A novel supercritical CO2 thermoacoustic circulation pump: Flow rate modeling and enhancement

Pumps are essential in many supercritical CO2 applications. This study proposes a novel thermoacoustic circulation pump. Numerical simulations, theoretical analysis, and experiments were carried out to model and enhance the mass flow rate G in a circulation loop. Based on a numerical simulation, the process in the loop is identified as an isentropic charge–discharge cycle, leading to the theoretical expression G0=3600ΔpfV/a2, where Δp is the pressure amplitude, f the oscillation frequency, V the loop volume, and a the speed of sound. Comparison with experimental results yields an improved expression, G=nG0 with n>1. The amplification factor n originates from the interaction between fluid inertia and compliance of the circulation loop, resulting in transient pressure overshoots and amplified density oscillations. Guided by this improved expression, several strategies for enhancing G are experimentally validated, such as enlarging V and maximizing the product Δpf by tuning the resonator tube length, increasing the charging pressure, and raising the hot-end temperature. In contrast, reducing a by raising the ambient temperature toward the pseudocritical point is found to weaken oscillations and eventually reduce G. The prototype achieves a peak mass flow rate of 17.39 kg/h. With no moving parts and the capability to harness low-grade heat, the thermoacoustic circulation pump provides a sustainable solution for supercritical CO2 pumping, underscoring its strong potential for practical applications.