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Motivated by exploring the near-wall transport phenomena involved in bioconvection fuel cells combined with electrically conducting\ud nanofluids, in the present article, a detailed analytical treatment using homotopy analysis method (HAM) is presented of non-similar\ud bioconvection flow of a nanofluid under the influence of magnetic field (Lorentz force) and gyrotactic microorganisms. The flow is induced\ud by a stretching sheet under the action of a oblique magnetic field. In addition, nonlinear radiation effects are considered which are\ud representative of solar flux in green fuel cells. A second thermodynamic law analysis has also been carried out for the present study to\ud examine entropy generation (irreversibility) minimization. The influence of magnetic parameter, radiation parameter and bioconvection\ud Rayleigh number on skin friction coefficient, Nusselt number, micro-organism flux and entropy generation number (EGN) is visualized\ud graphically with detailed interpretation. Validation of the HAM solutions with published results is also included for the non-magnetic case in\ud the absence of bioconvection and nanofluid effects. The computations show that the flow is decelerated with increasing magnetic body\ud force parameter and bioconvection Rayleigh number whereas it is accelerated with stronger radiation parameter. EGN is boosted with\ud increasing Reynolds number, radiation parameter and Prandtl number whereas it is reduced with increasing inclination of magnetic field.

Incompressible, steady-state, boundary layer magneto-bioconvection of a nanofluid\ud (containing motile gyrotactic micro-organisms) over a nonlinear inclined stretching sheet\ud subjected to non-uniform magnetic field is studied theoretically and numerically. This regime\ud is encountered in novel bio-nano-material electroconductive polymeric processing systems\ud currently being considered for third generation organic solar coatings, anti-fouling marine\ud coatings etc. Buongiorno’s two-component nanofluid model is deployed with the OberbeckBoussinesq approximation. Ohmic dissipation (Joule heating) is included. The governing\ud nonlinear partial differential equations are reduced to a system of ordinary differential\ud equations and appropriate similarity transformations. The normalized system of equations with\ud associated boundary conditions features a number of important dimensionless parameters\ud including magnetohydrodynamic body force parameter (M), sheet inclination (δ), Brownian\ud motion nanoscale parameter (Nb), thermophoresis nanoscale parameter (Nt), Richardson\ud number (Ri=GrRe2\ud , where Gr is thermal Grashof number and Re is Reynolds number),\ud buoyancy ratio parameter (Nr), Eckert (viscous dissipation) number (Ec), bioconvection\ud Rayleigh number (Rb), Lewis number (Le), bioconvection Lewis number (Lb), Péclet number\ud (Pe), nonlinear stretching parameter (n) are solved with a variational Finite Element Method\ud (FEM). Validation is conducted with earlier published studies of Khan and Pop (2010) for the\ud case of non-magnetic stretching sheet nanofluid flow without bioconvection. Further validation\ud of the general magnetic bioconvection nanofluid model is achieved with a generalized\ud differential quadrature (GDQ) numerical technique developed by Bég and Kuharat (2017). The\ud response of non-dimensional velocity, temperature, nanoparticle concentration, motile microorganism density function, local skin friction coefficient, Nusselt number, Sherwood number,\ud wall motile density gradient function to variation in physically pertinent values of selected\ud control parameters (representative of real solar bio-nano-magnetic materials manufacturing\ud systems) are studied in detail. Interesting features of the flow dynamics are elaborated and new\ud future pathways for extension of the study identified in bio-magneto-nano polymers (BMNPs)\ud for solar coatings.

2D steady incompressible laminar Newtonian viscous convection-radiative heat transfer in a rectangular solar collector geometry is considered. The ANSYS FLUENT finite volume code (version 17.2) is employed to simulate the thermo-fluid characteristics. Extensive details of computational methodology are given to provide engineers with a framework for simulating radiative-convection in enclosures. Mesh-independence tests and validation are conducted. The influence of aspect ratio, Prandtl number (Pr), Rayleigh number (Ra) and radiative flux model on temperature, isotherms, velocity, pressure is evaluated and visualized in colour plots. Additionally, local convective heat flux is computed, and solutions are compared with the MAC solver for various buoyancy effects achieving excellent agreement. The P1 model is shown to better predict the actual influence of solar radiative flux on thermal fluid behaviour compared with the limited Rosseland model. With increasing Ra, the hot zone emanating from the base of the collector is found to penetrate deeper into the collector and rises symmetrically dividing into two vortex regions with very high buoyancy effect. With increasing Pr there is a progressive incursion of the hot zone at the solar collector base higher into the solar collector space and simultaneously a greater asymmetric behaviour of the dual isothermal zones.

