Printer Friendly

Experimental investigation and performance analysis of thermosyphon solar water heater.

Introduction

The utilization of solar energy is important in a developing nation like Nigeria where electrical energy is expensive and energy production is too low to meet requirements. According to Agbo and Oparaku (2006), the need for domestic hot water in the country is currently met through the use of electricity, kerosene and wood as the major energy sources. At the moment, most homes in urban areas use electric ring boiler for the purpose of water heating, and some others depend on kerosene and wood, as stated by Agbo and Unachukwu, (2007).

The supply of electricity in Nigeria is very unpredictable due to the inherent problems in the systems such as irregular supply of natural gas (Agbo and Oparaku, 2006; Agbo and Okeke, 2007; Bello et al, 2010), the fluctuation of water levels in hydro-power sites, obsolete equipment and human sabotage in electric utility network. There are also environmental implications as a result of deforestation through the depletion of available fuel-wood in the country (Agbo and Oparaku, 2006).

In Awka, the problem of electricity supply is not different. Therefore it has become necessary to explore other means of meeting the need of hot water for households, hospitals, schools and industries in this locality especially during the harmattan and peak rainy seasons, through a simple and cheap system (thermosyphon solar water heater) that will run on a free and natural resource, the sun.

Solar energy can be used in three processes: (a). Thermal:--this is the system in which the incident radiation is absorbed and turned into heat. (b). Chemical:--this is the system in which the radiation between 0.3[micro]m and 1.0[micro]m can cause chemical reactions, sustain growth of plants and animals and through photosynthesis convert exhaled carbon dioxide to breakable oxygen. (c). Electrical:--here part of the radiation in the band between 0.33[micro]m and 1.2[micro]m can be converted directly into electricity by photovoltaic cells (Folaranmi, 2009; Nwokoye, 2006).

A solar water heater (SWH) is an environmentally friendly device which absorbs free and renewable solar energy to produce hot water, economically, reducing the use of conventional energy such as electricity by up to 80%. The solar hot water system produces hot water of 50oC to 70oC depending upon the season, location, solar intensity and number of solar collector panels. Solar heating systems are generally composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage, and a reservoir to store the heat for subsequent use. These systems have a wide range of applications from domestic use to commercial applications at hotels, resorts, lodges, community centers, hospitals and even for process heat applications such as paper, dyeing and laundry industries (Agbo, 2006; Agbo et al, 2005).

Many different designs of solar water heating systems are possible and they are classified as either passive or active and direct or indirect (Kreider and Kreith, 1981; Agbo, 2006; Ogueke et al, 2009). Passive systems rely on natural convection to circulate the water through the collectors. Thermosyphon systems are passive systems. Active systems use electrically driven pumps and valves to control the circulation of the heat absorbing liquid. This allows greater flexibility than their passive counterparts since the hot water storage tank does not have to be above or near the collectors. Also, active systems are designed to operate year round without any danger of freezing. The drain-down, pressurized glycol, and drain-back are active systems.

In indirect or closed-loop systems, the heat transfer fluid is treated water, a refrigerant, or a non-freezing liquid such as an anti-freeze solution, hydrocarbon oil, or silicone. The heat it draws from the absorber plate is transferred to the portable water through a heat exchanger such as a coil either inside or wrapped around the storage tank. (Kreider and Kreith, 1981; Kreider and Kreith, 1982).

The thermosyphonic solar water heating systems have been the subject of a large number of investigations. Shitzer et al (1979) carried out a detailed study on a typical commercial solar water heating system in thermosyphonic flow, manufactured in Israel. The system used for this experiment consisted of two flat plate collectors painted matt black connected in parallel and a 140l storage tank. Each collector employed eight evenly spaced parallel pipes embossed by semi-circular grooves formed in the flat plate. This work provided the much needed detailed information on system behavior.

