Parametric optimisation of supercritical CO₂ thermal-hydraulic characteristics in micro-channels using response surface methodology

ABSTRACT

This study aims to determine the optimum geometrical and operating parameters of supercritical carbon dioxide (ScCO₂) flow through a straight pipe for enhanced heat transferusing the Response Surface Method (RSM). Inlet pressure, inlet temperature, mass flow rate, and pipe inner diameter are selected as design variables while Nusselt number (Nu) and pressure drop are chosen as response functions. The ranges of the input variables considered in the study are inlet pressures (7–10 MPa), inlet temperature (35–80 °C), mass flowrate (0.02–0.05 kg/s), and tube inner diameter (2.8–4.5 mm). The accuracy and validity of the developed mathematical models are validated by comparing the simulation results with published experimental values. The sensitivity analysis results of Nu indicated that the best heat transfer in ScCO2 cooling is found to be associated with the lowest inlet pressure and temperature, the lowest tube diameter, and the highest mass flow rate. Moreover, the best flow conditions with minimum pressure drop are associated with the highest and lowest inlet pressure and temperature, respectively, as well as the highest tube diameter and lowest mass flow rate. These parameter combinations could help reduce the pumping power associated with a high pressure drop.

KEYWORDS:

• Numerical simulation
• supercritical carbon dioxide
• heat exchanger
• heat transfer
• pressure drop
• response surface methodology (rsm)

Acknowledgments

The authors would like to thank the Ministry of Higher Education Malaysia and Universiti Malaysia Pahang (www.ump.edu.my) for the financial support given under project no. FRGS/1/2019/TK03/UMP/02/18 and RDU190319, respectively.

Data availability statement

The ScCO₂ thermophysical property data used to support the findings of this study are openly available in the NIST Chemistry WebBook, NIST Standard Reference Database Number 69 at 10.18434/T4D303, reference number [41]. The remaining data used to support the findings of this study are available within the article.

Additional information

Notes on contributors

N.T. Rao

Mr N. Tiwaan Rao was the postgraduate student at the Faculty of Mechanical Engineering, University of Malaysia Pahang.

A. N. Oumer

Dr Ahmed N. Oumer, N. T.Rao’s supervisor, College of Engineering, University of Malaysia Pahang. His research interest is in the area of thermo-fluids and CFD.

M.M. Noor

Dr M. Mat Noor, is senior lecture at the Faculty of Mechanical and Automotive Engineering Technology, University of Malaysia Pahang (UMP). He is also the director of UMP press.

K. Kadirgama

AP Ir Ts Dr Kumaran Kadirgama is an associate professor at the Faculty of Mechanical and Automotive Engineering Technology, University of Malaysia Pahang. He is a technologist as well. He has published significant number research papers in the are of heat transfer, tribology, and nanofluids.

F. Basrawi

AP Dr Firdaus Basrawi is an associate professor at the Faculty of Mechanical and Automotive Engineering Technology, University of Malaysia Pahang. His research interest is in the area of renewable energy, heat transfer.

J. P. Siregar

Dr Januar P. Siregar is a senior lecture at the college of engineering, university Malaysia Pahang. His research interest is in the application of natural polymer composites.