A numerical study of convective heat transfer in an annular pipe solar collector system is conducted. The inner tube contains pure water and the annular region contains nanofluid. Three-dimensional steady-state incompressible laminar flow comprising water-based nanofluid containing a variety of metallic nano-particles (copper oxide, aluminium oxide and titanium oxide nano-particles)is examined. The Tiwari-Das model is deployed for whichthermal conductivity, specific heat capacity and viscosity of the nanofluid suspensions is evaluated as a function of solid nano-particle volume fraction. Radiative heat transfer is also incorporated using the ANSYS solar flux and Rosseland radiative models. The ANSYS FLUENTfinite volume code (version 18.1) is employed to simulate the thermo-fluid characteristics. Mesh-independence tests are conducted. The influence of volume fraction on temperature, velocity, pressure contours is computed and visualized.Copper oxide nanofluid is observed to achieve the best temperature enhancement. Temperature contours at cross-sections of the annulus are also computed.

Nanofluids are complex colloidal suspensions comprising nanoparticles (metallic or carbon based or both) suspended in a base fluid (e.g. water). The resulting suspension provides demonstrably greater thermal performance than base fluids on their own without the agglomeration or sedimentation effects associated with larger (micron-sized) particles. The substantial elevation in thermal conductivity achieved with nanoparticles has made nanofluids very attractive for numerous energy applications including solar collectors. Solar energy is a clean, renewable source available and is essential for all life to exist on earth. Current technology which harvests solar energy with heat transfer fluids (HTFs) e.g., Direct Absorber Solar Collectors (DASCs), Flat Plat Solar Collector (FPCs), Parabolic Trough Solar Collector (PTSCs) etc, still requires continuous improvement in achieving higher efficiencies and greater sustainability. Nanotechnology has emerged as a significant area in recent years and features the use of sophisticated “green” nanomaterials embedded in conventional engineering materials. In this PhD a range of different DASC geometries are explored (annular, trapezoidal, prismatic, quadrilateral, biomimetic channel etc) with a variety of real nanofluids (water-based with metallic nanoparticles such as silver, copper, gold, zinc, titanium etc or carbon based e.g. diamond, graphite etc). Viscous incompressible laminar flows using Newtonian fluid models (Navier-Stokes equations) with thermal convection and radiative heat transfer are considered both with and without thermal buoyancy. Several thermal radiative flux models are deployed to mimic solar radiation effects such as the Rosseland model, P1 Traugott model, Chandrasekhar discrete ordinates model (DOM). ANSYS FLUENT and MAPLE symbolic software are used as the numerical tools to solve the relevant boundary value problems. Generally, the Tiwari-Das nanoscale model is used although the Buongiorno two-component nanofluid model (with thermophoresis and Brownian motion) has also been deployed. Extensive visualizations of streamline and isotherms are computed. Validation with alternative numerical methods and experimental studies is also included. Comprehensive appraisal of the relative performance of different nanofluids is evaluated. Generally, non-magnetic nanoparticles are studied although for the biomimetic channel (solar pump) case magnetic nanoparticles are addressed. The simulations show the significant improvement in thermal conductivities (and thermal efficiency) achieved with different types of geometry and nanoparticle type. Aspect ratio and inclination effects are also considered for some DASC cases. Extensive physical interpretation of thermofluid characteristics is provided. Where possible key dimensionless scaling parameters (Rayleigh number, Nusselt number, Prandtl number, Rosseland number etc) are utilized. The analyses reported herein constitute significant novel developments in solar collector nanofluid dynamics and many chapters have been published in leading international journals and conferences. The results have furnished good guidance for solar designers to assist in the selection of different geometries, nanoparticle types and volume fraction (percentage doping) for larger scale deployment in the future. Furthermore, some pathways for extending the current simulations to e.g. non-Newtonian nanofluid physics, turbulence etc are also outlined.

Heat transfer is one of the most critical aspects of the rocket propulsion design process. According to released heat, thermal loads are extremely large, and thermal insulation is frequently necessary in the motor combustion chambers and nozzles. In high temperature conditions, large thermal dilatations are present, and also the motor’s parts mechanical characteristics decreases. These occurrences are very important in the motor design process, and they are directly dependent from them temperature field. This is the reason why precise heat transfer calculation is necessary. Non-eroding metallic throat inserts made with pure tungsten, tungsten-rhenium alloys, and tungsten-rhenium alloys doped with hafnium carbide are now common. Combustion gas temperatures can rise up to 3,000 Celsius. Very high heat transfer rates from hot gases to the chamber wall must be designed for. Important research areas related to heat transfer of rocket nozzle include the internal and external heat transfer coefficient predictions, metal temperature distribution, wall cooling methods, and ceramic coatings among others. Life extension of the nozzle, which consists of an expensive super alloy, is very effective for reduction of the running costs of a power generation plant. Accordingly, it is very important for the life assessment of the nozzle to predict the operating conditions and to establish a basis for the criteria of repair. In order to assess the life of the nozzle accurately, it is necessary to estimate its temperature distribution by prediction of the thermal environment. A cooling system is essential therefore in order to maintain engine integrity. To elucidate aspect ratio effects in rocket channel cooling, we present ANSYS FLUENT CFD single-phase, two-dimensional turbulent forced convection simulations. We have used the data provided by Forrest of MIT. Extensive visuals of temperature, pressure and velocity contours are given. Mesh independence is included. Interesting thermal fluid dynamics characteristics are elucidated.

