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    Buhar Sıkıştırmalı Soğutma Çevriminde R134a Yerine R1234yf ve R1234yf/Al2O3 ile R1234yf/CNTs Nanosoğutucu Akışkanların Kullanımının Termodinamiğin I. ve II. Kanunları Bakımından Analizi
    (2021) Bilen, Kemal; Dagıdır, Kayhan; Arcaklıoğlu, Erol
    Bu çalışmada; soğutucu akışkan olarak R134a kullanılan bir Buhar Sıkıştırmalı Soğutma Sisteminde (BSSS’de), R134a’nın alternatifi olarak görülen R1234yf soğutucu akışkanı, alüminyumdioksit (Al2O3) ve karbon nanotüp (CNT) nanoparçacıkları ilavesiyle iş akışkanı olarak kullanılmıştır. Soğutma sistemi aynı şartlarda, yalnızca iş akışkanı değiştirilerek, termodinamik bakımdan teorik olarak incelenmiştir. İncelemeler, farklı buharlaşma ve yoğuşma sıcaklıkları için geniş bir aralıkta gerçekleştirilmiştir. BSSS’de iş akışkanı olarak R134a ve R1234yf kullanımına yönelik -7 C buharlaşma ve 45 C yoğuşma sıcaklıklarındaki analizler sonucunda, sistemin soğutma tesir katsayısı (COP) R134a için 1.950 ve R1234yf için 1.824 olarak hesaplanmış, COP değerleri arasında %6.46’lık bir fark ortaya çıkmıştır. Bu sonuç, ikinci kanun verimleri (ekserji verimleri) arasında ise %6.44’lük bir fark oluşturmuştur. Bu fark göz önüne alınarak, Al2O3 ve CNT nanoparçacıklarının ilavesiyle elde edilen R1234yf/Al2O3 ve R1234yf/CNTs nanosoğutucu akışkanları için analizler tekrar edilmiştir. Analizler sonucunda, COP değerinin ve ekserji veriminin, nanoparçacık hacimsel oranı ile artmakta olduğu görülmüştür. Bununla birlikte, -7 C buharlaşma ve 45 C yoğuşma sıcaklıklarında, R1234yf/Al2O3 kullanılan sistemde, R134a’nın tek başına kullanıldığı duruma göre COP değerindeki ve ekserji verimindeki artışların sırasıyla %18.46 ve %18.43 değerlerine kadar ulaştığı tespit edilmiştir. R1234yf/CNTs kullanılması durumunda ise bu artışlar sırasıyla, %6.92 ve %6.89 değerlerine ulaşmaktadır.
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    Öğe
    Buhar Sıkıştırmalı Soğutma Sisteminde F-gaz Yönetmeliği Çerçevesinde Enerjetik ve Ekserjetik Bakımdan Deneysel Bir İnceleme
    (2023) Dagıdır, Kayhan; Bilen, Kemal; Cansevdi, Bekir
    Bu çalışmada; mekanik buhar sıkıştırmalı bir soğutma sisteminin termodinamik analizi enerjetik ve ekserjetik yaklaşımlarla deneysel olarak gerçekleştirilmiştir. Deney tesisatındaki ekipman detaylı olarak tanıtılmış ve her bir ana eleman için termodinamik bağıntılar elde edilmiştir. Bu çalışmanın amacı; soğutma, iklimlendirme ve ısı pompası uygulamalarındaki florlu sera gazlarının kullanımına getirilen kısıtlamalara uyum sürecinde, özellikle bu alanlarda faaliyetlerini sürdüren ticari işletmeler ve Ar-Ge merkezlerinin sürece adaptasyonuna katkı sağlamaktır. Çalışma kapsamında, iş akışkanı olarak florlu sera gazları arasında yer alan R134a kullanılarak hem mevcut R134a’lı sistemlere hem de değişim sürecindeki R134a’nın alternatiflerinin kullanımının planlandığı tasarım aşamasındaki sistemlere yönelik test ve analiz prosedürü ve deneysel veri sunulması hedeflenmektedir. Bu kapsamda, R134a kullanılan sistem yaklaşık 10 kW sabit soğutma kapasitesinde çeşitli (-5, 0 ve 5 ℃) buharlaşma ve (40, 45 ve 50 ℃) yoğuşma sıcaklıklarında test edilmiş ve elde edilen deneysel bulgular araştırmacıların kullanımına sunulmuştur. Ayrıca, benzer şartlardaki sistemlerin karşılaştırılabilmesi için sistem karakteristiklerinin bir göstergesi olan P-h ve T-s diyagramları paylaşılmıştır. Çalışma sonucunda, deneysel veriler yardımıyla elde edilen çıktılar ve sistemin simülasyonu için gerekli