Optimum Design of Drip Irrigation System using Microtubes as Emitters

Transcription

1 Optiu Design of Drip Irrigation Syste using Microtubes as Eitters A thesis subitte in fufient of the requireents for the egree of Master of Engineering Air Keshtgar B. Eng (Irrigation an Drainage Engineering) Schoo of Civi, Environenta an Cheica Engineering Coege of Science, Engineering an eath RMIT University February 2012

2 DECLARATION I certify that except where ue acknowegeent has been ae, the work is that of the author aone; the work has not been subitte previousy, in whoe or part to quaify for other acaeic awar; the content of the thesis is the resut of work which ha been carrie out since the officia coenceent ate of the approve research progra; an, any eitoria work, pai or unpai, carrie out by a thir party is acknowege. Air Keshtgar 20 February 2012 ii

3 ACKNOWLEDGEMENTS In the first pace, I wou ike to recor y gratitue to Dr Muhae Bhuiyan for his supervision, avice an guiance fro the very eary stage of this research. e provie e unfinching encourageent an support to iprove this work in various ways; I a inebte to hi for his patience an scientific inspirations. Many thanks go in particuar to Dr Sujeeva Setunge for a her support an avices. I wou ike to express y sincere gratitue to Ehsan Keshtgar an Ai Muhaa Baie, postgrauate stuents of IT for their precious tie spent on teaching e Visua Basic. I a gratefu to Cheica, Civi an Environenta Engineering staff ebers for their assistance through the course of stuy. I greaty owe y success to y beove parents an wife for their kinness, continuous encourageent an patience. iii

4 ABSTRACT Drip irrigation is a syste in which water is suppie irecty to pant roots with a pressure an fow rate to eet the crop water requireent. Drip irrigation systes are in extensive use aroun the wor since its acceptance for easy contro of the appie water voue an thus to irrigation anageent. These systes are copatibe for a wie range of crop variety, soi type, ciate an an surface espite of few potentia constrains. Cogging an eission non-unifority, for a ong tie, have been the ajor obstaces in the eveopent of rip irrigation. It wou be a serious probe in areas with brackish water where the probes of precipitation of caciu carbonate, organic aterias an suspene sans are severe. Instaation of fiter equipents before suppy to the syste has sove a part of the probe but cou not eiinate it entirey so far an thus irrigators have to use ifferent ethos to reove the precipitations by aci, which has averse infuence on soi an crops. In orer to obtain the best eission unifority (EU) in uneven ans the pressure reguators an pressure copensating eitters (a gaget) have been use. owever, pressure copensating eitters ten to be ore copex an costy than noncopensating eitters an are not easy to appy. In this stuy, the possibiity of utiizing sa iaeter pipes approxiatey 2 to 4 cae icrotubes have been iscusse for enhancing the ischarge unifority of the rip irrigation an ecreasing the ifficuties encountere by those eitters ue to cogging an bockage. Microtubes have any avantages copare to other types of eitters in ters of cost an practica appications. As these sa size pipes are ae of fexibe aterias, can be ajuste in shape an ength without ifficuty. By ajusting the icrotube engths at ifferent points aong the atera accoring to energy hea eveope, an equa outfow can be eivere to eveny space pants in the fie. ere icrotubes act as eitters. The variation of the icrotube engths is ae for issipating the extra heas above a thresho vaue. This thresho energy hea vaue has been set, at the very ast icrotube of the en-atera in a given anifo (or subunit), equa to the frictiona an other inor iv

5 energy heas ost for that iniu ength icrotube require to reach the pant uner consieration. A subunit consists of a anifo fro where ateras are eerging at a reguar interva. As such, ateras can aso be iagine as arger eitters aong the anifo of an irrigation subunit. These arger eitters wou have a characteristic pressure-ischarge reationship, for a hyrauicay cacuate set of icrotube engths that are eitting equa ischarges aong the en-atera, to estabish a base energy hea at the en point of the anifo. At this juncture there wou have two options for the esign of the succeeing ateras. In one option cae Pre-efine Eission Unifority, the ength of a the icrotubes in the succeeing ateras wi have the sae set of engths as has been cacuate for the en-atera. This configuration of the icrotube setup wi eiver variabe ischarges, which cou be ajuste within the eission unifority (EU) assigne by the esigner. In other option cae Fu Eission Unifority, the esigner wi vary a the icrotube engths in a the successive ateras so as to eiver equa ischarges an thereby to achieve fu eission unifority (EU). In the first option on Pre-efine EU, as the sae set of icrotube engths wi be fitte to the other successive ateras, the characteristic pressure-ischarge reationship fro the en-atera can be appie to these other ateras to extrapoate their corresponing ischarges. The energy hea in the en-atera can be ae with the energy require in the preceing reach of the anifo to obtain the energy in the inet of the foregoing atera. The variation of ischarge in anifo ine has been efine by eission unifority (EU) of the syste an can be assigne by the esigner to fin the optiu anifo ength to have the EU within that range. In this research two progras eveope to esign an optiu rip syste with certain eission unifority. The first progra is a stanaone progra that can be run for ifferent ischarges, the outcoe of this progra is the set of icrotube engths, nuber of cois an the pressure heas of the very ast atera. When a set of ischarges an corresponing pressure heas are known, the reationship an hyrauic paraeters of pressure-ischarge reationship cou be obtaine. Severa case scenarios for three typica icrotube iaeters of 2, 3 an 4 have been perfore within four noina atera sizes of 10, 12, 14 an 16, an the esign charts an tabes are eveope for three terrain sopes of 0, 0.25 an 0.5%. At the secon step these resuts an hyrauic characteristics of arger eitters (ateras) appie to a anifo v

