application of taguchi-grey method to evaluate …...cycles (rankine or carnot). according to...

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http://www.iaeme.com/IJMET/index.asp 52 [email protected] International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 10, October 2019, pp. 52-63, Article ID: IJMET_10_10_005 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=10 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication APPLICATION OF TAGUCHI-GREY METHOD TO EVALUATE THE PERFORMANCE OF ENERGY PRODUCED BY USING TRILATERAL FLASH CYCLES AND LOW-GRADE RENEWABLE HEAT Mohammed Yunus* and Mowaffq M. Oreijah Mechanical Engineering Department, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah, KSA *[email protected] ABSTRACT Increased in population and automation of process have upsurge the demands of fossil fuels drastically. Although the solar, bio-mass, geothermal etc. energy renewable resources are easily available for extraction, the contemporary topics like very high initial costs and power developing costs have curtailed their progress. Improvements on current power production methods demand implementing a strong thermal system to draw energy from low-grade renewable heat sources as most of the present techniques can only extract high temperature resources and are very expensive. A proposed binary system having Trilateral-Flash-Cycle (TFC) and a reaction turbine would tackle the contemporary topics with low operation cost and widely utilize the available sources to generate direct power by means of a hydrothermal with the reduced greenhouse gas emissions. The performance characteristics measured were efficiency, Gross power and nozzle flow area have been optimized for input factors such as speed, isentropic efficiency, binary working fluids and turbine diameters using hybrid Taguchi based grey relation analysis (GRA) where experimental trials carried out with Taguchi L 9 orthogonal array. The multiple response optimization and ranking of input parameters were productively completed by GRA to find the effect of each of it. Analysis of variance produced the higher significant factor from selected parameters with percentage of their contribution and was confirmed with an affirmation (verification) test for the obtained optimal set of factors. Thus, the hybrid GRA with Taguchi technique design provides the optimal design parameters affecting multi-performances of TFC system. Key words: Taguchi-Grey Relation; Trilateral- Flash-Cycle; Geo-thermal energy; Binary working Fluids; Thermal efficiency and ANOVA

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  • http://www.iaeme.com/IJMET/index.asp 52 [email protected]

    International Journal of Mechanical Engineering and Technology (IJMET)

    Volume 10, Issue 10, October 2019, pp. 52-63, Article ID: IJMET_10_10_005

    Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=10

    ISSN Print: 0976-6340 and ISSN Online: 0976-6359

    © IAEME Publication

    APPLICATION OF TAGUCHI-GREY METHOD

    TO EVALUATE THE PERFORMANCE OF

    ENERGY PRODUCED BY USING TRILATERAL

    FLASH CYCLES AND LOW-GRADE

    RENEWABLE HEAT

    Mohammed Yunus* and Mowaffq M. Oreijah

    Mechanical Engineering Department, College of Engineering and Islamic Architecture,

    Umm Al-Qura University, Makkah, KSA

    *[email protected]

    ABSTRACT

    Increased in population and automation of process have upsurge the demands of

    fossil fuels drastically. Although the solar, bio-mass, geothermal etc. energy

    renewable resources are easily available for extraction, the contemporary topics like

    very high initial costs and power developing costs have curtailed their progress.

    Improvements on current power production methods demand implementing a strong

    thermal system to draw energy from low-grade renewable heat sources as most of the

    present techniques can only extract high temperature resources and are very

    expensive. A proposed binary system having Trilateral-Flash-Cycle (TFC) and a

    reaction turbine would tackle the contemporary topics with low operation cost and

    widely utilize the available sources to generate direct power by means of a

    hydrothermal with the reduced greenhouse gas emissions. The performance

    characteristics measured were efficiency, Gross power and nozzle flow area have

    been optimized for input factors such as speed, isentropic efficiency, binary working

    fluids and turbine diameters using hybrid Taguchi based grey relation analysis (GRA)

    where experimental trials carried out with Taguchi L9 orthogonal array. The multiple

    response optimization and ranking of input parameters were productively completed

    by GRA to find the effect of each of it. Analysis of variance produced the higher

    significant factor from selected parameters with percentage of their contribution and

    was confirmed with an affirmation (verification) test for the obtained optimal set of

    factors. Thus, the hybrid GRA with Taguchi technique design provides the optimal

    design parameters affecting multi-performances of TFC system.

