Modeling of the Seawater Greenhouse Systems

Transcription

1 Modeling of te Seawater Greenouse Systems M. Amidpour Associate Professor Head of epartment of Energy System Engineering K.N.oosi University of ecnology, eran, Iran G.R. Salei P.. Student of Fluid Mecanical Engineering Islamic Azad University Nowsar Nowsar,Iran B. Gorbani M. Amadpour M.Sc. of Energy System Engineering M.Sc. of Energy System Engineering epartment of Energy System Engineering Islamic Azad University akestan Branc,akestan K.N.oosi University, eran, Iran Abstract e Seawater Greenouse system uses sunligt, seawater and air to provide freswater and cooled and umid air, so tat in addition to provide te water required for greenouse, supply more sustainable environmental condition from cultivation of crops in arid coastal regions. In tis system ambient air is passed troug te two evaporative cooling pads, wic plant growt area is placed between tose pads, by fans tat placed end of te building, and ten returned taking umidity on te tube-and-fin condenser. In order to decrease te entrance eating load to te plants, use pipe arrays to provide sade. is paper tries to describe simulation te Seawater Greenouse considering condition of te Bandar Abbas City in IRAN. ifferent cycles of Sea water greenouse, including arrangements, was modeled and obtained te beavior of eac cycle one of te results of tis paper is presenting an enanced model to earn more produced water. Next, optimal working conditions are specified for absorption cillers and after tat, te effect of te termoeconomic parameter on te maximum termoeconomic criterion, coefficient of performance and te specific refrigeration load corresponding to te maximum value of te termoeconomic criterion are investigated. Keywords- greenouse; seawater; design; modeling; evaporator I. INROUCION e earliest solar distillation plant on record was designed and built in 7 by Carles Wilson in Cile albert et al. 7. It was furter developed at te University of Arizona in in cooperation wit te Georgia Institute of ecnology and te University of Sonora, Mexico at Puerto Peñasco,New Mexico. Hamed and etal in Farid in and Goosen and etal in ad presented a well detailed study about sun fres water making plans and policies. But, te seawater Greenouse istory returned to. e first experimental project started in enerife in. is prototype Seawater Greenouse was planned in England and constructed in enerife. e increasing water requesting growt and water providing resources sortage are two certain and predictable problems in century. Now, te great areas in te world suffer from drougt. e deserts are developing and in comparison, raining as a fixed movement. Wile water requesting ave been two times in present years, request forwarding from refresing resources amount is following at te same way. About 7% total water uses are in farming and ten water crisis can be review in so close relationsip wit food materials producing and economy development and creating. Custom and traditional farming wic just need few undred liters water just produces one kg output and it is because of tis farming style inefficiency in water management. e farming and its increasing water requesting will be an important pressure point in wic seawater Greenouse will elp using and incorporating natural processes in order to provide low-cost resolution for presenting permanent and similar model in arid coastal regions to decrease tis pressure. Seawater Greenouse provides an ambient in wic plants sweating is as low as possible. So, Greenouse produces its needed sufficient water during sun distillation operation. II. NOMENCLAURE diameter...m E tickness...m F Seeing surface... g Acceleration due to gravity... ms - entalpy... kjkg - eat transfer coefficient... wm - k - I solar radiation intensity...wm - k ermal conductivity... wm - k - M mass... kg M flow rate... lits - Nu Nusselt number... p pressure... pa pr Prandtl number... Q Heat transfer...kj

