The magnetic treatment of hard water is an alternative, simple approach by which the hard water that needs to be treated flows through a magnetic field. This field is created by inducing current in a coil wrapped around a pipe. Consequently some of its properties, such as total dissolved salts (TDS), conductivity (Ec) and PH change. The primary purpose of hard water treatment is to decrease TDS in the incoming liquid stream. Using performance data from the application of different magnetic field densities on the different flow levels of water, empirical mathematical models were developed relating the salt removal percentage (SRP) to operating flow rate and current of the coil. The obtained experimental results showed that the SRP increased with increasing the current at low flow rates (up to 0.75 ml/s).
Journal of Advanced Research (2011) 2, 351–355 Cairo University Journal of Advanced Research SHORT COMMUNICATION An empirical model for salt removal percentage in water under the effect of different current intensities of current carrying coil at different flow rates Rameen S AbdelHady a,*, MohammedAdel A Younes a, Ahmed M Ibrahim b, Mohammed M AbdelAziz b a b Mechanical and Electrical Institute, National Research Center, Ministry of Water Resources and Irrigation, Egypt Electrical and Machine Power Department, Faculty of Engineering, Cairo University, Egypt Received 26 October 2010; revised December 2010; accepted 31 January 2011 Available online 12 March 2011 KEYWORDS Magnetic field; Water; Flow rate; Salt removal percentage; Empirical model Abstract The magnetic treatment of hard water is an alternative, simple approach by which the hard water that needs to be treated flows through a magnetic field This field is created by inducing current in a coil wrapped around a pipe Consequently some of its properties, such as total dissolved salts (TDS), conductivity (Ec) and PH change The primary purpose of hard water treatment is to decrease TDS in the incoming liquid stream Using performance data from the application of different magnetic field densities on the different flow levels of water, empirical mathematical models were developed relating the salt removal percentage (SRP) to operating flow rate and current of the coil The obtained experimental results showed that the SRP increased with increasing the current at low flow rates (up to 0.75 ml/s) ª 2011 Cairo University Production and hosting by Elsevier B.V All rights reserved Introduction * Corresponding author Tel.: +20 105004402, +20 106364994, +20 22751997; fax: +20 42188948 E-mail address: rameens@hotmail.com (R.S AbdelHady) 2090-1232 ª 2011 Cairo University Production and hosting by Elsevier B.V All rights reserved Peer review under responsibility of Cairo University doi:10.1016/j.jare.2011.01.009 Production and hosting by Elsevier Hard water is water that has a high mineral content The main components of these minerals usually are calcium (Ca2+) and magnesium (Mg2+) ions, in addition to dissolved metals, bicarbonates, and sulfates Calcium usually enters water as either calcium carbonate (CaCO3) in the form of limestone and chalk, or calcium sulfate (CaSO4) in the form of several other mineral deposits The main source of magnesium is dolomite (CaMg(CO3)2) The total water ‘hardness’ (including both Ca2+ and Mg2+ ions) is expressed as parts per million (ppm) or weight/volume (mg/l) of calcium carbonate (CaCO3) in water i.e., the total dissolved salts (TDS) Due to the hardness of water, scale is formed The problem of scaling causes loss of 352 R.S AbdelHady et al production or process time and deterioration of equipment and equipment failure; it also increases energy consumption and loss of turnover The methods by which the TDS of water can be reduced and thus scale treated can be chemical or physical The chemical method has been shown to be very effective; however, it can cause environmental pollution through the disposal of treated water [1] The physical methods such as magnetic treatments have attracted much attention for over 100 years Donaldson [2] suggests that the magnetic treatment can not only reduce the scaling potential of water but can also cause existing scale to dissolve over an extended period of time Hasson and Bramson [3] recorded no change in either the rate of scale