Bolaji (2006) worked on the flow design and collector performance of a natural circulation (thermosyphon) solar water heater at Ado-Ekiti, Nigeria. His results show that the system performance depends very much on both the flow rate through the collector and the incident solar radiation. Again he observed that the water temperature in the system is a function of solar radiation and the ambient air. He established that the collector efficiency increases as the flow rate and the incident solar radiation increases.

Kalogirou (2004) reported on the performance and environmental life cycle analysis of thermosyphon solar water heaters. He presented a description of the constructional and thermal characteristics of thermosyphon units followed by a study on the performance characteristics and environmental protection offered by the systems. According to his report, a thermosyphon system suitable for Mali consists of one flat-plate collector panel 1.35[m.sup.2] in aperture area and a 150L hot water cylinder. The thermosyphon system was modeled with TRNSYS and simulated with the weather conditions of Bamako, Mali.

Chuawittayawuth and Kumar (2002) carried out experimental investigation of temperature and flow distribution in a thermosyphon solar water heating system. The results obtained were compared with the theoretical models. The measured profile of the absorber temperature near the riser tubes (near the bottom and top headers) conforms well to the theoretical models. The result shows that the temperature of water in the riser depends on its flow rate.

Karaghouli and Alnaser (2001) analyzed the thermal performance of the thermosyphon water heater unit using data of several sunny, cloudy and hazy days in winter in Bahrain. The performance of this unit was studied under various maximum daily solar intensities and the results obtained show that the system has an average efficiency of 38% with storage tank temperature above 50[degrees]C.

Materials And Methods

A natural circulation pressure type (thermosyphon) solar water heater was designed and instrumented for the experiments. It is made up of a single flat plate collector, a storage tank and connecting pipes. The collector plate (absorber plate), which is painted matt black is made of galvanized steel and has a total aperture area of 1.55[m.sup.2]. Eight evenly spaced parallel, 1.25cm, galvanized pipes (water flow tubes) were welded to the collector surface. These flow tubes were linked together through the supply and drain headers (1.88cm pipes). Thermometer sockets were installed on the collector plate, supply and drain headers to provide points for measuring collector plate-, water inlet- and outlet temperatures respectively. The wind speed was obtained from the Nigerian Meteorological Agency Awka.

The storage tank was cylindrical in shape with a storage capacity of 70.8 litres. It was made from a 5mm galvanized steel plate. A cylindrical metal casing of the same material houses the storage tank with a lagging material in-between. This was to reduce or prevent heat loss to the surrounding. A pressure release valve was installed at the top of the tank to prevent excessive pressure build up in the tank. The storage tank was placed on a metal stand having a height of about 2m from the ground surface. Connecting pipes (1.88cm pipes) supply water to the tank and collector inlet and also drain water from the collector. Thermometer sockets were provided at the upper and lower parts of the tank for temperature measurement. A 'Multi-vane Wheel Liquid Sealed Water Meter' (LXSY-15) (ISO4064B compliant) was connected between the collector inlet and the water supply pipe from the tank to measure the water flow rate in [m.sup.3]/hr.

The collector assembly was placed in a north-south direction and inclined at an angle of 16.12[degrees] to the horizontal with the top of the collector having a distance of more than 30cm below the bottom of the storage tank. A Taylor Hygrometer was used to measure the relative humidity while a Mercury-in-glass thermometer with a precision of 0.5[degrees]C was used for temperature measurement. A Solarimeter (Daystar meter, DS-05A) was used for measuring the incident solar radiation in W/[m.sup.2].

