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DESIGN AND CONSTRUCTION OF A PYRAMID-SHAPED SOLAR
There is almost no water left on earth that is safe to drink without purification after 20-25 years from today. This is a seemingly bold statement, but it is unfortunately true. 1% of Earth’s water is in a fresh, liquid state, and nearly all of this is polluted by both diseases and toxic chemicals. For this reason, purification of water supplies is extremely important. Keeping these things in mind, we have devised a model which will convert the dirty/saline water into pure/potable water using the renewable source of energy (i.e, solar energy). The basic modes of the heat transfer involved are radiation, convection, and conduction. The results are obtained by evaporation by evaporation of the dirty/saline water and fetching it out as pure/drinkable water. The designed model produces 2.5 litres of pure water from 20 litres of dirty water during twelve hours. The efficiency of both plant is 64.37%.
TABLE OF CONTENTS
TABLE OF CONTENT…….…….…………………………..…..…..IV
LIST OF FIGURES ………………………………………………….VI
1.1 INTRODUCTION 2
1.2 STATEMENT OF PROBLEM 3
1.3 AIM AND OBJECTIVE 4
1.4 SIGNIFICANCE OF THE STUDY 4
LITERATURE REVIEW 4
2.1 INTRODUCTION 4
2.2 REVIEW OF PREVIOUS WORK ON SOLAR DISTILLER 5
2.3 RELATED THEORY 7
3.1 MATERIALS USED 9
3.2 METHOD 10
4.1 RESULTS AND DISCUSSION 14
5.1 CONCLUSION AND RECOMMENDATIONS 23
5.2 REFERENCE 24
LIST OF FIGURES
Figure 2.1: Experimental Set up of Solar Still 5
Figure 2.2 diagrammatic sketch and general dimensions of Pyramid solar still. 6
Figure.2.3 Single Slope Still 6
Figure 3.1: pyramidal and triangular solar shaped still 10
Figure 3.2: A typical thermoelectric Pyranometer 12
Figure 3.3: An Anemometer 12
Figure 3.4: thermocouple thermometer 13
Figure 3.5: graduated cylinder 13
Figure 4.1: temperature of glass and water for both stills 18
Figure 4.2: Triangular solar still (water and glass temperature) 19
Figure 4.3: Pyramidal solar still (water and glass temperature) 20
Figure 4.4: cumulative and specific yield for both still 21
Distilled water is needed for drinking, irrigation and for many other applications. A diversity of approaches are used for these portions of fresh water from saline water; namely multi stage flash (MSF), multiple effect (ME), reverse osmosis (RO), electro dialysis, ion exchange, phase change, and solvent extraction. These methods are expensive, however, for the production of small amount of fresh water. The development of solar distillation has demonstrated its suitability for the desalination process when the weather conditions are suitable and the demand is not too large, i.e. less than 200 m³/d. The problem of low daily productivity of the solar stills triggered scientists to investigate various means of improving the stills productivity and thermal efficiency.
Different aspects of triangular-shaped solar stills (CSS), also called double slope stills, have been studied. Production in this still is influenced by the orientation, as shown by (Singh et al., 1995) who found the maximum yield for a cover with east–west. Detailed studies of heat transfer coefficients can also be found, (Sharma and Mullick, 1991), in which energy transfer mechanisms, such as convection, evaporation and radiation are investigated, and new empirical relations to estimate cover temperatures are proposed. To model heat and mass transfer in solar stills ( Dunkle, 1961) proposed the use of a correlation of the form where C is 0.075 and n is 1/3 for air enclosed between horizontal parallel plates. This correlation is expressed in terms of a modified temperature difference that includes molecular weight and buoyancy, and considers the cover as a single element. This has been the most widely accepted model for solar stills and describes the basic heat and mass transport mechanism between heated water mass and a condenser.
1.2 PROBLEM DESCRIPTION AND SIGNIFICANCE
Many parts of the world do not have access to a suitable source of clean drinking water. Most of the water available in streams, lakes, rivers, sea, etc. carries parasites or diseases, or is simply not fit for consumption and therefore is a significant health hazard. Areas without access to clean water are also usually poverty stricken and do not have the infrastructure necessary to create and support large scale water purification plants. Thus, there is need for a small scale, affordable water purification system for individual families or villages. Africa has the second largest population of people without access to clean drinking water.
1.2AIM AND OBJECTIVES
a. The aim of this project is to construct pyramid-shaped solar.
b. To compare and evaluate the triangular and pyramid-shaped solar stills.
1.3 SIGNIFICANCE OF THE STUDY
The energy from the sun used to distil water is free cost, but building the still makes the cost of the distilled rather high, water at least for large-scale uses and such as agriculture and flushing away wastes in industry and homes. Consequently, the solar still is used principally to purify water for drinking and for some business, industries, laboratories, and green house applications; it also appears to be able to purify polluted water.
This chapter contains the review of earlier work on various constructions of solar stills using saline water.
