Enhanced solar still productivity using transparent walls with an integral trough and organic porous absorber material

This experimental work has been conducted to compare the performance of the modified stills with that of the conventional still. Three modified stills (S1, S2, and S3) and conventional still (S4) were fabricated, each with 0.5 m² of the basin area. S1 and S3 had transparent double glass walls with air in between acting as insulation, whereas S2 has a single transparent wall. S4 has insulated plywood walls painted black from inside. A mixture of coco peat and charcoal was used in S1, S2, and S3, whereas there was no basin material for S4. Experiments were conducted by changing the water quantity in the solar still ranging from 5 to 10 kg. Maximum distillate output of 5.46 l/m²-d was obtained for S2, whereas it was 3.80 l/m²-d for S4 for an average solar radiation intensity of 675 W/m² (24.3 MJ/m²-d). Use of transparent walls with troughs to collect condensate increased the condenser area by 78.4%. The distillate water cost per liter was estimated as Rs. 0.86 (0.013 US$) and Rs. 1.61 (0.025 US$) for S2 and S4, respectively. Energy payback time for S2 was estimated as 4 months. Theoretical and experimental values showed that there is a significant loss of incoming solar radiation due to wall shadow.     

An investigation of double-glass-covered trapezoidal salt-gradient solar pond coupled with reflector

In the present study, a trapezoidal salt-gradient solar pond (TSGSP) has been investigated experimentally. The top surface of solar pond has been covered with double-glass cover in order to reduce the evaporative and convective losses from the top. This results in increase of temperature even in the top zone of the solar pond and leads to more volume utilization for heat storage in the pond. A reflector made of aluminium sheet has been used to enhance the solar intensity on the solar pond during sunny hours. A procedure, to determine optimum tilt angle of reflector in order to utilize maximum amount of solar energy at noon, has been proposed. The use of reflector enhanced the average solar intensity on the top surface of solar pond by 22%. The maximum average temperature of trapezoidal solar pond with glass cover and reflector has been observed to be 70.5°C. The thermal efficiencies of LCZ, NCZ and UCZ for the trapezoidal solar pond with double-glass cover and reflector have been estimated to be 32.73%, 23.22% and 5.30%, respectively. In addition to experimental investigation, the sunny area ratio of TSGSP has been theoretically computed and compared with the cuboid solar pond having same top surface area and depth in order to see the effect of pond shape on sunny area ratio. The average yearly sunny area ratio of trapezoidal solar pond has been determined to be 11% higher than that of cuboid one.     

Experimental investigation of a solar water distillation-cum-drying unit

In this communication, a new design of solar-energy-based water distillation cum drying unit with parabolic reflector has been designed, fabricated, and tested. Bitter gourd and potato slices are chosen as a drying commodity. Thermal performance of the developed system has been evaluated based on the experimental results and using linear regression analysis. Heat transfer coefficients (convective, evaporative, and radiative) for solar distillation system have been observed to be 2.48–4.09, 13.25–52.38, and 8.75–9.66 W/m²°C, respectively. Overall thermal efficiency and exergy efficiency for the distillation system has been found to be 18.77% and 1.2%, respectively. The convective heat transfer coefficient for potato slices are observed higher for initial hours and decreases as the day progresses. The average convective heat transfer coefficients for bitter gourd and potato slices have been observed as 2.18 and 5.04 W/m²°C, respectively. Experimental error in terms of percent uncertainty for bitter gourd and potato slices are found to be 42.93% and 37.06%, respectively. The present design of solar distillation and drying in a single unit could be beneficial for the development of remote, arid, and rural areas.     

