Exergy analysis of vacumm tube solar collectors with a boiler according to different parameters

Bu tezde boyler destekli vakum tüplü güneş kollektörünün farklı çalışma debilerindeki enerji ve ekserji analizi, farklı ara akışkanlara göre yapılmış ve değerlendirilmiştir. Sistemin kapalı devre çalışmasında, iki farklı ara akışkan olarak, ısı transfer yağı ve % 40 antifriz-su karışımı kullanılmıştır. Deney sisteminin kapalı devresinde, ara akışkanlar üç farklı çalışma debisinde dolaştırılmıştır. Çalışma debileri 0,277kg/s, 0,383kg/s ve 0,494 kg/s'de gerçekleştirilmiştir. Deney sisteminde, debinin artmasıyla kollektör giriş sıcaklığının arttığı, kollektör sıcaklık farkının (giriş ve çıkış sıcaklık farkı) ve çıkış sıcaklığının azaldığı tespit edilmiştir. Deneyde, debinin artmasıyla sistemin ve kollektörün enerji ve ekserji verimleri artmıştır. Ara akışkan olarak ısı transfer yağıyla yapılan deneylerde, kollektörün enerji ve ekserji verimlerinin, %40 antifriz-su karışımına göre daha iyi olduğu gözlemlenmiştir. Fakat sistem verimi açısından ise %40 antifriz-su karışımı, ısı transfer yağına göre daha iyi bir sonuç vermiştir.In this thesis, the energy and exergy analysis of boiler-supported solar vacuum tubes at different operating flow rates were done and evaluated with respect to different intermediate fluids. In a closed-circuit experimental system the heat transfer oil and 40% antifreeze-water mixture were used as two different intermediate fluids. These different intermediate fluids were circulated at three different operating flow rates in the closed circuit experimental system. The experiments were done at 0,277kg/s, 0,383kg/s and 0,494 kg/s flow rates, respectively. It was observed that with an increase in flow rate in the experimental system; collector inlet temperature increased, but, collector temperature difference (difference between inlet and outlet temperature) and outlet temperature decreased. During the experiment, with an increase in the flow rate; the sytem and the collector energy and exergy effiencies increased. It was also observed that the collector energy and exergy efficiencies of the heat transfer oil was much better than those of 40% antifreeze-water mixture. However, from system efficiency point of view 40% antifreeze-water mixture of the system gave better results compared to those of the heat transfer oil

The Effect of Waste Ballast Aggregates on Mechanical and Durability Properties of Standard Concrete

The acquisition and transportation of aggregate exacerbate the negative impact of concrete on the environment, and waste materials are considered an effective solution to this crucial problem. One of these waste materials is waste ballast (WB), which is needed for new infrastructure along with increasing rail track technology. In this study, the effect of WB aggregate (which is basalt-based) on the mechanical and durability properties of standard concrete was examined. Coarse aggregate was replaced with WB aggregate at the rates of 50%, 75% and 100%. The slump, compressive strength, flexural strength, capillary water absorption, rapid chloride permeability and water penetration tests on the mixtures were performed. According to the results of this study, the utilization of WB improved the compressive strength and flexural strength of the mixtures by about 15% and 7%, respectively. Moreover, the capillary water absorption, rapid chloride permeability and water penetration values of all the concrete mixtures with WB were lower than the control mixture. In addition, the correlation relations between the mechanical and durability properties indicated that they have a strong relationship with each other. All the results of this study demonstrated that the utilization of WB instead of coarse aggregate improved the mechanical and durability properties of concrete. WB can also provide a more sustainable material formation by minimizing the negative environmental effects of concrete production

Application of ECC as a Repair/Retrofit and Pavement/Bridge Deck Material for Sustainable Structures: A Review

