REVVING UP HEAT-TRANSFER PERFORMANCE OF DOUBLE PIPE HEAT EXCHANGER USING DIVERSE MOLAR Ag-GO HYBRID NANOFLUIDS: AN EMPIRICAL AND NUMERICAL STUDY USING CENTRAL COMPOSITE DESIGN

Abstract

This study seamlessly integrates empirical and numerical approaches to enhance the efficiency of a double pipe heat exchanger (DPHX) using varied molar concentrations (0.03, 0.06, and 0.09 M) of Ag-doped GO hybrid nanofluids as the working fluids within the heat exchanger's annulus. Remarkable improvements in the heat exchanger's performance were achieved by increasing the molar concentration of Ag-GO hybrid nanoparticles, along with the Reynolds number (ranging from 250 to 1451) and the mass flow rate (ranging from 8 to 47 g/s) of the hybrid nanofluids. The utilization of a 0.09M Ag-GO hybrid nanofluid at a Reynolds number of 1451 and a flow rate of 47 g/s resulted in outstanding enhancements in heat-transfer coefficient (62.9%), and Nusselt number (33.55%) surpassing the base fluid. The empirical results of Nusselt number and heat-transfer coefficient were optimized and analyzed using the central composite design approach (CCD) with response surface method, incorporating the Graetz number, varied molar concentrations of Ag-GO, and thermal conductivity of the hybrid nanofluids as input factors. The optimized second-order polynomial quadratic equation model demonstrated excellent compatibility and optimal performance of the heat exchanger, supported by variance analysis. Additionally, CCD optimization confirmed a notable desirability function (0.99) and emphasized the significant influence of the input factors on the output responses. In conclusion, the Graetz number exhibited prominent influence among the input factors, alongside the molar concentration and thermal conductivity of hybrid nanofluids, effectively enhancing the performance of the DPHX.