Experimental and numerical analysis of a helical coil solar cavity receiver: Thermal oil as the heat transfer fluid

The paper presents the novel design of double glazing helical coil solar cavity receiver for solar thermal applications. Performance model has been developed for the experimental setup based on energy balance equations. The results obtained were compared with horizontal tube receiver for the same experimental setup. The result shows that the 87.96% improvement in the convective heat transfer coefficient for the double glazing helical coil solar cavity receiver. Maximum conversion efficiency achieved is 21% more than that would be obtained for horizontal tube receiver. This paper also investigates how the quality of vacuum degraded with the temperature of the glass cover.     

Performance investigation of a new solar desalination unit based on sequential flat plate and parabolic dish collector

A new system composed of a sequential flat plate and parabolic dish solar collector was applied to enhance the solar desalination productivity. Heated saline water was desalinated using the evaporation/condensation principle and an effort was made to achieve higher distillate production compared to previous studies. Desalination efficiency values were calculated between 23% and 57%. Maximum desalinated water productions were obtained as 1,038 mL/m².h in autumn and 1,402 mL/m².h in summer. The cost of solar desalination system was found as economically feasible with 3 years’ payback period and the produced water cost of 0.014 $/L. Physicochemical analyses revealed that as a result of the desalination process, salinity level decreased from 35.6‰ to 0.0–0.1‰, chloride concentration decreased from 21,407 mg/L to 10 mg/L, and electrical conductivity decreased from 53.1 mS/cm to 0.11 mS/cm.     

Experimental investigation of groundwater contamination by surface sources: Determination of adsorption capacity,diffusion, and sorption potential of selected anions in different soils

The present study investigated the fate and transport of two significant anions through soil to explore their potential as groundwater contaminants. The retention properties of chloride and sulfate in soils having several significantly different characteristics (soil‐1 and soil‐2) were determined using adsorption test and adsorption‐diffusion column experiments. The maximum adsorption capacity of chloride was 3.7 and 1.16 mg/g, respectively, in soil‐1 and soil‐2, with organic matter (OM) content of 3.92% and 4.69%, respectively. The sulfate adsorption obtained was 24.09% and 13.83%, respectively, in the two soils. The anions exhibited monolayer adsorption in the soils with replacement of hydroxyl ions from soils as the major mechanism of adsorption. On the other hand, the adsorption capacities obtained from the adsorption‐diffusion column experiment were about 100 times lower compared to that of the column tests of both of the soils. The maximum adsorption capacity of chloride was 0.03 mg/g and 0.01 mg/g, respectively, in soil‐1 and soil‐2, whereas that of sulfate was 0.04 mg/g and 0.03 mg/g. The empirical relation for depth of penetration (d) from a known spillage onto the soil surface was determined as a function of sorption capacity (S) and initial anion concentration (C) as d = 0.0073e^(?57S)C and d = 0.0038e^(?35S)C for chloride and sulfate, respectively.     

Experimental investigation on effect of an absorber plate covered by a layer of sand on the efficiency of passive solar air collector

A passive flat-plate solar air collector was constructed in the laboratory of New and Renewable Energy in Arid Zones, Ouargla University, South East Algeria. The absorber of the passive flat-plate solar air collector was laminated with a thin layer of local sand. This acted as a thermal packed bed with a collecting area of 0.5 m² (1 m × 0.5 m). Three series of experiments were performed. The first consisted of choosing the best sand brought from three different places of the Algerian desert. The second consisted of studying the effect of the thickness of the sand layer on the daily efficacy of the collector. The influence of the sand diameter was investigated in the third series. The experimental results showed that: All collectors covered with sand had higher efficiency than those without. It was noticed that, for a fixed mass of sand (given thickness of the sand layer), the improvement of the collector was inversely proportional to the sand particle diameters. The maximum efficiency approximates 62.1% for a particle diameter 0.063 mm, compared to 41.71% for a diameter 0.250 mm.The efficiency of the collector for a fixed particle diameter increases with the increase in the thickness of the sand layer. The collector with thickness sand layer 0.84 mm gave the best efficiency of 46.14% compared to 27.8% for 0.28 mm of thickness sand layer.     

