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• Twisted tape (TT) has been employed in LFR solar system. • Impose of trapezoidal tank boosts the optical performance. • Effect of perforated barrier twisted tape has been simulated via FVM. • Augmenting TR, WR causes friction faction to increase about27.09 % and 9.22 %. In current suggested design for domestic usage, arrangements of mirrors have been implemented as primary reflector. Impose of trapezoidal tank intensifies the optical performance and alumina-water has been utilized as operating fluid which is practical due to kind of application. For modeling, finite volume approach was imposed and extracted heat flux from solving the pure radiation were added as source term of turbulent modeling of nanomaterial flow. Twisted tapes (TT) were installed within the pipe to augment the convective flow. Inlet temperature (T in), flow rate (V •), twist (TR) and width (WR) ratios are variables for various cases. Irreversibility and thermal behavior were reported for all cases. With existence of cavity, the optical efficiency enhances up to 73.5 %. For lowest values of other parameter, augmenting TR and WR cause friction faction to increase about 27.09 % and 9.22 % but increasing V • leads to decline of f about 29.77 %. With assumption of lowest values of other variables, augmentation of TR, V • and WR leads to intensification of Nu about 4.83 %, 146.4 % and 1.69 %. As T in intensifies, η t h declines about 23.7 % when V • = 6.3, WR = 0.56, TR = 2.With enhance of TR and WR, η t h goes up about 0.11 % and 0.037 % with considering lowest values of other variables. [ABSTRACT FROM AUTHOR]

• Heat transfer intensification of nanofluid within a Solar LFR was investigated. • Mirrors with involve of parabolic secondary reflector has been employed. • With selection of nanomaterial higher thermal performances was obtained. • For Re = 8000, T in = 298.15, η e x augments about 1.47% with growth of fin length. • Although growth of T in offers lower thermal performance. In current solar unit, mirrors with involve of parabolic secondary reflector has been employed to enhance the absorbed radiation flux. The optical efficiency with involve of modified secondary reflector augments about 21%. The absorbed flux profile was added in energy equations as source term and three dimensional turbulent flows have been analyzed. Bottom of the pipe facing with mirrors has greatest radiation flux and its value is 7500 W/m2. The top point of pipe has higher radiation flux than left and right sides because of presence of secondary reflector. Water as base fluid inside the pipe was mixed with Al 2 O 3. Besides, install of fins has been considered as second approach to help the thermal performance. With increase of fin length and Re, swirl flow enhances and superior cooling obtains which offers thinner boundary layer. At highest values of other factors, growth of Re leads to 0.43% reduction in temperature while rise of T in makes temperature to augment about 9.97%. The value of η e x for T in = 323.15 is 97.43 times greater than that of T in = 298.15 when Re = 8000 and t = 0. With select of highest values of Re and lowest values of T in , the finned tube (t = 3 mm) has greatest thermal efficiency. [ABSTRACT FROM AUTHOR]