6 ine to esign a copete syste. The outcoe of the secon progra is the nuber of ateras require to eterine the Pre-efine EU an finay cacuate the pressure hea of the syste. In the other option on Fu EU, in orer to ake a fow rates of the ateras equa (EU = 100%), ajustent of the icrotube engths corresponing to the tota inet heas are appie for a successive ateras. For this option ike the Pre-efine EU, aso three typica icrotubes an three atera sizes appie aong with three terrain sopes of 0, 0.25 an 0.5%. The resuts of a those ayout cobinations show that correation between icrotube ength variation an energy rop ratio can be generaize for a icrotube an atera sizes in a given sope. To eveop the generaize equations for icrotube ength an energy rop ratio, Energy Grae Line approache has been consiere. Therefore, the set of esign tabes an graphs incorporate with a genera equation as the outcoe of this option, are provie for esigners to avoi any coputer siuation. When the require ischarge an iaeters of icrotube, atera an anifo an soe groun conitions are given, the ength of the icrotubes, the pressure heas, eission unifority (in percentage) an the best subunit iensions can be obtaine. The resuts of stuy show that arger sizes icrotubes have higher variation of ength, whie appying arger fow rates can ecrease the ength variation aong the atera. Few exapes are prepare to eonstrate the rip irrigation esign paraeters in typica subunit sizes. vi

7 Tabe of Contents DECLARATION.ii ACKNOWLEDGEMENTS.iii ABSTRACT.iv Tabe of Contents.vii List of Figures ix List of Tabes.. x Abbreviations an Notations xi Chapter 1 Introuction Drip Irrigation Avantages of Drip Irrigation Probes of Drip Irrigation Objectives of the Propose Stuy Scope of Stuy Thesis Outine 6 Chapter 2 Literature Review Microtubes an Eitters Design Consierations for Eitter aong the Lateras Pressure Distribution aong the Latera Manifo Design Chapter Suary. 15 Chapter 3 Theoretica Deveopent Layout of a Typica Irrigation Subunit Basic yrauics Pressure-Discharge Reationship Eission Unifority (EU) Pre-efine EU Syste Fu EU Syste Chapter Suary. 28 Chapter 4 Moe Deveopent Microtube Eitter Design Design for Pre-efine EU Design for Fu EU Deveopent of Moe Agorith Progra Progra Progra Chapter Suary. 36 vii

8 Chapter 5 Resuts an Discussion Microtube Design for the En-atera Microtube Design for a Pre-efine EU Microtube Design for Fu EU Energy Graient Line Anaysis Microtube Length Coputation Chapter Suary. 58 Chapter 6 Typica Design Exapes Irrigation Design Paraeters Syste Design Exapes on Pre-efine EU Exapes on Fu EU. 68 Chapter 7 Concusions an Recoenations Concusions Design using Pre-efine Eission Unifority (EU) Design using Fu Eission Unifority (EU) Recoenations for Future Works 71 References 73 Appenices Appenix A Output Tabes fro Progra Appenix B Output Graphs fro Progra viii

9 List of Figures Figure 1.1 A typica rip irrigation syste 2 Figure 3.1 Scheatic ayout of a rip irrigation subunit using icrotubes as eitters.17 Figure 3.2 Scheatic ayout of a singe atera aong with varying engths of icrotubes; etais A an B shows the instaation ethos for aking cois.18 Figure 3.3 Energy grae ine an hea osses in one sie of the atera ( h e = entrance oss, h v = veocity oss, h c = coi hea oss, h f (n) = icrotube friction hea oss at n, an h f (n) = atera friction hea oss between n an n 1)...21 Figure 3.4 Scheatic ayout of a typica subunit with Fu EU..7 Figure 4.1 Fow chart of Progra 1 to cacuate the icrotube engths, inet pressure hea an nuber of cois in the en-atera...32 Figure 4.2 Fow chart of Progra 2 to ajust the nuber of ateras require for a pre-efine EU..34 Figure 4.3 Fow chart of Progra 3 to copute the new set of icrotube engths for successive ateras to achieve fu eission unifority.35 Figure 5.1 Pressure-ischarge reationships for ateras as arge eitters ( = 10, in = 1.25, n = 10, = 1 an S = 0 %) 40 Figure 5.2 Coparison between siuate ( i vs i ) an Eq (5.2) erive energy graient ines 47 Figure 5.3 Siuate energy graient ines for typica ateras; a) for = 12, S 0%, b) 16, S 0%, c) 12, S 0.25% an ) 16, S 0.25% (there are 10 trees pace at an interva of 1 space aong the ateras) 49 Figure 5.4 Figure 5.5 Figure 6.1 Microtube tota ength ifference for typica ateras; a) for 12, S 0%, b) for 14, c) for 16 S 0%, ) for 12, S 0.25%, e) for 14, S 0.25% an f) for 16, S 0.25% (there are 10 trees pace at an interva of 1 space aong the atera) Microtube ength ifference istribution for any ischarge, an icrotube an atera size (this graph is erive for 10 trees pace at an interva of 2 space aong the atera).54 Scheatic ayout of the pot use for grape.64 ix

10 List of Tabes Tabe 5.1 Tabe 5.2 Tabe 5.3 Tabe 5.4 Tabe 6.1 Tabe 6.2 Tabe 6.3 Tabe 6.4 Tabe 6.5 Longest ength icrotube ax (), an i, i 5 (), nuber of cois c an inet pressure hea require T () for the given icrotubes an ischarges ( = 10, in = 1.25, n = 10, = 1 an S = 0 %; the shae ces are consiere as unreaistic range of tota heas) 38 Pressure-ischarge reationships for ifferent ateras with in = 1.25, n = 10, an = 1 ; a) for S = 0%, b) for S = 0.25%, an c) for S = 0.50%...41 EU an nuber of ateras in one subunit with in = 1.25, n = 10, an = 1; a) for S = 0%, b) for S = 0.25%, an c) for S = 0.50%...43 Coefficients of Eq (5.4) for iniu possibe engths of icrotube in; a) for =12 an b) for =16 (these tabes are erive for ateras at an interva of 1 space aong the anifo, where 10 trees are pace at an interva of 1 space aong each of the atera) 55 Input ata reate to pot, irrigation piping syste an soi for case stuies...61 Assue an output ata reate to irrigation to Grape...62 Output ata for siuation of Case Stuy on Grape 62 Assue an output ata reate to irrigation to Grape...65 Output ata for siuation of Case Stuy on Toato..66 x

