The air-lift pump is a well-established method for vertical transport of liquids and solid-liquid mixtures. The objectives of the present study are to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters for the use of the pump for two-phase mixtures of air and water when a compressor is readily available. This paper is focused on the general mathematical functions applicable to air-lift pump installations. The effect of various design parameters on the performance of air-lift pump is presented. A user-friendly computer program is developed on the basis of the optimization of influencing variables. This program will be useful for the design and installation of an air-lift pump handling air-water mixtures. A comparative study of an air-lift pump with a centrifugal pump handling two-phase mixtures is also discussed in the paper.

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In this work, we have selected three number of stepped type solar stills of the same overall dimensions 620 mm (W) × 808 mm (L) but with different absorber surface areas due to the variation in the shape of the basin surface. The other design parameters like depth of water, thickness of glass cover, insulation thickness, type of condensing cover, absorbing material provided over the basin, and angle of inclination of the still were kept constant to study the effect of shape of the absorber surface over the distillate yield obtained. The shape of the absorber surface provided in the basins of solar stills A, E and F was flat, convex and concave respectively. When the convex and concave type stepped solar stills are used, the average daily water production has been found to be 56.60% and 29.24% higher than that of flat type stepped solar still respectively. Also an economic analysis was made. The payback period of flat type, convex type and concave type stepped solar still is 823 days, 525 days and 637 days respectively. Thus, the convex type solar still gives the returns within the least possible time as compared to other two types of stepped solar stills. The laboratory tests were conducted to test the quality of water after distillation. The tests indicate that the quality of water in terms of pH, electrical conductivity, total hardness, TDS, Alkalinity, Nitrates etc. is well within the desirable limits as prescribed by WHO for Indian specific conditions.

S. B. Thakre et al. AB STRACT:Oxidation ditch process is used to treat the municipal and domestic sewage. The untreated sewage generates fouling smell, harmful bacteria, etc. which is hazardous for public health and degrades the environment by librating noxious gases. This paper examines the use of curved blade aerator for oxidation ditch process. The rotor, which controls the aeration, is the main component of the aeration process. Therefore, the objective of this study is to find out the variations in overall oxygen transfer coefficient and aeration efficiency for different configurations of aerators by varying the parameters like speed of aerator, depth of immersion and blade tip angles so as to yield higher values of overall oxygen transfer coefficient and aeration efficiency. Four aerators of different configuration were developed and fabricated in the laboratory and were tested for above mentioned parameters. A mathematical model is developed for predicting the values of k L a and aeration efficiency which has R 2 values of 0.97 and 0.99 for experimentally determined and calculated values. In laboratory studies, the optimum value of overall oxygen transfer coefficient and aeration efficiency were observed to be 10.33/h and 2.269 kg O 2 /kWh for aerator speed of 48 rpm, 5.5 cm depth of immersion and 47 o blade tip angle for curved blade aerator.

The main objective of this work is to design a high efficiency curved-blade-surface mechanical aerator for oxidation ditch, which is used to treat municipal and domestic sewage. Aeration experiments were conducted in oxidation ditch made up of mild steel sheets to study the design characteristics of curved blade surface mechanical aerator. The paper critically examines six different configurations of aerators, which were developed, fabricated and tested in the laboratory for its various dynamic parameters, such as diameter of aerators (D), speed (N) and immersion depth (h). Out of the different configurations tested, the curved blade rotor (CBR) emerged as a potential aerator with blade tip angle of 47°. The overall oxygen transfer co-efficient (K L a) was observed to be as high as 10.33 h -1 and the optimum aerator efficiency (AE) was found to be 2.269 kgO 2 /kWh. The standard aeration efficiency (SAE) of CBR was observed to be higher as compared to other aerators used for oxidation ditch process. Dimensional analysis was used to develop equations that describe the aerator's behavior. Further, a CFD model is also developed for better understanding of the process that takes place inside the ditch. To prepare it 3D and steady flow, k-e turbulence model of flow was used and the simulation runs were carried out for one phase model to generate the data so as to compare it with experimentally observed values.

Airlift pumps are finding increasing use where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids must be handled and when a compressor is readily available. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters The effects of design parameters viz. mass flow rate of air, immersion ratio, diameter of rising main etc. on the performance of airlift pump are presented. The larger diameter of rising main is found to be suitable for high flow rate of water. The injecting device used in the system has considerable effect on the performance of the pump. The paper is focused on the general mathematical expression to determine the effective diameter of nozzle applicable to air lift pump installations in the diameter range of 25.4 mm ≤ d ≤101.6 mm.The various types of flows are visualized in the rising main of a pump and the corresponding airlift pump performance is analyzed. It is observed that the slug flow is more predominant for improving the performance of the pump.

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