Fresh water is scarce, making it a worldwide issue. In order to address global freshwater demand, a filtration technique is needed. Solar distillation (SD) that purifies brackish and subterranean water has been proven to be a promising green technology. It produces distilled water which can be used as potable water for drinking and other purposes. The designs, operations, and configurations of several inverted solar stills are thoroughly examined in this article. All techniques for solar water distillation to separate saltwater from freshwater have the same fundamental idea. It has been demonstrated that for a specified mass of water in the top basin, the daily output of an inverted absorber double-basin solar still (IASS) grows with increasing water depth in the bottom basin. Nevertheless, as the water depth in the bottom basin rises from 1 cm to 5 cm, the output of an inverted absorber double-basin solar system falls by about 27%. At water depths of 4, 6, and 8 cm, the daily yields from inverted absorber solar stills paired with a refrigeration cycle (RIASS) were 6.4, 10.08, and 9.5 L/day, respectively. The results also showed a substantial rise in water temperature in the inverted absorber solar still as a result of lower bottom heat loss and larger absorptivity. In this study, the emphasis on energy, efficiency, and environmental concerns remains with the modified multi-wick basin-type inverted absorber solar panel. The performance of the inverted trickling solar still was assessed with a 60 ppm average salinity under various sun radiation, feed water flow rate, and existence conditions for natural convection. It was found that the still could produce 2.55 L/day m² of fresh water, a 15% increase. Brackish water with a salinity of 6000 ppm was used to test the still in November at tilt angles of 47° and 32°. Condensate production at the specified angles was 2.8 and 2 L/d, respectively. A total output of 6.907, 5.681, and 4.650 kg/m²/day was also generated using the modified multi-wick basin-type inverted absorber solar still (MMWBIASS) at water depths of 1, 2, and 3 cm, respectively. With black cotton wicks, the MMWBIASS had a total thermal efficiency of 34.04%, 28.17%, and 23.61%.

Purpose: The purpose of this paper is to carry out a detailed investigation to study the natural convection of a non-Newtonian nanofluid flow between two vertical parallel plates. In this study, sodium alginate has been taken as a base fluid and nanoparticles that added to it are copper and silver. Maxwell–Garnetts and Brinkman models are used to calculate the effective thermal conductivity and viscosity of nanofluid, respectively. Design/methodology/approach: The authors used two methods in this study, namely, Galerkin’s method and homotopy perturbation method. Findings: This paper investigates the velocity and temperature profile of nanofluid and the real fluid flow between two vertical parallel plates. The impacts of physical parameters such as nanofluid volume fraction and dimensionless non-Newtonian viscosity are discussed. Originality/value: Coupled non-linear differential equations are solved for velocity and temperature. A model is proposed in such a way that the authors may get the solution of real fluid from the nanofluid by neglecting the nano term. The authors do not require a further calculation for real fluid problem.

Free convective flow in a cubical cavity loaded with copper-water nanofluid was examined numerically by employing a non-homogeneous dynamic model, which is physically more realistic in representing nanofluids than homogenous ones. The cavity was introduced to a horizontal magnetic field from the left sidewall. Both the cavity’s vertical left and right sidewalls are preserved at an isothermal cold temperature (T_c). The cavity includes inside it four isothermal heating blocks in the middle of the top and bottom walls. The other cavity walls are assumed adiabatic. Simulations were performed for solid volume fraction ranging from (0 ≤ ϕ ≤ 0.06), Rayleigh number varied as (10³ ≤ Ra ≤ 10⁵), the Hartmann number varied as (0 ≤ Ha ≤ 60), and the diameter of nanoparticle varied as (10 nm ≤ d_p ≤ 130 nm). It was found that at (d_p = 10 nm), the average Nusselt number declines when Ha increases, whereas it increases as (Ra) and (ϕ) increase. Furthermore, the increasing impact of the magnetic field on the average Nusselt number is absent for (Ra = 10³), and this can be seen for all values of (ϕ). However, when (d_p) is considered variable, the average Nusselt number was directly proportional to (Ra) and (ϕ) and inversely proportional to (d_p).

The numerical analysis of MHD-free convective heat transfer and its interaction with the radiation over a heated flame inside a porous semicircular cavity loaded with SWCNTs–water nanofluid was explored for the very first time in the present work. The two circular arcs of the upper wall of the enclosure were preserved at a constant cold temperature, whereas the middle region of it was considered adiabatic. The midland region of the lower wall was heated partially, while other regions were also assumed adiabatic. An internal hot flame was included inside the cavity, while the cavity was exposed to a magnetic field. The results were illustrated for Hartmann number (0 ≤ Ha ≤ 100), Rayleigh number (10⁴ ≤ Ra ≤ 10⁶), heated region length (0.1 ≤ L ≤ 0.3), solid volumetric fraction (0 ≤ φ ≤ 0.04), Darcy number (10⁻³ ≤ Da ≤ 10⁻⁵) and radiation parameter (0 ≤ Rd ≤ 1). It was found that decreasing L is the best option for enhancing natural convection. Moreover, it was noted that (Nu_out) is directly proportion to (Ra), ($\varphi$), (Rd) and (Da) increase. In contrast, it was in reverse proportion to (Ha). Furthermore, the results showed that augmentation of about (4%) and a decrement of (56.55%) are obtained on the average (Nu) on the heated length by increasing the radiation and the Hartmann number, respectively. Moreover, raising the radiation number from (0 to 1) causes an augmentation of about (73%) in the average (Nu) of the heated flame. Results also indicated that increasing the Hartmann number will cause a decrement of about (82.4%) of the maximum velocity profile in the vertical direction.

In this article, numerical study of nanofluid flow between two inclined planes is carried out under the influence of magnetic field. Water-based nanofluid with nanoparticle of Copper (Cu) is taken into consideration for the present investigation. An efficient numerical method namely Optimal Homotopy Analysis Method (OHAM) is employed to get an approximate series solution for the related governing differential equation. A new approach is proposed to determine the convergence controller parameters used in OHAM. For the validation of the proposed technique, the convergence of the obtained results is shown for different values of involved parameters. Moreover, residual errors for the different number of terms in the obtained series solution are represented graphically. Obtained numerical results from the proposed method are incorporated with the previous results and they are found to be in very good agreement. Impacts of involved parameters like nanoparticle volume fraction, Hartmann number and Reynolds number on non-dimensional velocity are also discussed.