[FIGURE 1 OMITTED]

The Working Principle Of The Experimental Setup:

Fig. 1 is the experimental set-up. When solar radiation from the sun is absorbed by the blackened absorber plate, it is converted to heat. The heat is transferred to the flow tubes by conduction. The water in the flow tubes is in turn heated by convection process between the tubes and the water molecules. The heated water becomes warmer and less dense than the water in the storage tank. This density difference results in buoyancy force, often referred to as the thermosyphon head (Agbo and Unachukwu, 2007), which creates a continuous convective circulation of water from the bottom of the tank to the bottom of the collector, up through the collector flow tubes, and back into the top of tank. This process continues until the period when the plate temperature attains the highest value. The steady circulation of water in the collector loop results in the rise of water temperature in the tank. Mixing between the water at upper and lower parts of the tank, results in a uniform water temperature in the tank at sunset. At sunset the water supply line is locked to stop water circulation in the loop. This is to prevent further fall in temperature of the water in the tank since the absorber plate temperature is now the same as the ambient temperature and will increase heat loss if circulation is not discontinued at such period.

Results And Discussion

The experimental investigation of the performance of a thermosyphon solar water heater was performed at the Nnamdi Azikiwe University Awka. Measurements of the incident solar energy and other system parameters were carried out at intervals of one hour between 0600 hours and 1800 hours each day.

Tables 1-6 show the daily Average values of solar radiation, mass flow rate, relative humidity and wind speed for the month of November 2009 to April 2010. Figs. 2-7 show the variation of the daily average mass flow rate with number of days for November 2009 to April 2010.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Figures 2-7 show the variation of the daily average mass flow rate with number of days for November 2009 to April 2010. The results show that in the month of November 2009, the maximum daily average value of 0.178kg/s[m.sup.2] was obtained on day 8 when the daily average solar radiation was highest. The minimum value of 0.057kg/s[m.sup.2] was recorded on day 7 when the daily average solar radiation is lowest. These results show that the water flow rate and hence the performance of the system depend on the level of solar radiation. This agrees with the result of a similar work by Bolaji (2006). Similarly, the wind speed has a maximum daily average of 1.10m/s on day 29 and a minimum value of 0.33m/s on day 5. The daily average values of the mass flow rate on day 29 and day 5 were 0.064kg/s[m.sup.2] and 0.170kg/s[m.sup.2] respectively. These results again show that the wind speed contributed to the thermal losses of the flat-plate collector. Increased wind speed resulted in lower heat gain, hence lower mass flow rate. On the other hand, reduced wind speed gave rise to higher system heat gain and higher mass flow rate. This result is in agreement with a similar work by Agbo and Okoroigwe, (2007).

In the month of December, the mass flow rate obtained a maximum daily average value of 0.211kJ/s[m.sup.2] on day 15 while a minimum value of 0.170kg/s[m.sup.2] was recorded on day 25. These results were obtained on the days in which the daily average solar radiation was also maximum minimum respectively. This also shows the dependence of water flow rate on solar radiation. The wind speed recorded maximum and minimum daily average values of 0.96m/s and 0.51m/s on day 29 and 13 respectively. On these days the mass flow rates were 0.174kg/s[m.sup.2] and 0.175kJ/[m.sup.2] respectively. These results again agree with the fact that wind speed affects the heat gain of a flat-plate collector.

In January 2010, the maximum daily average of 68.23%, 0.175kg/s[m.sup.2] and 1.52m/s were recorded for the relative humidity, mass flow rate and wind speed on day 14, 18 and 28 respectively. A minimum daily average of 11.23% and 0.51m/s on day 18 and day 8 for the relative humidity and wind speed respectively. These results show that the mass flow rate obtained was a function of solar radiation and relative humidity. The less humid the ambient air becomes, the higher the heat gained by the system hence higher water flow rate

In February 2010, relative humidity, mass flow rate and wind speed recorded maximum values of 82.15%, 0.180kg/s[m.sup.2] and 1.53m/s respectively on day 12, 14 and day 6. Relative humidity and wind speed recorded minimum values of 29.31% and 0.05m/s respectively on day 14 while the mass flow rate recorded minimum value of 0.165kg/s[m.sup.2] on day 12. These results again show that the mass flow rate obtained depends on the level of solar radiation received by the collector, relative humidity and wind speed. The maximum value of relative humidity obtained on day 12 is due to low solar radiation on that day which is attributable to cloud cover, dust haze and the aerosol particles in the air which attenuate the solar radiation by way of shading, reflection and scattering among others.