    Key words: Taguchi-Grey Relation; Trilateral- Flash-Cycle; Geo-thermal energy;

    Binary working Fluids; Thermal efficiency and ANOVA

  • Application of Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat

    http://www.iaeme.com/IJMET/index.asp 53 [email protected]

    Cite this Article: Mohammed Yunus and Mowaffq M. Oreijah, Application of

    Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat. International Journal of

    Mechanical Engineering and Technology 10(10), 2019, pp. 52-63.

    http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=10

    1. INTRODUCTION

    Energy retrieving from the largely available clean and renewable sources (especially from

    low amount of heat) would become the significant solution for meeting demand such as dual

    (binary) power system (BPS) to convert into electricity. BPS is successfully applied in geo,

    solar-thermal energy and retrieval of waste heat from industries and industrial wherein ORC

    (Organic Rankine Cycle) is mature technique employed to retrieve sources of geothermal

    energy in various parts of the world (Oreijah et al., 2019). It is high time to investigate other

    possible techniques for improving the efficiencies of available BPS using other thermo

    principles of cycle such as Trilateral Flash Cycle (TFC). TFCs are employed for retrieving

    excess amount of heat present in the low-grade heat resources compared to other conventional

    cycles (Rankine or Carnot). According to (DiPippo et al., 2007), the main advantages of TFC

    are the employing hot fluid not vapor while entering the expander. Therefore, there is no extra

    energy is needed drawing from developed energy for phase transformation (fluid to vapor).

    As a result, the net power developed by converting into mechanical from thermal-energy is

    larger in contrast to conventional cycles. The main motive for TFC implementation is to

    reduce the irreversibility in the heat transfer process occurs between the primary hot source

    (low-grade waste heat) and the working fluid (coolants) in binary power system. As the

    source temperature increases, recovering capacity of binary working fluid increases and in

    turn thermal energy for each unit heat source at a given mass flow rate and temperature

    increases power output. As far as the efficiency of TFC remains lesser than other conventional

    cycles but in terms of overall efficiency based on full conversion of thermal (from heat

    resource) into the mechanical energy is still higher due to utmost capability of TFC for

    extracting the sensible heat of hot source in contrast to other conservative cycles. Besides,

    various scientists have reported that no appropriate expander (or turbine) was cascaded for

    TFC system to exploit the enormous quantity of the obtained thermal energy. Presently

    available screw type expander has not proved efficient in TFC based system.

    Bryson (2007) noticed the work yield is due to the energy change in the course of heating

    less than that dissipated in cooling. All Heat engines (ORC and TFC) use this as key principle

    as at present, they are most successful equipments to produce electricity from various thermal

    sources economically. Using new improved heat engines, cycles, heat sources, working fluids

    and plans for power production by employing low amount temperature sources which leads to

    redesigning cycle basic factors in BPS would improve solution for existing technology

    economically. The basic devices required are condensers, expanders (or turbines), electrical

    generators, heat exchanger, and the secondary working fluid.

    (Eastop & McConkey, 1993) noticed that standard RC run by a working fluid (WF) water

    works only when the thermal source is above 1800C (SKM, 2005) whereas for low amount

    temperature thermal resources (LGTR) available below 1500C, therefore water cannot be used

    as the WF. RC can be operated employing LGTR with the help of WF other than water

    having low saturation temperature at atmospheric pressure. Such WFs are mostly hydrocarbon

    organic fluids boil at very low temperatures and few have been effectively employed in BPS.

    Therefore, ORC uses organic fluid into RC (Ian K Smith & Marques, 1994) constitutes the

    same apparatus of RC but need modification of cycle factors to work with LGTR. In 1960, the

    first industrial ORC was developed to use the LGTR (Sawyer & Ichikawa 1980). In 1987,

  • Mohammed Yunus and Mowaffq M. Oreijah

    http://www.iaeme.com/IJMET/index.asp 54 [email protected]

    Tabor and Bronicki studied for using 4 kW solar turbines in ORC and modified to

    commercial ORC with Italian company, Ormat (Garg, 1987). Currently, Ormat produces

    ORC based systems for geo-thermal and waste heat recovery at high MW thermal energy

    level.