parametreler belirlenmiş ve paylaşılmıştır. Sonuç olarak, buharlaşma ve yoğuşma sıcaklıklarının sistem performansı üzerinde önemli bir etkiye sahip olduğu görülmüştür. Buna göre; 0 ℃ sabit buharlaşma sıcaklığında, yoğuşma sıcaklığının artmasıyla kompresör gücünde %30 ve toplam ekserji kaybında %48’e varan artış, EER değerinde ise %23’e varan azalış tespit edilmiştir. Benzer şekilde; 45 ℃ sabit yoğuşma sıcaklığında, buharlaşma sıcaklığının düşmesiyle kompresör gücünde %36 ve toplam ekserji kaybında %54’e kadar artış, EER değerinde ise %27’ye varan azalış saptanmıştır.
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    Energy and exergy analysis of R1234yf using instead of R134a in a vapour compression refrigeration system: an experimental study
    (Inderscience Enterprises Ltd, 2023) Bilen, Kemal; Dagidir, Kayhan; Arcaklioglu, Erol; Cansevdi, Bekir
    In this study, the refrigerant R1234yf was experimentally investigated using energy and exergy approaches in a refrigeration system, as an alternative to R134a. The effects of replacing R134a with R1234yf on the system performance were discussed without making any modifications to the system. The results indicated that the compressor power input increased by 5%, cooling capacity decreased by 10%, and the energy efficiency ratio decreased by 15% in the system using R1234yf compared to R134a. Additionally, the total exergy destruction rate and second law efficiency of the system were found to be approximately equal for both refrigerants. Therefore, it can be concluded that using R1234yf resulted in a decrease in energetic system performance, while it did not have a notable effect on exergetic performance.
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    EXPERIMENTAL INVESTIGATION OF EFFECTS OF NANOREFRIGERANTS ON VAPOR COMPRESSION REFRIGERATION SYSTEM USING R1234yf INSTEAD OF R134a
    (2024) Bilen, Kemal; Dagıdır, Kayhan; Arcaklıoğlu, Erol
    In this study, the usage of refrigerant R1234yf was experimentally investigated with the addition of various nanoparticles instead of R134a as a working fluid in a VCRS. Firstly, the usage of pure R1234yf instead of R134a was experimentally investigated with energy and exergy approaches without any modification in the VCRS. As a result of pure refrigerant experiments, it was determined that the compressor power input increased by around 9%, cooling capacity decreased by around 8% and EER decreased by around 17% in the system using R1234yf compared to the system using R134a. Additionally, it was determined that the second law efficiency of the VCRS reduced by around 8% in the system using R1234yf compared to the system using R134a. Then, Al2O3, graphene or CNT nanoparticles were added for compensate for performance drops to the VCRS using R1234yf via compressor oil at various mass fractions. Thus, the best enhancement in the system performance parameters was obtained with the usage of R1234yf including 0.250% graphene by mass. Accordingly, it was observed that the cooling capacity of the system with R1234yf including 0.250% graphene by mass was improved up to 24% and 14% compared to the VCRS with pure R1234yf and R134a, respectively. Consequently, the EER value of the VCRS with R1234yf including 0.250% graphene by mass was enhanced up to 32% and 13% compared to the system using pure R1234yf and R134a, respectively. Additionally, the second law efficiency of the system slightly increased with the usage of R1234yf including 0.250% graphene by mass.