In March 2010, the maximum daily average of the measured solar radiation was recorded on day 2 while its minimum value was recorded on day 14. The relative humidity obtained a maximum daily average of 78.92% on day 13 and day 23 while the minimum value of 41.23% was obtained on day 7. The mass flow rate and wind speed obtained maximum values of 0.194kg/s[m.sup.2] and 1.46m/s respectively on day 2 and day 13 while their minimum values of 0.01kg/s[m.sup.2] and 0.15m/s were recorded on day 14 and day 2 respectively. These results again show the dependence of mass flow rate on solar radiation and wind speed.

In April 2010, similar trends were repeated though with a higher wind speed which is characteristic of the beginning of rainy season. The maximum daily average solar radiation was measured on day 15 while the minimum value was obtained on day 23. The maximum and minimum daily averages of 87.31 % and 45.92% for the relative humidity were recorded on day 18 and day 21 respectively. The wind speed attained a maximum daily average of 2.02 m/s on day 9. Its minimum of 0.43m/s was recorded on day 26 and day 28 simultaneously. The mass flow rate recorded a maximum value of 0.180kg/s[m.sup.2] on day 15 and day 20 simultaneously. Its minimum value of 0.03kg/s[m.sup.2] was recorded on day 23 when the measured solar radiation was lowest. These results show that the mass flow rate depends on the level of solar radiation as well as the wind speed.

Conclusion And Recommendation:

This research has shown that thermosyphon solar water heater performed creditably in Awka and it is positioned to meet the hot water need in this locality if adopted. The results have revealed that the performance of the solar water heater depends very much on the level of solar radiation, mass flow rate through the collector, relative humidity as well as the wind speed.

References

Agbo, S.N., G.O. Unachukwu, S.O. Enibe and C.E. Okeke, 2005. Solar Water Heating for resident University Students, Nig. J. Solar Energy, 15: 85-92.

Agbo, S.N., 2006. Effect of Hot Water Withdrawal Rate on the Mean System Temperature of a Thermosyphon Solar Water Heater; The Pacific Journal of Science and Technology, 7(2): 199-203

Agbo, S.N. and O.U. Oparaku, 2006. Positive and Future Prospects of Solar Water Heating in Nigeria, The pacific J. Science and Technology, 7(2): 191-195.

Agbo, S.N. and C.E. Okeke, 2007. Correlation Between Collector Performance and tube Spacing for Various Absorber Plate Materials in a Natural Circulation Solar Water Heater. Trends in Applied Science Research, 2(3): 251-254.

Agbo, S.N. and E.C. Okoroigwe, 2007. Analysis of Thermal Losses in the Flat-Plate Collector of a Thermosyphon Solar Water Heater, Research J. Physics, 1(1): 35-41.

Agbo, S.N. and G.O. Unachukwu, 2007. Design and Performance Features of a Domestic Thermosyphon Solar Water Heater for an Average-Sized Family in Nsukka Urban. Trends in Applied Science Research, 2(3): 224-230.

Bello, A.M.A., V. Makinde and H.T. Sulu, 2010. Performance Tests and Thermal Efficiency Evaluation of a Constructed Solar Box Cooker at a Guinea Savannah Station (Ilorin, Nigeria), J. American Science, 6(2): 32.

Bolaji, B.O., 2006. Flow Design and Collector Performance of a Natural Circulation Solar Water heater, J. Engineering and Applied Sciences, 1(1): 7-13.