deposition or the deposit tendency after tests of 15–35 h duration and concluded that antiscale magnetic treatment (AMT) was ineffective at the very high levels of supersaturation employed The effect of magnetic field on the scaling rate is studied by various authors including Ellingsen and Kristiansen [4] who studied the effect of field strength on the scaling rate The authors found the precipitation rate to increase with increasing magnetic flux With only a few exceptions, the reported effects in single phase solutions have amounted to a change of no more than a few percent in certain fundamental solution parameters, namely light absorbance or transmission [5–8], conductivity or pH [9], viscosity [10], and water absorption [11] A number of these authors have proposed mechanisms to explain the observed changes These have included changes in the water of hydration of the calcium ion, alteration of the molecular rotation of water adsorbed onto materials [11], and a localized pH shift resulting from the electric currents generated by Lorentz forces Here the effect of magnetic flux on TDS is studied, which was not done by the above studies Apart from inducing direct magnetic flux, the application of induced magnetic flux by means of solenoid type equipment has been reported Antiscale magnetic treatment is a green method of TDS reduction because it does not use chemicals and it removes the option of treatment of process water before disposal The principle behind the technology involves using a varying electric current in a solenoid wrapped around a pipe to create an induced electromagnetic field inside the scale-producing solution From the laws of physics, electrical current flowing through a wire creates a magnetic field around the wire Due to both the complexity of the phenomena involved and the lack of significant research in this field, no satisfactory mathematical models have been developed SRP is influenced by many factors, such as the detailed velocity field, density and viscosity of the fluid, direction of the magnetic field, and the effective length of the magnetic probe on the pipe Random environmental factors and inlet conditions cause dramatic changes to the density and velocity field, which in turn cause major variations in SRP In the absence of a more valid practical approach, empirical models, sometimes called ‘‘regression models’’, can be helpful in this research Experimental The apparatus used is shown in Fig The apparatus consists of a coil of length L = 15 mm, inner diameter equals 10 mm, outer diameter equals 30 mm with number of turns N = 1100 wound with a copper wire of 1.5 degauss, maximum voltage V = 12 V, maximum current I = 240 mA, with iron housing, placed on a teflon pipe of mm inner diameter and mm outer diameter of 50 cm length The direction of the magnetic field is bilateral to the direction of water flow connected with a water flow system and a laboratory DC power supply In the flow system water passes through the tubing system ending with a syringe needle to let the water flow through the coil as shown in Fig 1; the input saline water with TDS above 180 ppm, which is considered to be very hard water, is supplied to the current-carrying coil through a tank of a capacity of 10 l; input water flow rate is controlled through valves, each calibrated to a certain flow rate RAW WATER Conductivity Sensor Current Carrying Coil DAQ Tubing system Water flow by gravity DC Power Supply 0-30 volts 0-3 amp LAP TOP connected To DAQ card Regulated valve (Syringe needle) PRODUCT Fig Experimental setup schematic diagram An empirical model for the effect of magnetic field on water The laboratory DC power supply type GPR-3030 of dimension 102(W) · 165(H) · 300(D) mm is used at various voltages ranging from to 30 V and to A applied on the coil to control the magnetic field density The conductivity sensor, which consists of a 9-V battery, battery snap connectors, k-X resistor and two alligator clips straightened and dipped into the teflon pipe one cm apart, is connected to the DAQ card through a USB cable that is connected to the computer system The positive electrode of the battery is connected to the resistor and to one of the clips and the other clip is connected to the negative electrode [12] The NI USB 6008 data acquisition card was