scholarly journals Solar Still Efficiency Enhancement by Using Graphene Oxide/Paraffin Nano-PCM

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 2002 ◽  
Author(s):  
Mohammad Reza Safaei ◽  
Hamid Reza Goshayeshi ◽  
Issa Chaer
Keyword(s):  
Nusselt Number ◽  
Graphene Oxide ◽  
Phase Change Materials ◽  
Convection Heat Transfer ◽  
Water Desalination ◽  
Design Parameters ◽  
Melting Time ◽  
Solar Still ◽  
Fourier Number ◽  
Productivity Improvement

Solar-driven water desalination technologies are rapidly developing with various links to other renewable sources. However, the efficiency of such systems severely depends on the design parameters. The present study focused on using graphene oxide (GO) with the Φ = 0.2, 0.4 and 0.6 wt.% dispersed in paraffin, as phase-change materials (PCMs), to improve the productivity of a solar still for desalination applications. The outcomes showed that by adding more graphene oxide to paraffin, the melting temperature got reduced. Solar still with GO/paraffin showed 25% productivity improvement in comparison with the solar still with only PCM. The obtained Nusselt number during the melting time also represented that free convection heat transfer into the melted region of the solar still has been enhanced by adding dispersed GO to the PCM, compared to the base paraffin. Also, increasing the hot wall temperature augments the Nusselt number. Finally, an empirical equation was derived to correlate the average Nusselt number as a function of Rayleigh number (Ra), the Stefan number (Ste), the subcooling factor (Sb), and the Fourier number (Fo). The obtained correlation depicted that Nusselt number enhancement has a reverse relation with Fourier number.

scholarly journals Influence of Nano Phase Change Materials on the Desalination Performance of Double Slope Solar Still

2021 ◽  
Vol 4 (2) ◽  
pp. 105
Author(s):  
T Sasilatha ◽  
Elavarasi R ◽  
V. Karthikeyan
Keyword(s):  
Thermal Properties ◽  
Phase Change ◽  
Phase Change Material ◽  
Phase Change Materials ◽  
Saline Water ◽  
Thermal Characteristics ◽  
Water Desalination ◽  
Insulation Material ◽  
Solar Still ◽  
Change Material

Solar still is the ancient low cost device to distillate the saline water. Paraffin is a kind of phase change material which has a thermal storage characteristic and it can absorb and release a large amount of latent heat during the phase transition process. Ethylene Glycol was used as a PCM to study the thermal characteristics of water and absorption rate. A Nano phase change material plays a vital role in solar energy conversion and is used to enhance the thermal conductivity behavior on thermal energy storage systems. Materials at the nanoscale have a larger surface area and it has higher thermal properties than the macro particles. Incorporating NPCM into basin material helps to improve the productivity and the evaporation rate. The performance of the single basin double slope solar still was higher than the single slope solar still. Despite significant efforts, there are some challenges, such as the thermo physical properties of basin material, flow rate, insulation material and thickness that must be overcome in order for this technique to be useful in practice. In this paper, a detailed comparison of the various solar stills, designs, fabrications and water production analyses are discussed. Hence it is confirmed that NPCM has a higher potential than PCM for saline water desalination processes. This study confirmed that the Paraffin composites are stable up to 160°C and it increases the efficiency due to increased thermal properties of NPCM.

Effect of absorber plate surface shape and glass cover inclination angle on the performance of a passive solar still

2019 ◽  
Vol 30 (6) ◽  
pp. 3183-3198 ◽  
Author(s):  
Hamid Reza Goshayeshi ◽  
Mohammad Reza Safaei
Keyword(s):  
Inclination Angle ◽  
Water Desalination ◽  
Surface Shape ◽  
Design Parameters ◽  
Solar Still ◽  
Absorber Plate ◽  
Daily Production ◽  
Content Type ◽  
Glass Cover ◽  
Inclination Angles

Purpose Solar-driven water desalination technologies are rapidly developing with various links to other renewable sources. However, the efficiency of such systems severely depends on the design parameters. This paper presents results from an investigation on the effect of the glass cover inclination angle on the performance of two stepped solar still geometries (flat and convex) and the amount of produced distilled water. Design Methodology Approach Studied inclination angles of 25°, 27.5°, 30°, 32.5° and 35° were chosen, while other design parameters were fixed. Findings The investigation showed that the unit with the convex absorber plate had higher average water daily production rate, compared to the output of the flat absorber plate unit. The results also depicted that the inclination angle of the still has a noticeable effect on the performance of solar stills. The value of the critical angle is 32.5°, and the higher inclination angle results in less heat transfer coefficient. This value can be used for design purposes and erases the typical assumption to use lower angles to optimize the productivity of the still. Practical Implications Finally, obtained data were used to correlate the Nusselt number for the flat and convex surfaces with different inclination angles of the glass cover. Originality Value The outcome of this investigation may find applications to develop highly efficient solar stills to secure more drinkable water in warm, dry lands.

scholarly journals Experimental and Theoretical Investigations of a Modified Single-Slope Solar Still with an External Solar Water Heater