Folaranmi, J., 2009.'Design, Construction and Testing of a Parabolic Solar Steam Generator', Leonardo Electronic Journal of Practices and Technologies, 14, pp.115-133 [online]. Available at: http://lejpt.academicdirect.org/A14/115_133.pdf (Accessed 27 August 2010)

Kalogirou, S., 2004. Performance and Environmental Life Cycle Analysis of thermosyphon Solar Water heaters, http://openarchives.gr/visit/412512 (Retrieved 18/03/2010)

Karaghouli, A.A. and W.E. Alnaser, 2001. Experimental study on thermosiphon solar water heater in Bahrain; Renewable Energy, 24(3-4): 389-396.

Kreidar, J.F. and F. Kreith, 1981. Solar Energy Handbook, McGraw-Hill Book Company, New York, pp 11-1 to 11-4, 13-4 to 13-5.

Kreidar, J.F. and F. Kreith, 1982. Solar heating and cooling, active and passive design, Second Edition, Hemisphere Publishing Corporation, Washington DC 127-138.

Nwokoye, A.O.C., 2006. Solar Energy Technology: Other Alternative Energy Resources and Environmental Science, Rex Charles and Patrick Limited, Nimo, 426pp.

Ogueke, N.V., E.E. Anyanwu and O.V. Ekechukwu, 2009. A review of solar water heating systems, J. Renewable Sustainable Energy, 1, 043106, 21.

Shitzer A., D. Kalmanoviz Y. Zvirin and G. Grossman, 1979. Experiments with a flat plate solar water heating system in thermosiphonic flow, Solar Energy, 22(1): 27-35.

(1) G.N. Okonkwo and (2) A.O.C. Nwokoye

(1) Department of Science Laboratory Technology, Federal Polytechnic, Bida

(2) Department of Physics and Industrial Physics, Nnamdi Azikiwe University, Awka

Corresponding Author: G.N. Okonkwo, Department of Science Laboratory Technology, Federal Polytechnic, Bida

E-mail: godfreyok1@yahoo.com
Table 1: Daily Average solar radiation, mass flow
rate, wind speed and various daily average
temperatures for November 2009

Day    Solar rad.      Water flow rate   Wind speed
       (W/[m.sup.2])   (Kg/[sm.sup.2])   (m/s)

1      375.23          0.062             0.47
2      385.24          0.108             0.36
3      414.68          0.171             0.56
4      401.38          0.170             0.34
5      404.21          0.170             0.33
6      390.11          0.154             0.51
7      356.26          0.057             0.61
8      416.56          0.178             0.70
9      363.65          0.058             0.55
10     386.34          0.111             0.71
11     392.22          0.157             0.76
12     389.96          0.147             0.71
13     395.35          0.163             0.66
14     378.89          0.065             0.61
15     376.19          0.063             0.56
16     368.86          0.060             0.50
17     371.20          0.061             0.78
18     369.97          0.060             0.87
19     382.31          0.098             0.85
20     387.44          0.121             0.67
21     393.64          0.161             0.94
22     388.87          0.143             0.59
23     384.49          0.106             0.47
24     380.77          0.088             0.67
25     375.82          0.062             0.86
26     391.21          0.157             0.54
27     385.01          0.107             0.45
28     379.64          0.071             1.07
29     376.87          0.064             1.10
30     366.58          0.060             0.89

Table 2: Daily Average solar radiation, mass flow
rate, wind speed and various daily average
temperatures for December 2009

Day     Solar rad.      Mass flow rate    Wind speed
        (W/[m.sup.2])   (Kg/[sm.sup.2])   (m/s)

