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Güneş enerjili sıcak su sistemlerinin tasarım için modellenmesi ve simülasyonu

Başlık çevirisi mevcut değil.

  1. Tez No: 75124
  2. Yazar: MEHMET EVREN YET
  3. Danışmanlar: PROF. DR. AHMET KUZUCU
  4. Tez Türü: Yüksek Lisans
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Makine Teorisi ve Kontrol Bilim Dalı
  13. Sayfa Sayısı: 102

Özet

ÖZET Bu çalışmanın başlangıç noktası, bireysel güneş enerjili sıcak su sistemlerinin dış görünüş bakımından yarattığı görüntü kirliliği ve çirkinliği yanında, gün içindeki sıcak su ihtiyacını karşılamada yetersiz kalışının ve bireysel güneş enerjili sıcak su sistemleri yerine, bir çok yazlık binadan meydana gelen tüm bir sitenin sıcak su ihtiyacının merkezi bir güneş enerjili sıcak su sistemi ile karşılanabilmesi için çok büyük bir ilk yatırım maliyetinin gerekli olmasının göz önüne alınmasıyla, mesken grupları için, güncel ısıtma kontrolü teknolojilerinin kullanılabileceği boyutta, en ekonomik ve tatmin edici bir güneş enerjili sıcak su sistemi yapısının araştırılmasıdır. Bu çalışmada, Antalya ili içinde yer alan birbirine yakın beş adet yazlık binanın veya villanın günlük sıcak su ihtiyacının, kollektörler vasıtasıyla güneş enerjisinden faydalanılarak elde edildiği bir pompalı - kapalı devreli kollektörlü - kontrollü sistemin modellemesi, boyutlandırılması ve simülasyonu işlemleri gerçekleştirilmiştir. Mayıs, Haziran, Temmuz, Ağustos, Eylül ve Ekim aylan baz alınarak, bu aylardaki anlık tüm ışınım değerlerinin gün içinde zamana göre değişimleri sistem girişi olarak alınarak, yazlık binalarda ikamet eden insanların günlük sıcak su ihtiyacının gün içinde zamana göre değişiminin, bir su sarfiyatı senaryosu olarak sisteme etkimesi sonucunda sistemin belirli güneş ışınımı değerleri altında istenen miktarda ve sıcaklıkta kullanım suyunu sağlayıp sağlayamadığı benzetim ve simülasyon yolu ile gözlenmeye çalışılmıştır. Simülasyon işleminden önce sistem modellenmesi, diğer bir deyişle sistem elemanlarının matematiksel modelleri elde edildikten ve boyutlandırılması tamamlandıktan sonra simülasyon aşamasına geçilmiştir. Simülasyon programında Fortran programlama dili kullanılmıştır. Program içinde, kollektörlerin içinden geçen ısı taşıyıcı akışkanın ve bu akışkanın karışmadan ısısını aktardığı depo suyu sıcaklığının zamana göre türevleri Runge-Kitta adım adım integrasyon yöntemi ile integre edilerek sıcaklık değerleri olarak sonuçlar elde edilmiştir. Sisteme gönderilen kullanım suyu sıcaklığının istenen değer etrafında kontrol edilmesi işlemi için ise bir adet üç yollu motorlu kontrol vanası kullanılmıştır. Üç yollu vananın çalışma prensibi, kullanıcılara beslenen kullanım suyu sıcaklığının istenen değerinin, program içinde hesap ettirilen belirli bir kontrol katsayısı doğrultusunda depo suyu ile şebeke suyunun belirli debi değerleri ile karıştırılması sonucunda elde edilmesidir. Elde edilen sonuçlar, sıcak su ihtiyacının, termosifon gibi ferdi su ısıtıcıları ile elde edilmesi işlemi ile karşılaştırılmıştır. Antalya ili içinde yer alan birbirine yakın beş adet yazlık binanın sıcak su ihtiyacının karşılanmasında termosifonların kullanılması durumunda harcanacak bedelin yaklaşık %92' sinin tasarlanan pompalı - kapalı devreli kollektörlü - kontrollü sistem ile güneş enerjisi kullanılması durumunda tasarruf edilebileceği belirlenmiştir.

