Abstract
In this study, the dynamic melting process of the phase change material (PCM) in a vertical cylindrical tube-in-tank thermal energy storage (TES) unit was investigated through numerical simulations and experimental measurements. To ensure good heat exchange performance, a concentric helical coil was inserted into the TES unit to pipe the heat transfer fluid (HTF). A numerical model using the computational fluid dynamics (CFD) approach was developed based on the enthalpy-porosity method to simulate the unsteady melting process including temperature and liquid fraction variations. Temperature measurements using evenly spaced thermocouples were conducted, and the temperature variation at three locations inside the TES unit was recorded. The effects of the HTF inlet parameters were investigated by parametric studies with different temperatures and flow rate values. Reasonably good agreement was achieved between the numerical prediction and the temperature measurement, which confirmed the numerical simulation accuracy. The numerical results showed the significance of buoyancy effect for the dynamic melting process. The system TES performance was very sensitive to the HTF inlet temperature. By contrast, no apparent influences can be found when changing the HTF flow rates. This study provides a comprehensive solution to investigate the heat exchange process of the TES system using PCM.
Highlights
Over the last decade, a variety of solar energy utilization systems have been extensively used in actual applications [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]
This study provides a comprehensive solution to investigate the heat exchange process of the thermal energy storage (TES) system using phase change material (PCM)
The thermal energy gathered by the solar collector is stored in the TES unit, while during the evening or on cloudy days, when the solar radiation drops down to zero or is at an insufficient level, the previously stored thermal energy is released as a low-grade heat source to the evaporator
Summary
A variety of solar energy utilization systems have been extensively used in actual applications [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. These systems are deemed to be an attractive approach for solving global energy shortage problems due to its renewable and sustainable nature. A balance between the energy supply and demands is achieved, which greatly improves the system durability
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