1       539.23          0.202             0.78
2       562.38          0.209             0.76
3       409.00          0.176             0.80
4       518.38          0.196             0.78
5       486.38          0.189             0.60
6       546.62          0.203             0.66
7       518.31          0.196             0.76
8       385.46          0.174             0.66
9       451.54          0.179             0.55
10      483.92          0.188             0.65
11      479.31          0.185             0.55
12      575.31          0.199             0.62
13      525.23          0.175             0.51
14      554.46          0.206             0.66
15      588.69          0.211             0.65
16      482.62          0.187             0.66
17      437.85          0.176             0.67
18      389.15          0.174             0.83
19      428.69          0.176             0.85
20      403.69          0.175             0.62
21      369.31          0.172             0.63
22      462.38          0.183             0.62
23      428.31          0.176             0.66
24      403.69          0.175             0.69
25      348.92          0.170             0.83
26      457.92          0.182             0.70
27      375.85          0.173             0.70
28      416.88          0.176             0.69
29      396.37          0.174             0.96
30      406.63          0.175             0.81
31      401.50          0.175             0.64

Table 3: Daily Average solar radiation, mass flow rate, wind speed
and various daily average temperatures for January 2010

Day   Solar rad.      Relative       Mass flow rate    Wind speed
      (W/[m.sup.2])   Humidity (%)   (Kg/[sm.sup.2])   (m/s)

1     419.00          49.22          0.173             0.78
2     427.38          40.62          0.174             0.70
3     389.54          54.00          0.170             0.93
4     362.23          57.38          0.170             0.69
5     334.62          60.81          0.160             0.66
6     337.54          59.85          0.160             0.76
7     356.31          59.00          0.168             0.69
8     413.08          49.85          0.173             0.51
9     436.77          32.15          0.174             0.65
10    322.00          61.28          0.164             0.88
11    372.92          57.04          0.170             1.12
12    311.54          62.62          0.164             1.12
13    358.62          58.31          0.170             0.95
14    263.54          68.23          0.161             0.78
15    399.46          51.54          0.173             0.80
16    354.08          59.09          0.165             0.68
17    419.85          45.78          0.173             0.80
18    478.31          11.23          0.175             1.23
19    379.08          55.24          0.171             0.96
20    458.31          19.15          0.174             0.88
21    345.15          59.69          0.165             1.09
22    316.85          62.08          0.164             0.62
23    358.77          57.64          0.171             0.81
24    351.46          59.66          0.166             0.81
25    304.08          64.23          0.162             0.83
26    303.85          64.69          0.162             1.01
27    400.85          50.18          0.173             1.31
28    463.11          15.38          0.174             1.52
29    384.16          54.35          0.172             0.78
30    390.36          53.45          0.172             1.01
31    310.56          62.69          0.163             0.97

Table 4: Daily Average solar radiation, mass flow rate, wind speed
and various daily average temperatures for February 2010

Day    Solar rad.      Relative       Mass flow rate    Wind speed
       (W/[m.sup.2])   Humidity (%)   (Kg/[sm.sup.2])   (m/s)

1      267.77          67.54          0.167             1.22
2      301.85          64.69          0.170             1.37
3      398.38          63.38          0.171             1.27
4      359.77          63.46          0.171             1.02
5      475.38          41.36          0.173             1.14
6      405.77          61.92          0.171             1.53
7      482.31          38.48          0.174             1.32
8      296.54          66.54          0.170             0.97
9      323.23          64.46          0.171             0.69
10     243.85          70.00          0.166             1.02
11     492.62          37.67          0.175             1.01
12     59.69           82.15          0.165             1.28
13     515.46          36.44          0.176             0.35
14     564.00          29.31          0.180             0.05
15     418.46          61.15          0.172             0.29
16     459.31          48.23          0.173             0.48
17     482.23          38.68          0.174             0.85
18     461.85          47.31          0.173             1.20
19     416.00          61.31          0.172             1.18
20     549.92          30.56          0.177             1.05
21     346.69          63.92          0.171             1.11
22     430.85          57.98          0.172             1.18
23     447.62          50.77          0.173             1.32
24     442.92          57.78          0.172             1.22
25     445.27          55.08          0.173             0.95
26     446.44          52.15          0.173             1.18
27     444.68          55.62          0.172             1.05
28     445.56          54.24          0.173             0.91

