1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
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Item Solar Energy Based Desalination System Using Humidification- Dehumidification Process(National Institute of Technology Karnataka, Surathkal, 2022) ., KumaraSolar desalination is one of the most promising techniques used in the production of fresh water for many decades. The technique has evolved with a number of innovations in recent years with which it can compete with water technology market as well. A combination of solar desalination and paddy grass humidifier represents a distinguished technique in solar desalination process. The current research work is aimed at addressing water scarcity problems faced across the globe. This thesis attempts to incorporate Humidification-Dehumidification Desalination Technique (HDHT) using artificial and bio-based packing materials. A detailed thermodynamic analysis was conducted for Paddy Grass Humidification Dehumidification Desalination System (PHDD) in current study through mathematical and experimental methods. In order to produce the maximum amount of fresh water, two configurations were developed and analyzed under weather conditions prevalently observed in the southern states of India. First, the experiments were carried out with artificial packing material (Polypropylene) with and without baffle plates. Next, bio-based packing material (Paddy grass) was used in the second set of configuration with and without baffle plates. The study found that 0.39, 0.46, and 0.73 kg/h of fresh water was produced respectively for without, artificial and bio-based packing materials. The rate of fresh water production got increased to 17% and 46% respectively for artificial and bio-based materials. There was an increase observed in Gain Output Ratio (GOR) as well, in the range of 0.28, 0.40, and 0.65 for without, artificial, and bio-based packing materials. GOR got increased up to 30% and 56% when using artificial and bio-based packing materials respectively. When the inlet temperature of cooling water, to the dehumidifier, was reduced from 40ºC to 20 ºC, it increased the production of distilled water significantly. The performance of PHDD system was evaluated through various physical parameters such as solar collector area, reservoir water tank volume and the temperature of water reservoir. The author conducted cost benefit analysis of the system against other desalination methods. In this analysis, the amount of potable water produced, the amount of energy consumed and iv the cost incurred upon components were compared. The results revealed that irrespective of paddy grass area, the volume of the storage water tank, below and above 40 L, is not considered to be optimal. The cost analysis conducted for the present work proved that the system can function at low maintenance cost in comparison with other similar studies and the price of the yield is approximately 19$/m3. The solar collector area exerts a significant influence upon the augmentation of water yield. The optimal ratio of water reservoir to collector area was 13 L/m3. The present study infers from the experimentation procedure that the bio-based paddy grass packing material is highly advantageous for small-scale fresh water production in remote regions.Item Solidification Analyses and Heat Treatment of Modified And Refined Al-Si Alloys -A Study(2016) V, Vijeesh; Narayan Prabhu, K.The present work involved the study of the effect of addition of cerium (Ce), phosphorus (P) and strontium (Sr) on cooling curve parameters, heat transfer characteristics, microstructure and mechanical properties of Al-8Si, Al-13Si, Al-14Si and Al-22%Si alloys. Melt treated alloys were solidified against sand base and against stainless steel, brass, and copper chills to assess the effect of cooling rate on silicon morphology. Thermal analysis parameters of melt treated alloys were determined by recording the temperature of the liquid metal solidifying against the chill. The addition of Ce significantly influenced both primary and eutectic phase nucleation temperatures and increased the undercooling temperatures. Newtonian and Fourier analysis techniques were used for the calculation of solid fraction and latent heat of solidification. The heat flux across the casting/chill interface was estimated using inverse modeling technique. The interfacial heat flux between the chill and the alloy increased with Ce and Sr melt treatment and decreased on addition of P. The effect of melt treatment and chilling on microstructure was assessed by measuring (i) the grain size (ii) roundness of eutectic silicon (iii) fineness of primary silicon. Ce treated alloys solidified against sand base at a slow cooling rate resulted in refinement of eutectic silicon along with the formation of AlSi-Ce ternary intermetallic compound. The addition of Ce to alloys solidified against chills resulted in complete modification of the eutectic silicon. The addition of Ce also resulted in fine equiaxed grains in Al-8Si alloys and refined the primary silicon in hypereutectic Al-Si alloys. The addition of Ce simultaneously modified and refined both primary and eutectic phases, whereas, Sr and P modified eutectic silicon and refined primary silicon respectively. On addition of Ce, P and Sr there was a significant improvement in the mechanical properties of the alloys. The combined addition of Ce with Sr to Al-Si alloys resulted in further improvement of mechanical properties. Al-8Si, Al-14Si and Al-22Si alloys were subjected to T6 heat treatment. The ageing temperature and time were selected based on a series of trial experiments. The tensile strength of all untreated alloys increased when subjected to heat treatment, whereas, the heat treatment had deleterious effect on the mechanical properties of melt treated alloys except on P treated alloys.