Vertical Single-Effect Diffusion Solar Still Coupled with a Tilted Wick Still: An Experimental Study

Mohd Zaheen Khan

doi:10.7176/apta/84-01

Abstract

A single-effect diffusion still, instead of a multiple-effect diffusion (MED) still, combined with a tilted wick (TW) still was investigated experimentally under actual weather conditions to investigate whether the natural convection can transport the vapor from the TW still to an MED still adequately. It was found that the single-effect still can be heated by vapor from the TW still and solar radiation absorbed on the single-effect still. From the experiments in summer and autumn, it was found that a MED still can be heated in both seasons whether the MED still absorbs solar radiation directly or not. The experimental results agreed with the calculation results. The total daily amount of distillate, Σm d,total, did not correlate with the daily horizontal solar radiation, ΣG day , but strongly correlated with daily solar radiation incident on the still, ΣG still . The maximum of Σm d,total obtained in experiments was about 4.88 kg/m 2 day when ΣG day and ΣG still were 13.6 and 18.4 MJ/m 2 day, respectively Keywords: Outdoor experiment, Solar still, Solar desalination, Tilted wick, Multiple-effect DOI: 10.7176/APTA/84-01 Publication date: August 31 st 2021

Highlights

Solar powered stills come in many types, but multiple-effect diffusion stills (MED stills) and tilted wick stills (TW stills) are two of the most common
TW stills (configured much like the TW unit (TWU) in Fig. 1) basically involve a wick and transparent cover, and salt water flows into the wick continuously
The performance of MED stills tends to be much more efficient than single-effect stills, since evaporation and condensation are repeated using the same energy. This type of still was proposed by Dunkle [1] in 1961, and he constructed a five-effect vertical MED still combined with a solar absorber, and performed experiments as well as numerical analysis

Summary

Graphical Abstract

Abstract A single-effect diffusion still, instead of a multiple-effect diffusion (MED) still, combined with a tilted wick (TW) still was investigated experimentally under actual weather conditions to investigate whether the natural convection can transport the vapor from the TW still to an MED still adequately. It was found that the single-effect still can be heated by vapor from the TW still and solar radiation absorbed on the single-effect still. From the experiments in summer and autumn, it was found that a MED still can be heated in both seasons whether the MED still absorbs solar radiation directly or not.

Introduction

Theoretical analysis

Results and discussion