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Asian Journal of Applied Science and Engineering, Volume 3, No 1 (2014) ISSN 2305-915X

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ASIAN JOURNAL OF APPLIED SCIENCE AND ENGINEERING

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Editor-in-chief

Dr. Asma Ahmad Shariff Center for Foundation Studies in Science, University of Malaya, Malaysia

Managing Editor

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King Saud University, Saudi Arabia (Plant Production)

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ASA University Bamgladesh, Bangladesh (Statistics)

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Quaid-e-Azam University, Pakistan (Health Systems & Policy)

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Dr. Halenar Igor

Slovak University of Technology in Bratislava, Slovakia (Architecture)

Dr. Mohammad Hadi Dehghani

Tehran University of Medical Sciences, Iran (Environmental Toxicology & Nanotechnology)

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University of Oklahoma, USA (Medical Physics)

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Varendra University, Bangladesh (Theoretical Physics)

Dr. Lutfar Rahman

Rajshahi University Bangladesh (Mathematics)

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Bahir Dar University, Ethiopia (Electrical Engineering)

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University of Guilan, Iran (Stochastic Processes)

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University of Roorkee, India (Computer Programing)

Dr Sudhir K Samantaray

Panjab University, India (Psychology)

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Dr. Md. Fazlul Babi

University Sains Malaysia (USM), Malaysia (Material Science)

Dr. Mohammad Ali Shariati

Isfahan University of Technology, Iran (Food Science and Technology)

Dr. Nguyen Thanh Hao

Industrial University of HoChiMinh City, HoChiMinh, Vietnam (Heat and Refrigeration)

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Asian Journal of Applied Science and Engineering

Blind Peer-Reviewed Journal

Volume 3, Number 1/2014 (Fifth Issue)

Contents

1. Mud in Urban Context: A Study on Rammed Earth as Building Material in Dhaka City

09-19

Syma Haque Trisha & Mahbuba Afroz Jinia

2. Investigation of the Efficiency of Vibro-Isolating Supports of Optical Tables

20-25

Vladas Vekteris Artras Kilikeviius

Vadim Mokin &

Andrius Gedvila

3. A 12-Element Chemical Reactor Network for Carbon Oxide Emission Prediction in Gas Turbine Combustor

26-34

Nguyen Thanh Hao

4. Effects of Nitrogen Application on Growth and Yield of Snowpeas (Pisum sativum)

35-43

Njoroge, P.K. Shibairo, S.I.

Githiri, S.M. &

M.W.K. Mburu

5. Evaluation of the Correlation between Selected Quality Indices of Activated Carbon: A Review

44-52

Benjamin Edem Meteku

6. Customer Satisfaction of Internet Banking in Bangladesh: A Case Study on Citibank N.A

53-64

K. M. Anwarul Islam & Umme Salma

Call for Papers - Volume 3, Number 2/2014 (Sixth Issue) 65-68

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Mud in Urban Context: A Study on Rammed

Earth as Building Material in Dhaka City

Syma Haque Trisha1 & Mahbuba Afroz Jinia2 1Lecturer, Department of Architecture, Stamford University, Bangladesh

2Senior Lecturer, Department of Architecture, Stamford University, Bangladesh

ABSTRACT

Traditional mud houses are integral part of Bangladeshi culture from the ancient period. But with the course of time urbanization, industrialization & technology have achieved an infinite development & people began to forget their origin -mud or earth. At present that time has come to rethink the existence-relationship with earth. Architects have started realizing the destructive effects of different building materials like concrete, C.I. sheet,

mud is being used in urb an areas even in capital Dhaka not only by poor

sometimes in the form of fusion as rammed earth construction, sometimes as interior cladding or plastering material & sometimes for resear ch. Sometimes mud is being used realizing it as an eco friendly material & sometimes it is being used only for aesthetical purpose. But for benefit & sustainability, every building material should be chosen after understanding its environmental & economic issues which can enhance a new horizon in construction arena being a true friend of nature & culture & create a revolution. This paper reviews and argues the environmental (temperature, relative humidity, carbon -di -oxide emission, other climatic effects) & economic benefits (manufacturing & maintenance cost) of using rammed earth as a building material for urban construction in Bangladesh in context of Dhaka. A critical literature review & field survey using experimental & qualitative approach was adopted i n this paper to investigate whether rammed earth construction & mud plastering is feasible in Dhaka compared to the conventional brick construction. Key words: climatic -effects, cost, feasibility, rammed earth, urban.

INTRODUCTION

pproximately h alf of people of the world live in earthen house because its availability and permanent solution in cheaper cost. The construction technique of earthen house is derived by the craftsmen by themselves so it is simple to build for the users. In

Bangladesh still most of the people live in earthen house. Earth structures are found almost every area in our country with different construction technique and style, for example the Rajshahi region double storied mud house are found but at Jessore region singe storied mud

A



house are mostly found. The planning of these houses are also different from each other. In some region house made with mud cube mixed with rice husk another part of the country wall construct with direct layer of clay. These entire houses are climate responsive and mostly acceptable to the society. Regarding the traditional mud construction lots of study has done. Rammed earth is an ancient or traditional construction technique used in many countries of the world. The most common technique of the ram med earth construction is pouring and ramming Soil within the form work which is similar to modern concrete. At present rammed earth construction & mud plastering is being used in Dhaka for research works, low cost construction, residential & recreational purposes both for construction & interior design breaking the tradition of conventional brick buildings. The objective of this paper is to find out

using critical li terature review & field survey with experimental & qualitative approach.

RELATED LITERATURE

Rammed earth is a method of building walls whereby a mixture of earth is compacted in layers between forms. Each layer of earth is approximately 15 cm deep. As each form is filled, another form is placed above it, and the process begins again. This is continued until the desired wall height is achieved (HBRI report, 2009). Forms can be stripped off as soon as the form above is begun, as the compressed earth wall is self-supporting immediately. The clay and moisture content of rammed earth is relatively low compared to that used for mud brick or other earth building methods .A wider range of soils are suitable when a small amount of cement is added to the mix. The result, known as stabilized rammed earth, is a strong masonry product which provides excellent thermal mass. Ordinary mud constriction is popular in Bangladesh but the there is no significant rammed earth structure in this country . According to Climate Classi fication, Bangladesh may be placed in a zone called Composite

tropics of Cancer and Capricorn, which are sufficiently far from the equator to experience marked seasonal variations in solar radiation and wind direction (Atkinson, 1953) .These climates are normally said to have two distinct seasons, a hot-dry and a warm -humid season, and often a third, best described as cool-dry. In different seasons average air temperature, comfort range. In Dhaka carbon-di -oxide emission level & energy consumption is also very high. Stabilized earth construction is environmentally sustainable compare to conventional (fr ied brick, concrete, etc.) building materials & would be appropriate in the case of urban building construction in Bangladesh .Promotion & implementation of earth as an alternative urban construction material is worthwhile & significantly helpful in achiev ing environmental sustainability ( Zami & Lee, 2009). Earth buildings have inspired many who are searching for ways of living that are in harmony with the environment & enable what

(Dayaratne, 2003).In Dhaka Building material is available but expensive in comparison with living cost. Therefore, rammed earth may work as a sustainable building material for Dhaka. However, replacing traditional buildings with modern ones does not necessarily lead to progress. While recognition of the building traditions is necessary it should be consistent with improvement techniques that address problems. In that way it will be possible to build & preserve a culturally suitable, regional, rural earth architecture which will be contemp orary & durable as well (Ahmed, I.1994). To explore and transform the rammed earth construction technique in urban areas it is important to find out its feasibility & sustainability not only in environmental & economic context or as a fusion of traditional mud structure but in a holistic manner.