11 ABBREVIATIONS AND NOTATIONS c - nuber of cois D - iaeter of coi () - iaeter of the pipe () - iaeter of atera () - iaeter of icrotube () - iaeter of anifo () g - acceeration ue to gravity ( 2 ) s - tota hea rop up to the en of the atera i - tota hea rop at a ength ratio i sub - pressure hea of sub-unit T - anifo hea () h e - entrance hea oss () h v - veocity hea oss () h c - coi hea oss () h f - frictiona hea oss () h f (n) - icrotube frictiona hea oss at icrotube position n () i x / X - a ength ratio for a given position x fro the atera inet to the tota atera ength X k - ischarge coefficient that characterizes icrotube eitters - ength of the pipe () in - iniu icrotube ength () - ength of the icrotubes () - nuber of ateras n - icrotube nuber Q - anifo ischarge (itre/hr) Q - average of owest ¼ of the atera fow rates (itre/hr) Q a - average of a the atera fow rates in the syste (itre/hr) xi

12 q R e - icrotube ischarge (itre/hr) - Reynos nuber R i - hea rop ratio aong a atera S - sope of atera ine - istance between icrotubes () v - veocity of fow (/s) X - tota ength of the atera () x - ischarge exponent that characterizes the eitter fow regie; given position fro the inet atera xii

13 Chapter 1 Introuction 1.1 Drip Irrigation Drip or tricke aso cae icro or ocaize irrigation is a pressurize syste to irrigate the crops an orchars, consists of an extensive network of pipes usuay of sa iaeters that eiver water irecty to the soi near the pant. The syste usuay possesses fertiizer injection syste, suppying pants with neee nutrients. In rip irrigation the objective is to provie each pant with a continuous reaiy avaiabe suppy of soi oisture, which is sufficient to eet transpiration eans (Keer an Karei, 1974). A fiter is use to reove suspene aterias, organic atter, san an cay to reuce bockage of the eitters. Aong with puping station, contro vaves are instae to provie require pressure heas to the syste (ensen et a., 1980; Brats an Wu, 1979b). The syste contains eitters, ateras, anifo an ainine, which suppies water fro the source to pant root zone. The ainine eivers water to anifo an anifo eivers water to ateras. The eitters, which are attache to ateras, istribute water to pant root zones. Lateras are noray one size pipes, ae of poyethyene (PE) with iaeters 10 to 16 in range, proviing better fushing, easy instaation an aintenance characteristics (ensen et a., 1980, Pero, 1977). Manifo an ainine are either in eiu ensity poyethyene (PE) or rigi PVC with iaeters 20 to 100 in range (Wu an Gitin, 1977b). Eitters are pant s point sources of water an esigne to provie sa an argey equa aount of ischarges of pant requireent. Eitters are of any kins, such as, orifices, nozzes, porous pipes, icrotubes, etc to issipate the pressure in the pipe istribution networks by eans of a narrow nozze or ong fow path, an thereby ecreasing the water pressure to aow ischarges of ony a few itters per hour (Vereiren an Jobing, 1980, Brats an Wu, 1979). Then water is istribute by its nora oveent through the soi profie. Figure 1.1 shows an exape of a typica rip irrigation syste consisting of eitters, ateras, anifo, ainine an fiter equipents. 1

14 Figure 1.1 A typica rip irrigation syste (source: Avantages of Drip Irrigation Drip irrigation offers unique agronoica an econoica avantages for the efficient use of water. It is consiere as the ost water saving etho of irrigation, thus very iea for use in areas with iite water resources. It is aso beneficia in teperate areas where other surface irrigations such as foo an furrow irrigations or pressurize systes such as sprinker are subject to big water oss ue to evaporation. Since the syste s eission can be controe by tie anageent or using ifferent types of eitters, the probe of eep percoation an oss in the sois can be reuce an saves water in root zone an subsequenty appication efficiency cou be achieve. This syste can be appie very efficienty to sa trees an wiey space pants such as toatoes, citrus an grapes (Benai an Ofen, 1984) (Wu an Gitin, 1977b). In ari regions with goo anageent the ratio of transpire to appie water is usuay at east 0.9 (ensen et a., 1980). Water appication efficiencies approach 100 percent an water savings of 30 to 50 percent over other irrigation ethos are obtaine for crops an conitions favouring rip irrigation (ensen et a., 1980). Insect, isease an fungus probes are reuce by iniizing the wetting of the soi surface. Fewer wees, ess soi crusting, reuce cutivation an thus ess soi copaction interference with harvesting are other benefits of rip irrigation (ensen et a., 1980). 2

15 The possibiity of appying the fertiizer an pesticie by injection into irrigation water an eiver to pant root zone can hep to ecine the eep percoation of this iportant input an increase their efficiency. Use of saine water is not recoene in sprinker systes, which cause eaf burn. owever, saine water can be appie in rip irrigation systes. Saine water shou be appie with caution because sats ay cause eitter cogging an require frequent soi eaching to prevent sat accuuation in the soi (Vereiren an Jobing, 1980) Probes of Drip Irrigation Cogging of the sa conuits in the eitters is the ost serious probe of rip irrigation syste. San an cay partices, ebris, cheica precipitants an organic growth can bock fows through eitters. The cogging occurs grauay an reuces the fow rates of eitters an causing poor water istribution (Vereiren an Jobing, 1980). This probe wi ea to poor prouctivity in fars or orchars because soe parts of the an obtain ore water whie other parts o not eet the iniu requireent of pants ue to evaporation. Cogging occurs ainy ue to passage of water through the very fine pores of the eitters. Thus, eitters with saer passages are ore susceptibe to bockage. The eivere water contains suspene partices, sats an issove fertiizers which create severe probes that require teious efforts an skie an-power to resove. Using aci injection an/or repacing new eitters are the ain coon soutions for cogging probe which both are tie consuing an ipose huge running cost to the syste (Gibert et a., 1981). Moreover, uneven fow rate ue to pressure hea oss is another ajor probe of this syste. Drip irrigation systes o not appy water with perfect unifority aong the crop rows. Soe of the variabiity is cause by anufacturing iperfection in the eitters, but the ajor probe crops up fro the stance of the syste esign, in ters of the frictiona oss in the irection of fow through the atera pipe or tubing where eitters are attache (Myers an Bucks, 1972). Drip irrigation usuay operates uner ow pressure (ess than 100 kpa). Pressure istribution insie a atera or anifo wi be greaty affecte by the friction an sope of the pipe aying. This variation of pressure wi change the ischarge of eitters aong the ine. owever, an iea rip irrigation wi be one which can irrigate unifory that each eitter eivers equa ischarge as require by the pant per irrigation (Wu an Gitin, 3