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    Experimental investigation of usage of POE lubricants with Al2O3, graphene or CNT nanoparticles in a refrigeration compressor
    (Beilstein-Institut, 2023) Dagidir, Kayhan; Bilen, Kemal
    In this study, the use of nanolubricants containing Al2O3, graphene, and carbon nanotubes (CNTs) at different mass fractions in a refrigeration compressor was experimentally investigated. The required electrical power of the compressor was measured to determine the effect of the use of nanolubricants. Nanoparticles used in the preparation of nanolubricants were gradually added to the lubricant to determine the optimum nanoparticle mass fraction for each nanoparticle type. Thus, it was found that the compressor operated safely and efficiently with nanolubricants. Furthermore, the optimum mass fractions were determined to be 0.750% for Al2O3, 0.250% for graphene, and 0.250% for CNTs for operating conditions of this study. As a result, the required electrical power of the compressor decreased by 6.26, 6.82, and 5.55% with the addition of Al2O3, graphene, and CNT nanoparticles at optimum mass fractions of 0.750, 0.250, and 0.250% to the lubricant, respectively, compared to the compressor using pure oil. Moreover, density and dynamic viscosity of the nanolubricant samples used in the experiments were also measured, and their kinematic viscosity, which is an important parameter for lubricants, was calculated. It was determined that the kinematic viscosity continuously increased with increasing nanoparticle fraction. In conclusion, nanolubricants containing nanoparticles above the optimum mass fraction increase the required electrical power of the compressor. It is concluded that nanoparticle fractions should not be used above the optimum value in nanolubricant applications.
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    The effect of nanorefrigerants on performance of the vapor compression refrigeration system: a comprehensive review
    (Taylor & Francis Inc, 2022) Bilen, Kemal; Dagidir, Kayhan; Arcaklioglu, Erol
    Nowadays, most refrigeration systems are based on vapor compression refrigeration cycle. These systems have been extensively studied and improved until today, hence enhancing the performance of these systems is rather difficult. Despite this limitation, several researches are still being carried out in order to improve the performance of these systems, and the usage of nanorefrigerants in vapor compression refrigeration systems is a most promising research field. Nanorefrigerants that are mixtures of nanoparticles and pure refrigerants are new kinds of refrigerants. In this review study, the effect of nanorefrigerants on the vapor compression refrigeration system performance is presented. It is observed that the usage of nanorefrigerants in the vapor compression refrigeration systems improves the coefficient of performance up to 43.93% and 56.32% in the theoretical and experimental studies, respectively.
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    Thermodynamic analysis of usage of R134a, R1234yf, R450A, R513A and R515B in the mechanical vapor compression refrigeration system
    (Gazi Univ, Fac Engineering Architecture, 2024) Bilen, Kemal; Isik, Bilal; Dagidir, Kayhan; Arcaklioglu, Erol
    R134a, which is used as a working fluid in Vapor Compression Refrigeration Systems (VCRS), is one of the refrigerants that is planned to be discontinued the usage due to the global warming. For this reason, researchers have tended to developing alternatives to R134a. In this context, in this study, the usage of R134a and its alternatives R1234yf, R450A, R513A, and R515B refrigerants were theoretically examined with the help of a theoretical model developed in the Engineering Equation Solver (EES) program using experimental data in terms of first and second laws of thermodynamics in a mechanical vapor compression refrigeration system. Analyses were performed for constant cooling capacity at various evaporation and condensation temperatures. In this study, the effects of the refrigerant type on the compressor power, heat rejection rate from the condenser, Coefficient of Performance (COP), second law efficiency, and mass flow rate of the refrigerant were determined. In addition, the results obtained under the same conditions for R134a and its alternatives were compared. As a result, compressor power increased by 5.62% for R1234yf, 2.35% for R450A, 3.41% for R513A, and 2.88% for R515B compared to R134a. Thus, it was observed that COP decreased by 5.32% for R1234yf, 2.30% for R450A, 3.30% for R513A, and 2.80% for R515B compared to R134a. Similarly, it was observed that the second law efficiency decreased by 5.32% in case of the usage of R1234yf, 2.30% in case of the usage of R450A, 3.29% in case of the usage of R513A, and 2.80% in case of the usage of R515B compared to R134a. Hence, it has been determined that the closest refrigerant to R134a in terms of the COP and the second law efficiency is R450A.
