The use of passive baffles to increase the yield of a single slope solar still

Abstract

Despite their relative simplicity, single slope solar stills remain one of the most viable solutions to the production of freshwater from saline and non-potable water sources. Over the years, numerous researchers have attempted to improve the yield of single slope solar stills through changes to their geometry and the use of various design modifications. Despite this long history of research, one modification that has not been fully explored is the use of passive baffles to alter the natural convection inside them.Though baffles have frequently been used to suppress natural convection in enclosures, there may also be the opportunity to use them to enhance natural convection. This judicious placement of baffles to enhance the natural convection could potentially improve the yield from single slope solar stills, however it has not been well explored in the literature.To address this issue, this work examined the effect of vertically mounted passive baffles on the natural convection inside a single slope solar still geometry. In this vein, a computational fluid dynamics simulation was conducted for a still containing a baffle, with the results validated experimentally using particle image velocimetry. On this basis, subsequent simulations explored the effect of baffle length and position on stills with cover angles from 10˚-60˚. The results showed that baffles did have a marked influence on the natural convection flow field and could increase the natural convection heat transfer coefficient, which is directly proportional to a solar still's yield, by up to 20%.It was also found that short baffles enhanced natural convection at low cover angles, while baffles mounted close to the front of a still provided an improvement to the transfer processes over the widest range of conditions. Finally, the work led to the development of a relationship to describe the effect of baffles on natural convection, as shown in Equation 1, that it is hoped will aid designers of single slope solar stills in the future. 𝑁𝑢′ = 𝑅𝑎′ 0.188 * 𝐴𝑅 −0.29 * (cos 𝜃) −0.5 * ( 𝑏 𝐵

Enhancing performance of solar stills ‐ A review

“…The maximum efficiency was recorded when the blade was positioned at X = 0.23, where X is the ratio of blade location and the average of H r (right side height) and H l (left side height), and Y = 0.38, where Y is the ratio of blade height and average of H r and H l , over the glass cover. Like study, 19 this study also demonstrates that baffles located closer to the shorter side of the still have a higher efficiency.…”

“…where Y is the ratio of blade height and average of H r and H l , over the glass cover. Like study, 19 this study also demonstrates that baffles located closer to the shorter side of the still have a higher efficiency. cooler increased the production rate by 6.8%.…”

“…From the data collected, the productivity was maximum when the baffle was mounted 1/2nd from the left wall. Serradj et al 19 used both CFD simulation and experimental data to study the effects of vertically mounted passive baffles on a productivity of the solar still. Using the assumption that the flow is two‐dimensional, a simulation of a narrow baffle over the trapezoidal enclosure was performed with a narrow baffle connected to its topmost surface and a varying cover angle.…”