Three dimensional problems reflect more imperative understanding to real world issues in comparison to two dimensional problems. Keeping this fact in mind, a mathematical model is designed to deliberate the 3D magnetohydrodynamic couple stress nanofluid flow with joule heating and viscous dissipation effects past an exponential stretched surface. The analysis is performed keeping in mind the physical effects of Brownian motion and thermophoresis combined with convective heat condition. This

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... r also distinctly introduces a more realistic boundary constraint for nanoliquid flow model. For instance, zero mass flux condition has been instituted for the first time for 3D couple stress nanofluid model as far as the exponential stretched surface is concerned. Self-similar transformations are engaged to obtain a system of ordinary differential equations possessing high nonlinearity from the system of boundary layer partial differential equations. Analytic solution is constructed in the form of series using Homotopy Analysis Method (HAM). Numerically calculated values of Skin friction and local Nusselt number are also given with suitable analysis. Moreover, the influences of sundry parameters on velocity distribution, and heat and mass transfer rates are deliberated and depicted through relevant graphs. The results obtained clearly show that the Biot number and Hartmann number possess increasing effect on temperature distribution. To authenticate our obtained results, a comparison in limiting case is also given. The term "nanofluid" refers to the nanoparticles (having size less than 100 nm) suspended into the base fluid. Typical examples of nanoparticles include metals such as Copper, Aluminum and Silver, oxides e.g., Aluminum Oxide, carbides such as Silicon Carbides, nitrides like Silicon Nitride and Aluminum Nitride, and nonmetals such as graphite or carbon nanotubes. The customary fluids are ethylene glycol, water, and oil. The amalgamation of nanoparticles with the common fluid tremendously improves the thermal traits of the base fluid. Choi and Eastman 1 were the pioneer to introduce the term nanofluid and the fact that several heat transfer physiognomies of the base fluids, such as thermal conductivity is enhanced by insertion of nanoparticles into it. Later, Wang and Arun 2 deliberated that convective characteristics of base fluid are enhanced by addition of metallic and non-metallic particles into it. This was followed by an experimental study by Eastman 3 who claimed that thermal conductivity of the ethylene glycol is improved by 40% once copper nanoparticles are inserted in it. Subsequently, Eastman 4 also examined that the shape of nanoparticles has a pivotal role in increasing the thermal conductivity of base fluid. The decree of Eastman was verified by Murshed 5 who studied that the amalgamation of water with spherical shaped nanoparticles (Titanium oxide) with sizes more than 40 nm, increases the thermal conductivity of the base fluid by 33%. The use of nanofluids is very common in cooling the transformers and nuclear reactors. In medical, magneto nanofluids are also being utilized in cancer treatment, hyperthermia and