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Title:	Heat transfer enhancement of triplex tube thermal energy storage with phase change material
Authors:	Abduljalil Ali Ali Al-Abidi (P56236)
Supervisor:	Kammaruzzman Sopian, Prof. Dato' Dr.
Keywords:	Dissertations, Academic -- Malaysia Heat -- Transmission Heat storage
Issue Date:	24-Feb-2014
Description:	Thermal energy storage such as phase change materials (PCMs) has a significant role in reducing the mismatch between energy supply-demand and improving the efficiency of solar thermal energy systems. A major problem with this kind of thermal storage application is its low thermal conductivity that causing long time for charging and discharging process. In this research, a new technique to enhance the heat transfer in the PCM thermal energy storage by increasing the heat transfer area is applied by using a triplex tubes heat exchanger (TTHX). The main objective for this research is to study the application of TTHX with PCM in the middle tube as thermal energy storage. Numerical model for the TTHX with PCM was developed by using FLUENT 6.3.26 software under ANSYS to study the phase transition characteristic of PCM, melting, solidification, and temperature and time required for those processes. Different heat transfer enhancements investigated numerically include the TTHX with internal fin, TTHX with external fin, and TTHX with internal-external fin to improve the thermal performance of the thermal storage. The effect of the number of fins, fin length, fin thickness, Stefan number, TTHX materials, and the PCM unit geometries were investigated. TTHX with and without fins are fabricated and tested to investigate the melting of the PCM under non-steady and steady states heat transfer fluid(HTF) inlet temperature. Three techniques were investigated: heating the inside tube, heating the outside tube, and heating both sides tube for the TTHX without fins. The thermal energy storage consists of TTHX comprising of three horizontally mounted concentric tubes with lengths of 500 mm. The inner tube has a radius of 25.4 mm and a thickness of 1.2 mm. The middle tube has a radius of 75 mm, and the outer tube has a radius of 100 mm. Both tubes have a thickness of 2 mm. The inner and outer tubes are used to hold the HTF (water), and the middle tube is filled with 5.6 kg of PCM (RT 82). Four longitudinal fins (fin pitch of 42 mm, length of 480 mm, and thickness of 1 mm) welded onto each of the inner and middle tubes on the thermal storage to improve the heat transfer in the PCM thermal storage. The computational results show that case G (8-cell PCM unit geometry) achieved the complete melting and solidification in short time 35%, 34.7 %with respect to TTHX without fins respectively. Complete melting using internal-external fin with 42 mm fin length was reduced to 43 % compared with that of TTHX without fin. The temperature difference between the HTF and the melting temperature of the PCM was around 3°C-8 °C. The effect of fin thickness was insignificant to the fin length and number of fins, which have a strong effect on the melting time. Experimental results indicated that the third case (i.e., heating both sides) for the TTHX without fins achieved complete PCM melting in 30% and 80% of the inside tube and outside tube heating methods respectively. No significant temperature variation in the axial direction was indicated. The radial and angular directions predict the heat transfer phenomena in the melted PCM. The results also indicated that the HTF inlet temperature has more effect on the PCM melting process than the HTF mass flow rate.,Certification of Masters/Doctorial Thesis' is not available,Ph.D
Pages:	236
Call Number:	TJ260.A245 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Solar Energy Research Institute / Institut Penyelidikan Tenaga Suria (SERI)

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