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Volume 5, Issue 4, 2026
Open Access
Research article
Unsteady Magnetohydrodynamic Sutterby Penta-Hybrid Nanofluid Flow Over an Extending Catalytic Surface for Wastewater Treatment
asaigeethan palanisamy ,
vishnu priya ponnulingam ,
siva raja ponnumperumal mathusoothanaperumal ,
yamuna subramaniyan ,
saravana moorthy krishnasamy
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Available online: 09-15-2026

Abstract

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An unsteady magnetohydrodynamic boundary-layer model was developed for a Sutterby penta-hybrid nanofluid flowing over an extending catalytic surface, with particular emphasis on transport mechanisms relevant to wastewater treatment. Water was employed as the base fluid, while polystyrene, poly (acrylic acid), poly (acrylic acid)-block-polystyrene (PAA-b-PS), cerium oxide, and copper oxide were incorporated to represent complementary functionalities associated with colloidal stabilization, contaminant adsorption, photocatalytic degradation, and antimicrobial activity. The coupled conservation equations governing momentum, energy, and species concentration were formulated in Cartesian coordinates, together with a Poisson equation for the pressure field. Appropriate similarity transformations were subsequently introduced to reduce the governing partial differential equations to a coupled system of nonlinear ordinary differential equations. Surface-catalyzed contaminant degradation was represented through reaction boundary conditions parameterized by Damköhler numbers. The resulting boundary-value problem was solved numerically using the MATLAB bvp5c solver. The computed results demonstrated that the hydrodynamic, thermal, and concentration boundary layers were strongly governed by the combined effects of magnetic forcing, Sutterby rheological behavior, nanoparticle loading, unsteadiness, and reaction kinetics. The effects of the magnetic field, Sutterby rheological parameters, nanoparticle loading, reaction kinetics, and pressure variations on the velocity, temperature, and contaminant-concentration distributions were systematically evaluated. The numerical results demonstrated that the coupled effects of magnetohydrodynamic forcing, Sutterby rheology, and penta-hybrid composition substantially modified momentum, thermal, and mass transport within the boundary layer. In particular, appropriate combinations of the governing parameters were shown to intensify thermal and solutal transport and promote contaminant degradation at the catalytic surface. Pressure variations were additionally demonstrated to influence boundary-layer development and species transport, thereby affecting the predicted contaminant-removal characteristics. These findings establish a theoretical framework for understanding coupled magnetohydrodynamic, non-Newtonian, heat-transfer, and reactive mass-transfer phenomena in multifunctional nanofluid systems and provide potential guidance for the development and optimization of advanced wastewater-treatment processes.

Abstract

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Geothermal brine retains considerable thermal energy before reinjection, but its potential for additional power generation is not always fully utilized. Low-temperature solar preheating offers a possible route to increase heat recovery without altering the geothermal source conditions. This study investigates the integration of a field-tested trickle solar collector as a preheater for a small-scale geothermal organic Rankine cycle (ORC), with particular attention to energy performance, exergy efficiency, heat-transfer feasibility, and working-fluid selection. A thermodynamic model was developed using experimental collector data and a geothermal brine stream entering at 188 ℃ and leaving at the 90 ℃ reinjection limit. The brine mass flow rate was fixed at 1.690 kg/s, corresponding to a pinch-feasible 100-kW n-pentane reference cycle. Heat-transfer feasibility was evaluated over the complete counter-current temperature profile using a minimum approach temperature of 10 K. The tested collector produced an average useful heat output of 752.4 W per module and reached a maximum outlet temperature of 51.5 ℃. A field of 88 modules, with a total aperture area of 91.52 m$^2$, supplied 45.024 kW of useful solar heat to the preheater. For the n-pentane cycle, solar preheating increased the net power output from 100 to 106.473 kW while the thermal efficiency remained at 14.377%. The exergy efficiency increased from 51.393% to 53.705%, and the minimum temperature approach remained feasible at 10.120 K. Under the same brine and pinch constraints, R245fa produced the highest net power of 110.961 kW, closely followed by R1233zd(E) at 110.547 kW. Preliminary heat-exchanger sizing yielded a logarithmic mean temperature difference of 12.757 K, a UA value of 3.529 kW/K, and a required heat-transfer area of 7.06–11.76 m$^2$. The results indicate that trickle collectors are better suited to low-temperature preheating than direct ORC evaporation. This integration provides a technically feasible approach to increasing power recovery from geothermal brine while maintaining the original reinjection temperature and thermodynamic operating limits.

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