 3000 mm and 2800 mm lengths of TTHX and fins, respectively. Numerical results indicated that the melting time was achieved using internal, internal-external, and external triangular fins at 11%, 12%, and 15%, respectively, compared with the cases employing longitudinal fins. The solidification time was also achieved using these configurations of triangular fins at 14%, 16%, and 18%, respectively, compared with the configurations employing longitudinal fins. A significant enhancement in the isothermal/liquid fraction contours of the nano-PCM in TTHX with longitudinal fins and TTHX with triangular fins configuration for the PCM melting and solidification was achieved. Effects of different designs, operation parameters, and materials for external triangular fins have been analyzed. Experimental results proved that the PCM did not entirely melt within the charge time (4 hours) for the inside heating at 97 °. The PCM melting and solidification for both-sides heating/freezing were successfully accomplished at 90 ° in lesser time than the outside heating/freezing method. The changes in the mass flow rates of 0.27, 0.49, and 0.62 kg/sec on the PCM average temperature in the axial/angular direction were investigated. The mass flow rate for the non-steady state at 0.49 kg/sec consumed a short time to achieve PCM melting and solidification, compared with the 0.27 and 0.62 kg/sec with different charging and discharging temperatures, respectively. By the weight, dispersing 10% nanoparticles improved the charging and discharging processes in lesser time than the pure PCM. The most efficient configuration for achieving melting and solidifying the PCM is the external triangular fins-nanoparticle. Close agreement between simulation and experiment results have been obtained.,Ph.D.
Pages:	217
Call Number:	TJ260.A238 2018 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Solar Energy Research Institute / Institut Penyelidikan Tenaga Suria (SERI)

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