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Buhar sıkıştırmalı bir soğutma sisteminde R22 yerine N20 ve R444B soğutucu akışkanlarını kullanmanın termodinamik performansa etkisi
(2016) Devecioğlu, Atilla Gencer; Oruç, Vedat
Bu çalışmada buhar sıkıştırmalı bir soğutma sisteminde R22 soğutucu akışkanı yerine N20 ve L20 (R444B) soğutucu akışkanının kullanılmasıyla enerji ve ekserji parametreleri teorik olarak incelenmiştir. Aynı çalışma şartları altında farklı evaporasyon sıcaklıkları (-15?C, -10?C, -5?C, 0?C) ve kondenser sıcaklıkları (30?C, 40?C, 50?C) için enerji parametrelerin mukayesesi yapılmıştır. Üç soğutucu akışkan için de performans katsayılarının (COP) aynı mertebede olduğu görülmüş ancak en yüksek COP değeri R22 durumunda elde edilmiştir. N20 veya R444B kullanacak olan cihazların, R22 ile çalışan sistemlere göre daha büyük kondenser yüzey alanlarının olması gerektiği anlaşılmıştır. İncelenen soğutucu akışkanlar içerisinde R22'nin ekserji veriminin daha yüksek olduğu tespit edilmiştir.
A COMPARATIVE ENERGETIC ANALYSIS FOR SOME LOW-GWP REFRIGERANTS AS R134a REPLACEMENTS IN VARIOUS VAPOR COMPRESSION REFRIGERATION SYSTEMS
(2018) Oruç, Vedat; Devecioğlu, Atilla G
In this study, the energy parameters (i.e., cooling capacity and COP) were theoretically investigated for three different vapour compression refrigeration system (basic cycle, basic cycle with liquid-to-suction heat exchanger and two-stage cascade cycle) for which R1234yf, R1234ze(E), R513A, R445A and R450A alternative refrigerants with low GWP value were used instead of R134a. The studied refrigerants demonstrated similar thermodynamic behaviour. The exergetic efficiency of the systems was also compared. The comparison of the energy parameters was carried out for two different evaporation temperatures (-30 and 0?C) and two condensing temperatures (40 and 55?C). According to the calculation results, R450A which almost has the same COP values as R134a comes into prominence with 58% lower GWP value compared to R134a. Among the studied refrigeration cycles, system with LSHEX can be suggested for providing a better effect in terms of COP for the considered refrigerants and temperature cases as well as assumed system parameters. It was seen for the investigated cycles that the highest exergetic efficiency could be obtained in the case of R445A.
Drop-in assessment of plug-in R404A refrigeration equipment using low-global warming potential mixtures
(Oxford University Press, 2022) Devecioğlu, Atilla G.; Oruç, Vedat
This study analyzes the performance of plug-in refrigeration equipment, which has the condenser on the system and delivers heat to the indoor medium, using mixtures with low-global warming potential (GWP). The theoretical drop-in replacement of R404A that is widely used in the plug-in refrigeration equipment is investigated utilizing refrigerants with GWP < 150 such as R454C, R455A, R457A and R465A. In the study, four cases of evaporation temperatures (−25°C, −15°C, −5°C and 0°C) and two cases of condenser temperatures (30°C and 40°C) were considered for freezer and chiller modes of the equipment. According to the obtained results, the power consumption of R404A is determined to be higher than other refrigerants for both studied condenser temperatures. The mass flow rate circulating in the system decreases using R404A’s alternatives. Furthermore, the highest coefficient of performance (COP) is reached with R457A, which has a greater COP than R404A about by 8.5%. The compressor discharge pressures of alternative refrigerants are smaller compared with R404A as well. The reduction in CO2 emission is also presented in terms of total equivalent warming impact (TEWI) computations. The conducted analysis points out that it will be possible to use directly the investigated mixtures (especially R457A and R455A are most promising ones) in plug-in refrigeration devices as alternatives to R404A without performing any constructional modification in the system.