16 1973). Severa anufacturers have esigne eitters to reuce ischarge variations cause by friction-inuce pressure changes in the atera pipes. These eitters are copex an susceptibe to cogging to ipose huge initia an operationa costs to the syste. In another instance, a graphica proceure was eveope by Wu an Gitin (1973) using sipe eitters of ifferent iaeters aong the atera pipe to copensate its frictiona osses, which in practice is very har to insta. In ters of econoica consieration, rip irrigation requires high capita cost as we as aintenance. Researches showe that ue to big initia an running costs, the syste has iite appication in sa pots of the eveoping countries (Singh et a., 2009). 1.2 Objectives of the Propose Stuy Microtubes aso cae spaghetti tubes are sa bore poyethyene tubes, in the range of 1 to 4 in interna iaeters, are use as eitters in rip irrigation syste. These sabore tubes can be use as pressure copensating eitters in rip irrigation syste. Utiizing these fexibe tubes as an aternative to oern ripping eitters wi reuce the risk of cogging significanty as they have siper passages than those eitters. Microtubes have been successfuy use as eitters in rip irrigation syste with the benefit of having equa fow rates at a outets aong the ateras without significant probe of cogging (Vereiren an Jobing, 1980). The varie tota heas aong the ateras can be copensate by using a set of varie icrotube engths to provie requisite frictiona osses an thereby to eiver equa fow rates to pants. Otherwise, ateras wou have ischarge varying fow rates accoring to its varying inet tota heas. These inet heas, inee vary ue to frictiona osses in the succeeing anifo reaches for its ensuing ischarges. When each icrotube works as an eitter an ischarges equay (eission unifority, EU = 100%) at ifferent points aong a particuar atera, the atera at that tie can aso be iagine as an eitter aong the given anifo (Keer an Karei, 1974). Thus on the other han, if we want to stanarize a set of varie icrotube engths for an inet hea of a given atera, it wou eiver proportionatey varying ischarges accoring to the inet heas of the successive ateras. Because this stanarize set of icrotube engths are erive base on an inet hea of a given atera to eiver equa ischarges, the given 4

17 atera wou have a characteristic pressure-ischarge reationship, which can subsequenty be appie for successive ateras with varying inet heas to prouce consequentia ischarges. These ischarges as wou vary aong the anifo ine, a iiting eission unifority (EU) set by the esigner, wou ictate the resuting ength of the anifo with the nuber of ateras to ecie about the iensions of the irrigation subunit. Coputes coes are written to cacuate the icrotube engths an tota heas aong the ateras within a subunit for a given ischarge or ischarges set through EU. These ischarges are projecte accoring to the ean of the pants an the iiting percent of EU. The iaeters of the icrotube an atera, groun sope, an spaces between pants are use to copute the tota heas of the syste an the ength of anifo require to fufi the consiere EU. In one coe the ateras are iagine as arge eitters aong the anifo an the set of icrotube engths are propose to be sae for a the ateras, thus eission unifority wou ictate the subunit iensions. In the other coe, for a given subunit, varying icrotube engths aong each atera are cacuate to prouce equa ischarge throughout the syste to achieve 100 percent EU. Therefore, the specific objectives of this research are as foows: 1. To eveop coputer progras, one is for pre-efine EU (EU = 90%) set by the esigner an the other one is for a Fu EU syste. 2. To use the above coputer progras for severa typica scenarios, specific esign tabes an graphs wou be eveope to eterine appropriate icrotube an anifo engths. 3. To appy the propose techniques to few typica esign exapes. 1.3 Scope of the Stuy A suit of coputer coes have been written using Visua Basic as a graphic user interface (GUI) progra which can easiy be run by orinary hoe coputers. In orer to achieve the best accuracy using the progra, the esigner shou consier soe constraints that wi be iscusse ater. The progras that have been eveope to siuate the syste are as foow: 5

18 i. Deterination of icrotube engths an inet pressure hea of the en-atera in this coe the icrotube an atera iaeters an icrotube spacing an nuber shou be known. ii. Deterination of ength an inet pressure hea of the anifo assuing each atera in the anifo works as a arge eitter in this part the fow rates of a successive ateras have been copute for a given EU using the resuts fro first coe an the corresponing pressure-ischarge reationship. This coe has been eveope base on the practice of convenience that the entire syste appies the sae set of icrotube engths as obtaine in en-atera. iii. Design an iea rip syste with 100 percent EU using varie icrotube ength a over the syste this coe aso works base on the resuts of first coe to initiate an create new series of icrotube engths for each atera separatey. Design tabes an graphs have been generate for irect cacuation of icrotube engths. iv. To eonstrate the functionaity of the above two agoriths, reevant esign paraeters for rip irrigation syste are appie to few case stuies. These case stuies prepare with the reevant soi an an paraeters for toato an grape pants, appropriate to appy in rip syste. 1.4 Thesis Outine This thesis consists of seven chapters an few appenices after the ist of references. Chapter 1 escribes backgroun inforation about rip irrigation, its avantages an probes, sets the objectives of the stuy an provies scope of work of this research. The ain purpose of Chapter 2 is to fin the ost reevant works an stuies to iprove the unerstaning of the probe, an then getting faiiarity with techniques an anaysis. 6

