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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)


Fangyu Cao
George Mason University; Advanced Cooling Technologies, Inc., Lancaster, PA 17601, USA

Ying Zheng
Advanced Cooling Technologies, Inc., Lancaster, PA 17601, USA

Chien-Hua Chen
Advanced Cooling Technologies, Inc., Lancaster, PA 17601, USA

Richard Bonner
Advanced Cooling Technologies, Inc., Lancaster, PA, USA

DOI: 10.1615/IHTC16.ecs.022260
pages 4253-4259

PALABRAS CLAVE: Energy efficiency, Thermal storage, Phase change material, Melting point


Thermal energy storage systems that rely on the latent heat of fusion of a phase change material (PCM) for enhanced performance are typically constrained by the fixed melting point of the PCM. This constraint is particularly evident in power plant cooling applications. In this application, the PCM absorbs excess heat from the process steam during the comparatively hot day and then regenerates during the comparatively cold night. The time shifting of the heat transfer provides a colder sink temperature to the steam during the hours of peak demand, which in turn increases the efficiency of the power plant. However, the utilization of PCMs latent heat is highly dependent on the melting point of the selected PCM and the ambient temperature. The selection of a low melting point PCM provides higher efficiency if the night time ambient temperature is sufficiently low to regenerate the PCM; however, it is likely that an aggressively low melting point PCM may not be completely regenerated during warmer seasons where the nighttime temperature fails to fall below the melting point of the PCM. Consequently, the choice of a fixed melting point PCM limits the optimally performance to one season in the power plant cooling application. In this research, Advanced Cooling Technologies, Inc. has developed a technique to control the melting point of a calcium chloride hydrate PCM. A bench scale test facility was designed to tune the hydration level in the PCM and further control the phase transition temperature of the PCM. Testing results show that the lower-melting point CaCl2·6H2O (29 °C) can be tuned to a higher melting point CaCl2·4H2O (39 °C) by removing moisture with dry air flow. This process can be reversed by adding liquid water. Properties of the PCMs before and after the tuning processes were characterized to verify that the tuning process is controllable and reversible. Our system level models indicate that the melting point tunability feature can further save up to 1.6% of energy in the power plant cooling application when year-round usage is considered.

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