TAGUCHI Method for Optimizing The VORTEX FLOW in Non Chemical Water Treatment Processes In Cooling Towers

Transcription

1 TAGUCHI Method for Optimizing The VORTEX FLOW in Non Chemical Water Treatment Processes In Cooling Towers K. Naveena Latha*, Dr. P. Ram Reddy**,Dr. D.V. Ravi Shankar***, *Faculty in Mechanical Department, TKR ENGG COLLEGE **Professor In Mechanical Engineering, FORMER REGISTRAR- JNTU HYDERABAD *** Professor In Mechanical Engineering, Principal Of TKRCET Keywords: Taguchi Method, Raw Water (RW), Treated Water (TW), Settling Time (ST), Optimization, Vortex Flow, Differential Air Pressure, Flow Rate, Non-Chemical water treatment, Air Compressor, tangential flow in the nozzle, different flow rates, Acrylic tube length, Nozzle diameter, Total Dissolved Solids (TDS), Hardness of water (CaCo3). Abstract The proposed research work is focused on optimising the experimental analysis by multiple array using the TAGUCHI Method for experimenting and concluding ways and means to enhance the cooling tower life by natural mechanical methods. Water is the prime utility need for any industry and it is important to conserve and judiciously use in the industrial processes. While major industries use ground water as the major source, it is necessary that the water is treated properly for it reusability. The treatment of industrial water is needed to avoid sizeable problems like Scaling and choking of fins due to continuous evaporation leading to increase in the dissolved salts concentration.this attracts frequent replacement of the filling material which is an expensive task. The cost of such replacement estimates at around 30% of the total cost of Cooling tower which is considerably high. The Vortex Flow mechanism combined with Hydro Dynamic Cavitation is successful in treatment of water by natural means with out using any Chemicals. The Process involves the flow of water through a closed conduit named CAVITAION CHAMBER wherein the water is subject to the Hydro Dynamic Cavitation through Vortex Mechanism. This process converts the dissolved calcium and magnesium into calcium carbonate (CaCO3) & magnesium carbonate (CACO3) which is further removed through a separate Filtration Process. The TAGUCHI method is helpful in optimizing the parameters experimented in the process of designing this Cavitation Chamber 1

2 1.0 Introduction The Taguchi Way of Optimizing Overview of Taguchi Method A Historic Perspective to Modern Industrial Implementation The Post Second World War Scenario observed a lack of proper communication System in the Japanese Technology. A rather sustainable system was in need and the Japanese have set up a n extensive research Facilities for implementing the same namely Electrical Communication Laboratories ( ECL ) under the leaderhip of Dr.Genichi Taguchi.(1) It was observed that a great deal of time and money was expended in engineering experimentation and testing while little emphasis was given to the process of creative brain storming to minimize the expenditure of resources. Dr.Taguchi exposed an excellent philosophy for quality control in manufacturing processes. Three core concepts of quality have been suggested by Dr.Taguchi which have been set as bench mark universally. 1. The Quality should be designed into the product and not inspected into it. 2. Quality is best achieved by minimising the deviation from a target. The product should be so designed that it is immune to uncontrollable environmental effects.. 3. The Cost of Quality should be measured as a function of deviation from the standard and the losses should be measured system wise. [1]. To achieve the desirable product quality by design, Dr.Taguchi recommended a three stage process. 1. System Design 2. Parameter Design 3. Tolerance Design 1.The Vortex Flow CAVITATION CHAMBER - System Design The Vortex flow Cavitation chamber is so designed to create an immense cavitation effect for the water flowing through it. The design basically comprises of a chamber and two oppositely facing convergent nozzles to create the cavitation effect along with the vortex flow. The operating phenomenon is discussed below. 1. Water from the sump is pumped under pressure into the cavitation chamber, where it is forced to rotate at high velocity through nozzles. 2. The opposing water streams collide in the cavitation zone, causing millions of high energy, micro-sized cavitations bubbles to rapidly form and collapse. This stresses the bacteria and forces calcium carbonate to form a precipitate in the water[3]. 3. The treated water exiting the cavitation chamber is returned to sump where the precipitated calcium carbonate is removed by the filtration system[4]. 1.1.Convergent Nozzle Design Parameters 2

