Solar/Supercritical CO2 Thermal and Energy Enhancement Laboratory (STEEL)

WCEC developed the Solar Thermal and Energy Enhancement Laboratory (STEEL) to advance research in heat exchanger technology for a variety of applications such as solar power generation, thermal desalination, waste heat utilization, and solar fuels. The STEEL facility is equipped with a 7-m parabolic solar dish that is capable of concentrating sunlight by nearly 1,000 times at the focal area. The facility is also home to a high pressure (200 bar), high temperature (up to 700°C) supercritical carbon dioxide (sCO2) flow loop. The combination of the parabolic dish and the sCO2 loop give the STEEL lab a unique set of capabilities in the area of high temperature and high pressure heat transfer research, along with heat exchanger technology development. View detailed specifications of the STEEL facility



HVAC refrigerants with low global warming potential have significant environmental benefits, but also have flammability concerns; in the interest of safety they are best kept in hermetically, factory-sealed heat pump packages outside homes. To do this, a secondary fluid, such as water, is needed to transfer heat between the air within the HVAC air handler and the refrigerant outside the home. The configuration of a water-to-air heat exchanger (HX) is critically important in determining its effectiveness in terms of thermal performance. Typical finned-tube HXs in air handlers and current state-of-the-art, chilled, water-to-air HXs have significant limitations.

This project, funded by the U.S. Office of Naval Research, uses advances in microchannel technology and additive manufacturing (AM) of plastics to develop a low-cost, highly-effective Microchannel Plastic Heat Exchanger (MPHX). This MPHX could improve conventional air handlers, saving energy and reducing cost.

Based on our prior experience in heat recovery applications, we proposed a conceptual design for a MPHX that consists of multiple “water plates” (WP) in parallel through which cooled or heated water flows. The WPs are joined together by inlet and outlet headers. The internal architecture of each WP consists of a staggered array of microscale pins around which water flows. The WPs are attached together laterally by external fins that form honeycomb air flow passages. Air flows between the WPs and through the fins and exchanges heat with water within the plates.

We developed a thermo-fluidic model for performance predictions of this concept. The performance of MPHX is compared with a finned tube HX. The calculations show that for identical approach temperatures and flow rates the effectiveness of MPHX increased 35% compared to the finned tube design.


Microchannel solar receiver development
With funding from the Department of Energy’s SunShot initiative, Oregon State University (OSU) developed a solar thermal receiver based on flow of sCO2 through microchannel pin fin arrays. WCEC characterized the heat transfer performance of flow through the arrays using surrogate fluids and developed correlations to predict the thermal performance. Researchers are currently preparing to test a 15 cm x 15 cm receiver developed by OSU.

Microchannel waste heat recuperator for sCO2 cycles
With funding from the Office of Naval Research and the US Department of Energy, UC Davis and Carnegie Mellon University researchers collaborated to design and fabricate a novel additively-manufactured heat exchanger for waste heat recovery and for indirect fossil-fired sCO2 cycles.

WCEC will test multiple recuperator modules together to address scalability of the design.

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