RT info:eu-repo/semantics/doctoralThesis
T1 Advanced modeling and optimization of the oxy-combustion net power cycle and heat transfer in supercritical CO2 microflows for high-performance compact heat exchangers
A1 Velázquez Palencia, Iván
A2 Universidad de Valladolid. Escuela de Doctorado
K1 Termodinámica
K1 Power cycle
K1 Ciclo de potencia
K1 Heat transfer
K1 Transferencia de calor
K1 Supercritical CO2
K1 CO2 supercrítico
K1 CO2 capture
K1 Captura de CO2
K1 22 Física
AB This PhD thesis contributes to the technological advancement and performance improvement of the NET Power thermodynamic cycle, an innovative oxy-combustion-based energy production technology that employs supercritical CO2 (scCO2) as a working fluid. A major objective is to conduct a comprehensive experimental and computational investigation on heat transfer in horizontal scCO2 microflows within the operating conditions of the NET Power cycle, reaching up to 30 MPa. This study aims to constitute a first research step towards the replacement of the currently established printed circuit heat exchanger units by novel, high-performance, and compact micro shell-and-tube heat exchanger (MSTHE) units for the low-temperature section of the NET Power cycle recuperator, the key component of the cycle for achieving high thermal efficiencies.The study begins by performing a complete detailed thermodynamic model of the most advanced NET Power cycle embodiment. The binary interaction parameters of several equations of state are optimized to characterize the working fluid properties, under the specific pressure, temperature, and composition ranges of the cycle. A novel hybrid optimization algorithm is developed to propose the optimal set of operating parameters for maximum cycle efficiency. Moreover, the part-load performance of the cycle is analyzed, offering new valuable insights into its operational flexibility, and defining the operating boundaries of the recuperator for conducting the subsequent heat transfer investigation. An experimental system is built to conduct pioneer heat transfer experiments, up to 30 MPa, in scCO2 flows through a uniformly heated, horizontal microtube. The effect of key parameters such as the pressure, mass flux, heat flux, inlet fluid temperature, buoyancy and thermal acceleration, on the heat transfer performance are investigated through sensitivity studies. To predict the heat transfer coefficients, empirical models, including an artificial deep neural network, are developed. These models provide a foundation for the thermal design of MSTHE units for the low-temperature section of the recuperator. Then, the empirical heat transfer model is integrated into a one-dimensional thermal-hydraulic model to assess the MSTHE performance. The results demonstrate high operational effectiveness and structural advantages of MSTHE over conventional heat exchange architectures, positioning MSTHEs as a promising high-performance, and cost-effective alternative for future deployment.
YR 2025
FD 2025
LK https://uvadoc.uva.es/handle/10324/79917
UL https://uvadoc.uva.es/handle/10324/79917
LA spa
NO Escuela de Doctorado
DS UVaDOC
RD 11-ene-2026