Energetic performance analysis of R466A as an alternative to R410A in VRF systems
(Elsevier B.V., 2020) Devecioğlu, Atilla Gencer; Oruç, Vedat
In this study, utilization of R466A with low-GWP is investigated in variable refrigerant flow (VRF) systems. R410A is widely used in VRF systems. Only non-flammable refrigerants are allowed for these systems since they require high amount of refrigerant charge. However, most of refrigerants, which have low-GWP and may be suitable for air-conditioning systems, are flammable. The analysis was carried out for both cases of cooling mode and heating mode. Three evaporation temperatures (4, 8 and 12 °C) and three condenser temperatures (40, 50, 60 °C) were considered for cooling mode in the study. In heating mode, three different evaporation temperature values (−10, −5 and 0 °C) while single condenser temperature of 45 °C were used for the investigation. The results pointed out that both cooling capacity and heating capacity amounts of R466A were greater in comparison with R410A. COP values of R466A were determined as higher than R410A about by 5–15% and 4% in cooling mode and heating mode, respectively. Thus, R466A can be utilized as a suitable refrigerant for VRF systems and air-conditioners as an alternative to R410A. In the short term, R466A can be directly used without performing any constructional modification in the system operating with R410A.
Experimental and numerical analysis of a parabolic trough solar collector for water heating application
(Taylor & Francis, 2022) Özcan, Abdulkadir; Devecioğlu, Atilla Gencer; Oruç, Vedat
The aim of this study is to obtain hot water utilizing a parabolic trough solar collector. The copper tube and aluminum absorber tube were placed separately through the focus point of the parabolic reflector. The steady mass flow rate of water was changed for five cases of 0.0017 to 0.0083 kg/s and the thermal efficiency of the system was computed for each absorber tube. The amount of solar radiation, mass flow rate as well as water temperatures at inlet and outlet of the absorber tube were measured during the investigation to have the experimental data. The maximum efficiency values were found as 74.5% for copper tube absorber while it was 72.7% for copper tube absorber when mass flow rate was 0.0083 kg/s. The problem was also modeled with CFD and temperatures at the outlet of absorber tube were found by numerical simulations (area-weighted average method) which showed a deviation of 6.5% as an average compared to experimental results.
Experimental assessment of the retrofit of an internal heat exchanger in refrigeration systems: The effect on energy performance and system operation
(Pergamon-Elsevier Science LTD, 2020) Oruç, Vedat; Devecioğlu, Atilla G.
The aim of this experimental study is to retrofit a refrigeration system with an internal heat exchanger (IHX) and to assess its effect on the energy performance of the system. The separate IHX cases in the investigation are tube-in-tube type and plate type and these are also compared with the system without any IHX. R404A and R442A refrigerants are tested in a single stage vapour compression refrigeration system. In the experimental work evaporation temperatures of −5°C and 0°C are considered while the condenser temperatures are 30°C and 50°C. The results indicated that both utilised types of IHX elements improved the energy performance of the system while the benefit with the tested plate type IHX case was better. Also, the alternative refrigerant R442A can be preferred as a substitute for R404A due to the enhanced energy performance of the system. The thermal effectiveness of IHX devices and the volumetric efficiency of the compressor are considered as well for the evaporation and condenser temperatures covered.
Experimental comparison of R404A and R452A in refrigeration systems
(Taylor & Francis, 2021) Devecioğlu, Atilla G.; Oruç, Vedat
In this study, R404A and R452A refrigerants used in refrigeration systems were compared experimentally. The energy performance of the system was investigated for widely used evaporation temperatures (−5, 0, +5 °C) and condenser temperatures (25, 35, 45 °C). It was seen that COP was higher but power consumption of system was lower using R452A as a substitute for R404A. When R452A was used, COP was improved about by 3% to 8% compared to R404A. Furthermore, cooling capacity decreased about by 2% for condenser temperatures of 25 and 35 °C while it increased at condenser temperature of 45 °C. Power consumption of system was also reduced nearly by 5%. Mass flow rate of refrigerant was lower when the system was operated with R452A. In the middle term, R452A could be a suitable alternative refrigerant for commercial refrigeration applications due to its low GWP value and better energy performance compared to R404A.