METHODOLOGY

Fig. 1 shows conceptual framework & Fig. 2 shows methodology of the study. Step 1: Soil map analysis: Soil map is studied to know the soil quality of which areas of Dhaka is suitable for rammed earth construction. Clay soil with plastic quality is the most suitable for the rammed earth construction. Step 2: Sampling: Among the suitable areas two buildings are chosen in Housing & building research institute (HBRI),Dhaka in Darus salaam road which have c oncrete plain roof , plinth , almost similar surroundings , orientation & architectural features like opening, shading, interior -exterior relationship but have facades of different material of rammed earth & exposed brick. For interior mud plastering anoth er building is chosen in Dhanmondi at Dhaka Art Center named Caf Ajo. Step 3: Instrumental survey: For physical dimensions an instrumental survey is carried out to know length, breadth (thickness) and height of each faade with opening areas using measuring tape. Step 4: instrumental survey with treatment-experimental approach: Indoor -outdoor air temperature & relative humidity level is measured with thermo hygro meter(air temperature & relative humidity measuring device) using treatment keeping the openi ngs close & open & convenient time sampling at noon & evening period in two days & measured at 1m high from ground floor level almost at the middle of the room. Table 1 shows instrument specification. Step 5: market survey & literature review: Market surve y & literature review is done to know energy consumption, carbon di oxide emission & manufacturing, maintenance cost. Step 6: observation & questionnaire survey-open ended: Observation & open ended questionnaire survey is done to find out other advantage, disadvantage & climatic effects.

Brand name KTJ-max-m in thermo hygro clock

Model no. TA218B

Origin China

Table 1: instrument specification

Fig. 1: conceptual framework of the study



Fig. 2: methodology of the study

ANALYSIS Soil quality Fig.3 shows in Dhaka earthen construction is only 15 to 20 percent. The red clay soil found in Pubail, Uttara,Mirpur, Azimpur area is suitable for earthen construction most of the areas have become urbanized the new growing areas where yellow, grey & red mud found is suitable for rammed earth construction. Fig. 3: earthen construction in Bangladesh



PHYSICAL FEATURES

Building location, orientation & outdoor features (surroundings) Proper build ing orientation is one of the features rightly emphasized from the early stages of design. The most coveted orientation for Dhaka, .i.e. north-south, is impossible for a given site, because of the site's geometry and orientation. Fig. 10 shows both the building are a little inclined with north -south orientation with dense green areas & water body, on the west & meadow on the north east corner as site force.



Indoor features

Both the building has no occupancy during survey with earthen furniture in rammed earth building & conventional wooden furniture in brick building. Fig. 12 shows some earthen furniture at HBRI.

Material Fig. 11 & 13(b) shows rammed earth wall is layered (500 mm to 700mm) in which red soil gravel & brick chips can be seen. Fig. 13(a) shows the conventional building is built with first class exposed brick of 250mm thick wall.



Window opening, orientation & shading In a recent study window orientation for buildings in Dhaka was studied aiming to exclude solar radiation during the hot periods of the day. It is a known fact that southern and western walls of a building receive huge amounts of solar radiation during the course of each day in our hemisphere. When these walls are pierced by windows, direct radiation from the sun penetrates into the indoor areas, thus creating an even greater source of heat (Ahmed, Z.N., 1982) When a window is provided with shading, the shaded part of the window receives no direct radiation, though it continues to receive its share of diffuse radiation f rom the sky. In both of the case studied window is provided in all facades with large cornice. Table 2 shows window area & Fig.4, 5,6,7,8, 9 shows facades of the both buildings. In both cases indoor air temperature would be controlled not only by openings but also by the dense foliage of trees.

AIR TEMPERATURE & RELATIVE HUMIDITY

Thermal comfort is strongly related to the thermal balance of the body and this balance is influenced by environmental parameters like air temperature (Ta), mean radiant temperature (T), relative air velocity (v), and relative humidity (RH) (ASHRAE Standards, 1974) . Air temperature determines the convective heat dissipation, together with any air movement. Humidity of the air also affects evaporation rate as moisture conte nt of the air is related to wetness of skin, which in turns affect comfort sensation. (Mallick, 1996) For Dhaka, The indoor air temperature for comfort with no air movement are within the

The mean comfort temperature for this range is 28.9 0C for air velocity up to 0.15 m/s. For higher velocities of 0.3 m/s to 0.45 m/s the upper and lower limits of comfort temperature increase between 2- . (Mallick, 1996) Table 3 shows, both rammed earthen & brick building helps to keep indoor temperature lower than outdoor either with or without air movement during hot sunny days & keep indoor temperature comfortable. Here indoor air temperature is a litt le bit high than comfort level but lower than outdoor. According to Fig.14 in case of both treatments rammed earth is much more effective than brick wall. For mud plaster the difference is very low & it works almost as exposed brick faade in respect of in door outdoor temperature variation. During cool evening period rammed earth also shows much effectivity than others. It helps to keep indoor temperature higher & near comfort range than brick faade or mud plastered wall.



Table 3: survey data of air temperature & relative humidity with treatment at rammed earthen, exposed brick building & mud plastered on brick wall

Fig.15 shows, for relative humidity level all the material keeps indoor humidity level lower than outdoor in case of both treatment during both cool evening & sunny days. But

humidity variance between indoor & outdoor is lower than others. Humidity depends much on air movement & outdoor air humidity content. In this site outdoor humidity level is naturally high for the presence of water body & dense trees. However, in all cases the indoor humidity level increased in open condition of doors & windows.



LIMITATION OF THE STUDY

Lacking of air velocity data minimizes the analysis. Otherwise more detail analysis can be possible.

ENERGY CONSUMPTION & CARBON-DI-OXIDE EMISSION

Air pollution is one of the major environmental problems nowadays, especially for developing countries such as Bangladesh and brickfields have been identified as a vital pollutant source of the major cities of the country .Numerous brick -making kilns operating in the dry season are one of the major sources of air pollution in cities and a significant factor is that brick kilns are usually clustered near big sites in different parts of Bangladesh (Ahmed & Hossain ,2008). However manufacturing of bricks is a burning question for air pollution in Dhaka. Some studies have shown that, in the Indian context, building a square meter of masonry wit h stabilized earth block consumes energy 15 times less than country fired bricks (Maini,2005).Table 4 shows rammed earth construction is more eco-friendly than fired bricks and their manufacture consumes less energy and pollute less than fired bricks.

Total faade area without opening =[(length breadth total no. of faade) - total opening area] = [(2.4 4.7 4) - 7.57] = 37.55 sqm. For country fried brick , energy consumption = 1657 37.55 = 62220.35 MJ [energy/consumption/sqm.= 1657 MJ] (Maini,2005 ) Carbon di oxide emission = 126 37.55 = 4731.3 kg [Carbon di oxide emission/sqm. = 126 kg] (Maini,2005)

Table 4: calculation of energy consumption & Carbon di oxide emission of Rammed earth building (HBRI), if brick used in place of mud

MANUFACTURING & MAINTENANCE COST

Prime material of rammed earth construction is earth. It is available in site .There is no need to buy mud for construction which lessens the manufacturing material cost largely. However, rammed earth construction need 90% of its cost for shuttering & polishing as maintenance material. In case of plastering it is cheaper than cement but the difference is not so high. Table 5 shows a comparison of manufacturing & maintenance cost of rammed earth construction & mud plastering with convention al exposed brick wall & cement plaster.