2021 ◽  
Vol 13 (22) ◽  
pp. 12414
Author(s):  
Naseer T. Alwan ◽  
Sergey E. Shcheklein ◽  
Obed Majeed Ali ◽  
Milia H. Majeed ◽  
Ephraim Bonah Agyekum
Keyword(s):  
Thermal Performance ◽  
Water Desalination ◽  
Solar Water Heater ◽  
Solar Still ◽  
Water Heater ◽  
Productivity Improvement ◽  
Improvement Rate ◽  
Solar Water ◽  
June July ◽  
The Cost

One of the key impediments to the wide utilization of solar water desalination systems is limited production. Hence, this study aims at increasing the thermal performance of a single-slope solar still by increasing the surface area of evaporation and absorption exposed to sunlight. A hollow rotating cylinder was installed inside the still structure; this modified system was then joined with an outside solar water heater for productivity improvement. The obtained results show that a 0.5 rpm rotational speed ensured that the cylinder’s surface was kept wet. A mathematical model has been formulated using the finite difference method and the Fortran 90 programming language to assess the thermal performance productivity of two solar stills (conventional solar still (CSS) and modified solar still (MSS)) modelled under different conditions. The experimental and theoretical results are well agreed, with an error of 6.14%. The obtained results show that the maximum productivity recorded in July 2019 was about 11.1 L/m2 from the MSS and 2.8 L/m2 from the CSS, with an improvement rate ranging between 286% and 300% during June, July, August, and September 2019. The production cost per liter of distilled water from the modified and conventional solar stills was 0.0302 USD/L and 0.0312 USD/L, respectively, which indicates a noticeable reduction in the cost of distillate water production.

Forced convection heat transfer study of a blunt-headed cylinder in non-Newtonian power-law fluids

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jaspinder Kaur ◽  
Roderick Melnik ◽  
Anurag Kumar Tiwari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Total Drag ◽  
Shear Thinning Fluids ◽  
Power Law Fluids

Abstract In this present work, forced convection heat transfer from a heated blunt-headed cylinder in power-law fluids has been investigated numerically over the range of parameters, namely, Reynolds number (Re): 1–40, Prandtl number (Pr): 10–100 and power-law index (n): 0.3–1.8. The results are expressed in terms of local parameters, like streamline, isotherm, pressure coefficient, and local Nusselt number and global parameters, like wake length, drag coefficient, and average Nusselt number. The length of the recirculation zone on the rear side of the cylinder increases with the increasing value of Re and n. The effect of the total drag coefficient acting on the cylinder is seen to be higher at the low value of Re and its effect significant in shear-thinning fluids (n < 1). On the heat transfer aspect, the rate of heat transfer in fluids is increased by increasing the value of Re and Pr. The effect of heat transfer is enhanced in shear-thinning fluids up to ∼ 40% and it impedes it’s to ∼20% shear-thickening fluids. In the end, the numerical results of the total drag coefficient and average Nusselt number (in terms of J H −factor) have been correlated by simple expression to estimate the intermediate value for the new application.

scholarly journals Reviewing the Exergy Analysis of Solar Thermal Systems Integrated with Phase Change Materials

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 724
Author(s):  
Macmanus Chinenye Ndukwu ◽  
Lyes Bennamoun ◽  
Merlin Simo-Tagne
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Second Law Of Thermodynamics ◽  
Heat Transfer Fluid ◽  
Solar Still ◽  
Thermal Systems ◽  
Solar Systems ◽  
Exergy Balance ◽  
Change Material

The application of thermal storage materials in solar systems involves materials that utilize sensible heat energy, thermo-chemical reactions or phase change materials, such as hydrated salts, fatty acids paraffin and non-paraffin like glycerol. This article reviews the various exergy approaches that were applied for several solar systems including hybrid solar water heating, solar still, solar space heating, solar dryers/heaters and solar cooking systems. In fact, exergy balance was applied for the different components of the studied system with a particular attention given to the determination of the exergy efficiency and the calculation of the exergy during charging and discharging periods. The influence of the system configuration and heat transfer fluid was also emphasized. This review shows that not always the second law of thermodynamics was applied appropriately during modeling, such as how to consider heat charging and discharging periods of the tested phase change material. Accordingly, the possibility of providing with inappropriate or not complete results, was pointed.

Improved Melting and Solidification in Thermal Energy Storage Through Topology Optimization of Highly Conductive Fins

2017 ◽  
Author(s):  
Alberto Pizzolato ◽  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Topology Optimization ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Optimization Method ◽  
Periodic Pattern ◽  
Melting Time ◽  
Bottom Part

Thermal energy storage units based on phase change materials (PCMs) need a fine design of highly conductive fins to improve the average heat transfer rate. In this paper, we seek the optimal distribution of a highly conductive material embedded in a PCM through a density-based topology optimization method. The phase change problem is solved through an enthalpy-porosity model, which accounts for natural convection in the fluid. Results show fundamental differences in the optimized layout between the solidification and the melting case. Fins optimized for solidification show a quasi-periodic pattern along the angular direction. On the other hand, fins optimized for melting elongate mostly in the bottom part of the unit leaving only two short baffles at the top. In both cases, the optimized structures show non-intuitive details which could not be obtained neglecting fluid flow. These additional features reduce the solidification and melting time by 11 % and 27 % respectively compared to a structure optimized for diffusion.

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