2 ynolds number... emperature... k U Specific energy... kjkg - V velocity... ms - stefan-boltzmann constant... wm - k - V viscosity... ms - V transmittance... ms - Entering air to first evaporator Entering to first evaporator out from first evaporator Air out from first evaporator 5 Entering to pipes array 7 Entering air to growing space Air out from roof space Air out from growing space Entering water to second evaporator Entering air to second evaporator out from second evaporator Air out from second evaporator Entering water to condenser 5 out from condenser water production 7 Air out from condenser absorptance Emittance lative umidity content III. MOELLING AN OPIMISAION In Seawater Greenouse, te planting place is between two evaporative cooling pads wic te first one is responsible for providing umid and cool ambient and te second pad performs air saturation operation as muc as possible. In te greenouse, for decreasing sun sining load was used pipe arrays carrying seawater to sadowing. ese pipes feed te second evaporative pad troug water wic eated by te sun. And so tat elp umidify te air. e first evaporator e first stage in Greenouse simulation is te study of te evaporative cooling pad in te front of greenouse. Energy and mass balance for evaporator gives: m m m m ( m m m m ( e entrance air mass obtained wit equation : m m Air ( e evaporative water amount will take from: m m m Air ( ( f, (5 f, ( f (7 f ( f (, ( f, ( In tis stage, te evaporator takes umid by passing te umid surface and so getting saturation and results visible drop temperature. e growt area: Air after passing troug te evaporator enters te growt space. Before air entering in plants growt space, part of it directs to te space in up. is part as an important role in freswater production and simulate as follow: e roof: I Up Up ( F.. F... e left: F F I... F... e rigt: I... Sky F F....Sky.Sky.. F.Sky.. Sky Sky ( ( s carrying seawater:..i ( F.. ( F F,,.... e :.(. F,.. F Up F,,.... Up e k I e Greenouse out air : F,... (5 Nu.k L ( Nu 5 L, (.7 7 Pr (7 Pr f ( V.L L, ( f,pambient, ( V. m ( f Ambient, P, ( k f, PAmbient, ( e passing water from te pipes: Nu k (

3 Nu. Pr. L.( Pr L (5 Pr f ( m (7 f, P ( Ambient k f ( In tis stage, by taking two control volumes around te Greenouse up and down space tat separating by te pipes carrying seawater, we ave te following equations. m ( m Up Up Up m 7 7 m ( f (, ( f (, ( e Greenouse mean temperature at up and down space and te mean temperature of te pipes passing water are defined according to, 5 and : Up ( 7 (5 5 ( e entering air divided into two brances tat flowing down branc as te duty of umidification and cooling of te ambient and te up branc as te duty of by removing te eat gained from sun by pipe arrays and applying it increasing umidity capacity of air in exit. ese two brances were mixed by near te second evaporator and caused increasing air temperature and moisture capacity. ese combinations write as follow:,p, (7 f Ambient f, PAmbient, ( e second evaporator: is evaporator analyzes suc as te first one Condenser: According figure, te governing equations are as following: m m m 5 5 m m 7 7 ( m m 7 m Air ( 7 ( m m ( m7 f ( 5 f (5 ( f (, P, (5 7 f 7 Ambient 7 7 f 7, 7 ( Finally, all of tese equations stimulate and solved by EES program. IV. RESUL AN CONCLUSION Bandar Abbas ave cosen as stimulation reference, and was simulated based on te following te following amounts: P Ambient KPa, V m s, I 5W m, L m,., m kg s, m Lit s FigureI sows te difference temperature between te inlet and outlet of te first evaporator as function of te mass flow rate of entrance air and te relative umidity of entrance air. Wit increasing mass flow rate, and was increased and it caused more evaporation and te temperature of air was decreased. FigureII sows te difference temperature between te inlet and outlet of te first evaporator as function of te mass flow rate of sea water and te relative umidity of entrance air. As sown in te figure, te more increasing mass flow, te more decreasing temperature drop. Furtermore, te more increasing umid, te more decreasing temperature difference. FigureIII sows water producing water according to entrance air mass flow and various air umid. As you see in tis figure, entrance air increasing as affected water producing tendency increasingly and as ad an important step toward its decrease. FigureIV sows water producing mass flow based on seawater mass flow and various airs umid. As ave sown seawater mass flow increasing causes temperature dropping, ten more warm air goes to te roof and its entrance will be warmer and caused te exit water will be warmer, tis increases water inclination to evaporation and umid absorbing more. ese events in addition to warmer air gets condense better in condenser will increase producing water in it and also we see clearly increasing in seawater mass flow will increase te producing water. FigureV sows Greenouse floor temperature based on entering air mass flow and various air umid. As ave considered, increasing entrance air mass flow will decrease te outlet temperature of te first evaporator, and it results in more eat transfer to greenouse floor and decrease its temperature. In addition, entrance air mass flow increase affects and Nu and increasing and absorbs multiple eat, so we can say te iger umid will be as te same as more soil temperature. As we see in tis figure, entrance mass flow increasing as decrease eat, and more umid, will increase Greenouse floor in a certain air mass flow. FigureVI sows te temperature of Greenouse floor as a function of seawater mass flow and various airs umid. It is cleared tat te increasing water producing mass flow as increased soil temperature. It appens more in muc umid. V. CONCLUSION e difference cycles was simulated ere to find te optimum cycles in tis Greenouse. e stimulations were ruined according te Bandar Abbas conditions. e first cycle wic as sown by C in te figures, is te simplest one and te