2.2 LITERATURE REVIEW ON SOLAR WATER DISTILLER
Algaim et al. (2013) reported on a pyramidal solar still (PSS) and a single basin solar still (SBSS), a transparent glass with a thickness (4 mm) were built which have the same dimensions of absorber plate that contains the Saline water, and the constructions were made under different atmospheric circumstances of Basra city (Iraq). An experimental investigation was carried out on two solar stills under the same conditions. The still has consists from the basin total area of 0.25 m2.We found in this experimental study that the efficiency of the single basin solar still (SBSS) is (55%) and increases to(66.5 %) of the pyramidal solar still (PSS).
Shah et al (2011) reported on an attempt has been made to unearth the effect of different thicknesses glass cover on passive single-slope single basin solar still in winter climatic conditions of Mehsana (23°12’ N, 72°30’) from September, 2010 to Feb. 2011. Experiment used three identical size solar stills having three different thicknesses of glass cover of 4 mm, 8 mm and 12 mm. Here, Dunkle model is used for comparison of various heat transfer coefficients of solar stills. The objective of the present paper is to evaluate the behavioural variation in various parameters on solar still. Six month study shows that, lower glass cover thickness increases the distillate water output, water temperature, evaporative heat transfer coefficient, convective heat transfer coefficient as well as efficiency of solar still. Hence, 4 mm glass cover thickness is most prominent thickness of present experiment.
Figure:2.1 Experimental Set up of Solar Still
Fath et al (2003). Reported on an analytical study as well as thermal and economical comparison between two solar stills configurations; the Pyramidal and single slope. A mathematical model has been developed to simulate the two configurations and study their thermal performance. The weather meteorological data of Aswan City (south of Egypt) was used, and the daily total energy received by each still basin was calculated. The main performance parameters such as still productivity and efficiency have been presented for the whole year. In addition, the economical assessment of the distilled water production cost has been carried out. On the basis of the yearly performance results, the single slope still was found to be slightly more efficient and Economical than the pyramidal one.
Figure.2.2, Diagrammatic sketch and general dimensions of Pyramid solar still.
Figure.2.3, Single Slope Solar Still
2.3 THEORETICAL ANALYSIS
Various designs of solar stills have been proposed in an attempt to improve the performance of solar stills. Hence the need for the characterization of various designs of solar stills is felt greatly to compare the relative performance of different solar stills. There are quite a few expressions given by various authors for internal convective heat transfer coefficient all based on Dunkle's relations who analyzed the enclosure as a parallel cavity. The theoretical analysis is composed from three sections. The first section is the effect of the modified basin packed layer on the heat transfer parameters without vibratory effect. The second section is the system dynamic modelling, and the third section is the effect of both helical wired packing layer and vibratory effect on the overall heat transfer coefficient.
The total horizontal insolation is given by: -
Where represents the diffused radiation on a horizontal surface and he total insulation on inclined surface from horizon by angle b is given by:
Where is the angle of incidence calculated as:
STILL HEAT BALANCE
GLASS COVER HEAT BALANCE
3.1 METHOD AND MATERIALS
The solar stills used are shown in Figures 3.1 and 3.2 below They were developed at the National Centre for energy research and development, Usmanu Danfodiyo University sokoto. Figure 3.1 is a pyramid shaped solar still while Figure 3.2 is a triangular shaped type with its top inclined at an angle of 30° to the horizontal. The pyramid shaped solar still is designed so that water settling on the inside surface of the transparent top cover easily drips down and solar radiation can be received round the top. The stills are made of the same materials for efficient comparison. Their top is covered with glass material while the sides and the base are made of alminium still reinforce with still 0.005 m thick. The effective total absorber area is 0.6 m2.triangular steel basins of area 0.5 m2 and height 0.06 m2 as shown in Figures3.1 and 3.2 respectively. The basins serve as the container for the unclean water.
During the study, twenty litres of unclean water was poured into each of the trays for distillation. The water evaporates only to condense on the underside of the transparent cover, leaving other constituents of the unclean water behind. The gentle slope of the glass directs the condensate to a collection trough from where the water runs out to a storage vessel. Periodically, the temperatures of the unclean water, the base of solar still, transparent glass and the ambient were measured using I-Bk thermocouples. At sunset of each day the volume of water distilled in the container is measured.
Figure 3.1, pyramidal and triangular solar shaped still
The dimension of the still is taken below as follows
Pyramidal and triangular still
a. Height of the still = 0.24384m
b. Length of the still = 1.524m
c. Base of the still = 0.762m
3.2.2 MATERIALS USED IN MEASUREMENT
Below are the materials used in measurement during the course reading
iii. thermocouple thermometer
iv. graduated cylinder (or measuring cylinder)
Figure 3.2 below is a Pyranometer which measures the hemispherical solar irradiance, or broadband solar radiation within a 180-degree field of view; this may be considered the global solar radiation of a given hemisphere.
iii. THERMOCOUPLE TERMOMETER
Figure 3.4 below show a thermocouple thermometer is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots
Figure 3.2, A typical thermoelectric Pyranometer.
Figure 3.3, An Anemometer
Figure 3.4, thermocouple thermometer
iv. GRADUATED CYLINDER (OR MEASURING CYLINDER)
Figure 3.6 below shows a graduated cylinder (or measuring cylinder) is a piece of laboratory glassware used to measure the Volume of liquids.
Figure 3.5,graduated cylinder