Table 5: comparison of manufacturing & maintenance cost of rammed earth construction & mud plastering with conventional exposed brick wall & cement plaster.

Others: From observation & questionnaire survey some merits & demerits of rammed earth construction are found, such as: Demerits

Crack

Erosion at rainy days Merits

Noise reduction

Less construction time

Strong & durable

Recyclable

DISCUSSION & CONCLUSION

From analysis it can be stated that for availability of material rammed earth is suitable only in the growing new areas of Dhaka. It keeps indoor air temperature & humidity level near comfort range than brick though mud plaster is not much effective in thi s regard. As

processing or causes no pollution even for transportation & consumes less energy, it can be an alternative of brick. If the maintenance cost can be afforded at primary level (almost two years according to HBRI) it is beneficial in the long run for its longevity. However, if compared with land value of Dhaka it is not feasible for height restriction & thickness of wall .Even rainy season makes the structure vulnerable causing erosion & scorching dry summer causes crack. Therefore, using layers & textured shuttering a traditional pleasing look can be achieved which is architecturally pleasing. In a nut shell it can be said that Rammed earth in context of Dhaka is comfortable

quality according to area basis its construction is possible & its architecturally gives a traditional look. But for crack, erosion, height restriction, com parison with land value results it can be used as building material only for special causes where green architecture is the primary & dominating issue.



REFERENCES

[1] ick -34.

[2] Ahmed, I. (1994), Earth Architecture of Bangladesh & future directions for its conservation & upgrading, Protibesh, Vol.8, Issue 1, pp 73-81.BUET.

[3] Ahmed ,Z.N.

[4] pp55-74 .

[5] Atkinson, G.A.( 1953) Tropical Architecture and Building Standards, conference on Tropical Architecture.

[6] Dayaratne, R. (2003), Earth Architecture for contemporary living: prospects & new initiatives, Open house international, Vol.28, Issue 3, pp 23-33.University of Bahrain.

[7] House & building research institute(HBRI) report, Hands on Workshop on modern structure & architecture(rammed earth construction), 2009

[8] Mallick, F.H. (1996), Thermal Comfort and Building Design in the Tropical Climates. Energy and Buildings, Vol.23, pp161-167. Elsevier.

[9] -India.

[10] Schedule of rates, Public Works Department, 2008 [11] Zami, M.S. & Lee, A. (2009), Reducing carbon dioxide emission by the adoption of contemporary

earth construction in urban Bangladesh, Protibesh, Vol.13, Issue 2, pp 25-33.BUET.

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Investigation of the Efficiency of Vibro-

Isolating Supports of Optical Tables

Department of Mechanical Engineering, Vilnius Gediminas Technical University, LITHUANIA

ABSTRACT

The main tasks of this work are to investigate experimentally the vibration behaviour of the optical tables and the floor structure and to establish the vibration transmission factor of vibro -isolating supports. It is established that the vibration frequency of the table is low, about 1 Hz. Therefore it is possible to mount the laser and optomechanical convergence system of multiple pump beams to the optical table, because the transmission factor of vibro -isolating supports varies from 0.879 to 0.968. Key words: Optical Table, Vibro -Isolating Supports, Vibration Acceleration, Vibration Transmission Factor

1 INTRODUCTION

asers and their systems are sensible to vibrations and acoustic noise. Noise and vibrations can arise from sources inside or outside the building, for example, from passing cars, wind, heating, ventilation and air conditioning systems, etc [1].

Therefore precision balances, optical microscopes, lasers must be well isolated from vibrations to ensure their proper performance. Ultrastable Fabry Perot cavities used to stabilize lasers also require vibration isolation [2]. Although these cavities are primarily sensitive to horizontal motion, vertical motion of the ground and optical table can distort the c avity and thus displace the reflecting surfaces [2]. Similarly, in precision atom interferometer measurements, a single optical element must be constrained to move such that it accelerates uniformly with respect to free falling atoms over a time scale as long as 1 s [2, 3]. In atom interferometer measurement of g, for instance, it is necessary to stabilize the position of a mirror to a small fraction of the wavelength of light for times approaching 1 s. The typical level of background vibrations in the frequency range between 0.1 and 10 Hz would completely wash out the interferometer fringes [2]. A mechanical spring can adequately isolate key elements from background vibrations, but only in a certain frequency range. Vibrations occurring at frequencies below the natural resonance frequency of the spring-mass system will pass through the spring virtually undiminished. Above the natural resonance frequency of a spring -mass system with negligible damping, vibrations are reduced by a factor proportional to -2 [2]. Standard optical tables floating on compressed air have resonance frequencies around 2 Hz and thus isolate the

vibrations slower than 2 Hz requires a different approa ch. Custom designed optical tables are

L



usually used in laser centres and laboratories to mount such equipment. The aim of this work is to evaluate the efficiency of vibro-isolating supports of optical tables .

2 OBJECT OF INVESTIGATION

Rigid tables assembled on vibro -isolating supports are shown in Figure 1 (2, 3). Vibration behaviour of two similar tables located at different technological premises was investigated. Arrangement of accelerometers is shown in Figure 2.

Figure 1: Experimental vibration isolating tables, which are rigidly connected to one another: 1 accelerometer mounting place; 2, 3 investigated table; 4 Machine Diagnostics Toolbox (type 9727, Bruel&Kjaer)

Figure 2: Arrangement of accelerometers on vibration isolating tables: 1 block; 2 accelerometer (type 8344, Bruel&Kjaer); x, y, z coordinates A lightweight honeycomb table structure was used. Mechanical properties of the honeycombs depend on the size of the cells, thickness of the walls and material properties. Honeycomb tables are characterized by excellent vibration damping properties; they are much lighter than conventional granite tables. One of the most important properties of the vibro -isolating supports of such tables is vibration tran smission from floor to the table top. In order to establish vibration transmission characteristics two points were chosen (Figure 2).



3 RESULTS OF INVESTIGATION

Results of measurements of vibrations of the floor and the 1st table are presented in Figure 3 and Figure 4. Statistical parameters of the vibration acceleration signal are presented in the Table 1.

Figure 3: Vibration acceleration of the 1st table measured in vertical direction (a) and vibration acceleration spectrum (b) (results obtained from accelerometer 8344 data)

Figure 4: Vibration acceleration of the floor surface measured in vertical direction (a) and vibration acceleration spectrum (b) (results obtained from accelerometer 8344 data) Table 1: Statistical parameters of the vibration acceleration signal (1st optical table)



Vibration transmission factor of vibration isolating supports was calculated as follows:

15.108447.0

09716.0

f

t

x

xtr

S

Sk

1)

where

txS is the standard deviation of the vibration acceleration of the table;

fxS is the

standard deviation of the vibration acceleration of the floor structure. Results of measurements of vibrations of the floor and the 2nd table are presented in Figures 57. Statistical parameters of the vibration acceleration signal are presented in the Table 2.

