Carbon nanotube nanofluid for the efficiency improvement in a CHP system: simulation and experimental investigation

Abstract

Due to the importance of combined heat and power (CHP) systems in ensuring the energy efficiency of thermal units as well as the ability of nanofluids to enhance the thermal efficiency of thermal equipment, a new nanofluid was synthesized and compared with some other thermal fluids. Multi-walled carbon nanotubes (CNTs) were employed as a multifunctional nanoplatform in a base fluid. Additionally, some physical and chemical surface modifications were conducted in order to improve not only dispersion but also stability of this nanofluid. The acid treatment and polymer wrapping (PEGylation) of CNTs were applied as chemical and physical modifications, respectively. These techniques assisted us to prepare a more stable thermal nanofluid in a CHP system. Furthermore, higher heat removal was achieved, compared to previously tested nanofluids. Because of the extensive and various methods in surface modification of the CNT together with the effect of this modification on the thermal behavior of nanofluid, it seems that the PEGylated and oxidized CNT nanofluid can play an important role in improving CHP heat removal and ensure higher heat recovery. Furthermore, the possibility of more power generation was investigated with the aid of Aspen HYSYS simulation software. Simulation results showed that there is a potential to produce 52.75 kW more power with implementation of an Organic Rankine Cycle (ORC) within the current system. The ORC’s thermodynamic efficiency was 10.29%.