Inscrição na biblioteca: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

THERMAL RESISTANCE NETWORK MODEL FOR A RECUPERATOR IN S-CO2 POWER CYCLE

Get access (open in a dialog) DOI: 10.1615/IHTC16.her.024078
pages 4919-4930

Resumo

Several studies have revealed that supercritical carbon dioxide (S-CO2) power cycles have the potential to attain higher cycle efficiencies than conventional steam Rankine or air Brayton power cycles. S-CO2 cycles have small footprint, offer simple layout with compact turbo machinery and heat exchangers. The design of recuperator/regenerator in the system plays a crucial role in determining cycle efficiency and performance. Therefore, a Printed Circuit Heat Exchanger (PCHE) with high effectiveness and low-pressure drop is preferable over conventional shell and tube or a tube in tube heat exchanger (HEx). Traditional procedures involving NTU and LMTD methods used for tube in tube or a shell and tube heat exchanger design do not capture the correct temperature profiles along the tube length due to nonlinear variation in physical properties of CO2 during the heat transfer process. The present paper proposes a novel thermal resistance network (TRN) model for a PCHE design which accounts for variation in properties of CO2 resulting from heat transfer between the hot and cold fluid streams in the HEx. The flow paths for hot and cold fluid streams are discretized to calculate temperature and pressure variations along the length of the heat exchanger. The model is coupled with REFPROP database to update the thermo-physical properties of hot and cold fluid streams. The lengths and hydraulic diameter of channel are iteratively varied to meet the design requirements of temperature and pressure drop across the cold and hot fluid streams. The PCHE stack comprises of multiple plates which are alternatively stacked vertically to form a counter flow HEx. The overall exposed surface area is minimized for a range of stack heights and widths to obtain a minimum PCHE foot print. The fidelity of the TRN model is demonstrated with a case study of a S-CO2 recuperator design. The inlet and outlet conditions for hot and cold streams are selected based on optimum cycle parameters for a simple recuperated S-CO2 Brayton plant developing a nominal power output of 10 MW.