Figure 5: Vibration acceleration of the 2nd table (with additional mass) measured in vertical direction (a)

and vibration acceleration spectrum (b) (results obtained from accelerometer 8344 data)

Figure 6: Vibration acceleration of the floor surface measured in vertical direction (a) and vibration acceleration spectrum (b) (results obtained from accelerometer 8344 data)



Figure 7: Vibration acceleration of the 2nd table (without additional mass) measured in vertical directio n (a) and vibration acceleration spectrum (b) (results obtained from accelerometer 8344 data) Table 2: Statistical parameters of the vibration acceleration signal (2nd optical table)

Me

asu

rin

g

po

int

Statistical parameter

Arithmetic mean, m/s 2

Standard deviation Sx, m/s 2

Standard deviation of the mean,

m/s 2

Minimum value xmin,

m/s 2

Maximum value xmax,

m/s 2

Variation, m/s 2

Sum

Ta

ble

with a

dditio

na

l ma

ss

On

th

e ta

ble

surf

ace

-1.49198E-4 0.06362 9.94039E-4 -0.198 0.206 0.404 -0.611

On

th

e flo

or

surf

ace

-1.34346E-4 0.06575 0.00103 -0.145 0.186 0.331 -0.55

Ta

ble

witho

ut a

dd

itio

nal m

ass

On

th

e ta

ble

surf

ace

5.30981E-4 0.05783 9.03581E-4 -0.158 0.164 0.322 2.1749

On

th

e flo

or

surf

ace

-1.34346E-4 0.06575 0.00103 -0.145 0.186 0.331 -0.55



Vibration transmission factors of vibro -isolating supports of the 2 nd table were calculated by formula (1):

,9676.006575.0

0.06362)(

f

t

x

xmasswithtr

S

Sk

.8795.006575.0

0.05783)(

f

t

x

xmasswithouttr

S

Sk

Obtained results show that transmission factor of the vibration isolating supports varies from 0.8795 to 1.15.

4 CONCLUSIONS

In accordance with the results of experiments, the following conclusions can be drawn:

Vibration behaviour of vibro -isolating supports of optical tables was investigated, vibration transmission factors were established.

Transmission factor of the vibro -isolating supports of the first table reached value of 1.15; therefore additional vibration isolation is required.

REFERENCES

[1] Mechanika 2006: Proceedings of the 11th international conference, April 6 -7, 2006, Kaunas University of Technology, Kaunas, Lithuania, 168-172.

[2] Weiss, D. S.; Young, B. C.; Chu, S. 1994. Precision measurement of / mCs based on photon recoil using laser-cooled atoms and atomic interferometry. Applied Physics B: Lasers and Optics, 59, 3, 217-256.

[3] Young, B. C. 1997. Ph. D. thesis. Stanford University.

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authors do not have copyright for their own papers, and cannot post their papers on their own websites, which presents a significant barrier to the sharing of knowledge, as well as being unfair to authors. Open access can overcome the drawbacks of the

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A 12-Element Chemical Reactor Network for

Carbon Oxide Emission Prediction in Gas

Turbine Combustor

Nguyen Thanh Hao

Industrial University of HoChiMinh City, VIETNAM

ABSTRACT

This study presents the use of a new chemical reactor network (CRN) model and non-uniform injectorsto predict CO emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics (CFD) combustion analysis with two injectors of CH4 -air mixture. Theinjectors of CH4 -air mixture have difference lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust

-uniform injectoris applied to improve the burning process of the turbine combustor. The results of the new CRN for CO prediction in the gas turbine combustor show very goodagreement with the experimental data from Korea Electric Power Research Institute. Key words: Chemical Reactor Networks (CRN), Computational Fluid Dynamics (CFD), Perfectly Stirred Reactor (PSR), Plug Flow Reactor (PFR), Gas Turbine Combustor, Carbon Oxide Emission (CO).

1 INTRODUCTION

rom the nineteen fifties, engineers have used chemical kinetic models to study the combustion process. The concept of modeling the flame by a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR) was introduced by S.L. Bragg and N.T.

Hao [1-2]. Zonal combustion modeling was proposed by Swithen bank as an improvement for combustor design via correlation parameters [3]. The flame volume was divided into zones represented by idealized reactor elements, such as PSR, PFR, and MIX [4-5]. The concept of modeling the combustor by MIXs and PSRs followed by two PFRs will be applied to predict CO emission in gas turbine combustor. In the PSR the chemical time is assumed to be much slower than the mixing time. Chemical reactor modeling of combustion systems is not necessarily limited to the use of extensive chemical reactor networks. Very simple two/three reactor models have been found useful in modeling research combustion reactors [6-7]. The new chemical reactor network modeling of the gas turbine combustor is constructed based on CFD-predicted flow patterns: flame shape and location , and entrainment of the dome air and gas from main recirculation zone into the flame. The new chemical reactor network modeling is shown the schematic layout of the 12 -element CRN developed herein. The chemical reactor network consists of 12 PSR, PFR, and MIX elements. The PSR

F



stands for perfectly stirred reactor (i.e., a continuously stirred tank reactor), in which mixing to the molecular scale is assumed to happen instantaneously compared to chemical reaction. The chemical reaction occurs homogeneously in the reactor.The PFR stands for plug flow reactor, in which the flow is assumed to move as a plug and the chemical reaction proceeds one-dimensionally, longitudinal mixing in the reactor is assumed to be zero.The MIX stands for an element in which the entering streams are uniformly mixed without chemical reaction.This research is somewhat different from the previous ones, being more descriptive and less theoretical. The CFD modeling has ability to provide the valuable insight on the flow and the temperatur e fields of the combustor, which are difficult to obtain from the experiment. While CFD is a valuable tool to predict the flow and the temperature fields, this method cannot incorporate the complicated chemistry of the detailed chemical kinetic mechanisms.

2 CFD ANALYSIS

The new CRN combustion model is constructed in this study based on the actual experiment and CFD-predicted flow patterns: the flame shape and location, the entrance of the dome air and gas from main recirculation zone into the flame. These flow patterns are treated by adjusting the flow splits between the corresponding elements of the network. The analysis includes a three-step EBU model which was performed using a simple interpretation of the results of the flame. The temperature was used t o separate the flame zone which was replaced by simple reactors. The schematic 3D drawing of the combustor with the air flow splits is shown in figure 2. The major design and operating parameters of the modeled combustor are similar to those of typical ind ustrial gas turbine combustor. The modeled combustor consists of the combustor liners, the swirl injector with main circuit, and the swirl pilot circuit. The mean axial velocity profiles of the injector are determined based on the profiles of the swirl ratio and the non-uniform swirl mixture injector. The CRN model is configured from the entrance, consider the mixture of fuel and air to the back-flash phenomenon occur because CH4-air separate analysis is applied to the entrance of the combustor. The k- turbulence model is used for wall insulation combustion chamber conditions. In Star -CCM, however,

these effects are modeled as in the standard k- model. The turbulent kinetic energy and turbulence dissipation rate are determined by solving their modeled transport equations. The simulation performed in the model of CH 4-air combustion is repeated using a three-step reaction of the following forms

CH4 + 0.5O2 CO + 2H2 (1)

CO + 0.5O2 CO2 (2)

H2 + 0.5O2 H2O (3)

The Reactions (1) (3) themselves are defined by specifying the amounts (in kilomoles) of the participating leading reactants, reactants and products. In the properties of Star-CCM window, these amounts are entered into each node for the stoichiometry coefficient. The overall structure of the gas turbine combustor system includes an air compressor, an air heater, a compressed natural gas, a combustor, two gas turbine burners, and an exhaust processing unit. The control instrumentation consists of the ICCD camera and the image processing controller, etc.