Experimental investigation of performance and emission characteristics of diesel engine using Jatropha biodiesel with alumina nanoparticles

Biodiesels have come up as a very strong alternative for diesel fuel. Biodiesels such as Jatropha Oil Methyl Ester (JOME) are comparable in performance with that of the diesel engine. The thermal efficiency of engines fuelled with biodiesels was found lower than conventional diesel fuel but due to the bio-origin, the emission characteristics are much better. However, biodiesel increases the NOx emissions as these are rich in oxygen, hence nanoparticles are used in this experiment to curb the high temperatures and reduce the NOx formation. The experiment on naturally aspired diesel engine was conducted with four prepared test fuels other than neat diesel and neat biodiesel. The 50 and 150 of alumina nanoparticles were added separately to the pure diesel and pure Jatropha biodiesel to form the nano emulsions using ultrasonicator. The properties of nanoemulsion were evaluated using dynamic light scattering technique using zetasizer. The performance and emission characteristics of multi-cylinder diesel engine with these nanoemulsions were compared with that of neat fuels. The results showed that using nanoparticles with diesel and biodiesel can contribute in a more efficient, economical, and eco-friendly engine operation.     

印染废水物化试验研究

通过对多种化学药剂处理印染废水原水和只经过生化的印染废水出水的试验研究,找出了药剂在各自最佳的反应条件下的处理成本和处理效果。结果表明,处理吨水成本最低而又处理效果较好的药剂为A料和石灰的组合,它对印染废水的原水色度、CODCr的处理效果可达85％、46％,对生化出水色度、CODCr的处理效果可达80．3％、47％。     

Experimental investigation on engine performances,combustion characteristics and emission of exhaust gases of VCR engine fuelled with cottonseed oil methyl ester blended with diesel

This research work investigates the engine performances, combustion characteristics, and emission of exhaust gases of variable compression ratio engine fuelled with cottonseed oil methyl ester (COME) and diesel at different blends. The analysis showed that heat release rate and cylinder pressure is higher for diesel than COME blends. Higher BTE is obtained at the maximum load condition. The higher BTE and lower SFC are obtained for blend B15 as 42.17% and 0.2 kg/kW-hr at brake mean effective pressure (BMEP) of 4.64 bar. Also it is found that the peak cylinder gas pressure and combustion duration increases when the BMEP increases. At the BMEP of 3.51 bar, higher HRR is observed as 18.12 J/deg. Increase in HRR is obtained as 6.07% for B30 at BMEP of 4.64 bar when compared to diesel. Ignition delay decreased by 13.16% for B100, by the increment of blend proportions when compared to diesel, at BMEP of 4.64 bar. Lower smoke, HC and CO emissions are observed when increasing the blend proportions, whereas the nitric oxide emissions increases due to the better combustion resulted in higher temperatures. At BMEP of 4.64 bar, the CO emissions are reduced to 25.24% for neat biodiesel when compared with the diesel.     

Investigation of modified horizontal wing cut twisted tapes fitted with rod and spacer at trailing edge on heat transfer properties in Double Glazing V-Trough solar water heaters

An experimental analysis of heat transfer efficiency in double glazing solar water heating system having full-length Horizontal wing cut twisted tapes having twist ratio 3 fitted with rod or spacer of dimensions 125 mm, 250 mm, and 500 mm as length at the trailing edges has been dealt in this work. The experimental results have been compared with a plain tube with similar operating conditions and concluded that variation in the Nusselt number, as well as friction factor, are ±12.56% and ±10.17%, respectively. The result of empirical correlation concludes that Nusselt number is maximal for horizontal wing cut twisted tapes having rod or spacer at its ends while comparing with full-length horizontal wing cut twisted tapes. The friction factor is low for full-length horizontal wing cut twisted tapes than the horizontal wing cut twisted tapes fitted with rod or spacer. The horizontal wing cut twisted tapes fitted with rod has superior performance than twist fitted with spacer.