19 In Chapter 3 the basic hyrauic principes are iscusse to estabish the theoretica eveopent of the propose rip irrigation syste esign. The chapter gives the unerpinning agorith of two anticipate approaches to siuate typica rip irrigation systes. The concept fro previous chapter is unertaken here in Chapter 4 to eveop few coputer progras/coes to sove the two approaches of rip irrigation syste esign. The two esign approaches eveope are: i) a syste with Pre-efine Eission Unifority, an ii) a syste with Fu Eission Unifority. The progra can be operate sipy to copute the pressure istribution, icrotube engths aong the ateras, an eission unifority (EU) of the syste. The resuts of the siuation for typica rip irrigation syste are suarize in Chapter 5. The chapter introuces few esign graphs an tabes using the concept of energy graient ine schee to show how the new process of coputation works. A typica ayout aong with soi, eteoroogica an reaistic irrigation paraeters is consiere in Chapter 6 to eonstrate fie esign exapes. The resuts of the exapes obtaine to evauate the functionaity of the propose agoriths. Finay Chapter 7 presents the concusions an recoenations for future research. 7

20 Chapter 2 Literature Review 2.1 Microtubes an Eitters During recent years, nuerous rip irrigation eitters with varying characteristics have becoe avaiabe in the arket. To have the best eission unifority an iniu fow rate fuctuation ue to pressure istribution, soe of the eitters have been esigne as pressure copensating eitter. Soe of the are sef ceaning or fushing to reuce the cogging but others can be cogge easiy an require sophisticate water fitration. Sooon (Sooon, 1979)) an (Keer an Karei, 1974) aong others have iste the esire quaities of those eitters in rip irrigation systes. Drip or tricke irrigation researchers have chosen two approaches to sove the cogging probes (Bucks et a., 1979). The first approach is to focus attention on iproving the quaity of water before it reaches the eitters. The secon approach is to eveop eitters or evices to reain free fro cogging. Extensive researches were one by Bucks et a. (1979) using 8 types of eitters an 6 ifferent treatent processes for water fro various sources. The stuy inicate that a cobination of suitabe physica an cheica treatents is neee to keep the eitters free fro cogging. Particuary fitration aong with p ajustent was essentia in orer to contro the cheica precipitation an bacteria growth. Furtherore, it showe that the expanabe iaphrag eitters treate by cheicas for bockage probes, afunction in its ong ter operations (Bucks et a., 1979). In a hyrauic perforance anaysis on various kins of eitters, ezarjaribi et a., (2008) cacuate the anufacturing variation coefficient, eitter ischarge coefficient an eitter ischarge exponent in orer to estabish fow sensitivity to pressure an copare anufacturers specifications. The resuts inicate that for the chosen eitters the anufacturers suppie ata are not reiabe for esign purposes. Reiabe fie tests are require prior to esign of a rip syste. In fact using the anufacturer s ata wi ea to non-unifority of ischarge throughout the syste (Özekici an Snee, 1995, ezarjaribi et a., 2008). 8

21 Recent stuies inicate that in eveoping countries the size of fars have been ecining ay-by-ay uner continuous popuation increase. Sa an hoers are not abe to utiize oern technoogies for those sa fars. The efforts to fin cheap an efficient etho of irrigation for such sa fars were investigate to raise the prouctivity without neeing to use sophisticate technoogies. In any of these works, icrotube has been recoene as a ow cost an easy to insta eitters. Researchers inicate that the cost is substantiay ess than conventiona eitter systes (Singh et a., 2009; Bhatnagar an Srivastava, 2003; Ea et a., 2009; Poak, 1998). When icrotube is use as an eitter in a rip syste this sa tube itsef issipates energy to fow a certain ischarge. The ost iportant variabe in its esign is the cacuation of energy osses ue to friction at the inner wa of the tube an other inor coponents ike entrance, exit, vaves, bens, etc. These energy osses aso represent the inet pressure of the icrotube since the outet pressure is zero (Khatri et a., 1979); (Bhuiyan, 1990) Use of icrotube as eitter was first conceptuaise by Vereiren an Jobing (1980). The sizes of the tubes were ess than 0.9 an suppose to be the sipest an cheapest aong a the water istributor evices. Microtubes as sa bore poyethyene tubes can be any sizes between 0.6 an 4.0 interna iaeters. The ischarge fro a icrotube varies accoring to the operating pressure, interna iaeter an ength of the tube. In other wors, for a given interna iaeter, the ischarge of a icrotube ay be kept constant uner various pressure conitions by ajusting its ength. Therefore, if the pressure istribution aong a atera is known, unifor istribution of water can be achieve by using appropriate engths of the icrotubes. In this ine of concept, Bhuiyan et a. (1990) propose an agorith to obtain a variabe set of icrotube engths as an eitter to eiver unifor ischarge aong a typica atera ine. Nowaays icrotubes are wiey use as an extension for icro-sprinker or icro-jet systes to increase the outet pressure an therefore to cover arger areas. These sa tubes are aso suitabe for unuating ans where the pressure of the syste varies consieraby accoring to ifferences in eevation. Thus their engths can be ajuste accoring to pressure heas to eiver a unifor ischarge. 9

22 Recenty Internationa Deveopent Enterprises (IDE), a non-profit organization base in Coorao, USA has suggeste the use of this sa iaeter poy tubes in ow cost rip irrigation kits. They beieve that by connecting icrotubes to pastic tape ro ateras an then to ow-height tank wou provie an easy to insta an cheap ow-pressure rip irrigation syste, speciay for eveoping countries in Africa an Southeast Asia (Ea et a., 2009). An experienta project was unertaken to use icrotube as eitter to irrigate ans with various sopes. The resuts showe a wie variation in eission unifority (EU) particuary with increasing upans. The reason of this wie variation is ue to the use of equa ength icrotubes throughout the syste. In another siiar stuy the eevate tank was provie to suppy unifor ischarge to ifferent hiy terraces in northwest iaayas (Bhatnagar an Srivastava, 2003). They recoene a star configuration ayout of icrotubes (1 iaeter) as eitters to service four rows by one atera. Their resuts show that this configuration iprove the eission unifority to 94-98%. In effect it is foun that the nuber of pants serve by this configuration is very iite copare to coercia type of rip irrigation systes. (De Aeia et a., 2009) worke on an epirica approach to eterine a new icrosprinker syste where icrotube engths can be ajuste to eiver a noina ischarge for a given pressure. They foun a set of pressure-ischarge an pressure-ength regression reationships for 1.07 an 1.5 icrotubes to eveop this new type of eitter. owever, it is foun that various fow regies have been ignore for its hea oss cacuations. Khatri et a. (1979) worke with seven ifferent iaeter icrotubes (0.8 to 4 ) to easure hea osses in the rip irrigation syste. The resuts showe that Darcy-Weisbach equation can be use aong with Basius friction factor equation for those hyrauicay sooth icrotubes. Anaysis was one for the separation of inor osses an to prouce coefficients for ifferent fow conitions. owever, finay it concue that the icrotubes are sighty soother than the hyrauicay sooth pipes as specifie in the Mooy iagra. Experienta resuts by (Watters an Keer, 1978) confire that the friction factor, f of the Darcy-Weisbach equation for sooth intereiate iaeter pipes (4 to 12 ) can be estiate by using Basius forua. They provie soe graphica soutions base on set of sipe equations to represent a wie range fow rates encountere 10

