Increasing Water Evaporation Rate by Magnetic Field - International ...

International Science and Investigation Journal

ISSN: 2251-8576

2013, 2(3)

Journal homepage: www.isijournal.info Received 28 July 2013; accepted 1 September 2013

Increasing Water Evaporation Rate by Magnetic Field Farhan Lafta Rashid1 , Nada Mohammed Hassan2 , Aqel Mashot Jafar3 and Ahmed Hashim4 Ministry of Science and Technology, Iraq-Baghdad 1 E-Mail: [email protected] 3 E-Mail: [email protected] 4 E-Mail:[email protected]

Abstract The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. In this paper, we present an investigation of water evaporation through magnetic field of 0.5 T, which was located at different location of tested water height (water-air interface, water mid height and bottom). An increase in evaporation time led to increase the evaporation rate, the preferred location of magnetic field is at the water-air interface which gave more evaporation rate (6% more than absence magnetic field) compared with other location, there is no effect was seen in the case of putting magnetic field at the bottom of water height. All results that obtained in the present work were compared with that obtained from equation (4). Keywords: evaporation enhancement, evaporation rate, magnetic field, Stefan Problem, diffusion. Introduction Since the middle of the last century, many studies have investigated the effect of a magnetic field on water, but the results of these studies were often contradictory. The issue was raised in the early 1950s when commercial “water conditioners” using permanent magnets were sold as a unit. It was said that such water conditioners could remove old scale and prevent new scale from forming in water pipes or water boilers if the water passed through a magnetic field created by the permanent magnet. However, a report in 1958 showed that water conditioners, or even a much stronger magnetic field, could not alter the scale-forming properties of water [1].


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A great number of papers on the effect of magnetic field on the physical and chemical properties of water [2–9]. Most of the arguments are actually related to the chemical substances in the water and not related to the properties of water itself. Other studies that have focused on the effect of a magnetic field on the physical and chemical properties of pure water have yielded inconsistent research results. For example, Toledo et al. [10] concluded that a magnetic field increases the surface tension. Nakagawa etal. [11] examined the effect of MF on water vapor-ization. They found that the MF enhances the water vaporization in air, but not in nitrogen.Furthe more, the magnitude of these effects depends on the field gradient product B dB/dx field, and the maxi-mum of the vaporization rate increment is asymmetric to the field axis. WU Song-hai et al.[12] found that The rate of the water evaporation increases as the intensities of magnetic induction increase. When the intensity of magnetic induction is constant, the water vaporization rate increases with the temperature. This paper presents an investigation of the evaporation of water in a small magnetic field located at different location on the tested water height. Theoretical Analysis Ficks' Law of Diffusion and Stefan Problem [13]: Consider a non-reacting gas mixture of species A and B. Ficks' Law describes the rate at which one species diffuses through other. For the case of one dimensional binary diffusion, Ficks' Law on a mass basis is:

m ."A  Y A ( m ."A  m ."B )  D AB

Where m ."A 

dYA dx

(1)

m .A is the mass flux of species A ( kg / m 2 .s ) A

YA is the mass fraction D AB is binary diffusivity ( m 2 / s ) Stefan assumes the following assumptions for equation (1): 1. Gas B is insoluble in liquid A ( mB." =0) 2. Steady state. 3. Liquid level is constant or interface regresses so slow, that its movement can be neglected.  dY m ."A  YA m ."A   D AB A dx

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

m ."A  Y A m ."A    D AB

dY A dx

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(2)

Rearrange equation (2) and integrate:

x



x0

YA

m."A

dx 



 D AB

m ."A, x

 ln



 D AB

1 dYA (1  YA ) YA ,i



(1  Y A ) (1  Y A,i )

(3)

m ." x Y A  1  (1  Y A,i ) exp(  A )  D AB

Boundary conditions: At x=L Y A  Y A , for equation (3): 

 D AB (1  Y A, ) m  ln L (1  Y A,i ) ." A

(4)

