![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
Abstract
Thermal energy storage is critical for reducing the discrepancy between energy supply and energy demand, as well as for improving the efficiency of solar thermal energy systems. Among the different types of thermal energy storage, phase-change materials (PCM) thermal energy storage has gained significant attention recently because of its high energy density per unit mass/volume at nearly constant temperature. This study experimentally investigates the using of a triplex tube heat exchanger (TTHX) with PCM in the middle tube as the thermal energy storage to power a liquid desiccant air-conditioning system. Four longitudinal fins were welded to each of the inner and middle tubes as a heat transfer enhancement in the TTHX to improve the thermal performance of the thermal energy storage. The average temperature of the PCM during the melting process in the TTHX with and without fins was compared. The PCM temperature gradients in the angular direction were analyzed to study the effect of the natural convection in the melting process of the thermal storage. The energy storage efficiency of the TTHX was determined. Results indicated that there was a considerable enhancement in the melting rate by using fins in the TTHX thermal storage. The PCM melting time is reduced to 86% by increasing of the inlet heat transfer fluid. The average heat storage efficiency calculated from experimental data for all the PCMs is 71.8%, meaning that 28.2% of the heat actually was lost.
NOMENCLATURE
| Cp | = | specific heat (kJ/kg-K) |
| HTF | = | heat transfer fluid |
| = | mass flow rate (kg/s) | |
| PCM | = | phase-change material |
| Q | = | heat energy (kW) |
| ri | = | inner radius (mm) |
| rm | = | middle radius (mm) |
| ro | = | outer radius (mm) |
| t | = | time (min) |
| T | = | temperature (°C) TTHX triple tube heat exchanger |
Greek Symbols
| η | = | energy efficiency |
| ρ | = | density (kg/m3) |
| Θ | = | angle in degrees |
Subscripts
| ch | = | charging |
| dis | = | discharging |
| in | = | inlet |
| out | = | outlet |
| PCM | = | phase-change material |
Additional information
Notes on contributors
Abduljalil Al-Abidi
Abduljalil Al-Abidi is an assistant professor in the Department of HVAC Engineering, Sana’a Community College, Yemen. He received his B.Sc. degree in mechanical engineering from Sana’a University, Sana’a, Yemen in 1999. In 2003 he received his master's degree in air conditioning engineering from Al-Balqa Applied University, Salt, Jordan. He received his Ph.D. from the University Kebangsaan Malaysia in 2014 in renewable energy. He is a member of the World Society of Sustainable Energy Technologies (WSSET). His research interest includes thermal energy storage, phase-change material, solar energy, and solar thermal cooling system.
Sohif Mat
Sohif Mat received his B.Sc. degree in mechanical engineering from the University of Malaya, Malaysia in 1983. In 1990 he received his Ph.D. degree in mechanical engineering from the University of Malaya, Malaysia. He is a principle research fellow at the Solar Energy Research Institute (SERI), University Kebangsaan Malaysia (UKM), in Bangi Malaysia. He is also a professor at UKM and the industrial relations coordinator of SERI, UKM. His research interest includes renewable energy, PCM, evaporative cooling, and solar thermal systems.
Kamaruzzaman Sopian
Kamaruzzaman Sopian received his B.Sc. degree in mechanical engineering from the University of Wisconsin–Madison in 1985, his master's degree in energy resources (solar energy) from the University of Pittsburgh in 1989, and his Ph.D. in mechanical engineering from the University of Miami–Coral Gables in 1997. He is a professor in the Department of Mechanical Engineering, University Kebangsaan Malaysia, and he is the director of Solar Energy Research Institute, at the same university. His research interest includes solar energy, photovoltaic power system, solar thermal systems, and renewable energy.
Yusof Sulaiman
Yusef Sulaiman is a principal research fellow at the solar energy research institute (SERI), National University of Malaysia in Bangi Malaysia. Prior to joining SERI he was a professor in the Physics Department, University Putra Malaysia (UPM), from 1973 until his retirement in 2004. He received his Ph.D. from the University of London in 1977 in nuclear physics. He has served as the head of the Department of Physics, UPM, and the Dean of Faculty of Science Environmental Studies, UPM. His current research interests include organic solar cells, photovoltaics and applications, and thermal cooling systems.
Abdulrahman Mohammad
Abdulrahman Mohammad is an assistant professor in the Department of Mechanical Engineering, Baqubah Technical Institute, Iraq. He received his bachelor's degree from the Collage of Military Engineering, Iraq, in 1994 and his master's degree from the same collage in 2002. He received his Ph.D. in 2014 from University Kebangsaan Malaysia in renewable energy. Currently, he is a lecturer. He has published about 25 research papers in international journals and conferences.