23 in rip irrigation systes. Experients by von Bernuth an Wison (von Bernuth, 1990) on arger iaeter pipes (14, 16 an 26 ) an for Reynos nuber ess than 100,000 aso showe that the Basius equation is an accurate preictor of the Darcy-Weisbach friction factors. It was concue that Basius equation has reasonabe accuracy for estiating friction factor for a range of tubes in turbuent fow conition. 2.2 Design Consierations for Eitters aong the Lateras The concept of best eission unifority was one of the key factors for the seection of atera ength an the nuber of eitters aong it. In this regar, Christiansen (1942) carrie out the first work for a pressurize sprinker syste. The paper propose a coefficient of unifority ( U ) for the syste base on getting the easure on average of c the absoute eviations of each observation fro the ean observation. In equation forat it can be written as: where, q U c (2.1) q 1 q n n i 1 n 1 q i q, q n q i i 1, an n = nuber of observe ischarge vaues. For a typica rip syste, the eitter fow rates epen on eitter characteristics, aging an variabiity in anufacturing of eitters, friction hea osses in the pipe network, topography of an an the nuber of cogge eitters in the syste. Ieay, the appication of water throughout the rip irrigation syste shou be absoutey unifor (Sooon an Keer, 1978). To achieve this objective Meyers an Bucks (1972) an Wu an Gitin (1973) have eveope a esign proceure using ifferent size pipes. The theoretica perforance of utiizing 5 ifferent size eitters aong a atera ine shows 3.3% eviation fro esign ischarge whist for a singe eitter size this vaue is +21% to -7.4% (Myers an Bucks, 1972). owe an ier (1974) propose a esign proceure base on Christiansen coefficient of unifority with consierations of eitter characteristics, frictiona hea osses an eevation ifferences of the topography. Wu an Gitin (1977) propose a technique to ivie a atera ine into severa sections an use ifferent size pipes for each section. Their stuy shows that this sipe fashion oifies the energy graient curve of each section to a straight ine except the ast section. They 11

24 aso concue when a atera or anifo is ivie into sections the ean ischarge of each can be use to estiate the tota energy rop by friction. This approach can be use for both unifor an non-unifor sopes; however, a sopes have to be own sopes. Wu an Gitin (1974, 1975) eveope a iensioness energy graient ine approach for irect cacuation of energy rop for a range of eitter fow variation (ess than 20%) aong a singe atera ine an a subain unit. Wu (1992) eveope a coputerise esign technique using energy graient ine etho to cacuate the fow rates. A step-by-step (SBS) cacuation has been carrie out to copare the resuts an fin out the eviations between two approaches. Karei an Peri (1977) suggeste a esign proceure for a singe atera by cacuating the pressure hea at each noe backwar fro the ownstrea noe. Pero (1979) eveope a graphica esign proceure using coputer progra for the esign of icroirrigation pipe syste. In this esign, fow rate is assue to be constant using ajustabe icrotube as feeer. The resuts of the siuation trias shou be potte to fin an optiu size for each atera. In another stuy, Pero (1977) eveope a pocket cacuator iterative proceure by eans of a series of iensioness soutions to esign a constant size atera with utipe outets. The copeent of the Christiansen coefficient is use as a criterion. Thus the average of the absoute eviations fro the ean outfow is consiere as a esign criterion. Finay a esign chart is presente to fin the perissibe nuber of outets for the given ean eviation. athoot et a. (1993) eveope a coputer progra that cacuates the veocity hea change an the variation of Reynos nuber aong the atera pipe. Sipe noniensiona charts are prepare for soe nuerica exapes to inicate that variation of Reynos nuber aong the atera is iportant. In this stuy the eitter spacing is unifor an the outfow of iniviua eitters is evauate stepwise fro the first eitter. The unifority of the syste is the ain esign criteria to fin the best atera ength. Kang an Nishiyaa (1996a, b) appie the finite eeent etho an goen section search to fin the operating pressure hea of the atera that can prouce the require 12