Table 5: Daily Average solar radiation, mass flow rate, wind speed
and various daily average temperatures for March 2010

Day   Solar rad.      Relative       Mass flow rate    Wind speed
      (W/[m.sup.2])   Humidity (%)   (Kg/[sm.sup.2])   (m/s)

1     530.46          63.69          0.188             0.83
2     537.54          65.08          0.194             0.15
3     461.38          64.00          0.172             0.89
4     485.54          47.54          0.171             0.91
5     497.31          50.85          0.175             0.97
6     516.77          49.15          0.183             1.08
7     445.77          41.23          0.170             1.33
8     394.31          55.77          0.132             1.25
9     487.00          59.38          0.173             1.36
10    135.54          69.46          0.020             1.06
11    349.31          72.08          0.173             0.92
12    425.77          66.38          0.162             1.36
13    234.00          78.92          0.104             1.46
14    116.15          63.62          0.010             1.15
15    455.77          75.00          0.165             1.18
16    442.08          75.69          0.168             0.53
17    407.08          71.85          0.160             0.97
18    204.54          60.00          0.081             0.80
19    277.92          58.38          0.173             0.71
20    287.00          61.08          0.106             0.95
21    319.23          69.00          0.124             1.04
22    267.15          76.15          0.103             1.13
23    424.00          78.92          0.169             0.72
24    369.46          69.15          0.151             1.07
25    465.00          56.23          0.172             0.87
26    410.31          51.15          0.142             0.98
27    432.15          50.54          0.161             1.15
28    421.23          51.00          0.158             0.97
29    443.12          60.00          0.163             1.04
30    406.06          62.00          0.157             1.16
31    415.03          58.00          0.161             1.33

Table 6: Daily Average solar radiation, mass flow rate, wind speed
and various daily average temperatures for April 2010

Day    Solar rad.      Relative       Mass flow rate    Wind speed
       (W/[m.sup.2])   Humidity (%)   (Kg/[sm.sup.2])   (m/s)

1      398.62          63.38          0.100             1.31
2      387.77          53.85          0.090             1.49
3      404.77          55.08          0.100             1.66
4      377.77          55.92          0.090             1.44
5      524.54          56.46          0.170             1.60
6      342.62          58.08          0.080             1.54
7      488.46          57.15          0.140             0.72
8      436.92          60.00          0.120             1.14
9      428.08          61.08          0.110             2.02
10     368.08          66.38          0.080             0.88
11     524.92          67.31          0.170             1.05
12     395.92          62.85          0.090             1.45
13     298.69          59.23          0.050             1.00
14     457.23          47.00          0.130             1.11
15     613.46          65.23          0.180             1.27
16     424.54          73.15          0.110             1.32
17     308.23          66.69          0.060             0.78
18     446.69          87.31          0.120             1.00
19     515.15          69.54          0.170             1.44
20     537.69          71.38          0.180             1.04
21     280.31          45.92          0.040             0.98
22     450.46          65.00          0.130             0.93
23     150.46          68.00          0.030             0.81
24     397.54          70.00          0.100             0.63
25     474.77          81.00          0.140             0.60
26     340.33          57.00          0.070             0.43
27     313.33          63.00          0.070             1.10
28     285.36          66.00          0.050             0.43
29     300.00          59.00          0.060             0.49
30     405.23          64.00          0.110             0.69
COPYRIGHT 2012 American-Eurasian Network for Scientific Information
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2012 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Original Article
Author:Okonkwo, G.N.; Nwokoye, A.O.C.
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Geographic Code:6NIGR
Date:Mar 1, 2012
Words:4970
Previous Article:Alkaloid fraction of jarong (Achyranthes aspera Linn) leaf induced apoptosis breast cancer cell through p53 pathways.
Next Article:Automatic mapping of lineaments using shaded relief images derived from digital elevation model (DEM) in Erbil-Kurdistan, northeast Iraq.
Topics:

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters