High Performance Membrane Heat Exchangers for HVAC

Over 15% of US energy use goes to building heating and cooling, with heat exchangers being the component that is both most expensive and most efficiency-limiting in these systems. Substantial improvements in energy efficiency and system cost can be enabled by developing more effective, lower cost heat exchangers. Heat exchanger effectiveness can be improved by increasing heat exchanger area, which is challenging and expensive with conventional materials. In this project, a low-cost, high-efficiency, high-area polymeric heat exchanger is being developed. This heat exchanger, acting as a drop-in replacement for conventional heat exchangers, will enable high-efficiency building cooling and heating at reduced cost. In Phase I, a polymer material, a heat exchanger geometry, and a polymer pouch manufacturing method were identified, and a prototype heat exchanger was constructed and tested. Performance exceeding a conventional heat exchanger was demonstrated, and cost modeling suggested cost savings in excess of 60%. In Phase II, a new material was selected to prevent water loss through the heat exchanger over the lifetime of the component, and manifolding methods were developed to join polymer pouches made of this material into a complete heat exchanger. Reliability tests were devised to demonstrate a 10-year lifetime, and the selected polymeric material was shown to have a lifetime over 30 years. Novel polymer pouch designs with the potential to outperform metal heat exchangers by 50% in the same envelope were developed. The results of the Phase I and Phase II research, along with the company’s progress toward developing a full heat pump system, have been leveraged to raise over $13M in venture capital funding and over $8M in grant funding from non-DOE sources. In the Phase IIB project, the remaining development work to commercialize polymer heat exchangers for heating and cooling applications will be conducted. A robust, low-cost, and easy-to-assemble frame will be developed, along with the liquid connections to integrate the polymer heat exchanger with an indirectly coupled heat pump system. High-throughput manufacturing methods inspired by the packaging industry will be adapted to the heat exchanger application, with automated production of polymeric heat exchangers occurring by the end of the project. The reliability tests developed in Phase II will be conducted on the PHXs produced using the automated production line, to ensure that the 10-year lifetime can be met. Initially, polymer heat exchangers will be deployed in residential heat pumps for heating and cooling, reducing energy costs and enabling novel architectures that improve the user experience. Once proven in this application, the technology will be extended to commercial building systems, where it has the potential to provide the same cost and energy savings.