Latent heat thermal energy storage systems are used to absorb thermal energy and store it for later use by melting or solidifying a phase change material (PCM). These types of systems have a broad range of applications, including but not limited to: concentrated solar power energy systems, waste heat recovery, cold energy storage, food drying and building heating and cooling. One problem associated with latent heat thermal energy storage systems is the low thermal conductivity of most commercially viable phase change materials. This can have a significant negative effect the thermal performance of the system by leading to much longer charging and discharging times. Several passive heat transfer enhancement techniques are used to resolve this issue. Common passive heat transfer enhancement techniques include inserting fins and extended surfaces into the PCM, embedding heat pipes or other passive heat transfer devices within the PCM, dispersion of highly conductive nanoparticles in the PCM, and impregnation highly conductive porous media with the PCM. The current study analyzes the effect of a fin based enhancement technique on the thermal performance of a latent heat thermal energy storage unit during charging and discharging processes experimentally and numerically. The experimental setup consists of an insulated cylindrical container filled with Rubitherm RT-55 PCM. The system is charged/discharged using cold/hot water as the heat transfer fluid (HTF) flowing within a pipe passing through the center of the container. Copper fins are attached annually around the central pipe inside the PCM. Twelve K-type thermocouples and two RTDs are located throughout the PCM container and HTF pipe respectively to measure the temperature during the charging and discharging processes. A transient two-dimensional numerical model along with enthalpy-porosity technique is developed using ANSYS FLUENT 19.0 to simulate the operation of the system. Baseline tests have been conducted for a system without fins to validate the numerical model. The results obtained from the numerical modeling are in good agreement with those of the experimental testing. Based on experimental testing, the total charging time of the system using hot water at 70℃ and flow rate of 7.57 L/min is around 45 hours which is very close to the prediction by the numerical model which is 46 hours. Further experimental testing and numerical modeling will be conducted to study the effect of number and geometry of the fins on the thermal performance of the latent heat thermal energy storage system during both charging and discharging processes.


Experimental and Numerical Study of a Latent Heat Thermal Energy Storage Unit Enhanced by Fins

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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