Nanofluids are currently being explored extensively in solar energy engineering to achieve improved performance in direct thermal absorber systems. Nanofluids achieve significant enhancement in the heat transfer performance i.e. thermal efficiency. Motivated by these developments in nano-technology, in this poster we present recent simulations of steady-state nanofluid natural convection in a solar collector enclosure. Two-dimensional, steady-state, incompressible laminar Newtonian viscous convection-radiative heat transfer in a rectangular solar collector enclosure geometry is modelled with ANSYS FLUENT finite volume code (version 18.1). The enclosure has two adiabatic walls, one hot (solar receiving) and one colder wall. The TiwariDas volume fraction nanofluid model is used and three different nanoparticles are studied (Copper (Cu), Silver (Ag) and Titanium Oxide (TiO2)) and water base fluid. The solar radiative heat transfer is simulated in the ANSYS workbench, with the elegant P1 flux model and the Rosseland model. The influence of geometrical aspect ratio (AR) and solid volume fraction for nanofluids is also studied and a wider range is considered than in other studies. These constitute novel contributions in the area of solar nanofluid collectors since these aspects are considered collectively. Mesh-independence tests are conducted. Validation with published studies from the literature is included for the copper-water nanofluid case. The P1 model is shown to more accurately predict the actual influence of solar radiative flux on thermal fluid behaviour compared with Rosseland radiative model. With increasing Rayleigh number (natural convection i.e. buoyancy effect), significant modification in the thermal flow characteristics is induced with emergence of different vortex regions. With increasing aspect ratio (wider base relative to height of the solar collector geometry) there is a greater thermal convection pattern around the whole geometry, higher temperatures and the elimination of the cold upper zone associated with lower aspect ratio. Titanium Oxide nano-particles achieve higher temperatures and a greater local heat flux at the hot wall. Thermal performance can be optimized with careful selection of aspect ratio and nano-particles and this is very beneficial to solar collector designers. The modelling approach can be extended in future to consider fully three-dimensional simulations and unsteady effects.

A numerical study of convective heat transfer in an annular pipe solar collector system is conducted. The inner tube contains pure water and the annular region contains nanofluid. Three-dimensional steady-state incompressible laminar flow comprising water-based nanofluid containing a variety of metallic nanoparticles (copper oxide, aluminium oxide and titanium oxide nanoparticles) is examined. The Tiwari-Das model is deployed for which thermal conductivity, specific heat capacity and viscosity of the nanofluid suspensions is evaluated as a function of solid nanoparticle volume fraction. Radiative heat transfer is also incorporated using the ANSYS solar flux and Rosseland radiative models. The ANSYS FLUENT finite volume code (version 18.1) is employed to simulate the thermo-fluid characteristics. Mesh-independence tests are conducted. The influence of volume fraction on temperature, velocity, pressure contours is computed and visualized. Copper oxide nanofluid is observed to achieve the best temperature enhancement. Temperature contours at crosssections of the annulus are also computed.

Novel bio-nano-electro-conductive polymers are currently being considered for third generation organic solar coatings which combine biological micro-organisms, nanofluids and magnetic polymer properties. Motivated by these developments, in this poster, we describe a mathematical model for simulating the manufacturing fluid dynamics of such materials. Incompressible, steady-state, boundary layer magnetobioconvection of a nanofluid (containing motile gyrotactic micro-organisms) over a nonlinear inclined stretching sheet subjected to non-uniform magnetic field is studied theoretically and numerically. Buongiorno’s two-component nanofluid model (developed at MIT) is deployed with the Oberbeck-Boussinesq approximation. Ohmic dissipation (Joule heating) is included. The governing nonlinear partial differential equations are reduced to a system of ordinary differential equations and appropriate similarity transformations. The normalized system of equations with associated boundary conditions features a number of important dimensionless parameters including magnetohydrodynamic body force parameter (M), sheet inclination (δ), Brownian motion nanoscale parameter (Nb), thermophoresis nanoscale parameter (Nt), Richardson number (Ri=GrRe2, where Gr is thermal Grashof number and Re is Reynolds number), buoyancy ratio parameter (Nr), Eckert (viscous dissipation) number (Ec), bioconvection Rayleigh number (Rb), Lewis number (Le), bioconvection Lewis number (Lb), Péclet number (Pe), nonlinear stretching parameter (n) are solved with a variational Finite Element Method (FEM). Validation is conducted with earlier published studies for the case of non-magnetic stretching sheet nanofluid flow without bioconvection. The response of nondimensional velocity, temperature, nanoparticle concentration, motile micro-organism density function, local skin friction coefficient, Nusselt number, Sherwood number, wall motile density gradient function to variation in physically pertinent values of selected control parameters (representative of real solar bio-nano-magnetic materials manufacturing systems) are studied in detail. Interesting features of the flow dynamics are elaborated of relevance to the performance of bio-magneto-nano polymeric solar coating