3 Table:1:Nozzle dimensions Cover plate Diameter Nozzle inlet diameter Length of nozzle Nozzle exit diameters Width of the cover plate Water entry from Tangential hole of nozzle diameter Air entry from cover plate nozzle 75 mm 30 mm 75 mm 16,14,12and 10 mm 20 mm 8 mm 3 mm 1.2 Design parameters of filtering tank & acrylic tube: Table: 2: Tank & acrylic tube dimensions Length Width Height Acrylic tube length 130 cm 130 cm 130 cm 200,300,400mm Fig: 3 Line Diagram of the Complete Assembly of Cavitation Chamber. 3

4 Fig: 4: layout of tangential flow Nozzle Fig. 5 Isometric Views of Convergent Nozzles Fig 6. Isometric View of Cavitation Chamber 4

5 2.Assembly Of Cavitation Chamber With Filtration Tank: The Cavitation Chamber consists of two convergent nozzles and these set up is immersed in a tank so that the water can be re-circulated in the tank. 1HP motor is connected to circulate water from tank to nozzles, and all pipe fittings are made properly, A flow meter is connected to the nozzles and fitted properly to the tank. An air compressor at a capacity of 8bar is attached to the nozzles, and the flow can be regulated through a value. 3.Experiments Ground water sample is collected, and water analysis has done as per IS: 10500:2012.so, the results obtained are SI.NO. Table: 3: Ground water sample results Characteristic Test method Results Acceptable Limit 1 Total Dissolved Solids, mg/l IS:3025(pt-16) 946 < Total Hardness as CaCo3,mg/l IS:3025(pt-21) 528 < Calcium as Ca,mg/l IS:3025(pt-40) < 75 4 Magnesium as Mg,mg/l IS:3025(pt-46) 53.8 < 30 5 ph value IS:3025(pt-11) Experiment of Water at Pressure 1, 3, & 5bar (sample water collected after 30 min) The TDS values of RW & TW at differential Air Pressure 1,3 & 5 Bar with Cavitation Chamber Lengths of 200,300,400 mm and convergent nozzle of 12 mm exit diameter. Table No. 5. Result Readings S.no Pressure ( bar) Nozzle Dia (mm) Settling time (min) Cavitation Chamber length (mm) RW TW RW TW RW TW 1) ) ) )

6 3.1.2.The TDS values of RW & TW at differential Air Pressure 1,3, & 5 bar with Cavitation Chamber Lengths of 200,300,400 mm and convergent nozzle of 14 mm exit diameter. Table No. 6. Result Readings S.no Pressure ( bar) Nozzle Dia (mm) Settling time (min) Cavitation Chamber length (mm) RW TW RW TW RW TW 1) ) ) ) The TDS values of RW & TW at differential Air Pressure 1,3, &5 bar with Cavitation Chamber Lengths of 200,300,400 mm and convergent nozzle of 16 mm exit diameter. Table No. 7. Result Readings S.no Pressure ( bar) Nozzle Dia (mm) Settling time (min) Cavitation Chamber length (mm) RW TW RW TW RW TW 1) ) ) ) The results tabulated in all the 3 experiments conducted have shown a wide variation which further are supposed to be optimised. The best way available to optimise the parameters was the Taguchi Way. 6

7 4.0 The TAGUCHI OPTIMIZATION METHOD The Taguchi Optimising Strategy takes into consideration a special set of Orthogonal Arrays to layout the experiment. This ARRAY designated by Symbol L9 is used to design experiments involving up to Four 3 Level Factors. The ARRAY has 9 Rows and 4 Columns. Each row represents a trial condition with factor levels indicated by the number in the row. The Vertical Columns correspond to the factors specified in the study. The Variables considered here are the Length of Cavitation Chamber, Nozzle Exit Diameter and the Differential Air Pressures. The array takes into consideration the results arrived from the experiments made with variable Convergent Nozzle Exit Diameters and Cavitation Chamber lengths for fixed air pressure of 1, 3, & 5 bar. T able 8. Orthogonal Array L9 ( 3 4 ) FACTORS TRIAL NUMBER A B C D

