AngleDome, Gas flow conditioning through reflection

A Passive Momentum-Based System for CO2Enrichment via Selective Reflection, AngleDome Jae Un Kim Department of Physics, Ajou University, Suwon, Republic of Korea [email protected] Abstract We introduce AngleDome, a novel CO2enrichment device that operates using only the physical principles of momentum divergence, reflective wall geometry, and controlled collision sequencing. Unlike membraneor solvent-based systems, AngleDome requires no moving parts, sorbents, phase change processes, or vacuum cycles. Gas mixtures enter at controlled velocity, and molecular mass-dependent behavior results in lighter gases arriving earlier, while heavier CO2molecules maintain trajectory and reflect efficiently into a capture channel. Pathway distance is minimized to retain velocity gradients and enable controlled timing for enough separation. With expected CO2enrichment of 80%, the system achieves effective performance at significantly reduced installation and operating costs compared to VSA/PSA and MEA systems. AngleDome provides a physically-driven, passive alternative to industrial gas separation, offering extreme scalability and near-zero energy demand. 1. Introduction Gas separation is central to atmospheric management, clean energy systems, and carbon capture. Conventional methods predominantly rely on chemical selectivity (e.g., MEA), molecular sieving (PSA/VSA), or phase-change processes (cryogenic)—which, though effective, involve complex equipment, sorbent degradation, high operating costs, or significant thermal energy requirements. AngleDome departs from this paradigm by: •Using molecular momentum (p=m·v) as the selective driving force •Leveraging wall reflection angle, not materials, for directional control •Exploiting sequential collision dynamics for targeted CO2isolation 1 It is not a filter, It is a pathway design that lets gases separate themselves. 2. System Design Overview The system consists of: •A straight inlet channel (short and low-loss) •A reflective, dome-shaped interior geometry •A CO2capture channel •An outlet for background gas venting 3. Theoretical Basis 3.1 Momentum Divergence For a gas mixture under uniform temperature, molecules exhibit velocities inversely proportional to molecular mass: p=m·v Thus, lighter gases (e.g., N2, O2) arrive earlier than CO2 3.2 Selective Reflection The reflection angle θrat each wall interaction is dictated by: θr=f(θi, m, v, surface curvature) Only CO2achieves post-reflection direction that leads into the capture channel. 4. Sequential Interaction and Velocity Constraint Velocity preservation along the inlet path is essential: v(x) = v0·exp −µx ρD Lighter gases arrive first, And CO2arrives later, maintaing a coherent trajectory. tCO2> tbg but θCO2→capture path 2 Item AngleDome PSA/VSA MEA Moving Parts No Yes Yes Sorbent/Solvent None Yes Yes Energy Fan (W-level) Compressor (kW) Heat 100◦C+ CapEx Low Medium High OpEx Very Low Medium Very High Table 1: Comparison of cost and operation among CO2separation methods. 5. Gas properties and selective accumulation In the AngleDome structure, separation does not arise from reflection alone. The reflective geometry mainly aligns the flow, while the intrinsic properties of each gas determine how strongly it is decelerated, how long it remains near the wall, and how effectively it can re-enter the axial low-velocity core. Among common atmospheric gases, CO2is the only species that satisfies all of the necessary conditions for stable axial accumulation. 5.1 Definition of effective gas parameters For each gas species i, we introduce the following effective parameters: •Molecular mass Mi(g/mol) •Real-gas interaction factor Zi(dimensionless, 0 ≤Zi≤1) •Wall-residence factor Ri(dimensionless, 0 ≤Ri≤1) The real-gas factor Ziqualitatively represents how strongly gas ideviates from idealgas behaviour and how intensively it interacts with curved reflective surfaces. The wallresidence factor Rirepresents the tendency of gas ito remain in the near-wall region before returning to the main flow. For convenience, we define a composite wall–interaction parameter Ci=ZiRi,(1) which summarises the effective ability of each gas to lose momentum at the wall and to stay near the reflective boundary. 5.2 Why only CO2accumulates along the core axis Qualitatively, CO2differs from other major atmospheric gases (N2, O2, Ar, He) in three combined aspects: 1. It has a moderate but sufficiently large molecular mass (MCO2= 44 g/mol), which leads to stronger post-collision deceleration than N2or O2, while avoiding the excessive inertial rebound expected for very heavy species such as SF6. 3 2. It exhibits a relatively high real-gas interaction factor ZCO2, so that momentum loss at the reflective surface is enhanced within the curved AngleDome geometry. 3. It has a long effective wall-residence factor RCO2due to its strong quadrupole moment, which increases the probability of re-entering the axial low-velocity region under the existing pressure gradient. As a result, the composite parameter CCO2=ZCO2RCO2is significantly larger than that of other gases. CO2therefore experiences strong deceleration, prolonged interaction with the wall, and repeated re-entry into the central coreline, leading to a stable axial concentration peak. Lighter gases (N2, O2, He) retain more of their momentum and mainly escape through peripheral streamlines, while very heavy gases show large momentum loss but lack the necessary residence and re-entry behaviour. In this sense, the AngleDome should not be interpreted as a separator that relies on reflection alone; rather, it is a reflective structure that enables and amplifies the intrinsic property-driven divergence between CO2and other gases. 6. Conclusion AngleDome demonstrates that CO2enrichment can be achieved using only passive momentum selection, without compressors, pumps, membranes, or sorbent regeneration cycles. Because the system operates without external power input and contains no consumable materials, the long-term operating cost approaches zero, distinguishing it from conventional CO2capture technologies whose cost is dominated by energy and maintenance. This combination of (i) passive physics-based selectivity, (ii) structurally simple implementation, and (iii) near-zero operating expense makes AngleDome suitable for distributed applications such as indoor air conditioning, agricultural facilities, and closed environments where continuous low-cost CO2management is required. References •Bird, R. B., Stewart, W. E., & Lightfoot, E. N. (2002). Transport Phenomena (2nd ed.). Wiley. •Rochelle, G. T. (2009). Amine scrubbing for CO2capture. Science, 325(5948), 1652–1654. •Zhang, Y., et al. (2020). Membrane-based gas separation technologies for CO2 capture. Chemical Engineering Journal, 380, 122584. •Heidari, S., et al. (2022). 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