Concrete structures cannot efficiently perform their functions over time due to chemical and physical external effects. Thus, enhancing the relationship between repair and aged structures, and also improving the durability properties of concrete is crucial in terms of sustainability. However, high costs, negative environmental effects, and incompatibility problems occur in repair/retrofit applications. Furthermore, three-quarters of the failures in the repaired/retrofitted structures are caused by a lack of repair durability. The need for repair in pavement/bridge decks is also frequently encountered, and early-age performance problems with repair materials cause pavement/bridge decks to be unavailable for certain periods of time. Engineered Cementitious Composite (ECC) can be effectively used as repair/retrofit and pavement/bridge deck material. It also has a minimal need for repair/retrofit thanks to its high durability properties. This article presents state-of-the-art research regarding the application of ECC as a repair/retrofit and pavement/bridge deck material. Studies in the literature show that the repair/retrofit properties of ECC outperform conventional concrete and steel fiber-reinforced concrete. ECC can be a solution to high early strength and drying shrinkage problems frequently encountered in the use of repair materials. It could also be used for different repair applications such as cast, sprayed, and trenchless rehabilitation. Moreover, ECC might fulfill specific requirements for pavement, pavement overlay, tunnel pavement, airfield pavement, and bridge deck. These superior performances are attributed to ECC’s kink-crack trapping mechanism, uniquely large inelastic strain capacity, strain hardening, high tensile strain capacity, and multiple microcracking and ductile behaviors, especially bonding behavior and self-healing

Evaluation of the Performance of Different Types of Fibrous Concretes Produced by Using Wollastonite

Production of cement and aggregate used in cement-based composites causes many environmental and energy problems. Decreasing the usage of cement and aggregate is a crucial and currently relevant challenge to provide sustainability. Inert materials can also be used instead of cement and aggregates, similar to pozzolanic materials, and they have positive effects on cement-based composites. One of the inert materials used in cement-based composites is wollastonite (calcium metasilicate-CaSiO3), which has been investigated and attracted attention of many researchers. This article presents state-of-the-art research regarding fibrous concretes produced with wollastonite, such as mortars, conventional concrete, engineered cementitious composites, geopolymer concrete, self-compacting concrete, ultra-high-performance concrete and pavement concrete. The use of synthetic wollastonite, which is a novel issue, its high aspect ratio and allowing the use of waste material are also evaluated. Studies in the literature show that the use of wollastonite in different types of concrete improves performance properties, such as mechanical/durability properties, and provides environmental–economic efficiency. It has been proven by studies that wollastonite is a material with an inert structure, and, therefore, its behavior is similar to that of a fiber in cementitious composites due to its acicular particle structure

