International Journal of Energetica (IJECA) https://www.ijeca.info ISSN: 2543-3717 Volume 5. Issue 1. 2020 Page 37-42 IJECA-ISSN: 2543-3717. June 2020 Page 37 Experimental Investigation of the Effects of Preheating on Still Productivity Ridha Cherraye 1,2* , Bachir Bouchekima 1,3 1Laboratory of New and Renewable Energy in Arid Zones (LENREZA), University Kasdi Merbah Ouargla, 30000, ALGERIA 2 Department of process engineering, Kasdi Merbah University, Ouargla 30000, ALGERIA 3 Department of renewable energy, Kasdi Merbah University, Ouargla 30000, ALGERIA E-mail*: cherrayeridha@yahoo.fr Abstract – Single basin solar still (SBSS) has low productivity in this experimental research, some techniques have been employed to solve this problem, these techniques consist of using a flat plate collector. The main aim of this research was to make efficient use of the flat plate collector (FPC) to increase solar still productivity, and it works as a hybrid device. The model solar water heater for the flat plat collector (FPC) was coupled with a solar still, and the tests were repeated in 3 to 5 winter days, and the results were measured in the same way for each day. The results revealed that the productivity of the still increased 87 % when coupled with one, and decreased 20 % and 50 % when coupled with two and three flat plate collectors in southern Algeria, respectively. Keywords: Solar energy, solar desalination, solar still, flat plate collector, productivity. Received: 03/05/2020 – Accepted: 19/06/2020 I. Introduction Solar energy is one of the renewable energies; it is used in several fields, especially in solar distillation. Algeria has great energy potential in solar energy and it is favorable for solar distillation and heating of water. A study shows that any variation in solar radiation has an influence on the conventional solar still [1,2]. Several researches have been made in the south-eastern region of Algeria with the aim of treating polluted groundwater to transform it into pure portable water; researchers have conceived a small pilot distillation station in this area. Their studies aim at improving the efficiency of a small solar distillation station under real insulation for underground geothermal desalination of water in the arid regions, and also to generate drinking water in arid regions. The small station had more than 15 l/m 2 of daily capacity [3-5]. In the same direction, a simpler study shows step by step the conventional solar still construction which can produce between 4 to 6 l/m 2 per day [6]. The transformation of affected groundwater into pure water is the subject of several research projects around the world [7-9]. The main objective of any researcher in the field of solar distillation is to improve the performance of a solar still using several simple, complex, economical, environmental techniques. Among the techniques used, it is to take the glass cover (the condenser) as a factor of improvement; either by varying the angle of the cover (10, 15, 20, 30, 35 and 45 °) relative to the horizontal to determine the best angles which give the best performance of the still [10], either study the heat flow which passes from the interior of the still to the exterior via the cover [11], or to investigate the temperature gradient between the water and the cover [12] or to see the effect of double glazing on the performance of the solar still [13]. The use of a commercial refractor has improved the performance of solar stills and this has been proven experimentally [14, 15]. In solar distillers, the energy storage technique was used to increase productivity so that copper, stainless steel, mica, aluminum, sand and a black metallic plate of Zinc were dipped into the water basin and increased the productivity of pure water between 19 and 45 % [16, 21]. The preheating by an external solar device such as solar collectors is a relatively complex process used in active mailto:cherrayeridha@yahoo.fr Abder Image placée Ridha Cherraye et al IJECA-ISSN: 2543-3717. June 2020 Page 38 solar distillation [22, 26]. The aim of the present paper is to conduct an experimental study under the climatic conditions of south-east Algeria for the solar still in active mode. To improve productivity, various operational techniques have proposed. II. Experimental investigations II.1. solar still coupled with flat-plate collector . Figure 1 shows the schematic diagram of a flat plate collector coupled to a single slope solar still. In Figure 1 and 2 we see four identical stills that were made from different local materials in order to reduce cost and make construction easier. Solar stills coupled with 3 different number of FPCs, namely single collector, two collectors and three collectors, collector inclination of 30° is fixed for all experiments There were four phases in the experiment: witness still, still with one FPC, still with two FPCs connected in series and still with 3 FPCs connected in series. For all of the four experiments, the following parameters are measured on 12 h basis: The parameters, outer glass temperature, inner glass temperature, vapour temperature, water temperature, ambient temperature, incident radiation on glass cover and collector/collectors, inlet and outlet temperatures of collector/collectors and distillate output For the active solar still, Where mew is yield, L is latent heat, Ag and Ac are areas of glass cover and collector and I(t) and Ic(t) are incident radiations on still and collector. Figure .1. Line diagram of an active solar still coupled with flat-plate