Numerical modeling and analysis of nanofluids subcooled boiling in a horizontal circular tube

Subcooled flow boiling, characterized by large heat transfer coefficient (HTC), is widely encountered and of great significance in energy industry. To enhance its thermal efficiency for compact applications, nanofluids are employed by improving the thermophysical properties. This article numerically investigates nanofluids subcooled boiling in a horizontal tube under wide-range, multi-factor impacts, including Reynolds number of 40,000–50,000, nanoparticle type, that is, Al2O3, TiO2, Cu, and volume fraction of 1%–5%. The thermal equilibrium assumption and Eulerian multiphase model are utilized after numerical validations. Results indicate that the vapor volume fraction augments along the tube while nanoparticles reduce the vapor production during boiling. As for thermal and flow performance, nanofluids can enhance the HTC at the expense of a rising pressure drop. In the case of Al2O3/Water nanofluid, the maximum of HTC increases by 10.56%. In contrast, the pressure drop increases by 2.1 times when the Al2O3 concentration changes from 1% to 5%. The performance evaluation criterion (PEC) in this article always exceeds 1 for nanofluids, demonstrating that the heat transfer enhancement outweighs the pressure drop penalty, and the Al2O3/Water nanofluid show superior performance with PEC achieving 1.1. This work can provide support for a profound understanding and utilization of nanofluids subcooled boiling.