INVESTIGATING THE PERFORMANCE OF SUPERCRITICAL CO₂ HEATING: A COMPARATIVE STUDY OF VARIABLE AND UNIFORM PIN HEIGHT DESIGNS IN ADDITIVE MANUFACTURED MICRO-PIN RECEIVERS

There has been a recent investigation on connecting multiple micro-pin-based unit-cells (~17 cm x ~17 cm) fabricated via additive manufacturing in parallel to achieve Megawatt scale solar thermal heating of supercritical carbon dioxide. The use of additive manufacturing allows the geometry of each module to be tailored to the expected incident flux on that receiver location to maximize overall performance. In this paper, we extend our prior investigations by conducting simulations to explore a central receiver design consisting of multiple micro-pin modules with varying pin height for a given location, desired thermal duty, and maximum allowable surface temperature. This receiver's primary function is to heat supercritical carbon dioxide at a pressure of 20 MPa, elevating its temperature from 500°C to 720°C while ensuring its surface temperature remains below 800°C. The receiver's structural composition consists of hundreds of micro-pin array unit cells operating in parallel, all produced through additive manufacturing techniques. In this research, we will choose the pin diameter and spacing to guarantee satisfactory mechanical performance, treating the pin height as a variable that can be adjusted. The resulting variable pin height design is then compared to a receiver with a uniform pin height. The results of our research reveal that the receiver with variable pin height delivers higher temperatures, on average, while also exhibiting lower pressure drops when subjected to the same incident flux conditions and with the same surface area. This finding suggests that tailored receiver designs, accommodating varying pin heights, have the potential to enhance overall efficiency and reduce the levelized cost of energy. In future work, this methodology will be extended to more complicated tailored geometries and for designing receivers for producing process heat.