EFFECT OF RED MUD AS A NANOFLUID ON COOLING PERFORMANCE

Fluids such as water, oil, glycerin and ethylene glycol are conventional heat transfer fluids that are used in heat exchangers. Improving heat transfer and effectiveness of heat exchangers by means of fluids is one of the principle topics. A type of improvement works is adding solid materials that have high thermal capacity and conductivity into the fluid. Al2O3, CuO, TiO2, SiC, TiC, Ag, Au2, Cu2 and Fe are the most common materials as solid particles that are used for enhancing heat transfer of fluids. Early on, macro scaled additives were tried; however desired outcomes couldn’t be obtained due to fouling, blockage and sedimentation. Recently, studies on ability to be enhanced and improved in terms of heat transfer and hence heat exchangers with high effectiveness by the addition of nano-particles to fluid have become intensive. It is known that precious elements such as Al2O3, SiO2, Fe2O3, TiO2, Na2O, CaO, P2O5 are contained in the body of red mud that is a disposal material coming from the process of producing aluminum from bauxite. Thermal capacity and thermal conductivity of these matters are very high. Effects of nano scale red mud added into heat transfer fluid on the cooling performance are investigated in this work

ÇİFT FAZLI GÜNEŞ ENERJİSİ KAYNAKLI ISI POMPASI SİSTEMİNİN TEORİK ve DENEYSEL İNCELENMESİ

Bu çalışmada, soğuk iklim bölgelerinde konutların ısıtılması için hava-hava çalışan bir ısı pompasına çift fazlı güneş enerjisi destekli düzlemsel güneş kollektörü kaynak olarak kullanıldı. Çalışma, teorik ve deneysel olarak gerçekleştirildi. Teorik çalışmada, sistemin matematik modelini oluşturmak için, sisteme giren ve çıkan tüm büyüklükler ayrı ayrı ifade edildi. Daha sonra deneysel çalışmada öngörülen aylar için Konya Meteoroloji Bölge Müdürlüğünden alınan son 15 yıla ait veriler kullanılarak teorik sonuçlar elde edildi. Deneysel çalışma, Aralık, Ocak ve Şubat ayları için yapıldı. Çift fazlı güneş kollektöründe R–11, ısı pompası sisteminde ise R–22 akışkan olarak kullanıldı. Kollektördeki buharlaşmayı hızlandırmak için boru içerisine özel formda hazırlanan profiller yerleştirildi. Hava+su-hava çalışan sistemin konvansiyonel sisteme göre Isıtma Tesir Katsayısı (ITK)’ nda %24 lük bir artış sağladığı tespit edildi.  Ölçümlerden kaynaklanan hata nedeniyle deneysel sonuçlardan elde edilen ITK değerinin, teorik sonuçlara göre biraz düşük olduğu gözlendi

EXPERIMENTAL AND NUMERICAL ANALYSIS OF A TWO DIMENSIONAL HEAT TRANSFER ON OPEN CELL ALUMINUM FOAMS

Bu çalışmada açık hücreli alüminyum köpükler ısı değiştirici formuna getirilip iki boyutlu ısı transferi deneysel ve sayısal olarak incelenmiştir. 10, 20 ve 30 PPI (Number of Pores Per Inch) gözenek yoğunluklarına sahip açık hücre alüminyum köpükler sabit ısı akısı için ısı değiştiricinin kanatlarını oluşturmuştur. Alüminyum köpük üzerinde, X-Y düzleminde özellikle ısıtıcıya yakın bölgelerde sık olarak yerleştirilen ısıl çiftlerle sıcaklıklar ölçülmüştür. Elde edilen sıcaklıklar yardımıyla bütün yüzey üzerindeki sıcaklık dağılımı bulunmuştur. Grafikler, yüzey sıcaklıkları ve giriş sıcaklığı (?T) arasındaki farka dayalı olarak çizilmiştir. Ayrıca her üç ısı değiştirici için basınç düşüşü bulunmuştur. Sistem için iki boyutlu ısı transferi denklemleri sayısal olarak elde edilmiştir. Elde edilen denklemler merkezi fark yöntemi kullanılarak çözülmüştür.In this study, heat transfer was investigated in open cell aluminum foams formed into a heat exchanger experimentally and numerically as two dimensional. The open cell aluminum foams with pore density of 10, 20, 30 PPI were used as the heat exchanger fins formed for a constant heat flow. Temperatures were measured using thermocouples located on several points in the X-Y planes of the aluminum foams especially on areas near the heaters. The temperature distribution for the whole area was obtained from the measured temperatures,. The graphs were plotted based on the difference between the surface temperatures and the inlet temperature (?T). In aditıon for each of the three heat exchanger pressure drop was found. Two dimensional heat transfer equations for the system were derived in the numerical solution. Then the obtained equations were discretized by using the central difference method and finally solved