25 average eitter ischarge. A coputer progra eveope to cacuate the best subain position an the operating pressure by input the known paraeters such as average eitter ischarge, require water eission unifority an other conitions. Through a ifferent work, Vaesquino (2008) presente an aternative etho to siuate hyrauic perforance of ateras for sprinker an tricke irrigation systes. The etho estiates the outfow of siiar type of ateras but with ifferent engths. In this stuy two hea osses have been taken into account, one is transversa originating through the risers as a consequence of friction an oca osses an another one is ongituina originating aong the atera because of the friction an oca osses. The resuts of oe have been copare to step-by-step cacuation (SBS) an energy graient ine version (EGL) an it is concue that the resuts are coser to SBS etho, whie the eviation fro EGL etho is greater ue to consiering transversa hea osses. 2.3 Pressure Distribution aong the Latera Accoring to Christiansen work (Christiansen, 1942) for sprinker systes, a curve of pressure versus position aong the atera ine sees to have the sae genera shape regaress the aount of fow rate, hea oss an ength of ine. The fow conition in atera ine is steay an spatiay varie with eitter outfows, thus the istribution of ischarge aong the ine is increasing upstrea. Due to the variation of ischarge in the ine, the energy graient ine wi not be a straight ine but a curve of the exponentia type. Wu an Gitin (1975) eveope iensioness pressure curves for three types of fow regies in ateras. These iensioness curves propt the esigner to cacuate the energy rop aong the atera ine. They foruate a genera equation to cacuate the tota energy rop base on tota ischarge or average ischarge in the atera ine. So the soution is ony an approxiation since the energy graient ine is eterine by assuing a eitter fows are constant (or with sa variation). To overcoe the probe an increase the accuracy of esign this irect Energy Graient Line (EGL) approach oifie into Revise Energy Graient Line (REGL) approach using revise tota ischarge cacuation. It is concue that a ean fow approxiation can be use to eterine the ajuste tota ischarge for cacuating tota friction rop at the en of atera ine an use for irect cacuation for eitter fows for the REGL approach. It is aso concue that the coparison of EGL an REGL with Step By Step (SBS) etho for each eitter fro 13

26 ownstrea to upstrea shows ony 1% ifference in eitter fow variation as ong as the esign is ae within 20% eitter fow variation. Keer an Karei (1974) confire that genera shape an characteristics of the eitter hea-oss curve are essentiay inepenent of the eitter exponent an aount of hea osses. A etaie anaysis of any ateras using a coputer oe confire that for wie range of eitter characteristic vaues an pressure osses, the average pressure of the atera occurs at 40% of the atera ine. They aso foun that approxiatey 77% of the tota atera hea oss occurs between this 40% ength of atera ine fro starting point, eaving 23% between 60% of atera ine up to en. owe an ier (1974) presente esign equations for the eterination of atera ength to eet specific unifority criteria. The eitter fow function is utiize to eterine the aowabe pressure oss to eet the unifority stanars. Eitter fow variation is a function of the unifority coefficient. Thus, by knowing the eitter fow function, eevation change an esign unifority, the aowabe pipe friction oss can be copute. Then taking the pipe size, pipe roughness coefficient, reuction coefficient for iviing fow, average eitter fow rate, aowabe pipe friction oss eterine previousy, an either the nuber of eitters per atera, the atera ength can be eterine. For this purpose equations an iensioness graphs eveope to assist the esign of ateras. Design input ata incues the eitter fow function which cou be obtaine fro anufacturers specification an reuction coefficient for iviing fow an eitter friction an inet pressure of atera. When the aforesai ata are known the iensioness graphs can be use to eterine atera ength as a function of the nuber of eitters per atera. Yiiri (Yiiri, 2007) presente an anaytica technique to sove hyrauic esign probes of various types of utipe outet pipe ines in ifferent fow regies an unifor ine sope cases. This etho cou be generaize an appie for tricke, sprinker an even gate pipes. To cacuate the pressure an ischarge the iprove energy graient ine is eterine base on the average friction rop with a sipe exponentia function to express the non-unifor outfow concept. To eterine friction hea osses, the Darcy-Weisbach forua is use an the kinetic hea change is consiere whereas inor hea osses are negecte. To iprove the accuracy of the technique, 14

27 eterination of pipe segents in ifferent fow regies have been taken into account. For the unifority purposes, it is propose that the axiu ifference in the outet operating pressure hea aong the pipeine is ess than a percentage of the average pressure hea. The resut of soe exapes sove by this etho are copare to nuerica resuts of SBS etho carrie out by(athoot et a., 1993), which shows fairy sa ifference. 2.4 Manifo Design The esign of the anifo is siiar to the atera esign. owever, the spacing between outets is greater an arger fow rates are invove. The nuber of ateras an spacing between the eterines the anifo ength. The seection of the nuber of ateras epens on the consierations ike: a) keeping within esire pressure ifferences, b) econoic trae-off between the iaeter an of the ateras an the anifo, c) the etho of irrigation anageent, an ) the egree of autoation of the syste. Most of ateras an anifos in rip irrigation have been esigne base on a singe pipe size. The energy graient ine has been erive an presente by an exponentia curve that is use as basis for esigning ateras an anifo ines (Myers an Bucks, 1972, Wu an Gitin, 1973). owever, uner certain fie conitions, the ength of ateras an anifos ay be reativey ong an have non-unifor sopes, so the use of ifferent iaeter pipes is inevitabe. Wu an Gitin (1977a) propose a graphica etho to esign atera or anifo ine with varying pipe sizes. They showe that by choosing ifferent pipe iaeters the energy graient ine wi be cose to the sope of the pipeine an therefore, the pressure variation wi be reuce (Wu an Gitin, 1977a). 2.5 Chapter Suary This iterature review shows that cogging an non-unifority are the two ain probes of rip irrigation systes, which ifferent researchers trie to sove since ong back. Using icrotubes as eitters is a soution that has been stuie by very few researchers. The ost recent stuies show that the appication of this iea in soe eveoping countries for sa pots is efficient an hany for farers. 15

28 The hyrauic anaysis in orer to obtain the ischarge in any kin of eitter is another concern in rip irrigation esign. Resoution of this probe is iportant to eterine the efficiency of the syste, which is cae Eission Unifority (EU). Different ethos are iscusse to cacuate the eitter ischarge throughout the syste an each one has its own avantages an isavantages. Stepwise etho is the ost accurate etho but teious an tie consuing for anua cacuation, however coputer aie ethos can be introuce to reuce the tie an iprove the accuracy. 16

29 Chapter 3 Theoretica Deveopent 3.1 Layout of a Typica Irrigation Subunit Microtubes can be appie as eitters for unuating an hiy ans. Its ength can be ajuste accoring to the pressure istribution aong the atera ine an so equa ischarge cou be eivere to pants. Since the fow conition in the atera ine is steay an spatiay varie with ecreasing ischarge in the ownstrea irection, the resutant energy grae ine wou foow an exponentia curve. Figure 3.1 shows a typica subunit where icrotubes are eerging fro the ateras to function as eitters. It can be seen that the icrotubes have eerge fro one sie of the ateras so as to faciitate the operations of the far achineries an to reuce the copexity of pipe ayout. As can be seen the iniu pressure hea require, at the en of the very ast atera (en-atera) epens on the frictiona an other inor hea osses to overcoe. The frictiona hea oss prouce is irecty proportiona to the ength of the icrotube, which in turn is the istance between the atera an the pant where water to be ischarge. The choice of this istance wou epen on the irrigator s practice an the physica faciities to be operate in the fie. Figure 3.1 Scheatic ayout of a rip irrigation subunit using icrotubes as eitters 17