Equation (4) can be used to calculate the theoretical evaporation rate per unit area

Where m ."A is evaporation rate per unit area 

 is the average gas density in the container (Fig.(1)) and can be calculated from:





P 

( Ru / MW )T

P is the atmospheric pressure

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Ru is Universal Gas Constant

L is the interface depth from the top of container

T is Gas Temperature



MW  0.5( MWmix ,i  MWmix , )

Experimental Part Figure (1) shows the container (8 cm diameter, filled with water at depth of 3 cm from the top of the container) at which our experiments were take place, using magnetic field of 0.5 Tesla putted at different locations (interface , mid height and bottom) to increase water evaporation from the surface and take the measurements which involve time and net weight of the water in the container by using sensitive weight balance, in each measurement report the time from starting evaporation in order to divide the net weight on the time to give evaporation rate.

Figure (1) Diffusion of Vapor A through a Stagnant Column of Gas B, i.e., the Stefan Problem

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Results and Discussions Calculations of evaporation rate for the case of putting magnetic field of 0.5 Tesla at different locations of liquid A which compared with theoretical results obtained from equation (4), we can see from figure (2) ( putting magnetic field at the interface), at which we can see the relationship between evaporation rate and time , an increase in evaporation time led to an increase in evaporation rate, small increasing in evaporation rates were take place for using magnetic field if compared with the absence of magnetic field, because the magnetic field will increase the surface tension and lead to maximize the evaporation rate. Figure (3) shows the relationship between evaporation rate with time , one can observe that an increase in evaporation time will increase the evaporation rate, also very small increase in evaporation rate for the case of using magnetic field at mid height of liquid A if compared with absence of magnetic field. Figure (4) shows the relationship between evaporation rates with time, an increase in evaporation time will increase the evaporation rate, no change in evaporation rate for the case of using magnetic field at bottom of liquid A if compared with absence of magnetic field.

2.4E-04

E. R.Theo.(g/sec) E.R.Non Mag.

2.3E-04

Evaporation rate(g/sec)

E.R.with Mag.(g/sec)

2.2E-04 2.1E-04 2.0E-04 1.9E-04 1.8E-04 1.7E-04 1.6E-04 1.5E-04 0

1000

2000

3000

4000

5000

Time(sec)

Fig.(2) Water Evaporation Rate Versus Time for magnetic field at Interface

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E. R.Theo.(g/sec)

2.4E-04

E.R.Non Mag. E.R.with Mag.(g/sec)

Evaporation rate(g/sec)

2.3E-04 2.2E-04 2.1E-04 2.0E-04 1.9E-04 1.8E-04 1.7E-04 1.6E-04 1.5E-04 0

1000

2000

3000

4000

5000

Time(sec)

Fig.(3) Water Evaporation Rate Versus Time for magnetic field at Mid Height of Liquid A

E. R.Theo.(g/sec)

2.4E-04

E.R.Non Mag.

Evaparation rate(g/sec)

2.3E-04

E.R.with Mag.(g/sec)

2.2E-04 2.1E-04 2.0E-04 1.9E-04 1.8E-04 1.7E-04 1.6E-04 1.5E-04 0

1000

2000

3000

4000

5000

Time(sec)

Fig.(4) Water Evaporation Rate Versus Time for magnetic field at Bottom of Liquid A

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Conclusions From the present work, we can report the following conclusions: 1. An increase in evaporation time will increase in water evaporation rate. 2. No change in evaporation rate for the case of using magnetic field at bottom of liquid A if compared with the case of non-magnetic field. 3. The perfect location of magnetic field is at the interface which increases the surface tension and the evaporation rate.

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11. A. Szcze´ et al. (2010), Effects of static magnetic field on water at kinetic condition, journal homepage: www.elsevier.com/locate/cep. 12. WU Song-hai et al.(2006), Effects of Magnetic Field on Evaporation of Distilled Water, Journal of Petrochemical Universities, 2006-1.

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