Session: 09-18-01: Innovations in Storage, Recovery and Upgrade of Thermal Energy

Paper Number: 170557

A Polymer-Based Multilayer Spiral-Coil Heat Exchanger for Thermal Energy Storage Using Salt-Hydrate Phase Change Material 

The building sector accounts for 28-30% of the total energy consumption in the United States. Space heating and water heating are responsible for 38% of the thermal energy consumption in buildings. Nearly 33-35% of this thermal energy generated by burning fossil fuel is rejected to the environment as waste. Therefore, the International Energy Agency recommends electrification of heating by adopting heat pumps, as heat pumps are highly efficient and can output large amounts of thermal energy with a small input of electrical energy. Nevertheless, robust electrification of water heating in residential and multifamily buildings using heat pumps will create a fluctuating electricity demand on the grid  subject to occupants’ hot water use patterns. A thermal energy storage (TES) device with a suitable phase change material (PCM) can harmonize the energy demand and energy supply from the grid by implementing load shifting. A TES-PCM device can be charged using heat pump to store the heat at times when energy demand on the grid is low. The stored heat from TES-PCM device can be used to produce hot water for domestic use at times when peak load occurs. Thus, adoption of TES-PCM device integrated with heat pump system is a promising solution to prevent the grid failure during the peak load and thus to ensure the energy security of the country.

A major drawback towards implementing TES-PCM device for residential water heating is the high cost of PCM materials. To date, several PCMs are available in the market including waxes, fatty acids, organic PCMs and salt hydrates. Among these, salt hydrate PCMs are the cheapest (approximately US$10/kWh), but they are highly corrosive in nature. The conventional way to tackle this problem is to encapsulate the PCMs or utilize corrosion-resistant stainless-steel (SS) tubing in typical fin-and-tube heat exchangers used as TES-PCM device. As a result, the currently available TES-PCM devices are expensive. Herein, we propose the design of a polymer-based multilayer spiral-coil heat exchanger that can house salt-hydrate PCMs without encapsulation. The proposed design uses low-cost crosslinked polyethylene (PEX) tubes instead of SS to overcome the corrosion issue of salt-hydrates. The innovative multilayer spiral-coil design enhances the heat transfer surface area between the PCM and working fluid. Thus, the new design proposed in this study has great potential for market penetration by lowering the cost but maintaining the thermal performance similar to conventional TES-PCM device.

The thermal hydraulic performance of the proposed polymer-based multilayer spiral-coil TES-PCM device using so called “DURATEMP-58” as supplied by Insolcorp, LLC, a salt-hydrate PCM with solid-liquid transition temperature 58, and distilled water as coolant is evaluated experimentally. A test-loop comprising of a chiller, several balls valves, a needle valve, a turbine flow meter, two pressure sensors, several thermocouples (K type) and a National Instruments data acquisition system is built at the Oak Ridge National Laboratory, TN, USA. The thermal hydraulic performance evaluation of the prototype TES-PCM device is currently ongoing. The preliminary results show that heat exchange can effectively takes place between the PCM and coolant when PEX tube is used. The results also show that the thermal conductivity of PCM is the rate limiting step to enhance the heat transfer process rather than the thermal conductivity of PEX tubes. More details on the heat transfer and pressure drop at different coolant flowrates and coolant inlet temperatures will be reported later upon completion of the experimental runs.  

Presenting Author: Jubair Shamim Oak Ridge National Laboratory

Presenting Author Biography: Jubair has been actively conducting research in the field of thermos-fluid engineering since 2013. His research expertise/ interests include but are not limited to transport in porous media, functional materials for energy harvesting, thermal management of HVAC components and surfaces, and interfaces for enhanced dropwise condensation and anti-icing. His previous key research accomplishments are (i) the design and testing of a hybrid compression-adsorption heat pump system, (ii) the design of a multilayer fixed-bed binder-free desiccant dehumidifier using a distinct mesoporous silica gel, and (iii) the design of slippery superhydrophobic surfaces with low depinning force to suppress wetting transition and enhance condensate removal.

Jubair is an active member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). He also serves as the guest editor, review editor, and reviewer for several academic journals. Jubair received the JSRAE academic award in 2023 for his contribution to refrigeration and air-conditioning technology development. Outside of academic pursuits, he loves outdoor and sports activities, including cycling, swimming, tennis, and traveling.

Website: https://www.ornl.gov/staff-profile/jubair-shamim
Google Scholar: https://scholar.google.com/citations?user=f9WL5WcAAAAJ&hl=en

Authors:

Jubair Shamim Oak Ridge National Laboratory
Thien D. Nguyen Oak Ridge National Laboratory
Kashif Nawaz Oak Ridge National Laboratory