chosen for signal acquisition from the water conductivity sensor The card has analog inputs, analog outputs, and 12 bidirectional digital lines and a sampling rate of up to 10 ks/ s [13] The differential acquisition mode was chosen because it would provide more noise immunity and accuracy of measurement Magnetic eld calculation [14] H ẳ N Iị=L ð1Þ where H is the magnetic field intensity, which is the amount of magnetizing force It is proportional to the number of turns per unit length of a coil and the amount of electrical current passing through it in Amp turn/m, N is the number of turns of current carrying coil, I is the current applied on the current carrying coil and L is the length of the coil in meters BẳlH 2ị where B is the magnetic eld density, which gives the magnetic field’s magnitude (the number of flux lines per unit area) expressed in Tesla, l is the magnetic field permeability, which is the measure of the ability of a material to support the formation of a magnetic field within itself in Henry/m l ¼ lo à lr ð3Þ À7 where lo is the magnetic constant equals \ g \ 10 Henry/m and lr is the relative permeability equals (for air) The samples used for the magnetic treatment experiments were at room temperature The SRP is determined at four different flow rates (0, 0.25, 0.5, 0.75 ml/s), with thirty different magnetic field densities The parameters chosen in the experiment were flow rate and current of the current-carrying coil The range of current used is from to 200 mA with mA steps so the range of magnetic field intensity and magnetic field density becomes from 1.8 \ 10À3 T to 18.4 \ 10À3 T 353 The salt removal percentage used to determine the final desalinated product water at different magnetic field intensities is expressed as Eq (5): TDSout À TDSin SRP ¼ À à 100 ð5Þ TDSin where TDSout is the outlet TDS, which is the TDS at various currents of current-carrying coil (which represents the magnetic field applied on the pipe), and TDSin is the inlet TDS (which is the TDS at A on the pipe i.e., raw water) Salt removal percentage was fitted to the following formula: SRP ¼ að1 À eÀbI Þ ð6Þ The curve fitting parameters (a) and (b) Eq (6) are used to describe the relationship between SRP and the current applied on the current-carrying coil Results The obtained experimental results showed that the SRP increased with increasing the current at low flow rates (up to 0.75 ml/s) The model coefficients were derived from the combined analysis of well-correlated sets of data, thus giving a good indication for their possible general applicability The analysis of experimental data also gave a relationship between SRP and flow The exponential equation (Eq (6)) is applied and the effect of flow rate on the SRP appears on the values of the constants (a) and (b) The SRP as a function of current applied on current-carrying coil, at various flow rates is illustrated in Figs 2a–d The obtained constant values (a) and (b) at various magnetic fields from 1.1 T to 11.058 T and flow rate from mL/s to 0.75 mL/s are shown in Table The analysis shows that the constant values (a) and (b) decreased as the operating flow rate increased It indicates that the ability to increase the SRP is more effective at lower operating flow rates The plot constant value (a) and (b) (as y coordinate) to the flow rate (as x coordinate) as a linear trend followed the mathematical equation shown in Eq (7): yẳmxỵc 7ị Salt Removal Percentage Fit Model at ml/sec SRP=a*(1-exp(-b*I)) a=90 b=9.034 80 Sensor calibration Experimental Data Fit curve 99.5% Sodium Chloride NaCl with specifications according to British pharmacopoeia 2004 dissolved in ionized water was used as standard to calibrate the sensor in the tubing system by measuring TDS of this solution using a traditional calibrated portable pH/Ec/TDS/Temperature meter (Hanna with probe HI 991300), then passing it through the tubing cell system and reading the corresponding voltage of the sensor The Labview program was adjusted to automatically read the TDS in ppm The calibration equation (Eq (4)) is deduced by fitting the points to a straight line using the curve fit tool in Matlab with error 11.3588% and R2 (goodness of t) 0.9403 TDS ẳ 767:4V ỵ 6813 where V is the voltage of the sensor Salt Removal Percentage 70 60 50 40 30 20 10 0 ð4Þ Fig 2a 0.02 0.04 0.06 0.08 0.1 0.12 Current (A) 0.14 0.16 0.18 0.2 Effect of current applied on coil on SRP at ml/s 354 R.S AbdelHady et al Salt Removal Percentage Fit Model at 0.25 ml/sec SRP=a*(1-exp(-b*I)) a= 60 b=8.205 Salt Removal Percentage Fit Curve at 0.75 ml/sec SRP=a*(1-exp(-b*x)) a=2.5 b=5.376 1.8 50 Experimental Data Fit Curve Experimental Data Fit Curve 1.6 Salt Removal Percentage Salt Removal Percentage 1.4 40 30 20 10 1.2 0.8 0.6 0.4 0.2 0 Fig 2b 0.02 0.04 0.06 0.08 0.1 0.12 Current (A) 0.14 0.16 0.18 0.2 Effect of current applied on coil on SRP at 0.25 ml/s Fig 2d Salt Removal Percentage at 0.5 ml/sec SRP=a*(1-exp(-b*I)) a=40 b=7.562 35 0.04 0.06 0.08 0.1 0.12 Current (A) 0.14 0.16 0.18 0.2 Effect of current applied on coil on SRP at 0.75 ml/s Value parameters (a) and (b) at various flow rates Flow rate of water in mL/s Value parameter a Value parameter b 0.25 0.5 0.75 Experimental Data Fit Curve 30 Salt Removal Percentage Table 0.02 90 60 40 2.5 9.102 8.289 7.714 5.373 25 20 Substitution of Eqs (10) and (11) into Eq (8) provides an empirical model Eq (12) that describes the SRP as a function of current applied to the coil and flow rate 15 10 SRP ẳ 113 Q ỵ 90:5ị exp4:647 Q ỵ 9:287ị Iịị 12ị 0 Fig 2c 0.02 0.04 0.06 0.08 0.1 0.12 Current (A) 0.14 0.16 0.18 0.2 Effect of current applied on coil on SRP at 0.5 ml/s A statistical treatment known as linear regression can be applied to the data and these constants can be determined, where m is the slope of the line and c is the y-intercept Given a set of data with n data points, the slope and yintercept can be determined using the following equations: P P P n niẳ1 xyị niẳ1 x niẳ1 y mẳ 8ị P P n niẳ1 xị2 niẳ1 xÞ2 Hence Eq (8) is used to determine the slope of the line Pn P y À m ni¼1 x c ẳ iẳ1 n 9ị Eq (9) is used to determine the y-intercept Using the data in Table and applying Eqs (8) and (9) to deduce the slope and y-intercept, the Eqs (10) and (11) of constant values (a) and (b) become: a ẳ 113Q ỵ 90:5 10ị b ẳ 4:647Q ỵ 9:287 11ị where in Eq (12) Q is the flow in ml/s and I is the current applied on the coil in Ampere Validation of the general equation The flow rate was adjusted to 10 ml/min (1 = 60 s; 10 ml/ = 1/6 ml/s = 0.167 ml/s, which is in the range of the flow Table Salt removal percentage at different current intensities and 10 ml/min (0.167 ml/s) flow rate Current of coil Experimental Empirical salt Accuracy SRPexp ÀSRPemp j à 100 in ampere salt removal removal j SRPexp percentage percentage 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 9.2980 16.8503 32.2795 42.3386 47.7833 54.1806 58.8217 60.4449 64.8784 68.7636 13.0631 23.7451 32.4800 39.6228 45.4636 50.2398 54.1454 57.3391 59.9507 62.0862 40.4935 40.9179 0.6212 6.4145 4.8546 7.2735 7.9500 5.1382 7.5953 9.7107 An empirical model for the effect of magnetic field on water properties Among those physical properties are conductivity and thus TDS and pH Analyses of the performance data from the lab show that a simple empirical relationship in the form SRP ¼ að1 À eÀbI Þ can satisfactorily describe the salt removal percentage in terms of the operating flow rate The coefficients (a) and (b) were found to be flow rate-dependent according to a ẳ 113Q ỵ 90:5 and b ẳ 4:647Q þ 9:287, valid for operating flow rate 0–0.75 ml/s Emperical and Experimental Salt Removal Percentage at 10ml/min 70 Experimental SRP SRP deduced from Model Salt Removal Percentage 60 355 50 40 30 Acknowledgments 20 I would like to thank all the people of the Mechanical & Electrical Research Institute for their wonderful support 10 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Current (A) 0.16 0.18 0.2 0.22 Fig Experimental and empirical salt removal percentage at different applied magnetic fields at 10 ml/min flow rates at which the model was utilized) and the current of the coil ranged from to 200 mA The salt removal percentage experimentally reached 68% at 200 mA as shown in Table By applying Eq (9) putting I = 0.02–0.2 with 0.02 steps and Q = 0.1667 mL/s to deduce the SRP empirical gives results that are also shown in Table As seen in Table and Fig 3, the difference between the experimental SRP and the SRP deduced from Eq (12) gives results that are satisfactory; the model can predict the SRP approximately although the accuracy was higher than 