    TFC involves the expansion of saturated liquid inside the expander instead of saturated

    vapor but remains consisting of four processes similar to ORC as shown in figure 1. The

    processes start by compressing the WF in a saturated liquid phase by a fluid pump. The

    constant pressure WF enters the heat exchanger and heat gets added. The saturated liquid WF

    enters the Reaction Turbine with the isentropic expansion where the temperature and pressure

    of the WF decrease simultaneously. Finally, the WF gets condensed going into the condenser

    before inflowing to the pump to form a fresh cycle. The working theory of TFC was explored

    widely in 1992 (Ian K Smith, 1993; I. Smith, 1992). The TFC offers two benefits to use as an

    striking thermo principled cycle such as firstly, it corresponds the temperature profiles,

    secondly, it get operated at actual pressures to implement them efficiently practicable for the

    low-power functions (Zamfirescu & Dincer, 2008). The key output shows that the TFC best

    med the considered Kalina and ORC by an increment of 7 % under similar operating

    parameters. That was due to the ability of TFC to recover most of the heat from the heat

    source.

    The efficiency of the BPS can be improved by improving the efficiency of individual

    components among several techniques to develop the thermodynamic performance. Each

    component has various control parameters and optimum value of these factors will contribute

    to improvement of various outputs of TFC based BPS. As the trilateral shows an advantage of

    increasing the heat retrieval from heat resource, yet, required to develop an effective expander

    to improve the power utilization essentially due to the pressure difference of the WF. The

    expander (outflow reaction turbine) is the major unit in the BPS to extract the power and by

    thermal efficiency will be increased gradually with design parameters namely, diameters,

    speed of rotation. WF in BPS has the vital role in achieving efficiency and the productivity.

    Some characteristics of the WF are important for selecting the proper WF such as higher

    thermal conductivity, thermodynamically stable, compatible with a wide range of materials,

    low toxicity. Another output exit nozzle area to be optimized. In this work, multi optimization

    of outputs under various control factors listed in Table 1 are carried out using taguchi based

    grey relation analysis to find optimum values of control factors for improving the outputs.

    In the present complex and multi response system involving various factors

    simultaneously affecting it has to be evaluated for the developing design by knowing which of

    the parameters affect the system significantly. On the other hand, the relationship between

    various factors remains grey as information or data on them not clear or complete or doubtful

    as well as complex to achieve realistic and investigational data from much scattered for

    analysis. Various conventional statistical methods such as factor and regression analysis are

    commonly used for finding mutual effect of relationship of dependent and independent

    parameters between variables need vast data and should match the given characteristic

    distribution. It is very hard to attain the data on relationship of parameters using such

    methods. Hence, conventional multi output statistical techniques have difficulties in giving a

    realistic justification and to overcome these advantages, a new statistical method to be used.

    Taguchi based Grey relational approach (GRA) considered as well-organized tool which

    performs examination by arranging an outline for planning, predicting, and grouping of grey

    schemes. GRA offers advantages like miniature models without characteristic distribution,

    independent variables and a minimum amount of computation, with little information besides,

    being a clear-cut and precise technique for choosing factors with unique settings [4]. Hence,

    the GRA is utilized to carry out multi output optimization for developing GRG (grey

  • Application of Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat

    http://www.iaeme.com/IJMET/index.asp 55 [email protected]

    relational grade) with various grades to arrange the rank of the grey relationship within

    independent and dependent factors. The control factors (refer Table 1.) and the corresponding

    levels of each factor are used for optimizing the TFC based BPS generating power from low

    amount of temperature resources. Experimental trials were conducted using Taguchi L9

    orthogonal array[16]. GRA involve the steps are as shown in Figure 2.

    Table 1: Levels of Process factors for performance characteristics of TFC

    Process Parameters Notation Unit Levels of Parameters

    Level 1 Level 2 Level 3

    Reaction Turbine diameter D M 0.4 0.6 0.8

    Working fluids F - R134a R11 R113

    Rotational speed of Turbine R Rpm 3500 5000 8000

    Isentropic Efficiency E % 50 75 100

    Figure 2. Steps followed during Taguchi based hybrid GRA

    Transformation of measured values into non- dimension factors ranging the results from

    zero to one to consider the level of control parameters magnitudes is called as normalising [7,