(a) The Experiment Schematic Measurement

(b) The Control Instrumentation of Gas Turbine Combustor Figure 1.The Experimental Gas Turbine Combustor Model

The experiment parameters are based on combustion conditions (Figure 1). The external



temperature is 298K, after passing through compressor, the temperature is 650K. Pressure and other combustion parameters are based on the maximum load (1.0N load) and minimum load (idle load). In order to understand the effect of the injector CH 4-air mixing profile on the flame position and emission levels, this study will calculate profile of non-uniform injector. The mixture between fuel and air in both main injector and pilot injector are not the same. At the idle load, the overall equivalent ratio of the pilot injector is less than 0.7, the lower overall equivalent ratio is 0.166. The overall equivalent ratio of the main injector and pilot injector at the 1.0N load is 0.422, at the 0.8N load is 0.367, and at the 0.6N load is 0.314.

Figure 2.Computation Grid for CFD Modeling of Gas Turbine Combustor

The combustion chamber boundary is a cylindrical shape using the grid to reduce the computational time is shown in Figure 2. A two-dimensional grid consist of 190,000 cells is used. In order to adequately resolve the gradients that exist in the flame, the grid resolution is refined in the pilot flame region and the boundary layer effect. The results of the mass fraction of the gasturbine combustor at the entrance with overall equivalent ratio of 0.7 are shown in figure 3. The formation of CO emission in the combustor are determined by post -processing CFD solutions of the flow field.

(a) Flame Temperature Surface

(b) Ratio of Unburned Fuel in a Premixed Flame



(c) Mass Fraction of CO Surface

Figure 3.Temperature, Regress Variable and Mass Fraction of CO Contours Plot from Star-CCMSoftware Showing the Presence of the Different Combustion Zones

The temperature vectors plot from the 2D CFD simulation of the different load (1.0N, 0.8N, 0.6N, and idle) show the different combustion zones. The highest temperature of the flame in combustion chamber appear on the wall, in this case the temperature is up to 1903.5K. The temperature contours plot from the 2D CFD simulation show the different combustion zones (figure 4): main flame zone, main recirculation zone, pilot inner zone, pilot out post, pilot median zone, pilot recirculation zone. The development chemical reactor network modeling of the gas turbine combustor is constructed based on the CFD-predicted flow patterns such as the flame temperature and the volumetric zones (figure 4), and the entrainment of the dome air and gas from the main recirculation z one into the flame.

Figure 4.Flame Zone Mapping onto the CRN

3. CRN MODEL CONFIGURATION

The CRN model is constructed in this study based on the Figures 3 and 4. First of all, the recirculation zone consists of PSR which was fully mixed assumption. According to the results of Figure 4, the temperature of the flame was broken. At the idle state, the overall equivalent ratio distribution is up to 0.9. More than 0.05 units from overall equivalent ratio of 0.7 are divided into two entrances. The overall equivalent



ratio range from 0.6 to 0.7, one of area is subdivided into the entrance, so that the total entrances are two. Number of the flame zone is also divided into eight zones. The regions of overall equivalent ratio of 0.7 or more are approximately accounted 20% of the total. At the 0.6N load, 0.8N load, and 1.0N load state, when the overall equivalent ratio distribution is 0.85, the equivalent ratio does not exist and the flame zone is divided into eight zones. The regions of overall equivalent ratio of 0.7of 0.6N load is accounting approximately 12%, 1.0N load is approximately accounted 9% of the total. The CRN model is separated by a non-equivalent portion of the pilot flame was broken. Area consists of more than overall equivalent ratio of 0.8 is pilot out 2 to simulate the flame was on the wall. Area consists of more than overall equivalent ratio of 0.7 is pilot out 1, flame inside of the wall

is modeled. Overall equivalent ratio is less than 0.6 is accounting approximately a medium flame .

(a) The Schematic Layout of the 12-Element CRN Model

(b) The 12-Element CRN Model for Evaluating the CO Emission Based on CHEMKIN Softwar e Figure 5: 12-Element Chemical Reactor Network of the Gas Turbine Combustor

10% Pilot Recir.

Main Recir.

10%

80%

99%

1%

70%

30%

Immediate

Post-Flame

Dome Recir.

Main Pilot Post Pilot

Main Flame

Center

Post-Flame Main

Post-Flame Dilution Zone Air

MIX

MIX

PS

R

PS

R

PS

R

PS

R Main Injector

PS

R PFR PFR

Pilot Injector

PS

R

Air

Fuel

PS

R

PS

R

Fuel



The schematic layout of 12-element CRN is constructed in this study which based on the CFD-predicted results as shown in Figure 5. The PSR stands for perfectly reactor, in which mixing to the molecular scale is assumed to happen instantaneously compared to chemical reaction. The combustion occurs homogeneously in the reactor. The PFR stands for plug flow reactor, in which the flow is assumed to move as a plug and the chemical reaction proceeds one-dimensionally, longitudinal mixing in the reactor is assumed to be zero. the MIX stands for an element in which the entering streams are uniformly mixed without chemical reaction. The first element in the CRN arrangement is the MIX, which represent the cone shape zone of inlet mixture where the mixture is not ignited y et. The flame zone, the dome and the main recirculation zone, and the immediate post flame zone are modeled by using PSRs, while the post flame zones is modeled by using PFR.

4 RESULTS AND DISCUSSIONS

Figures 6 8 are used to show the mole fraction of CO emission results in three CRN model conditions. The amount of CO at low load appears significantly higher than others. Especially, the mole fraction of CO in cold condition is highest. In this situation, the effe ct of temperature on the formation of CO into the gas turbine combustor is played the role of great importance. The CO concentrations rapidly fall with temperature, as illustrated by each condition shown in

Figures 6 8. So that, the CO production mechanisms are also depending on the temperature input such as normal condition, cold condition or hot condition (boundary condition). The CO emission at the exit of the gas turbine combustor is essentially dependent on overall fuel -air equivalent ratio of the id le load, 0.6N load, 0.8N load, and 1.0N load. The formation of CO in the gas turbine combustor non -uniform inlet was applied using the new modified CRN predicts the CO emission is more closely to the experimental data.

Figure 6.Non-Uniformity Mole Fraction of CO in Normal Condition



Figure 7.Non-Uniformity Mole Fraction of CO in Cold Condition

Figure 8.Non-Uniformity Mole Fraction of CO in Hot Condition

5 CONCLUSIONS

The 12-element CRN mechanism has been applied CFD modeling of the gas turbine combustor in order to obtain insight on the flow, temperature, and species fields. The flow field information from the gas turbine combustor CFD has been analyzed to determine combustion zones in the combustor. These zones are modeled as chemical reactor elements in the CRN. The methodology of the CRN development is determined based on the agreement between CFD and CRN models.

The new CRN model using 12 idealized reactor scheme modeling has been developed based on CFD results for the gas turbine combustor with overall fuel -air equivalent ratio of the idle load, 0.6N load, 0.8N load, and 1.0N load. The formation of CO emission in turbine combustornon -uniform inlet prediction are more closely to the experimental data, especially at low overall equivalent ratio in normalcondition shown in Figure 6.



This research has shown that: o The combined CFD and CRN approach shows the ability to accurately predict CO

emission for lean premixed gas turbine combustor. o The simple CRN modelby applying non-uniforminlet is able to predict CO emission

more accurate than uniform inlet. o The simple CRN model can also be applied to the industrial combustors. The resulting CRN

incorporates important flow features and boundary conditions such as: fuel -air distribution, velocity pr ofile, entrainment of the main recirculation zone and the main flame .