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    Thermodynamic analysis of usage of R134a, R1234yf, R450A, R513A, and R515B in the mechanical vapor compression refrigeration system
    (Gazi Universitesi, 2023) Bilen, Kemal; Işık, Bilal; Dağıdır, Kayhan; Arcaklıoğlu, Erol
    In this study, the effects of the refrigerant type on the compressor power, heat rejection rate from the condenser, COP, second law efficiency, and mass flow rate of the refrigerant were determined in the VCRS. As a result, compressor power increased by 5.62% for R1234yf, 2.35% for R450A, 3.41% for R513A, and 2.88% for R515B compared to R134a. Thus, it was observed that COP decreased by 5.32% for R1234yf, 2.30% for R450A, 3.30% for R513A, and 2.80% for R515B compared to R134a. These COP values of the system were given in (Figure Presented). Purpose: In this study, it is aimed that the usage of R134a and its alternatives R1234yf, R450A, R513A, and R515B refrigerants are examined with the help of a theoretical model developed in the EES program using experimental data in terms of the first and second laws of thermodynamics in a mechanical vapor compression refrigeration system. Theory and Methods: In the study, the effects of the refrigerant type on the compressor power, heat rejection rate from the condenser, COP, second law efficiency, and mass flow rate of the refrigerant were determined using the theoretical model verified with the experimental data. Results: As a result, compressor power increased by 5.62% for R1234yf, 2.35% for R450A, 3.41% for R513A, and 2.88% for R515B compared to R134a. Thus, it was observed that COP decreased by 5.32% for R1234yf, 2.30% for R450A, 3.30% for R513A, and 2.80% for R515B compared to R134a. Similarly, it was observed that the second law efficiency decreased by 5.32% in case of the usage of R1234yf, 2.30% in case of the usage of R450A, 3.29% in case of the usage of R513A, and 2.80% in case of the usage of R515B compared to R134a. Hence, it has been determined that the closest refrigerant to R134a in terms of the COP and the second law efficiency is R450A. Conclusion: In conclusion, it has been determined that the closest alternative refrigerant to R134a in terms of performance parameters is R450A, followed by R515B. In future studies, it is recommended to investigate whether these two refrigerants can be used directly instead of R134a in existing systems using R134a. It is also beneficial to conduct research on the usage of these refrigerants for new refrigeration systems. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.
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    Usage of R513A as an alternative to R134a in a refrigeration system: An experimental investigation based on the Kigali amendment
    (Elsevier B.V., 2024) Dağıdır, Kayhan; Bilen, Kemal
    In this study, the use of the alternative refrigerant R513A instead of R134a in a mechanical vapor compression refrigeration system was experimentally investigated in terms of the first and second laws of thermodynamics on the basis of the Kigali Amendment. The investigations were carried out approximately at a cooling medium temperature (TL) of 0, 4, and 8 °C and a heating medium temperature (TH) of 30, 35, and 40 °C without any modifications to the system. The energetic and exergetic performance parameters obtained in this study were related to the amount of refrigerant in accordance with the criteria restricting the use of fluorinated greenhouse gases after the Kigali Amendment. Accordingly, the required refrigerant mass flow rate per unit energetic (power input, cooling capacity, COP value) and exergetic (total exergy destruction rate and exergy efficiency) performance parameters were determined. As a result, the system was found to operate safely when R513A was used instead of R134a without any modification. In addition, the refrigerant mass flow rate per unit power input was almost the same for both refrigerants. However, R513A was found to have approximately 15 % more refrigerant mass flow per unit cooling capacity than R134a. This resulted in the refrigerant mass flow rate per unit COP being approximately 20 % higher for R513A. On the other hand, the refrigerant mass flow rate per unit exergy efficiency calculated for R513A was found to be about 15 % higher than R134a. © 2024 The Author(s)