Experimental Investigation of Thermal Energy Storage (TES) Platform Leveraging Phase Change Materials in a Chevron Plate Heat Exchanger
Authors: Kumar Sunil , Thyagarajan Ashok , Banerjee Debjyoti 
Published: February 2023

The largest consumer segment of fresh water resources in the US are cooling towers that are deployed typically for cooling steam (from turbine exhaust) in condensers in thermal power plants. With growth in population and human economic activity (e.g., cooling of data centers) the fresh water resources are being stressed to capacity. Alternate technologies need to be developed to reduce consumption of fresh water in the process industries (including power plants). Dry cooling is an attractive option for obviating wet cooling (i.e., for obviating usage of cooling towers). Dry cooling platforms suffer from reduced operational efficiency, higher costs (both for capital costs and operating costs), weak resiliency and compromised reliability. Particularly, in arid climates, air cooled heat exchangers are inoperable during peak summer days when the ambient air temperature exceeds critical limits (e.g., when the ambient air temperature exceeds the temperature of the steam at the turbine exhaust). This may lead to abrupt power plant shutdown, which in-turn, is a recipe for disaster due to instability induced in the electric supply grid infrastructure due to abrupt shutdown of a power plant with significant power generation capacity (thus compromising reliability). Supplemental cooling can be used for improving the resiliency and reliability of these dry cooling platforms. Thermal Energy Storage (TES) platforms are an attractive option for supplemental cooling. Phase Change Materials (PCM) are often used for TES. Latent Heat Thermal Energy Storage Systems (LHTESS) are attractive for their small footprint accruing from the high latent heat values of PCM.

The objective of this study is to design, develop and test the performance of a candidates LHTESS platform. The scope of this study was limited to a Chevron Plate Heat Exchanger (CPHX). The thermal performance characteristics (e.g., power rating and heat-exchanger effectiveness) was determined experimentally for ascertaining the efficacy of the LHTESS during both melting and solidification of the PCM for different flow rates and inlet temperature values of the working fluid.

In this study, organic PCM (PureTemp29) was incorporated into a Chevron Plate Heat Exchanger (CPHX) to serve as a LHTESS platform. The PCM was commercially procured from Pure Temp Inc., Minneapolis, MN. The thermal-hydraulic performance of this LHTESS platform was explored in this study. The flow of hot Heat Transfer Fluid (HTF) through the CPHX leads to melting while flow of cold HTF leads to solidification of the PCM. Experiments were performed using hot and cold HTF (for operating temperatures ranging from 34°C–24°C) at different flow rates of the HTF (5, 8 and 10 GPH). The array of thermocouples were strategically mounted at different locations within the LHTESS containing the PCM. The transient temperature profiles recorded by the sensor array enabled the estimation of the fluctuations of the power ratings and energy-storage capacity ratings for the LHTESS. The bulk temperature of the HTF flowing between inlet and outlet ports of the LHTESS was correlated with the transient temperature profiles along with the location.