Abstract
Supercritical carbon dioxide (scCO2) has unique thermal properties with better flow and heat transfer behavior. However, the flow and heat transfer behavior of scCO2 using helical coil geometries have not fully documented yet. Therefore, the main purpose of this study is to investigate the flow and heat transfer characteristics of scCO2 in helical coiled tubes for heating process using computational fluid dynamics (CFD) method. For the simulation, commercial CFD software called ANSYS FLUENT is used. Helical coiled tube of inner and outer diameter 9.0 mm and 12.0 mm, respectively, with total length of 5500 mm, pitch distance of 32.0 mm and 6 turns of coils is considered. The model is intended to analyze the pressure drops, friction factor, Nusselt number, and goodness factor of scCO2. Three different inlet pressures (8.00 MPa, 9.03 MPa and 10.05 MPa) with three different uniform heat fluxes (20.5 kW/m2, 50.5 kW/m2 and 80.5 kW/m2) at constant inlet temperature of 27°C are considered. The numerical results are compared with experiment results from previous study to validate the developed model. The wall temperature results from the numerical analysis are in good agreement with the experimental data. From the numerical analysis, the Nusselt number increased significantly when the inlet mass flow rate and heat flux increased. Moreover, it was observed from the simulation results that an increment of average pressure drop by 900 Pa (19.57%) and average friction factor coefficient by 0.1536 (33.85%) when the pressure inlet increased from 9.03 MPa to 10.05 MPa. Hence, the results obtained from this study can provide information for further investigation of scCO2 for industrial applications
Highlights
Carbon dioxide (CO2) gas is an environmental friendly gas that have been reintroduced as it has zero ozone depleting potential (ODP) and zero effective global warming potential (GWP)
Many studies and experiments were done by researchers on scCO2 using one or two parameters for cooling or heating process for both numerical and experimental studies [5]
The main purpose of this study is to determine the thermo-fluid properties of scCO2 namely Nusselt number, Colburn factor, pressure drop and friction factor for three different inlet pressures
Summary
Carbon dioxide (CO2) gas is an environmental friendly gas that have been reintroduced as it has zero ozone depleting potential (ODP) and zero effective global warming potential (GWP). At the point where scCO2 reaches near to critical point, the physical properties shows extremely rapid variations with a change in temperature and pressure which is getting more attention by many researchers nowadays as it has high demand in many engineering applications [3]. It is used as working refrigerators fluid in air conditioning system The type of heat exchanger used to study the characteristics of scCO2 by researches are mostly in the form of vertical and horizontal tubes, miniatures, plates, fins and coils.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