30 Figure 3.2 shows the etais of a singe atera ine where icrotubes have varying engths to copensate the extra heas eveope aong the atera. It wi be eonstrate ater that to achieve equa ischarges q 1 q2... qn for up (positive) an fat (zero) sopes, the icrotube engths wou be ( n in ). The icrotube ength n at the en of the atera is taken as the iniu ength, eterine fro reaistic istances between pants an ateras. The increase in icrotube ength is neee to issipate ifference of extra hea (e.g., n 1 n ) an give equa ischarge for a the icrotubes in the atera. As shown in Figure 3.2 the increase ength of icrotubes can be wrappe aroun a stick (etai A), or the atera itsef (etai B), to keep a constant istance between atera an the pant. In this stuy the ter coi is use with a iaeter of 3 c (using etai A), which can be atere by the esigner in other circustances. It is to note that there wou have extra oss of energy ue to these coiing. Figure 3.2 Scheatic ayout of a singe atera aong with varying engths of icrotubes; etais A an B shows the instaation ethos for aking cois So with the given configuration, the varying ength icrotubes wou reease equa ischarges throughout the en-atera. To obtain these engths an the nuber of cois, the tota hea at each icrotube inet shou be cacuate. Subsequenty there wi be two ayout configurations, one wi have the sae set of icrotube engths in the foowing ateras of the subunit, which in turn wi require to iit 18

31 the nuber of ateras in the subunit to prouce a pre-efine eission unifority (EU), an the other one is to vary the icrotube engths throughout the subunit to eiver equa ischarges (EU = 100%). Let us nae these two configurations, one wi be cae Preefine EU ayout an the other one wi be cae Fu EU ayout. The conceptua setting of eission unifority (EU) of these two ayout configurations is iscusse in ore etais in the foowing sections. 3.2 Basic yrauic In this stuy Darcy-Weisbach equation is use to cacuate the frictiona osses in ifferent pipeines throughout the subunit. As ischarges aong the ines are spatiay varying, fow regies are going to change accoring to the veocity conitions in it. Reynos nuber ay be cacuate to know the fow regie an thereby to seect the appropriate equations for estiating friction factors of Darcy-Weisbach equation. Darcy-Weisbach equation to cacuate frictiona hea osses in pipes can be written in MKS units as 2 v h f f (3.1) 2g For ainar fow the friction factor f can be written as f 64 (3.2) R e For turbuent fow with Reynos nuber between 3000 an 100,000, Basius equation gives goo approxiation for coputing friction factor f, which can be written as where, 0.32 f (3.3) 0.25 Re R e = Reynos nuber, h f = frictiona hea oss, an = ength an iaeter of the pipes, g = acceeration ue to gravity, an v = veocity of fow. Equations ( ) can be cobine to obtain the equations for ainar (Eq 3.4) an turbuent (Eq 3.5) fows, respectivey: 1.32 q h f (3.4) q h f (3.5)

32 where, h f = frictiona hea oss (), q= ischarge (itre/hr), = iaeter of the pipe (), = ength of the pipe (). Kineatic viscosity of water at 15 C is taken as /s. Veocity an other inor osses of the syste can be written in genera for as 2 v h k (3.6) 2g where, k = hea oss coefficient, which in three ifferent inor oss coefficients are ifferentiate as: i) k e = 1.2, to cacuate entrance hea oss assuing the entrance fro atera as a re-entrant one, ii) k v = 1, to cacuate veocity hea, an iii) k c c 1.3, to cacuate coi hea oss, where 1.3 has been extrapoate (for D / 12.0 an = 360, where D an are the coi an icrotube iaeters an is the ange of ben subtene at the centre) fro Ito s iagra (Ito, 1960) on oss coefficient for sooth bens, c is the nuber of cois that can be copute fro ifference of two icrotube engths as D c 1. Ony whoe nuber of cois is taken for the cacuation of hea osses. n n Thus, Eq (3.6) can be rearrange to accooate for the above three ifferent inor osses as foows: 2 q h e (3.7) 4 2 q h v (3.8) 4 2 q h c (3.9) 4 Energy grae ine as shown in Figure 3.3 is reate to hea osses in one sie of the atera. Tota hea at the inet of the icrotube at point n can be cacuate by suing a the hea osses as foows: h e h h ( n) (3.10) v f n By pacing the icrotube with iniu ength at the point n, the baance of energy heas between two successive points, ( n 1) an n can be written as h e h h ( n 1) h ( n 1) h h h ( n) h ( n) S (3.11) v f c e v f f 20

33 where S an are sope of atera an istance between icrotubes, respectivey. Since the ischarges are sae in a the icrotubes, entrance an veocity hea osses are equa in a the icrotubes, so Eq (3.11) can be written as h f ( n 1) h ( n 1) h ( n) h ( n) S (3.12) c f f Figure 3.3 Energy grae ine an hea osses in one sie of the atera ( h e = entrance oss, h v = veocity oss, h c = coi hea oss, h f (n) = icrotube friction hea oss at n, an h f (n) = atera friction hea oss between n an n 1) By substituting fu expressions for each of the hea baance ters there wi be a tota four equations for four cobinations of ainar an turbuent conitions in atera an icrotubes as foows: 1. Fow regies are ainar in both the icrotube an atera n 1q cq 1.32 nq 1. 32nq S (3.13) 2. Fow regies are ainar an turbuent in icrotube an atera, respectivey n 1q cq 1.32 nq nq S 3. Fow regies are turbuent an ainar in icrotube an atera, respectivey (3.14) 21