REFERENCES

[1] Bragg, S.L. Application reaction rate theory to combustion chamber analysis, aeronautical research council pub. ARC 16170, Ministry of Defense, London, England, 1629-1633.

[2] N.T. Hao and Park JungKyu. CRN application to predict the NOx emissions for industrial combustion chamber. AJASE - Vol.2 - No.2/2013.

[3] Swithenbank, J. Combustion fundamentals. AFOSR 70-2110 TR. [4] Steel, R.C., Tarrett, A.C., Malte, P.C., Tonouchi, J. H., and Nicol, D. G., Variables affecting

NOx formation in lean -premixed combustion, Transactions of the ASME, Journal of

Engineering for Gas Turbine and Power, Vol. 119, pp. 102107, 1997. [5] Rubin, P.M. and Pratt, D.T. Zone combustion model development and use: Appl ication to

emissions control. American Sosiety of Mechanical Engineers, 91-JPGC-FACT-25. [6] Nicol, D. G., Malte, P. C., and Steele, R. C., Simplified Models for NOx Production Rates in

Lean-Premixed Combustion, ASME Paper 94-GT-432, 1994. [7] N.T. Hao and Park JungKyu. A CRN simulation for emission pollutants prediction in lean

premixerd gas turbine combustor, Asean Engineering Journal, Vol.1 - No.1 7/2011.

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Effects of Nitrogen Application on Growth and

Yield of Snowpeas (Pisum sativum)

Njoroge, P.K.; Shibairo, S.I.; Githiri, S.M.; & M.W.K. Mburu

Department of crop science, University of Nairobi, KENYA

ABSTRACT

An experiment was conducted at Kabete field station, University of Nairobi between March and July 2000 (season I) and between June and September 2000 (season II) to determine the effect of different rates of nitrogen (N) fertilizer application on growth and yield of snowpea.

periment was laid out in a complete randomized block design with three replicates. Four N levels (0, 50, 100 and 150 kg N ha-1) were split applied in equal halves as CAN (26% N) at 29 and 58 days after planting (DAP). Plant height, leaf area index, above ground dry mass, number of pods and pod dry weight were determined overtime. All the growth and yield parameters studied did not substantially benefit from N fertilizer application. It was therefore recommended that less N be applied for growth and yield of snowpeas.

INTRODUCTION

itrogen (N) influences the crop yields mainly through leaf area expansion, leaf area duration, and susceptibility to lodging (Addiscott et al., 1992). The growth rate and N composition of the new tissue determine demand for N by a plant.

The response of legumes to N application has been shown to depend on many factors among them its level. Lenka and SatPathy, (1976) reported that application of up to 40 kg N ha-1

increased vegetative growth, plant height and number of branches plant -1 in pigeon pea. In beans, a low level of N fertilization of less than 50 kg N ha-1 was found to give early vigorous growth (Westermann et al., 1981). Srivastava and Verma (1984) showed that application of 20 kg N ha-1 increased yields and quality traits in field pea ( Pisum sativum L. var. arvense). Gunawardena et al., 1997 worked with different cultivars of pea and observed significant differences in shoot growth among cultivars but not between N levels. Nitrogen application did not affect root dry matter at any stage for any of the cultivars. Increase in grain and shoot biomass in medium duration pigeonpea to N fertilizer applied at sowing on both Alfisols and Ver tisols have been reported (Kumar et al., 1981). Nitrogen applied at later stages of growth i.e., from flowering onwards, boosted final dry matter and grain yield, particularly on Vertisols confirming the inadequacy of the symbiosis on this soil (ICRISAT, 1987). Lack of response to N on three other soil types, namely Alfisols, Entisols and Inceptisols in India may perhaps be due to high levels of N in the soil pool, or because N-fixation was adequate to meet the N requirements of the crop in these soils (ICRISAT, 1987). In recent times, legumes are increasingly playing a central role in horticulture. In Kenya, much attention has been focussed on production of french beans (Phaseolus vulgaris L.) although

N



production of snowpeas (Pisum sativum) is increasingly becoming important. Response of snowpeas to fertilizer N in Kenya has not been documented. The objective of this study was to determine the effect of different levels of N application on growth and yield of snowpeas .

MATERIALS AND METHODS

Snowpea (Pisum sativum var. Oregon sugar pod II), produced by Royal Sluis and treated with Thirum (class 3) was used in this experiment. The experiment was conducted in two seasons at Kabete field station, University of Nairobi between March and July 2000 (season

I) and between June and September 2000 (season II). The site lies at latitude 1o15S and

longitude 36o44E (Jaetzold and Schmidt, 1983) at an altitude of 1940m above sea level. The mean maximum and minimum temperatures are 23 oC and 13oC respectively. The rainfall is bimodal, with long rains in March to June and short rains in October to December. The average rainfall is 1000 mm/year (Mburu, 1996). The soils have been described as humic nitisols according to FAO/UNESCO (1984) classification, with Oxic (Siderius 1976). The soil pH ranges between 5.2 to 7.2 in the topsoil and 5.2 to 7.7 in the subsoil. Available potassium (K), calcium (Ca), magnesium (Mg), and phosphorous (P) ranges from low to fai rly high levels. Total soil N is about 0.26 % (Njuguna, 1997). In this study, soil pH was determined using a pH meter, Soil N was determined by micro

CEC was determined using 1M KCL and 1M NH 4+Oac and organic carbon was determined using Walkley -Black method. Other soil parameters e.g. sand, silt and clay fractions, available Ca, Mg, Na and K were not determined. The results of soil analysis in the top 0-15cm before the experiment was conducted are shown in Table 3. The treatments consisted of four N levels i.e. 0, 50, 100 and 150 kg N/ha applied as calcium ammonium nitrate (26% N). For each of the N rates, split application with half at 29 days after planting (DAP) and the rest at 58 DAP was adopted in both seasons to increase fertilizer N recovery by the crop. These rates were adopted based on the 100 kg N/ha applied to snowpeas by farmers. The experiment was laid out in a randomized complete block design. Each treatment was replicated 3 times. Each experimental plot measured 2 m x 3 m. The plant spacing was 0.1 m x 0.75 m within and between rows, respectively. Seeds were hand sown in furrows on 26th March 2000 in season I and on 3rd June 2000 in season II. In both seasons planted seeds took eight days to emerge. The crop received 357 mm and 82 mm of rainfall in season I and season II, respectively. Supplemental sprinkler irrigation was done at 58 DAP (22 nd May 2000) in season I. In season II, it was done after planting, at 29, 44 and 58 DAP (1st, 16th and 30th July 2000) respectively. In both seasons, each duration of irrigation was three hours and this supplied approximately 10mm of rainfall. The crop was trained 3 weeks after planting in both season in order to reduce lodging, improve air circulation around the plant, reduce incidence of pests and diseases and improve light penetration through the canopy. Crop training was done using sisal strings tied from 0.2 m to 1.2 m above ground at 0.07m to 0.1m intervals. Weed control was done through manual cultivation. Two weedings were done before the canopy closed. Powdery mildew was controlled by alternate application of Antracol and Bavistin at 40g/15 l and 40g/20 l of water, respectively. Insect pests were controlled usin g Diazol at 30ml/15 l of water. All chemicals were applied at 10 to 14 day interval up to maturity .



