Lead Performer: Oak Ridge National Laboratory – Oak Ridge, TN
July 10, 2023
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Lead Performer: Oak Ridge National Laboratory – Oak Ridge, TN
Partners:
-- Honeywell
-- Emerson Climate Technologies
-- Hussmann
DOE Total Funding: $500,000
Cost Share: $300,000
Project Term: January 1, 2023 – January 1, 2024
Funding Type: CRADA
Project Objective
For this project, a distributed micro-cascade refrigeration system is proposed as an alternative to current-centralized refrigeration systems used in supermarket applications. This cascade system is configured to use low–global warming potential (GWP) refrigerants R-1234ze(E) or R-471A (GWP of <150) to provide direct expansion cooling for medium-temperature evaporators while acting as the high-stage fluid of the cascade cycle employed for low-temperature evaporators. All the components of the low-stage system are within a display case, making it self-contained and factory-charged, which significantly minimizes refrigerant leaks. Because of these characteristics, the low-stage system can employ flammable refrigerants (e.g., R-1234yf, R-455A, R454C, propane) or high-pressure refrigerants such as CO2. The condensing and evaporation temperatures of the low-stage system can be fixed, which allows for further optimization of the overall system to produce the highest possible coefficient of performance.
Low GWP refrigerants have drawn increasing attention as an alternative to HFC refrigerants that are regulated as a leading cause of global warming in the HVAC&R industry. The heat exchanger is a common yet extremely critical component of such systems, and heavily influences the overall performance. Consequently, a high efficient heat exchanger with utilization of low GWP refrigerants not only reduces the direct emissions caused by refrigerant losses but also reduces indirect emissions by particularly efficient system technology. Oak Ridge National Laboratory propose an activity to develop heat exchanger technology for refrigerants (<150 GWP) to enhance performance and reduce refrigerant charge (i) for liquid-to-refrigerant HXs (ex: plate HX) and (ii) for air-to-refrigerant HXs (ex: tube or microchannel HXs). The team will review state-of-the-art HX technology and build a facility to study both types of heat exchangers with various low GWP refrigerants. The comprehensive database or correlation for the low GWP refrigerants will be developed. The team will also target for reducing the refrigerant charge in air conditioning and refrigeration systems by improving the maldistribution, header, and heat exchanger design. Finally, a validated thermal-hydraulic performance model will be developed.
Project Impact
This effort will reduce greenhouse gas emissions in the supermarket sector by ~74%, equal to 46.4 million tons of CO2 annually, surpassing EERE's 2030 goal of 50-52%. This project will achieve up to 15% energy savings, notably around 6.75 TWh/year in the U.S. supermarket segment, making crucial steps toward decarbonization. Highly efficient, smaller, distributed systems could expedite deployment and broaden access, better reaching disadvantaged communities.
Contacts
DOE Technology Manager: Payam Delgoshaei
Lead Performer: Samuel Yana Motta