DETERMINATION OF WASTE PLANT BIOMASS POTENTIAL F OR ENERGY GENERATION AT BALCALI CAMPUS OF THE CUKUROVA UNIVERSITY

Bu çalışmanın amacı, Çukurova Üniversitesi (ÇÜ) Balcalı yerleşkesinde tarımsal kökenli biyokütle atıklardan, elektrik ve ısı enerjisi üretimi amacıyla sürdürülebilir bir şekilde yararlanmaktır. Tarımsal biyokütle atık potansiyeli, Ziraat Fakültesi Araştırma ve Uygulama Çiftliği Tarla ve Bahçe Bitkileri Şubeleri tarafından yetiştirilen ürünlerin bitkisel biyokütle atık potansiyelleri dikkate alınarak hesaplanmıştır. Tarla ürünleri arasında bitkisel kökenli biyokütle atıkların enerji üretimi amacıyla değerlendirilebilecek miktarı 819 ton/yıl olarak hesaplanmıştır. Toplam 490 da alanda tane mısır üretimi sonucunda, yılda 611 ton sap ve 115 ton sömek olmak üzere toplam 726 ton kullanılabilir bitkisel biyokütle atık oluşmaktadır. 2016−2017 üretim sezonunda buğday, mısır ve nohut atıklarının toplam ısıl değeri 15 090 MJ düzeyindedir. 2016−2017 üretim sezonunda yetiştirilen buğday, mısır ve nohut atıklarının ısıl değerleri sırasıyla, 1 522 MJ, 13 416 MJ ve 152 MJ olarak hesaplanmıştır. Bitkisel biyokütle atıklardan kazanılacak toplam ısıl değerin % 66,3’ünü tarla ürünlerinden açığa çıkan atıklar oluşturmaktadır. Tarla ürünleri atıklarından kazanılacak toplam ısıl değerin % 49,7’sini mısır sapı, % 9,3’ünü ise mısır sömeği atıkları oluşturmaktadır. Bahçe bitkileri budama atıkları arasında enerji üretimi amacıyla değerlendirilebilecek bitkisel biyokütle miktarı 434 ton/yıl olarak hesaplanmıştır. zeytin üretimi sonucunda açığa çıkan budama atıklarından enerji üretimi amacıyla kullanılabilecek miktar 125 ton/yıl olarak hesaplanmıştır. 2016−2017 üretim sezonunda bahçe bitkileri budama atıklarının toplam ısıl değeri 7 677 MJ düzeyindedir. Bitkisel biyokütle atıklardan kazanılacak toplam ısıl değerin % 33,7’sini bahçe ürünlerinden açığa çıkan budama atıkları oluşturmaktadır.The aim of this study is to utilize agricultural biomass wastes in the Balcalı Campus of Cukurova University in a sustainable manner for the purpose of generating electricity and heat energy. Agricultural biomass waste potential has been calculated by taking into account the plant biomass waste of the products grown by the Field and Horticulture Branches at the Faculty of Agriculture Research and Application Farm. Among the field products, the amount of biomass wastes of plant origin which can be used for energy production is calculated as 819 tons/year. As a result of grain corn production in 490 da area, 726 tons of usable plant biomass waste is generated. 66.3% of the www.iksad.org.tr İKSAD www.29ekim.org 29 EKİM BİLİMSEL ARAŞTIRMALAR SEMPOZYUMU 140 total thermal value to be gained from plant biomass wastes is composed of wastes released from field products. Total heating value of wheat, corn and chickpea wastes in 2016-2017 production season is 15 090 MJ. Thermal values of wheat, corn and chickpea wastes grown in 2016-2017 production season were calculated as 1522 MJ, 13416 MJ and 152 MJ respectively. 49.7% of the total thermal value to be gained from field products wastes consists of corn stalks and 9.3 % of corn wastes. Among the horticultural pruning wastes, the amount of plant biomass that can be evaluated for energy production was calculated as 434 tons/year. The amount of pruning waste produced as a result of olive production can be used for energy generation is calculated as 125 tons/year. In 2016- 2017 production season, total thermal value of horticultural pruning wastes is 7677 MJ. Pruning wastes generated from horticultural crops account for 33.7% of the total thermal value of plant biomass wastes

A novel method in the treatment of pulmonary contusion: Hyperbaric oxygen, an experimental study