MEASUREMENTS

Plant heights were measured at 31,38,45,58,71,84 and 97 DAP, on three plants randomly selected from the middle three rows using a meter rule. Leaf area index (LAI) was determined at 29, 43, 63, 77 and 94 DAP using the specific leaf area method (Norman and campbell, 1989). Using a cork borer, thirty 1-cm diameter discs were excised on 10 fully expanded leaves selected from three plants in each plot and put in 0.164m x 0.164m envelopes for drying. The remaining leaf portions were put in separate craft papers then oven dried (Model number TV80UL 508032, Memmert, Germany) to constant mass. The LAI was calculated using the following formula:

LAI = [L M x (LA discs /Lm discs)] x n (e.g. Mburu, 1996). Where LM= leaf dry mass, LA discs = leaf area (m2) of the discs, Lm discs = leaf dry mass (g) of the discs and n = number of plants per hectare.

Total above ground dry mass of snowpeas was determined on the three plants used for LAI determination. The leaves, leaf-discs, shoots and reproductive parts (pods, flowers and flower buds) were separately placed in craft papers and oven dried to constant mass. The snowpea pods were hand harvested from three plants randomly selected from three middle rows starting 68 DAP i.e. 1 st June 2000 in season I and 9th Aug. 2000 in season II. Harvesting was done twice a week for upto five weeks by carefully picking the mature pods. Mature pods were described as being uniformly green, intact, clean (free from any disease or physiological disorders), flat with seeds not exceeding 4 mm in diameter and pod width of 1.5 to 2 cm (HCDA, 1996). The pods were then put in separate craft papers and oven dried after counting the number of p ods.

STATISTICAL ANALYSIS

All the data collected was subjected to analysis of variance using GENSTAT 5 Release 3.2 statistical software (Lawes Agricultural Trust, Rothamsted Experimental Station, 1995).

Treatment effects were analysed by fitting orthogonal polynomial contrasts at P 0.05 (Steel and Torrie, 1981).

RESULTS

In both seasons, 50% flowering occurred at 58 DAP. Harvesting of pods started at 68 DAP and continued up to 100 DAP. The crop received 357 mm and 82 mm of rainfall in season I and season II, respectively. Nitrogen application did not affect plant height at all measurement durations in both experiments. On average the maximum plant height observed at the end of the experiment in both seasons was 0.86 m. There was no treatment effect on LAI at all measurement durations in both seasons (Figure 2). LAI increased up to 63 DAP and later declined. Influence of N application on total dry matter (TDM) at all measurement durations was not observed in both seasons (Figure 3). However at 43 DAP, TDM increased both linearly and quadratically in experiment II. TDM increased upto 77 DAP and decreased at 94 DAP in both seasons. Higher values of TDM were observed in season 1 than in season II. Application of N did not affect number of pods plant -1 in most measurement durations in both seasons (Table 1). However, at 68 DAP in season I, number of pods plant-1 increased linearly with increasing N. In season II at 86 DAP, the increase in number of pods plant -1 was quadratic. Application of 50 kg N ha -1resulted in the highest pod yield in both seasons. Pod production increased from 68 DAP up to 89 DAP, then decreased upto 100 DAP in both seasons. Pod production was high in season I than in season II. Overall, N



treatment did not affect pod dry mass plant -1 at all measurement durations in both experiments (Table 2). However, pod dry mass increased linearly and quadratically with increasing N at 68 DAP in season I. A quadratic response was observed at 72 DAP in season II. At 86 DAP, both linear and quadratic increases were observed in season II.

DISCUSSION

The anticipated increase in growth and yield of snowpeas from N application was not observed in the present study. In season I, the crop was better supplied with water. However, high rainfall after 1 st N application (146.1 mm) in three consecutive days may have leached some of the applied N. This can result in appreciable loss of topsoil nitrate and subsequent accumulation in the subsoil. Micho ri (1993) observed 2200 kg NO3-N ha-1 at 1 to 5 m depth under fertilized coffee in Kenya. In season II, the total amount of water supplied to the crop between 58 and 100 DAP (Figure 1) was not more than 30 mm. This would result in restricted pea growth and also N uptake. Lack of increase in growth and yield following N application have been observed in soybean (Meyer et al., 1974) and in cowpea (Agboola, 1976). Exactly why N fertilizer did not affect growth in this study was not determined. Whether N affect s growth of legumes depends on many factors including N fixation through symbiosis, soil N content, soil organic matter content and N uptake which is influenced by soil water supply. Many legumes have been shown to satisfy their N needs through its fixati on symbiotically with Rhizobia. For instance, Kumar (1980) estimated that pigeonpea could fix up to 69 kg N ha-1 per season, which accounted for 52 % of the total N uptake. Peas typically fix about 65 kg N ha-1 yr -1 with a range of 30 to 160 kg N hha-1 yr -1 (Tisdale et al., 1990). However, the amount of N fixed through symbiosis was not determined in this study. It has been reported that response to N is highly probable only when total soil N is low i.e. less than 0.2% (Landon, 1991). Soil N at the study site was 0.24 and 0.26% in season I and season II, respectively hence medium (0.2 to 0.5%). Therefore, response to added N was expected. This shows that, lack of response to N application on growth of snowpeas, in this study may not have been due to soil N per se. It has been reported that the level of soil organic matter affects crop response to applied N. Agboola, (1976) reported that on soils having 0.5% organic matter, grain yield of cowpeas was increased from 800 kg ha-1 on the check to 1850 kg ha-1 where 20 kg N ha-1 was applied. Although nutrient release from soil organic matter is normally more dependent on the portion of the organic matter in biologically active fractions than on total quantity of organic matter, he observed that in soils with 2% or more organic matter, there was no constant response to N fertilizer. The organic matter content in the soils of our study was 5.09% and 4.94% in experiment I and experiment II, respectively. It is therefore possible that, lack of response to N applicati on may have been due to the high soil organic matter content. In season II, there was increase in height with increase in N at 71 DAP and increase in TDM with increase in N at 43 DAP, respectively. This could be attributed to improved moisture availabilit y following supplemental irrigation, which was done at 29, 44 and 58 DAP. Begg and Turner, (1976) reported that there is a significant interaction between N uptake and water stress. They also observed that there is a reduction in N uptake induced by water stress. Leaf area index and above ground dry matter accumulation were higher in season I than in season II. Maximum LAI was observed at 63 DAP in both seasons but decreased more rapidly in season II than season I. i.e. at 94 DAP, LAI was 1.9 and 1.4 in seasons I and II, respectively. The variation in leaf growth between the seasons may imply that another factor other than N limited leaf growth and this was probably soil moisture availability. In Mexico, rainfall regimes