Özet (Çeviri)

SUMMARY This master thesis is named“Modelling & Simulation Of A Solar Energy Based Hot Water Systems For Design Purposes”. The first point of view of this study is the ugly appearance of the personnel solar energy based hot water systems and their insufficient capacity. The second point of view is the need for a high first investment for a central solar energy based hot water system to obtain the hot water need of a whole housing estate. Considering these point of views the main purpose of this study is to investigate the most economic and satisfying structure and dimension of a solar energy based hot water system for house groups, in which the daily heating control technologies can be used. In this study, the modelling, dimensioning and simulation of a controlled system -with closed circuit collectors and its circulation pump, a container and a three port seat valve-, which the daily hot water need of five summer houses close to each other in Antalya, a city at the South region of Turkey, just near the Mediterranian Sea, is obtained by the use of solar energy. The deviation of the momentary all radiation of the Sun during a day in the months May, June, July, August, September and October is considered as the input of this system. The deviation of the hot water need of the people living in these summer houses during the day is obtained as a scenario and considered as an effect to the system behaviour. With these input values and the scenario effect, using the modelling & simulation of the system, it is observed whether the system can obtain the required amount of hot water in the required temperature on the above mentioned months or not. After the modelling of the system, in other words, under the momentary all radiation deviation of the Sun and the daily hot water need deviation scenario, obtaining the mathematical models of the system instruments to examine the system behaviour, and dimensioning of the system instruments, the simulation stage begins. In the simulation program, under these defined inputs and effects, it is observed whether the system could obtain the required amount of hot water in the required temperature for the above mentioned months. The simulation program named as“SIM.FOR”, where“SIM”comes from the simulation, can be found in Annex A. The Fortran programming language is used in the simulation program. In this program, the deviation of the temperature of the heat transferring liquid passing through the collectors and the deviation of the temperature of the water in the container, are integrated using the Runge Kitta step by step integration method. The temperature values are saved in data files and then used in obtaining graphical representations in Microsoft Excel program. The heat transferring liquid passing through the collectors and the water in the container, which is sent to be used by the people, do not mix, because the heat transferring liquid travels in a. closed loop of collectors. A three port seat valve is used to control the temperature of the hot water in the required value which will be used by the people. The principle of the operation of this three port seat valve is to mix the water coming from the container and the water coming from the network system, according to a ratio estimated in the simulation program for obtaining the required temperature of the hot water to be used. xiBasic Design Properties Of The System: The heat transferring liquid is: %50 propylene glycol - water mixture Freezing Point: -33°C Specific Heat Coefficient: 3.64 KJ/Kg-°K Boiling Point: 11 0°C Density: 1025 Kg/m3 The mathematical models of the deviation of the temperature of the heat transferring liquid of all the ten pieces of collectors are: dTkoll.(l)/dt = Eg - hT(l)xFx 3.6x(Tkoll.(l)-Teevre) - qkoll.xcpegx(Tkoll.(l)-Tdönüş) / B dTkoll.(2)/dt = Eg - hT(2)xFx 3.6x(Tkoll.(2)-Tçevre) - qkoll.xcpegx(Tkoü.(2)-Tdönûş)7“B”dTkoll.(3)/dt = Eg - hT(3)xFx 3.6x(Tkoll.(3)-Tçevre) - qkoll.xcpegx(Tkoll.