Experimental investigation of a solar air heater with copper wool on the absorber plate
(Taylor & Francis, 2020) Biçer, Ayşe; Devecioğlu, Atilla G.; Oruç, Vedat; Tuncer, Zafer
The thermal performance of a novel solar air heater was experimentally studied in this paper. For this aim, a new solar air collector was designed using copper wool on its absorber plate to be a selective surface. Hence, the area of absorber plate was enhanced to absorb much amount of heat energy. The experimental study was conducted for both cases (presence and absence of copper wool on the absorber plate) to determine the effect of copper wool on the thermal efficiency of the collector. The mass flow rate values of the study were 0.035 and 0.044 kg/s. The results pointed out that fluid temperature at outlet of collector with copper wool was increased by about 8 to14%. Therefore, these collectors may be suitable for space heating and drying of food applications. However, copper wool caused more pressure loss through the collector by 40% compared to simple case of collector. The thermal efficiency of the collectors was obtained as 34 to 83% depending on experimental variable parameters. Similarly, effective efficiency of collectors was computed to be 24 to 70%. It is found that efficiency of the collector was improved when using copper wool on the absorber plate as well as increasing mass flow rate of air.
Experimental investigation of thermal performance of a new solar air collector with porous surface
(Elsevier Ltd, 2017) Devecioğlu, Atilla G.; Oruç, Vedat
In this study, thermal performance of a new solar air collector with porous absorber plate was investigated. The porous surface was accomplished by laying out the copper meshing on the absorbing plate. Hence, it was aimed that the plate could absorb more heat and the thermal boundary layer of the flow would be disturbed. The experimental data was acquired for mass flow rates of 0.031 and 0.038 kg/s. The thermal efficiency was determined as 25 to 57% while the thermal-hydraulic efficiency of the collector was calculated as 14 to 44% depending on the experimental case. It was seen that temperature of the fluid at outlet of the collector, useful heat amount and pressure loss were increased as mass flow rate was increased. The results presented that the increasing the mass flow rate and establishing the surface of collector as porous would improve the thermal efficiency of the collector.
Experimental investigation on the low-GWP HFC/HFO blends R454A and R454C in a R404A refrigeration system
(Elsevier SCI LTD., 2021) Oruç, Vedat; Devecioğlu, Atilla G.
This study experimentally compares the high-GWP R404A with two low-GWP HFC/HFO blends, R454A (35% R32 + 65% R1234yf) and R454C (21.5% R32 + 78.5% R1234yf). Three evaporation temperatures ( -5, 0 and + 5 degrees C) and three condenser temperatures (30, 40, 50 degrees C) were studied. For all covered cases of condenser temperatures, the measured compressor power consumption was reduced by about 6% and 15% for R454A and R454C, respectively compared to R404A. The cooling capacity of R454A was higher than R404A by 11%, approximately, although the mass flow rate values have been reduced using the studied alternative refrigerants. As a result, the COP values of R454A and R454C were greater than R404A by about 14% and 10%, respectively. Although the discharge temperatures of the alternative blends were determined to be higher than that obtained for R404A, they are suitable for the tested operating conditions. The proposed alternative refrigerants could be used directly in available R404A systems without any constructional modification requirement if safety concerns can be solved. Moreover, it is possible to have higher cooling capacity and COP values as well as reduced environmental impacts. (c) 2021 Elsevier Ltd and IIR. All rights reserved.
FARKLI BUHAR SIKIŞTIRMALI SOĞUTMA SİSTEMLERINDE R134a YERİNE DÜŞÜK GWP DEĞERLİ SOĞUTKANLARIN ENERJI PARAMATERELERİNİN TEORİK MUKAYESESİ
(Türk Isı Bilimi ve Tekniği Derneği, 2018) Devecioğlu, Atilla; Oruç, Vedat
Bu çalışmada, R134a yerine kullanılan düşük GWP değerine sahip R1234yf, R1234ze(E), R513A, R445A ve R450A soğutucu akışkanlarının, enerji parametreleri (soğutma kapasitesi, COP vb) üç farklı buhar sıkıştırmalı soğutma sistemi ( basit çevrim, iç ısı değiştiricili basit çevrim ve iki kademeli kaskad çevrim) için teorik olarak mukayese edilmiştir. Soğutucu akışkanların termodinamik özellikleri benzer davranışlar göstermektedir. Ayrıca sistemlerin ekserji verimleri de karşılaştırılmıştır. Yapılan çalışmada enerji parametreleri, iki farklı evaporatör sıcaklığı (-30 ve 0?C) ve iki farklı kondenser sıcaklığı (40 ve 55?C) için mukayese edilmiştir. Hesaplanan sonuçlara göre R450A, R134a ile hemen hemen aynı COP değerindedir. R450A’nın GWP değeri R134a ile karşılaştırıldığında %58 daha düşüktür. Çalışılan soğutma çevrimleri arasında LSHEX’li çevrim, varsayılan sistem parametreleri, sıcaklıklar ve tüm soğutucu akışkanlar için yüksek COP değerleri açısından önerilebilir. İncelenen çevrimler için en yüksek ekserji verimliliğinin R445A durumunda elde edilebildiği görülmüştür.