4 ifferential emperature temperature ifferential emperature temperature Produced Produced water canges in oter cycles are based on tis plan. C is a plan for decreasing te greenouse floor temperature. e air wic exits te condenser will be passed te under of te growt space in order to decrease Greenouse floor temperature. C is a similar plan wit te same goal by anoter approac. In tis cycle, te water wic exit te first evaporator is passed te under of Greenouse floor space, like previous plan, for decreasing te temperature. C, C5 and C ave considered in order to low cost and eac of tem includes tese canges: condenser feeding from te first evaporator exit water, pipes array feeding troug condenser exit and finally pipes array feeding by te second evaporator exit. Now, we study tese graps in detail: Considering present cycles we can sea wit increasing umidity te water producing was increased. Anoter important result will obtain from tis grap is:m: C>C>C>C5>C>C FigureVII sows water producing in different cycles according to various air umid, and describe cycle is te best in water production and providing pleasure eat for greenouse floor (in tis way and troug termal transmitting increasing to te air produces water and also says condenser feeding troug exit water from operator just low cost and asn't so profits in water producing.figureviii sows water producing in different cycles based on various entrance air mass flow rate: is grap interpretation is like grap 7 and te alone point wic isn't mentioned is in all cycles increasing entrance air mass flow equal water producing.figureix sows te location of different places in basic cycle. - - Inlet Air Mass Flow R.H. = R.H. =. R.H. =. R.H. =. FigureI. effect of eat inlet mass flow in iff Inlet Air mass Flow R.H. = R.H. =. R.H. =. R.H. =. FigureIII. effect of inlet mass flow in produced water Seaw ater Mass Flow R.H. = R.H. =. R.H. =. R.H. =. FigureIV. effect of sea water mass flow in produced water Sea water Mass Flow R.H. = R.H.=. R.H.=. R.H.=. FigureV. sea water mass flow in floor temp Seaw ater Mass Flow ifferential emperature R.H. = R.H. =. R.H. =. R.H. =. FigureII. effect of sea water mass flow in iff. R.H. = R.H. =. R.H. =. R.H. =. FigureVI. iff. em. in emperature

5 Produced Produced 5 Suggested Cycles R.H. = R.H. =. R.H. =. R.H. = FigureVII. effect of suggested cycles in produced water - 5 Suggested Cycles m = m = 5 m = m = 5 FigureVIII. effect of suggested cycles in produced water in mass m,, In Sky m, m m m 5 5 m,, m, Up Up, Up,, s Array m,, m m m Fan m 7 7 7, In m Growt Area 7, 7, 7 m,, m,, m, m, First Evaporator, Second Evaporator Condenser m, m, 5 5 FigureIX. Location of basic cycle

6 FigureX. Location of different places in basic cycle VI. REFERENCES []. ata Processing Center, Annual Weater port of te Year []. albert, S. G., Lof, C-M Wong and E. N. Sieder, 7. Manual on solar []. istillation of saline water. searc and evelopment Progress port No. 5, April. United States epartment of te Interior Contract No []. Yadav. Y. P. and L. K. Ja,. A double-basin solar still coupled to a collector and operating in te termo sipon mode. Energy, (: 5 5. [5]. Hamed, O. A., E. I. Eisa and W. E. Abdulla,.Overview of solar desalination. esalination, : []. Farid, M. M..cent developments in solar desalination. In: Management, Purification and Conservation in Arid Climates. Vol. II. Purification. M. F. A. [7]. Goosen and W. H. Sayya. ecnomic Publising Co., Lancaster, PA, pp. 77. []. Goosen, M. F. A., S. S. Sablani, W. H. Sayya, C. Paton, and H. Al-Hinai,.ermodynamic and Economic considerations in solar desalination. esalination, :. []. Paton, A. C. and P. A. avis,. International Engineering Conference (IEC Muta []. Muta University, JORAN, April -. Pages 5-5. []. Frank Incropera and avid ewite, [Introduction to Heat ransfer t Ed.] (