10% at lower current intensities Due to the low values of the SRP at these intensities, however, the model gives only a rough value; also it has been observed that at high current values the model-predicted values are less than the experimental values due to the approximation of the constant value (a); the parameter (a) represents the length on the y scale between the function’s height at x = and the asymptote approached by the function as x approaches infinity and it can be seen in Fig 2a–d that the created model values are less than the experimental values Discussion and conclusion The experimental work in determining the effect of operating flow rate allows us to conclude that flow rate influences salt removal percentage The results reveal that the removal percentage decreases as the flow rate increases Increased flow rate increases the drag force; therefore, particles are not easily aggregated or accumulated under high flow velocity [15] Increasing the current, i.e., increasing the magnetic field density, leads to an increase in the salt removal percentage because water molecules are electrically charged and have a small dipole and thus a small dielectric constant This dipole may be susceptible to the effects of exogenous electric and magnetic fields It is well known that the subjection of water to a small magnetic field can change its dielectric constant The change in the electric dipole of water can result in change of the physical References [1] Al Nasser WN, Shaikh AA, Al Ruwai AH, Hounslow MJ, Salman AD Determining the effect of electronic anti fouling system on the scaling behaviour by inline technique Online monitoring effect of EAF on calcium carbonate precipitation and deposition: particulate systems analysis 2008;1:112 [2] Donaldson JD Scale prevention and descaling Tube Int 1988:39–49 [3] Hasson D, Bramson D Effectiveness of magnetic water treatment in suppressing CaCO3 scale deposition Ind Eng Chem Process Des Dev 1985;24(3):588–92 [4] Ellingsen FT, Kristiansen H Does magnetic treatment influence precipitation of calcium carbonate from supersaturated solutions Vatten 1979;35:309–15 [5] Mirumyants SO, Vandyukov EA, Tukhvatullin RS The effect of a constant magnetic field of the infrared absorption spectrum of liquid water Russ J Phys Chem 1972;46:124 [6] Ivanova GM, Makhvev YM Change in the structure of water and aqueous solutions under the effect of a magnetic field Chem Abstr 1973;78:8107 [7] Bernardin JD, Chan SH Magnetic effects on simulated brine properties pertaining to magnetic water treatment Am Soc Mech Eng 1991;164:109–17 [8] Chou SF, Lin SC Magnetic effects on silica fouling Am Soc Mech Eng 1989;108:239–44 [9] Busch KW, Busch MA, Parker DH, Darling RE, McAtee Jr JL Studies of a water treatment device that uses magnetic fields Corrosion 1986;42(4):211–21 [10] Viswat E, Hermans LJF, Beenakker JJM Experiments on the influence of magnetic fields on the viscosity of water and a water-NaCl solution Phys Fluids 1982;25(10):1794–6 [11] Ozeki S, Wakai C, Ono S Is a magnetic effect on water adsorption possible? J Phys Chem 1991;95(26):10557–9 [12] Chemistry 130 laboratory Properties of ionic compounds http://capital2.capital.edu/faculty/wbecktel/ioniccmpds.htm; 2000 [accessed April, 2010] [13] Properties of DAQ card http://www.ni.com/; 2010 [accessed January, 2010] [14] Tipler PA, Mosca G Physics for scientists and engineers 6th ed W.H Freeman; 2007 [15] Othman F, Fauzia Z, Sohaili J, Niam FM An empirical model for desimentation of suspended solids under influence of magentic field In: Proceedings of the first international conference on national resources engineering and technology, July 24–25 Putrajaya, Malaysia; 2006 ... number of these authors have proposed mechanisms to explain the observed changes These have included changes in the water of hydration of the calcium ion, alteration of the molecular rotation of water. .. operating flow rates The plot constant value (a) and (b) (as y coordinate) to the flow rate (as x coordinate) as a linear trend followed the mathematical equation shown in Eq (7): yẳmxỵc ð7Þ Salt Removal. .. Discussion and conclusion The experimental work in determining the effect of operating flow rate allows us to conclude that flow rate in uences salt removal percentage The results reveal that the removal