collector III. Result and discussions III.1. Solar intensity, ambient temperature and wind speed We report in this study the comparative performance of a single basin active solar still with 30 condensing cover inclination with one FPC and two different numbers of FPCs connected in series and a single slope. The tilt angle and three different collector inclinations were fixed at 30° for the solar still (experimental result shows 30° was optimal inclination angle in winter at Ouargla’s city). Figure 3 shows the ambient temperature, wind speed and the varying intensity of solar for January the 18th and this day as is shown in the figure has the maximum irradiance (910 W.m-2) at 13:00 h, maximum wind speed (7.5 m.s-1) at 10:00h and maximum ambient temperature (20 °C) at 13:00h. Figure 3 also shows that the minimum irradiance (245 W.m-2) at 09:00 h and 17:00 h, and minimum wind speed (2 m.s-1) at 09:00 h, 17:00h and 18:00h, and minimum ambient temperature (11 °C) at 09:00 h. These results show beyond reasonable doubt that Ouargla has an attractive solar energy. Ridha Cherraye et al IJECA-ISSN: 2543-3717. June 2020 Page 39 Figure .3. Solar intensity, ambient temperature and wind speed vs local time (18/01/2015) III.2. Hourly variation of productivity Figure 4 shows that high productivity is achieved for the still coupled with 1FPCs in comparison to others to the 12h period. The distillation efficiency and the daily productivity are for the still coupled with three different FPC arrangements are shown in figure 6. The still with 1 FPC and 2 FPCs in series obtain respectively a maximum yield of 6.669 kg and 2.87 kg. The still with 3 FPC however has a productivity of 1.75 kg and 0.606 kg for witness solar still. Ir becomes obvious that the still with single FPC gives more yield than FPCs connected in series. The cause of this is that the still with one FPC has an increased area for solar radiation; maintain low temperature of condensing cover for more time (less than 60°C). Figure .4. Hourly variation of productivity III.2. Average daily production for different configurations Compared to the one with witness, the still with 1 FPC has a greater daily productivity by 1000%. In comparison to the one with a witness, the still with 3 FPCs in series has 300% less efficiency. The yield and still efficiency will increase with the increase in T which is a tendency that we can observe for the still with one FPC as well as for the still with 2 FPCs in series. However, the efficiency has decreased compared to other two cases, as the increase in area off sets the advantage of increase in yield for the still with 3 FPCs in series. Nevertheless, the productivity is found to decrease for the still with 3 FPCs in series due to the increase in collector area and the distillation efficiency is optimum for the witness still compared to other arrangements as shown in Figure 5. Figure .5. The average daily production for different configurations III.3. Hourly variation of temperatures Figure 6 shows the hourly water and condensing cover inside temperatures for still coupled with different numbers of FPCs in series. Because of more added area with 3 FCPs for solar radiation, maximum temperatures are obtained for the still with 3 FPCs connected in series when compared with witness, 2 FPCs and 1 FPC. There is significant increase for the still with 2 FPCs to 3 FPCs when there is water and condensing cover inside temperature because the local solar irradiation was very high during experimentation. Abdelkader Hima. et al IJECA-ISSN: 2543-3717. June 2020 Page 40 Figure .6. Hourly variation of temperatures IV. Conclusion  1 and 2 FPCs connected in series obtain more productivity compared to that with one FPC. Consequently, to enhance the distillate yield the one FPC is found to be more suitable. The partial pressure difference between water temperature and condensing cover temperature is found to be high, which directly influences the yield.  The still with 2 FPC and 3 FPCs connected in series have distillation efficiencies of 6% and 3% respectively. The still with single FPC obtains a distillate efficiency of 17% and consequently the witness solar stills with produces the optimum (20%).  The still with single FPC obtains a maximum yield of 6.669 kg whereas the yield is 2.87 kg for the still with 2 FPCs in series and 1.75 kg for 3 FPCs respectively.  For the still with 2 and 3 FPCs in series has an average daily yield is 380% and 73% less Respectively when compared to still with single FPC. For the still with 2 and 3 FPCs in series respectively,  when compared to that with single FPC the distillate efficiencies are 183% less and 466% less  To witness an increase in productivity it is not necessary to increase the number of collectors and to obtain the highest productivity there are several factors that must be studied. The study will be useful for designing efficient active solar distillation systems for the winter climatic conditions with 31.95°N, 5.4°E. Acknowledgment For providing the experimental facilities, we are very thankful to Dr. TEKHA Mohammed member in the LENREZA's Lab teacher in the department of Materials Science, Kasdi Merbah Ouargla University. Algeria. Ridha Cherraye et al IJECA-ISSN: 2543-3717. June 2020 Page 41 References [1] Mehdi Jahangiri, Somayeh Pahlavan, Akbar Alidadi Shamsabadi, Abderrahmane Khechekhouche, "Feasibility tStudy of Solar Water Heaters in Algeria", a Review, Journal of Solar Energy Research, 2018. Page 135-146. [2] A. 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