Rule-based Mamdani-type fuzzy modelling of thermal performance of fintube evaporator under frost conditions

Frost formation brings about insulating effects over the surface of a heat exchanger and thereby deteriorating total heat transfer of the heat exchanger. In this study, a fin-tube evaporator is modeled by making use of Rule-based Mamdani-Type Fuzzy (RBMTF) logic where total heat transfer, air inlet temperature of 2 °C to 7 °C and four different fluid speed groups (ua1=1; 1.44; 1.88 m s-1, ua2=2.32; 2.76 m s-1, ua3=3.2; 3.64 m s-1, ua4=4.08; 4.52; 4.96 m s-1) for the evaporator were taken into consideration. In the developed RBMTF system, outlet parameter UA was determined using inlet parameters Ta and ua. The RBMTF was trained and tested by using MATLAB® fuzzy logic toolbox. R2 (%) for the training data and test data were found to be 99.91%. With this study, it has been shown that RBMTF model can be reliably used in determination of a total heat transfer of a fin-tube evaporator

Rule-based Mamdani-type fuzzy modelling of thermal performance of fintube evaporator under frost conditions

Frost formation brings about insulating effects over the surface of a heat exchanger and thereby deteriorating total heat transfer of the heat exchanger. In this study, a fin-tube evaporator is modeled by making use of Rule-based Mamdani-Type Fuzzy (RBMTF) logic where total heat transfer, air inlet temperature of 2 °C to 7 °C and four different fluid speed groups (ua1=1; 1.44; 1.88 m s-1, ua2=2.32; 2.76 m s-1, ua3=3.2; 3.64 m s-1, ua4=4.08; 4.52; 4.96 m s-1) for the evaporator were taken into consideration. In the developed RBMTF system, outlet parameter UA was determined using inlet parameters Ta and ua. The RBMTF was trained and tested by using MATLAB® fuzzy logic toolbox. R2 (%) for the training data and test data were found to be 99.91%. With this study, it has been shown that RBMTF model can be reliably used in determination of a total heat transfer of a fin-tube evaporator

Comparison of the Protective Effects of Calendula officinalis Extract and Hyaluronic Acid Anti-adhesion Barrier against Postoperative Intestinal Adhesion Formation in Rats

Aim: Intra-abdominal adhesions that develop after abdominal surgery are still a cause of serious morbidity and mortality. This study compared the efficacy of a hyaluronic acid adhesion barrier and Calendula officinalis extract (COE) for inhibiting adhesion in rats. Method: We performed laparotomies in 30 rats and induced postoperative intraabdominal adhesions using a scraping model. The animals were divided randomly into 3 groups of 10 rats each. We performed only caecal abrasions and did not apply any substance in the control group (group 1). In group 2, we performed caecal abrasion and then applied the hyaluronic acid adhesion barrier to the abraded area. In group 3, we applied COE after the caecal abrasions. Results: There were no significant differences among the groups in terms of the macroscopic adhesion score. Histopathologically, there was a significant difference in microscopic adhesion scores between groups 1 and 2 (p=0.044). There was also a significant difference between groups 1 and 3 (p=0.010). There was no significant difference between groups 2 and 3 (p=1). Group 1 had the highest score for adhesions between the abdominal wall and intra-abdominal organs. Conclusion: Both the COE and hyaluronic acid adhesion barrier significantly reduced the incidence of postoperative intra-abdominal adhesions in a rat scraping model. Although the mechanism is not clear, the COE applied in the peritoneal cavity reduced the development of adhesions. There was no significant difference between the COE and hyaluronic acid adhesion barrier in terms of preventing adhesions. Although the COE is less expensive than hyaluronic acid adhesion barrier, toxicology studies must be performed before it is used in humans