Experimental study of the thermal characteristic of a double tube heat exchanger with tapered wire coil inserts using PCM-dispersed mono/hybrid nanofluids

ABSTRACTAn experimental study involving tapered wire coil inserts in a double-tube heat exchanger using water-based phase change material (PCM)-dispersed mono/hybrid nanofluids is conducted. The effects of the wire coils (WC) with nanofluids on the hydrothermal performance of this system are studied for different coil arrangements: converging wire coils (CWC), diverging wire coils (DWC), and converging-diverging wire coils (CDWC) and different Reynolds numbers. The experimental results indicate that among all the tested coil arrangements, the DWC presents a higher thermal performance factor (TPF) than the other arrangements. Using the DWC, the TPF of the Al2O3+PCM hybrid nanofluid is augmented by 3.98%, 9.61%, and 3.04% as compared to that for the plain wire coil (PWC), CWC, and CDWC, respectively. Besides, the DWC configuration exhibits the minimum entropy generation among all arrangements. For the Al2O3+PCM hybrid nanofluid using the DWC, the entropy generation is decreased by approximately 13.36%, 9.78%, and 5.78% as compared to that of the PWC, CWC, and CDWC at a volumetric flow rate of 15 lpm.KEYWORDS: Nanofluidstapered wire coildouble tube heat exchangerheat transfer enhancemententropy generationenergy efficiency Nomenclatures CWC=Converging wire coilCDWC=Converging-diverging wire coilDWC=Diverging wire coilcp=Specific heat (J/kg.K)d=Diameter (m)r=Radius (m)DWC=Diverging wire coilf=Friction factorh=Heat transfer coefficient (W/m2.K)k=Thermal conductivity (W/m.K)L=Tube length (m)m=Mass flow rate (kg/s)Nu=Nusselt numberΔp=Pressure lose (Pa)Pr=Prandtl numberQ=Heat transfer rate (W)Re=Reynolds numberS=Entropy (W/K)T=Temperature (K)Φ=Volume concentration (%)µ=Dynamic viscosity (Pa.s)ρ=Density (kg/m3)Subscripts=avg=Averagegen=Generationeq=Equivalenth, nf=Hot, nanofluidht=Convective heat transfer coefficienti, o=Inner, outerin, out=Inlet, outletnp=Nanoparticleit, ot=Inner tube, outer tubetot=TotalDisclosure statementNo potential conflict of interest was reported by the author(s).