Amaç: Bu çalışmada, daha önce pek çok alanda faydalı olduğu ispatlanmış olan hiperbarik oksijenin (HBO) pulmoner kontüzyondaki (PK) etkinliği ve tek taraflı PK modeli ile oluşturulan PK’da HBO’nun hangi patofizyolojik mekanizmalar üzerine etkisi olduğu araştırıldı. Çalışma planı: Çalışmada toplam 49 adet sıçan kullanıldı. Yedi adet sıçan kontrol grubu olarak seçildi. Kırk iki adet sıçana tek taraflı PK oluşturuldu ve sıçanlar kontüzyon grubu (n=21), HBO grubu (n=21) olarak iki ana gruba ayrıldı. Gruplar kendi içinde eşit üç alt gruba (n=7) bölündü. Hiperbarik oksijen grubunun birinci alt grubu tek doz, ikinci alt grubu iki doz ve son alt grubu üç doz HBO tedavisi aldı. Kontüzyondan 24 saat sonra her iki grubun birinci alt grupları, 48 saat sonra ikinci alt grupları ve 72 saat sonra üçüncü alt grupları sakrifiye edildi. Sağ akciğerden elde edilen doku örnekleri, tümör nekroz faktör alfa (TNF-a), malondialdehid (MDA), miyeloperoksidaz (MPO), histopatolojik inceleme ve apoptozis analizine tabi tutuldu. Bulgular: Kontrol grubuyla kontüzyon grubu karşılaştırıldığında MPO ve TNF-a düzeylerinde istatistiksel olarak anlamlı artış tespit edildi. Bu parametrelerde HBO tedavisi uygulanan sıçanlarda ise, istatistiksel olarak anlamlı olmayan azalma tespit edildi. Histopatolojik olarak yapılan inceleme sonucu kontüzyon grubunda alveoler hemoraji, ödem/konjesyon, alveol yırtılması ve lökosit sekestrasyonu skorlarında anlamlı artış tespit edildi. HBO tedavisi sonucu bu skorlarda istatistiksel olarak anlamsız, fakat önemli oranda iyileşme gözlendi. Apoptozis analizinde, kontüzyonun apoptotik hücre indüksiyonuna yol açtığı ve bu etkinin HBO tedavisi ile önemli oranda baskılandığı tespit edildi. So­nuç: Pulmoner kontüzyon, akciğer dokusunda ciddi lokal hasarın yanında, indirekt etki ile aktive olan inflamatuvar yanıt mekanizmaları ve açığa çıkan serbest oksijen radikalleri vasıtası ile doku hasarına neden olmaktadır. İki ve üç doz HBO uygulanan sıçanlara kıyasla, tek doz HBO uygulanan sıçanların TNF-a, MDA ve MPO düzeyleri açısından istatistiksel olarak anlamlı bir fark tespit edilmemesi, HBO tedavisinin en azından etki bakımından doz ve süre bağımlı olmadığını ortaya koymaktadır. Hiperbarik oksijenin apoptotik hücre ölümünü azalttığına inanmakla birlikte, HBO mekanizmasını tam olarak değerlendirmek için daha uzun süreçlerde gözlem yapılmasının gerektiğine inanıyoruz.Background: In this study, the effects of hyperbaric oxygen (HBO) -which was previously shown to have positive effects on different issues- on pulmonary contusion (PC) and the pathophysiological mechanisms of HBO which act on unilateral PC. Methods: A total of 49 rats were used in this study. Seven rats were used as controls. Unilateral PC was induced in 42 rats and the rats were divided into two main groups, including contusion (n=21) and HBO group (n=21). Each group was divided into three subgroups (n=7). The first HBO subgroup received a single dose of HBO therapy, while the second HBO subgroup received two doses and the third HBO subgroup received three doses. The first subgroups of each main group were sacrificed 24 hours after the contusion, the second subgroups were after 48 hours and the third subgroups were sacrificed after 72 hours. Tissue samples obtained from the right lung were considered for tumor necrosis factor-alpha (TNF-a), malondialdehyde (MDA), myeloperoxidase (MPO) and, histopathological study and apoptosis analysis. Results: When compared controls with the contusion group, a statistically siginificant increase in MPO and TNF-a levels was observed. In the HBO treated group, these parameters were decreased, however the decrease was not statistically significant. Histopathological examination revealed significant increases in alveolar hemorrhage, edema/congestion, alveolar distruption and leukocytic sequestration scores. HBO treatment resulted in a statistically nonsignificant, however dramatic improvement in these scores. Apoptosis analysis showed that contusion resulted in an apoptotic cell induction and this effect was significantly inhibited with HBO treatment. Conclusion: Pulmonary contusion results in a serious local injury, as well as tissue injury via indirect effect of activated inflammatory response mechanisms and exposed free oxygen radicals. Statistically nonsignificance between the TNF-a, MDA and MPO levels in rats receiving a single dose of HBO, compared to others receiving two or three doses suggested that its effect was independent from dosage and the time, at least. We believe that HBO treatment decreases apoptotic cell death and further long-term observations should be carried out to assess the exact mechanism of HBO

Maternal serum thiol/disulfide homeostasis in pregnancies complicated by fetal hypoxia

We aimed to evaluate maternal serum thiol/disulphide homeostasis in pregnancies complicated by fetal distress (FD). A total of 100 patients beyond the 34th week of pregnancy were included in this study, and they were divided into two groups. The study group included 50 patients who had been diagnosed with FD; the control group was composed of 50 patients who had shown no signs of FD and who had undergone an elective (previous) caesarean section (CS). The native thiol, total thiol and native thiol/total thiol (%) concentrations were lower in Group 1 patients than Group 2 patients (p < .001). The disulphide, disulphide/native thiol (%) and disulphide/total thiol (%) concentrations were higher in Group 1 patients than Group 2 patients (p < .001). This study suggests that maternal thiol/disulphide homeostasis is impaired in pregnancies complicated by FD.IMPACT STATEMENT What is already known about this subject? Oxidative stress (OS) has previously been investigated in FD. This study reports for the first time a new novel and automatic measurement method. What do the results of this study add? This study shows that the thiol balance shifts in the direction of disulphide in the cases of FD. What are the implications of these findings for clinical practice and further research? Thiol balance can be used for the timely diagnosis of FD