were shown to exert a marked influen ce on maize N responses (Rockfeller foundation report, 1963-64). Lower responses to N were obtained when either excess moisture or drought occurred. Amount of rainfall received in season I was 357 mm compared with the 82 mm received in season II. Adequate soil moisture is important since uptake of mineral nutrients takes place via water films surrounding the soil particles. However, excess moisture may cause leaching of the N below the root zone thereby interfering with its availability for plant uptake. Consequently, in dry weather as in season II, N uptake may have been low due to impaired absorption. Sheoran et al., (1981) reported that in pigeon peas, water deficit resulted in decreased water potential of the roots, nodules and leaves. This decreased water potential in the nodules resulted in decreased activities of nitrogenase, glutamine synthase, glutamate dehydrogenase and uricase, all of which are central in biological N fixation. Hence less N was obtained through symbiotic fixation in season II and this led to the observed low growth. Dry mass accumulation in many legumes may affect yield via its influence on the rate of pod set, seed set and seed dry mass (Weber et al., 1966). Generally, leguminous crops do not respond by yield increases to soil or applied N to the same degree as other crops based on their ability to fix N. Paterson et al., 1966 reported significant effect of N fertilization on pod yield in snap beans. A similar observation has been reported in pigeonpea following application of urea at a rate of 30 and 45 kg N ha-1 (Mukindia, 1993). However, findings of the present study indicated that N application did not affect both the number of pods plant -1 and pod dry mass. Pietri et al., (1971) observed similar results in pigeonpea. This was attributed to lack of effect of N on number of branches plant -1. It is not clear as to why pod yields in this study were not affected by N application. However, N may not have affected pod yield through its lack of effect on growth. Reduction in yield can be brought about by a reduction in any of the yield components such as number of branches plant-1, number of pods plant -1, number of seeds pod-1 and 100 seed mass (Ishag, 1972). In this study, the decrease in yields in season II was attributed to decrease in number of pods plant -1 formed under moisture limiting conditions. This has also been reported in beans (Hidalgo, 1978) and in cowpeas (Turk and Hall, 1980). Decrease in pod number could be due to reduced flower production and increased flower abscission in dry weather (Turk and Hall, 1980). Sheoran et al., (1981) attributed the lack of response of yield of pigeonpea on low growth caused by water deficit. It is therefore suggested that low snowpeas yields were observed in season II due to the low soil water content. Snowpeas plants did not substantially benefit in growth from N fertilizer application. It is possible that either snowpeas were able to fix enough N to meet their requirements or these N requirements were met from the soil supply. This study shows that N application does not increase pea yields. Lack of increase in pea yield is attributed to lack of effect of N on growth. It has further shown that pea yields will be increased with high than low soil moisture.

REFERENCES

[1] Addiscott, T.M., Whitmo re, A.L. and D.S. Powlson. 1992. Farming, fertilizers and the nitrate problem. Wallingford. pp 115.

[2] Agboola, A.A. 1976. Influence of soil organic matter on cowpea response to Nitrogen fertilizer. Agron. J. 70:25-28.

[3] Begg, J.E. and N.C. Turner, 1976. Crop water deficits. Adv. Agron. 28: 161-217. [4] Gunawardena, S.F.B.N., McKenzie, B.A., Hill, G.D. and K.M. Goh, 1997. Dry matter accumulation

and nitrogen partitioning between shoot and root of pea ( Pisum sativum L.) cultiva rs. Proceedings-Annual -Conference-Agronomy -Society-of-New-Zealand. 27: 129-133.



[5] HCDA, 1996. Horticultural crop development authority. Export crop bulletin No 1. [6] Hildalgo, R. 1978. Screening for drought tolerance in dry beans (P. vulgaris L.). Field bean

Abst. 3: 0552. [7] ICRISAT, 1987. Annual Report 1986. Patancheru, A.P., India: ICRISAT. pp.191-192. [8] Ishag, H.M. 1972. Physiology of seed yield in field beans. (Vicia faba L.) II. Dry matter

production. J. Agric. Sci. (camb) 80: 191-199. [9] Jaetzold, R. and H. Schmidt, 1983. Farm Management Handbook of Kenya. II-C pp. 144- 244. [10] Keya, S.O. and D.M. Mukunya, 1979. The influence of phosphorous and micronutrients on

nodulation of Phaseolus Vulgaris at Kabete, Kenya. Paper presented at the symposium on grain legume improvement in Eastern Africa, Nairobi, Kenya.

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bean seed production. Agron. J. 73: 660-664.



APPENDICES

Figure 1. Effect of different levels of N on leaf area index (LAI) in snowpeas in season I (a) and season II (b) (DAS= Days after sowing, N0 = 0, N1 = 50,N2 = 100 and N3 = 150 kg N ha-1, Vertical bars = Lsd bars at P = 0.05)

Figure 2. Effect of different levels of N on total above ground dry matter (AGDM) accumulation in snowpeas in season I (a) and season II (b), (DAS =Days after sowing, N0 = 0, N1 = 50, N2 = 100 and N3 = 150 kg N ha-1, Vertical bars = Lsd bars at P = 0.05)



Figure 3. Effects of different levels of P on plant height in snowpeas in season 1 (a) and season 2 (b), (DAS= Days after sowing, P0= 0 , P1= 57,P2= 114 and P3= 171kg P2O5 ha-1,Vertical bars = Lsd bars at P = 0.05). Table 1; Effect of different levels of N application on snowpeas number of pods plant -1 in season 1(March-June 2000) and II (June-sept. 2000)

N0, N1, N2, and N3 = 0, 50, 100, and 150 kg N ha-1, NS= Not significant, *= Significant (P 0.05), L = Linear, Q = Quadratic

Table 2: Effect of different levels of N application on snowpeas pod dry mass plant -1 in season 1(March-June 2000) and II (June-sept. 2000)

N0, N1, N2, and N3 = 0, 50, 100, and 150 kg N ha-1, NS= Not significant, *= Significant (P 0.05), L = Linear, Q = Quadratic



Table 3; Results of laboratory analysis of the soil from the experimental sites (0-15cm) Parameter Experiment 1 Experiment 2

pH (H 2O) 6.22 6.37 pH (CaCl 2) 5.36 5.39

%N 0.24 0.26 P (ppm) 17.9 18.7

%C 2.96 2.87 CEC (meq/100g) 14.3 14.1

pH (H 2O) = soil pH in water, pH (CaCl 2) = Soil pH in calcium chloride, %N = Percent nitrogen in the soil, P (ppm) = Soil phosphorous in parts per million , %C = soil organic carbon and CEC (meq/100g) = Cation exchange capacity.



Evaluation of the Correlation between Selected

Quality Indices of Activated Carbon: A Review

Benjamin Edem Meteku

Post Graduate Researcher, Chemical Engineering Department, Kwame Nkrumah University of Science and Technology, Kumasi, GHANA

ABSTRACT

The choice of activated carbon for use depends on the quality, which is measured by selected indices. The correlation between BET surface area, iodine number, ash content and bulk density, major quality indices for characterisation were investigated in this study. The iodine number and surface area were strongly correlated (R2= 0.9684 and 0.9577). The bulk density and ash content were highly correlated with surface area with coefficient of determination (R 2) values of 0.9040 and 0.9788 respectively for samples from same raw material under similar treatment. Th e ash content could also be used as an approximate estimate of iodine number and bulk density with R 2 values of 0.5966 and 0.6236 respectively. Key Words: activated carbon, adsorption, activity, correlation, coefficient of determination.

1 INTRODUCTION

ctivated carbon, an amorphous, porous form of carbon with high surface area is the most widely used industrial adsorbent [1], [2]. It is used in the manufacture of protective gas mask for the entrapment of toxic gases in the plant and also in the

manufacture respiratory devices for personal protection during chemical warfare [3]. In medicine; activated charcoal (carbon) is frequently used treating and managing severe, acute poisoning [4]. In hydrometallurgy, it is used in precious metal (such as Au and A g) recovery processes and also for the removal of organic pollutants in drinking water and industrial wastewater processing [5],[6]. Activated carbon is also used in the removal of compounds that adversely affect taste, colour and odour in food processing industries and also in the removal of dye in effluent streams in the textile industry [7][8]. The versatility of activated carbon for use in the fore stated processes is due to its large surface area, a property that enables it to be used effectively for adsorption. Depending on the intended use of activated carbon, various quality parameters including surface area, activity, bulk density and ash content are tested for in a sample. The surface area,

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