    8]. In order to perform this sequences of data from original set to comparable are to be

    converted. This process of generation of grey relationship of grey data uses various available

    techniques. In the present work, hybrid Taguchi GRA employed to optimize the performance

    outputs of TFC based BPS generating power from low amount of heat resources for their

    multi outputs like Thermal efficiency (ηtherm), Gross power (GP) and Exit Nozzle area (Anozzle)

    of a reaction turbine to increase the retrieval capacity of excess heat available. Multi output

    characteristics depend upon the quality exceptionality of the initial data which correspond to

    the sequence of initial (or original) reference and comparability (or normalized) using (x)

    (x), y =1, 2, 3, ..… p; x = 1, 2, 3, ..., q, where p and q are the experimentation runs and

    responses of data correspondingly. Also, depending upon its data quality, the main groupings

    recognized for normalizing the initial sequence by means of either “smaller-the-better” or

    “larger-the-better” referring Eq. (1) or Eq. (2) respectively [9]:

    ( )

    ( )

    ( )

    ( ) (1)

    ( )

    ( )

    ( )

    ( ) (2)

  • Mohammed Yunus and Mowaffq M. Oreijah

    http://www.iaeme.com/IJMET/index.asp 56 [email protected]

    Where, ( )

    ( ) are the maxima and minima values of ( ). But

    ( ) represent normalized or compatibility and

    ( ) is the initial sequences of the objective value. In this investigation, p = 9 and q = 3 are employed.

    Next step is to evaluate of coefficients such as deviation and grey relational using Eq. (3)

    and Eq. (4).

    ( )

    ( ) ( ) (3)

    Where, ( )

    ( ) ( ) are the reference (or ideal) sequence, compatible

    sequence and the . The grey relational (or distinguishing) coefficient lies in the range of 0 to 1) is evaluated using:

    ( ( )

    ( ))) ( )

    (4)

    Third step is to evaluate the GRGs, (

    ) acquired by the weighted summation of the ζ grey relational coefficients to signify the of correlation level between primary and

    compatible sequences estimated employing Eq. (5):

    (

    )

    (

    ( ) ( ( ))) (5)

    Finally, the GRGs are then ranked in descending order to attain the maximum value of it

    for signifying the well-built agreement occur connecting the ideal and the compatible

    sequences. The highest GRG value indicates the optimum set of combined control parameters

    to achieve the desired outputs.

    2. EXPERIMENTAL PROCEDURES

    Experiments were initiated by decreasing the flow rate of the WF (either R1341, R11 or

    R113) in a reaction turbine operated using TFC and WF flow rate is controlled by feed pump

    to increase it till it reaches the sensible heat. Before entering the turbine, WF remains in the

    saturated liquid phase. The experiments were carried out with certain factors at different

    levels values listed in Table 1. Hot source temperature of low amount heat renewable energy

    sources (solar or geo thermal) lies in the range of 125 to 75 ºC with constant flow rate of 0.56

    L/sec was maintained during simulation for all set of experiments. Whereas on the cooling

    section of the condenser, the temperature range of 19 to 26 ºC with a constant flow rate of

    0.52L/sec were maintained. Necessary measuring devices were used in the BPS test rig to

    measure the required responses (or thermal characteristics) and using data accumulator or

    acquisition system, temperatures and flow rate at all accessible points of cool and hot water

    were collected. Moreover, the electric DC generator was coupled to an electronic load device

    (having voltmeter and ammeter) capable of varying the magnitude of electric generator load

    to record the voltage and the current as the output (power). Accordingly, the developed power

    is noted down accurately from experimentation. Using digital strain display, the value of the

    output force is recorded as it can be changed into the torque of the turbine. Different control

    parameters having numerical values at three levels with the interaction effect were selected as

    shown in Table 1. In multi-response optimization, some quality characteristic loss is

    anticipated in comparison to an optimization of a single-response but always the total quality

    improves depending on appropriate method of choosing factors and their levels that affect

  • Application of Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat

    http://www.iaeme.com/IJMET/index.asp 57 [email protected]

    these quality characteristics for improving performance outputs of TFC based BPS. The

    output characteristics optimized were GP, ηtherm and Anozzle. The Taguchi process is employed

    for the carrying out of the experiment’s plan as per orthogonal array (OA) available for four

    factors at three levels.

    Four columns and nine rows of L9 OA is used in the present study to carry out the

    experiments for collecting responses of TFC based BPS (refer Table 2).

    3. MULTIPLE OUTPUT OPTIMIZATION OF CONTROL FACTORS BY

    GRA

    The estimation of performance based output characteristics is judged using greatest values of

    GP, TE and NA of BPS. The “higher-the-better” approach for responses is applied to perform

    normalization of GRA process by using Eq. (2) [yunus et al., 2015]. Taguchi method was

    used for optimization of the multiple-response of performance characteristics to recommend

    the field of higher heat withdrawal application. The pre-processed data of responses are listed

    in Table 3. The coefficient of grey relation (refer Table 4) of multiple responses estimated

    employing using Eq. (4) with the help of coefficients of deviation attained from Eq. (3). All

    the input factors considered for equal weight setting at a value of 0.5 were employed to

    estimate the GRG from Eq. (5). GRG of each experiment is presented in Table 4 [yunus et al.,

    2016]. Thorough investigations of data from Table 4 and Figure 3, signifies that experiment

    No. 3 is the best response from the set of all trials as it has large value of GRG, it means

    comparable and initial sequences are demonstrating a well-built relationship with each other

    [yunus et al., 2017]. GRA finds the most important factor depending on the theory; a

    combination of the different levels of input factors afford the largest mean output and is the

    optimum factors set for improving heat retrieval effect of TFC based BPS.

    Table 2. Experimental trials and data processing of output characteristics of TFC based BPS

    TFC performance

    Factors

    Isen

    trop

    ic E

    ffic

    ien

    cy

    Experimental Results Normalized Data

    Ru

    n n

    o.

    Rea

    ctio

    n

    Turb

    ine

    Dia

    met

    er

    Work

    ing F

    luid

    s

    Rota

    tional

    Spee

    d o

    f R

    T

    Outp

    ut

    pow

    er

    (KW

    )

    Ther

    mal

    Eff

    icie

    ncy

    (%

    )

    Nozz

    le E

    xit

    area

    (mm

    2)

    Outp

    ut

    pow

    er

    Ther

    mal

    Eff

    icie

    ncy

    Nozz

    le E

    xit

    are

    a

    Ideal

    Sequence

    1 1 1

    1 0.4 R13

    4a

    3000 50 339.7 3.4 44.77813

    7

    0 0 0.3004

    2 0.4 R11 5000 75 800.5 8 40.22282 0.5677 0.5672 0.245

    3 0.4 R11

    3

    8000 100 1151.4 11.5

    1

    70.91513

    4

    1 1 0.6203

    4 0.6 R13

    4a

    5000 100 939.4 9.39 26.38628

    4

    0.73882 0.7386 0.0753

    5 0.6 R11 8000 50 677.6 6.78 26.4006 0.4163 0.4168 0.0755

    6 0.6 R11

    3

    3000 75 740.8 7.41 101.9404 0.494 0.4945 1

    7 0.8 R13

    4a

    8000 75 924.5 9.25 20.2307 0.721 0.7213 0

    8 0.8 R11 3000 100 1083.5 10.8

    4

    32.9899 0.9163 0.92 0.1562

    9 0.8 R11

    3

    5000 50 641.9 6.42 74.4596 0.3723 0.3724 0.6637

  • Mohammed Yunus and Mowaffq M. Oreijah

    http://www.iaeme.com/IJMET/index.asp 58 [email protected]

    Table 3. Coefficients of deviation and grey relational of output characteristics of TFC based BPS

    Run No. Deviation Coefficient Grey Relational Coefficient

    GP ηtherm Anozzle GP ηtherm Anozzle

    Ideal Sequence 1 1 1 1 1

    1 1 1 0.6996 0.33333 0.3333 0.4168

    2 0.4323 0.4328 0.755 0.5363 0.536 0.3984

    3 0 0 0.3797 1 1 0.5684

    4 0.2612 0.2614 0.9247 0.6586 0.6567 0.351

    5 0.5837 0.5832 0.9245 0.4614 0.4616 0.351

    6 0.506 0.5055 0 0.497 0.4972 1

    7 0.279 0.2787 1 0.642 0.6421 0.3333

    8 0.0837 0.08 0.8438 0.8566 0.8621 0.3721

    9 0.6277 0.6276 0.3363 0.4434 0.44342 0.53

    Table 4. Grey relational grades and their order

    Run No. Grey Grade Order

    1 0.3611 1

    2 0.4902 4

    3 0.8561 9

    4 0.5554 6

    5 0.4247 2

    6 0.6647 7

    7 0.5390 5

    8 0.6969 8

    9 0.4723 3

    From greater average of GRG, optimum parameter level has been found as D1F3R3E3,

    i.e., Diameter of 0.4m, working fluid of isopentane, speed of 8000 rpm and isentropic

    efficiency of 100%. Output tables were produced employing the Taguchi method to estimate

    the average GRG for every level of input factor for performance characteristics of TFC based

    BPS (refer Table 6).

    Table 5. Mean grey relational grade at each level

    Input Parameters Grey Relational Grade

    Max.-Min. Rank Level 1 Level 2 Level 3

    Reaction Turbine Diameter 0.5691 0.5483 0.5694 0.0211 4

    Working fluids 0.5373 0.6644 0.4852 0.1792 2

    Rotational speed of RT 0.5742 0.5060 0.6066 0.1006 3

    Isentropic Efficiency 0.4194 0.5646 0.7028 0.2834 1

    Total mean grey relational grade = 0.5623

    The highest GRG values shown in Table 5 for a set of input factors are D1-F2-R3-E3. It

    represents the optimum set of TFC input parameters for the multi-outputs of performance

    measurements during assessment of extraction of high heat. D1-F2-R3-E3 combination

    indicates the Rotor diameter of 0.4m, the working fluid type of isopentane (R113), at a speed

    of 8000 rpm and isentropic efficiency of 100%. The main influence of averages of GRG vs

    levels is plotted in Figure 3. The dotted lines stand for the total GRG average.

  • Application of Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat

    http://www.iaeme.com/IJMET/index.asp 59 [email protected]

    Figure 3. Plot of total average of GRG vs. input parameters

  • Mohammed Yunus and Mowaffq M. Oreijah

    http://www.iaeme.com/IJMET/index.asp 60 [email protected]

    0.080.040.00-0.04-0.08

    99

    90

    50

    10

    1

    Residual

    Pe

    rce

    nt

    1.00.80.60.4

    0.04

    0.02

    0.00

    -0.02

    -0.04

    Fitted Value

    Re

    sid

    ua

    l0.040.020.00-0.02-0.04

    4

    3

    2

    1

    0

    Residual

    Fre

    qu

    en

    cy

    16151413121110987654321

    0.04

    0.02

    0.00

    -0.02

    -0.04

    Observation OrderR

    esid

    ua

    l

    Normal Probability Plot Versus Fits

    Histogram Versus Order

    Residual Plots for Grey Relational Grade

    Figure 4. Residual plots of GRG

    4. ANOVA (ANALYSIS OF VARIANCE) APPLIED FOR GRG

    Analysis of Variance has been used to find out the ranking or grading of GRG at 95%

    probability interval for examining the importance level of input parameters on multiple

    response of TFC using Minitab® 19 statistical software [yunus et al., 2016]. A total sum of

    squared deviations (SST) can be calculated using Eq. (6):

    ∑(yj ym)

    j

    (6)

    where, N = number of trials in OA, yj = average of GRG for jth

    trial and ym = total average

    of GRG. Average square (MS) is achieved by using Eq. (7) as follows

    (7)

    The most influential input factor on the multiple responses is having a large value of F (or

    small value of P). The % contribution of an input parameter can be estimated using an Eq. (8)

    and corresponding residual plot of GRG is shown in Figure 4 [15].

    (8)

    The ANOVA GRG results for of BPS have been determined (refer Table 6) and shows the

    isentropic efficiency is the only significant control factor multi-outputs considered

    simultaneously during high extraction of heat. The % contribution of input factor for

    isentropic efficiency in the multi-response performance is 25.96.

  • Application of Taguchi-Grey Method to Evaluate the Performance of Energy Produced by using

    Trilateral Flash Cycles and Low-Grade Renewable Heat

    http://www.iaeme.com/IJMET/index.asp 61 [email protected]

    Table 6. Analysis of Variance Results on GRG

    Source DF Adj SS Adj MS

    F-

    Value

    P-

    Value

    Reaction Turbine Diameter 2 0.000882 0.000441 0.00 0.996

    Working Fluids 2 0.050981 0.025491 0.61 0.493

    Rotational speed of RT 2 0.015835 0.007918 25.96 0.015

    Isentropic Efficiency 2 0.120527 0.060263 5.49 0.099

    Error 0 0 0

    Total 8 0.188225

    Regression equation

    GRG = 0.5623 + 0.006867 *D1 - 0.01400*D2+ 0.007133*D3 - 0.02500*F1+ 0.1021*F2 –

    0.07710*F3 + 0.01197*R1 - 0.05630*R2+ 0.04433*R3 - 0.1429*E1+ 0.002367*E2 + 0.1405*E3

    5. VERIFICATION OF RESULTS BY VALIDATING TEST

    The optimal set of input factors as D1-F3-R3-E2 for maximizing GP, ηtherm and Anozzle are

    optimized using hybrid Taguchi and Grey Relational Approach. A confirmation test was

    carried out by using an D1-F1-R1-E1 optimal setting. The results of the verification test were

    1151.4 KW for GP, ηthermal of 11.51% and Anozzle of 90.9mm2.The confirmation test result is

    observed better than the experiments carried out (refer Table 3). Subsequent to finding the

    optimal combination of TFC control factors and the most influential factor, the concluding

    stage to verify the feasibility of proposed combined Taguchi based grey method by

    conducting some confirmation tests. The optimal grey relational grade, гopt, is calculated as

    [15]:

    ∑ ( )

    (9)

    where, is the total GRG average, , is the GRG average of the of ith

    parameter of

    optimum levels, and c is the quantity of most influential as regards to TFC based BPS

    parameters[16]. In all outputs such as GP, ηthermal and Anozzle for an optimum set of control

    parameters were sufficiently higher as compared to those of initial setting of factors (having

    0.80). Three supplementary trials were conducted at various levels of optimum parameter set

    and the mean of these is considered in the verification test. The forecast GRG values and the

    result of the validation test are provided in Table 7. Performance based outputs such as GP

    has been enhanced from 1100 to 1150 KW, ηthermal is from 11.5 to 12% and Anozzle is

    improved from 85 to 90 mm2.

    Table 7: TFC based BPPS performance results using primary and optimum input factors

    Initial Process

    Parameters

    Optimal process parameters

    Prediction Experiment

    Level D1-F1-R1-E1 D1-F3-R3-E3 D1-F3-R3-E3

    Gross Power 1100 - 1151.4

    Thermal Efficiency 12 - 11.51

    Nozzle Exit Area 85.008 88.075 90.915134

    Grey Relational

    Grade 0.80 - 0.8561

  • Mohammed Yunus and Mowaffq M. Oreijah

    http://www.iaeme.com/IJMET/index.asp 62 [email protected]

    6. CONCLUSION

    BPS using low amount of heat energy available in of geo-thermal energy are employed

    proficiently for extracting least possible available heat derived from secondary WF. Response

    characteristics experiments such as Thermal efficiency (ηtherm), Gross power (GP) and Exit

    Nozzle area (Anozzle) were carried out using TFC and reaction turbine with various WF. The

    multi-responses were collected under L9 OA combination of control factors using Taguchi

    design approach. The assessment of GRG enumerates the general performance of input

    factors of TFC based BPS for developing power from low amount of heat sources. The

    highest GRG value was obtained when the diameter of turbine is 0.4m, WF of isopentane,

    Speed of 8000 rpm and isentropic efficiency of 100% for performance characteristics and

    these could be recommended levels of TFC based BPS control factors for maximizing

    responses measured. GRA Ranking determined by employing ANOVA method discovered

    that the speed of RT is the most significant control factor which affects the multi-output

    characteristics. The contribution of speed is relatively higher about 25.46% when compared

    with the other input factors. The optimal set of input factors upon a verification tests revealed

    the GRG enhancement is 0.8561 contrasts to primary combination values of input factors

    about 0.80 shows substantial improvement in the performances of TFC such as gross power,

    thermal efficiency and nozzle exit area have been validated. This investigation reduced time

    as well as cost including production cost to increase the quality. The optimization of

    combined multiple responses are significantly simplified with repeatability and

    possibility.Hence, the hybrid GRA and Taguchi design used for multiple-output optimization

    with set of optimal input factors helps in accomplishing substantial improvement of grey

    relation.

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