8 Each column contains Three Level 1, Three Level 2, Three Level 3 and Three Level 4 conditions for the factors assigned to the column. Level 4 is intentionally left mentioned as 0 ( NULL). Three Level Factors Combine in Four Possible ways, such as ( 1,1,1),(1,3,3),(2,2,3) and (3,1,3). When two columns of an array form these combinations, the same number of times, the columns are said to be balanced and orthogonal. Note that any two columns of an L9(3 4 ) have the same number of combinations of ( 1,1,1),(1,3,3),(2,2,3) and (3,1,3). Thus, all nine columns of an L are orthogonal to each other. Each parameter has three definite levels marked as 1,2,3 indicating the level of experimentation. The Nozzle Diameter is taken as the Parameter A and A1, A2 and A3 represents the air pressures 1,3 & 5 bar respectively. PARAMETER 12 mm 14 mm 16 mm Nozzle Diameter A 1 A 2 A 3 The Air Pressure is taken as Parameter B and the B1, B2 and B3 represent the lengths of 200,300 & 400 mm respectively. PARAMETER 1 bar 3 bar 5 bar Air Pressure B 1 B 2 B 3 The Cavitation Chamber length is taken as Parameter C and C1, C2 & C3 represent the Nozzle diameters of 12, 14 & 16 mm respectively. PARAMETER 200 mm 300 mm 400 mm Air Pressure C 1 C 2 C 3 8

9 The optimum range and the analysis of Variance is calculated by testing each factor at three levels (3 4 ) 81 possible design configurations.the size of the test matrix is still easily managed and every combination is investigated. For improving the accuracy of the several observations made, a statistical analysis is made for significant confirmation of the results. This statistical analysis is called ANOVA ( Analysis of Variance) 5.0 Analysis Of Results By TAGUCHI The results of the experiments are analysed to achieve one or more of the following objectives. 1. To establish the best or the optimum condition for a product or a process. 2. To estimate the contribution of individual factors. 3. To estimate the response under the optimum conditions. The optimum condition is identified by studying the main effects of each of the factors. The process involves minor arithmetic manipulation of the numerical results and usually can be done with the help of a simple calculator. The main effects indicate the general trend of the influence of the factors. Knowing the characteristic, i.e. whether a higher or lower value produces the preferred result, the levels of the factors which are expected to produce the best result can be predicted. The knowledge of the contribution of individual factors is a key to decide the nature of the control to be established on a production process. The Analysis of Variance (ANOVA) is the statistical treatment most commonly applied to the results of the experiment to determine the percent contribution of each factor. Study of ANOVA table for a given analysis helps to determine which of the factors need control and which do not. Once the optimum condition is determined, a final experiment is conducted to confirm the variance. Taguchi Suggests two different routes to carry the simple analysis. The Standard Approach, wherein the result of a single run,or the average or repetitive runs,are processed through main effect and ANOVA analysis. The S/N Analysis Approach This uses multiple runs and takes into consideration Signal to Noise Ratio (S/N) for the same steps in analysis. S/N analysis determines the most robust set of operating conditions from variations within the results. 9

10 Fig. 7. Analysis Of Variance for the OA as mentioned in Table 8 The figures illustrates that according to the experimented results as entered in the OA, the Variance observed was only 5.969% which is as per acceptable deviation standards for confirmation Study. Fig. 8. Optimum Parameter Confirmed by ANOVA The Figure 8 illustrates that the optimum parameters to arrive at the ANOVA of % is the Chamber Length of 200 mm, with a nozzle diameter of 12 mm and the air pressure of 3 bar. 10

11 Fig. 9. Main Effect of Parameters The above table illustrates the Sound To Noise (S/N) ratio of the various parameters at three levels of observation. CONCLUSION The TAGUCHI optimizing technique has concluded the Analysis Of Variance as % which is a standard Deviation acceptable in Quality analysis. The statistical analysis using Orthogonal array has shown a significant impact on the results obtained through experimental analysis. The Optimum Condition was observed at the below mentioned parameters for the Analysis Of Variance ( ANOVA) at %. FACTOR LEVEL COUNT MEASURE NOZZLE DIAMETER A 1 12 mm AIR PRESSURE B 2 3 bar CAVITATION CHAMBER LENGTH C mm This indicates that the TDS content has been reduced to an admissible range of ( Acceptable level of < 500mg/l ) when water is treated through the vortex flow assembly for a Cavitation Chamber Length of 200 mm with two Convergent Nozzle Diameters of 12 mm EXIT under Air pressure of 3 bar. Thus, it is concluded that the proposed assembly with the TAGUCHI optimized parameters can be successfully implemented for treatment of water in Cooling tower. 11

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