(3)-Tdönüş) / B dTkoll.(4)/dt = Eg - hT(4)xFx 3.6x(Tkoll.(4)-Tçevre) - qkoll.xcpegx(Tkoll.(4)-Tdönüş)7"B~ dTkoll.(5)/dt = Eg - hT(5)xFx 3.6x(Tkoll.(5)-Tçevre) - qkoU.xcpegx(Tkoll.(5)-Tdönüş)7B~ dTkoll.(6)/dt = Eg -hT(6)xFx 3.6x(Tkoll.(6)-Tçevre) - qkoll.xcpegx(Tkoll.(6)-Tort.(l))/ B dTk6U.(7)/dt = Eg - hT(7)xFx 3.6x(Tkoll.(7)-Tçevre) - qkoll.xcpegx(Tkoll.(7)-Tort.(l))/ B dTkoll.(8)/dt = Eg - hT(8)xFx 3.6x(Tkoll.(8)-Tçevre) - qkoll.xcpegx(Tkoll.(8)-Tort.(l))/ B dTkoU.(9)/dt = Eg - hT(9)xFx 3.6x(Tkoll.(9)-Tçevre) - qkoll.xcpegx(Tkoll.(9)-Tort.(l))/ B dTkoll.(10)/dt=Eg-hT(10)xFx3.6x(Tkoll(10)-Tçevre)-qkoll.xcpegx(Tkoll.(10>Tort.(l))/B Here; dTkoll.(x)/dt: The deviation of the temperature of the heat transferring liquid per time. (°K/h) Eg: Energy of the momentary all radiation of the Sun collected by the collectors. (W/m2) hT(x): Heat convection coefficient of the collectors (W/m2-°K) hT = 35.5 W/m2-°K F: Effective collector area (net area) (F=l.6 m2) Tkoll.(x): The temperature of the heat transferring liquid. (°C) Tçevre: The temperature of the environment. (°C) qkoll. : The flow rate of the heat transferring liquid travelling in the closed loop of the collectors. (Kg/h) Cpeg: The specific heat coefficient of the heat transferring liquid. (Cpeg = 3.64KJ/Kg-°K) Tdönüş: The temperature of the heat transferring liquid on the return way, after the heat is transferred to the water in the container. (°C) Tort.(l): The mean temperature of the heat transferring liquid after being heated in the first row of the five parallel collectors. (°C) Tort.(l) = (Tçıkış(l) + Tçıkış(2) + Tçıkış(3) + Tçüaş(4) + Tçıkış(5)) / 5 B = Mkoll. x Cpeg Mkoll.: The mass of the heat transferring liquid in one collector. XIIFigure S. 1. The flow in and flow outs of the container of the system. 1 : The mean temperature of the heat transferring liquid after being heated in the second and final row of the five parallel collectors. (°C) 2: The temperature of the heat transferring liquid on the return way, after the heat is transferred to the water in the container. (°C) 3: The flow out of the water in the container to the user. 4: The flow in of the cold water from the network system. The amount of water in the container is being kept the same all the time by the flow in of the cold water from the network system. As defined before, the heat transferring liquid travels between 1 and 2 in a closed loop, without mixing with the water in the container which will be used by the people. Obtaining the deviation of the temperature of the water in the container: dTdepo/dt = \(r\ x qpompa x Cppg x (Tort.(2)-Tdönüş)) + (ALFA x SS x Cpsu x (Tşebeke-Tdepo))) / Mdepo x Cpsu Here; Mdepo: The mass of the water in the container. Mdepo = Vdepo x gsu = 0. 140 m3 x 1000 Kg/m3 = 140 Kg Vdepo: Volume of the container. (Vdepo = 0.140m3) gsu: Density of water, (gsu = 1000 Kg/m3) Cpsu: Specific heat coefficient of the water Cpsu = 4.187 KJ/Kg-°K dTdepo/dt: The temperature deviation of the water in the container per time.(°C/h) Eg: Energy input in the container. Eg = 0 (There is no heating effect to the container from the environment!) Ekayip: Heat loss of the container by convection. Ekayip = 0 (Isolated container, no heat loss to the environment!) ti = 0.85 (The productivity coefficient of the heat transfer from the closed loop of the collectors to the water in the container) XUlqpompa: The flow rate value of the circulation pump of the closed loop of the collectors. (Kg/h) qpompa = 5 x qkoll. = 5 x 120 = 600 Kg/h Cppg: Specific heat coefficient of the heat transferring liquid. Cpeg = 3.64KJ/Kg-°K Tort. (2): The mean temperature of the heat transferring liquid after being heated in the second and final row of the five parallel collectors. (°C) Tort.(2) = (Tçıkış(6) + Tçıkış(7) + Tçıkış(8) + Tçıkış(9) + Tçıkış(lO)) / 5 Tçıkış(x): The temperature of the heat transferring liquid after being heated in that collector. (°C) Tdönüş: The temperature of the heat transferring liquid on the return way, after the heat is transferred to the water in the container. (°C) qs = qseb = ALFA x qkullanim = ALFA x SS qs: The flow out rate of the water in the container to the user, qseb: The flow in of the cold water from the network system. ALFA: The control coefficient of the three port seat valve. SS: The consumption deviation of the hot water during the day by users.(Kg/h) (SS = qkullanim) Tdepo: The temperature of the water in the container. (45-60°C) Tşebeke: The mean temperature of the cold water coming from the network system. Tşebeke = 25.2°C (The mean temperature for the above defined 6 months.) Controlling the temperature of the hot water to be used, by the three port seat valve: Figure S.2. The flow in and flow out of the three port seat valve. The control coefficient of the three port seat valve is defined as: 45 - Tşebeke ALFA = Tdepo - Tşebeke XIVs E ID E I i I s c i ?* Kİ EAccording to the simulation results, it has been observed that, the system can obtain most of the required amount of hot water in the required temperature. But, of course it takes time to obtain the required temperature in the early morning and the water is cooling down in the late evening when there is no more momentary all radiation of the Sun and of course after all the consumption during the day. The simulation shows us the system behaviour during 16 hours of a day. If the required temperature of the hot water should be kept same for 16 hours of a day, then the system should be supported by a heat exchanger. The required amount of energy to be supported by this heat exchanger is defined as follows: W = W + (H x Cpsu x SS(K) x (45 - Tdepo(K)) / Y Here; H: Calculation step time of the simulation. H = 0.02 hour = 1.2 minute Cpsu: Specific heat coefficient of water Cpsu = 4.187KJ/Kg-°K SS(K): Hot water consumption value in the Kth step of the simulation. Tdepo(K): The temperature of the water in the container in th Kth step of the simulation. Y: The mean productivity ratio of he heat exchanger. Y = 0.8 The results of the simulation are compared with that of a thermosiphon, which will be used in all summer houses separately, taking into consideration the amount of LPG gas used in the thermosiphon. The results are as follows: Table S. 1. The amount of energy need of the controlled system to be supported by a thermosiphon during a day. If the planned system is not controlled by a three port seat valve, the system behaviour is shown in Figure S.4. In this situation, the simulation results are as follows: Table S.2. The amount of energy need of the system without controlled by the three port seat valve, to be supported by a thermosiphon during a day. The specifications of the heat exchanger: Thermosiphon using LPG gas. Specifications of LPG gas: Heating value: 1 1000 kcal/m3 (1 1200 kcal/Kg) Unit Price: 120,000 TL/Kg (January 1998) Mean Productivity Value: 0.8 XVllIf the heat exchanger is used to obtain hot water: The amount of energy required to obtain the daily consumption of hot water: Wgereken = Msarfiyat x Cpsu x AT Here; Msarfiyat: The daily consumption of hot water of the three summer houses. Msarfiyat = 2150 Kg = 2150 It Cpsu = 4.187KJ/Kg-°K AT: The temperature difference between the cold network system water and the requested hot water temperature. AT = 45 - 25 = 20°C Thus; Wgereken = 2150 x 4. 187 x 20 * 180041 KJ And the amount of energy to be consumed by the heat exchanger: Wesj. = Wgereken / 0.8 = 22505 1.25 KJ The heating value of the LPG gas is: 1 1200 Kcal/kg = 46894.4 KJ /kg Therefore, the amount of the LPG gas needed for one day: MLPG = 22505 1.25 / 46894.4 = 4.8 Kg And the daily expense is calculated as follows: The daily expense: 4.8 x 120,000 = 576,000 TL The daily expenses of the planned system: In May, for any day: (17426.88 / 46894.4) x 120,000 = 44,595 TL In June, for any day: (7156.04 / 46894.4) x 120,000 = 18,312 TL In July, for any day: (6150.28 / 46894.4) x 120,000 = 15,378 TL In August, for any day: (7952.635 / 46894.4) x 120,000 = 20,350 TL In September, for any day: (15961.25 / 46894.4) x 120,000 = 40,844 TL In October, for any day: (54316.76 / 46894.4) x 120,000 = 138,993 TL The daily expenses of the system without controlled by the three port seat valve: In May, for any day: (1 14382.76 / 46894.4) x 120,000 = 292,698 TL In June, for any day: (77471.22 / 46894.4) x 120,000 = 198,244 TL In July, for any day: (55497.63 / 46894.4) x 120,000 = 142,015 TL In August, for any day: (56345.1 / 46894.4) x 120,000 = 144,183 TL In September, for any day: (84187.58 / 46894.4) x 120,000 = 215,431 TL In October, for any day: (129615.45 / 46894.4) x 120,000 = 331,678 TL XV111Comparison of the monthly expenses of the controlled system and the heat exchanger: Table S.3. Comparison of the monthly expenses of the controlled system and the heat exchanger and the saving rates Tabel S.4. Comparison of the monthly expenses of the controlled system and the uncontrolled system and the saving rates Here, the saving rates are calculated as follows: Considering the total expenses: Saving Rate (%) = 1 - (8,573,476TL / 40,638,044 TL) = 78.9% The saving amount for six months: As from the Table S.3, the saving amount for six months is calculated as: Seasonal Savings: 105,984,000 - 8,573,476 = 97,410,524 TL As seen from the table, once again, the total saving rate shows us, - when the hot water need of the five summer houses close to each other in Antalya, is obtained using this special controlled system via solar energy, instead of using heat exchangers using LPG gas in every house-, the system can save 91.9% of the expenses for the purpose of having hot water 16 hours of a day. And 78.9% of the energy need of the system is saved using the three port seat valve, as can be seen from Table S.4. Before the project stage of this special controlled system, first investment amount of the system instruments should be calculated. The first investment amount of the system instruments could be found expensive. But with a very careful and XIXappropriate selection of system instruments, the amortization period of such a system would be between 2 and 5 years, which is an acceptable period. Table S.5 First Investment Analysis Of the Controlled System TOTAL 4.220,00 The amortisation period of the planned system is calculated as follows: First Investment DM4.220,00x 12L595TL Amortisation period = Seasonal Savings 97,410,524TL = 5.2 years (1DM= 121,595TL) The main purpose of this study is to make the modelling and dimensioning of a special system using solar energy and simulating it for observing the saving ratio for expenses of obtaining hot water. We should also take into consideration the comfort it brings for the temperature of the hot water, where it is controlled by the system around the requested temperature. The results obtained, supports the advantages of the planned system. Specially, in the south and west regions of Turkey, where the radiation of the Sun is mostly appropriate, the hot water need of the buildings can be obtained using solar energy as done in the simulation of this study. Also, it is possible to use solar energy in heating of the buildings and in obtaining electrical energy (for example, sun batteries) and in other special applications. To benefit more from the natural and cheap energy sources like the solar energy, wind effect and streams, would bring savings in the expenses of the other energy sources and this would better the condition of the environment. Instead of obtaining energy via chemical ways (thermic and nuclear centrals), with the appropriate geographical characteristics of our country, we should benefit more from the natural sources defined above, by building solar energy centrals, wind generator centrals and dams etc. But the most important thing we should take seriously must be the public health of the society. And this will be achieved by using natural ways of obtaining energy. XX

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