Flow around a cylinder surrounded by a permeable cylinder in shallow water
(Springer, 2012) Özkan, Göktürk M.; Oruç, Vedat; Akıllı, Hüseyin; Şahin, Beşir
The change in flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by an outer permeable cylinder was investigated in shallow water using particle image velocimetry technique. The diameter of the inner cylinder and the water height were kept constant during the experiments as d = 50 mm and h w = 25 mm, respectively. The depth-averaged free-stream velocity was also kept constant as U = 170 mm/s which corresponded to a Reynolds number of Red = 8,500 based on the inner cylinder diameter. In order to examine the effect of diameter and porosity of the outer cylinder on flow characteristics of the inner cylinder, five different outer cylinder diameters (D = 60, 70, 80, 90 and 100 mm) and four different porosities (β = 0.4, 0.5, 0.6 and 0.7) were used. It was shown that both porosity and outer cylinder diameter had a substantial effect on the flow characteristics downstream of the circular cylinder. Turbulent statistics clearly demonstrated that in comparison with the bare cylinder (natural case), turbulent kinetic energy and Reynolds stresses decreased remarkably when an outer cylinder was placed around the inner cylinder. Thereby, the interaction of shear layers of the inner cylinder has been successfully prevented by the presence of outer cylinder. It was suggested by referring to the results that the outer cylinder having 1.6 ≤ D/d ≤ 2.0 and 0.4 ≤ D/d ≤ 0.6 should be preferred to have a better flow control in the near wake since the peak magnitude of turbulent kinetic energy was considerably low in comparison with the natural case and it was nearly constant for these mentioned porosities β, and outer cylinder to inner cylinder diameter ratios D/d.
Hcfc-22 yerine alternatif soğutucu akışkanların kullanıldığı split klima sistemlerinin enerji parametrelerinin araştırılması
(2014) Berk, Uğur; Vural, İbrahim; Devecioğlu, Atilla Gencer; Oruç, Vedat
[Abstract Not Available]
HCFC-22 YERİNE KULLANILAN BAZI HFC'LERİN ÇEVRESEL ETKİLERİNİN DENEYSEL OLARAK KARŞILAŞTIRILMASI
(2016) Devecioğlu, Atilla G; Oruç, Vedat
Bu çalışmada, HCFC-22 gazı yerine ozon tabakasına zarar vermeyen R417A ve R424A soğutucu akışkanlarının TEWI değerleri hesaplanıp, mukayese edilmiştir. Bir split klima cihazı için, ortalama 38?C çevre sıcaklığında, üç farklı soğutucunun tükettiği enerji miktarları deneysel olarak tespit edilmiştir. Soğutma ihtiyacı olan Mayıs-Eylül döneminde belli çalışma saatleri için yıllık enerji tüketimi hesaplanmıştır. Hesaplamalar sonucunda, GWP değeri yüksek olan R424A'nın doğrudan etkisi de yüksek olmuştur. R424A ve R417A'nın enerji tüketimleri R22'den %10 düşük olmasına rağmen, GWP değerlerinin yüksek olması sebebiyle, TEWI değerlerinin %2 -%4 oranında yüksek çıktığı tespit edilmiştir.
İklimlendirme sistemlerinde R22 yerine R442A kullanılmasının enerji parametrelerine etkisinin incelenmesi
(Dicle Üniversitesi Mühendislik Fakültesi, 2016) Devecioğlu, Atilla G.; Oruç, Vedat; Berk, Uğur; Ender, Sertaç
Bu çalışmada buhar sıkıştırmalı iklimlendirme cihazında R22 soğutucu akışkanı yerine R442A kullanılması deneysel olarak incelenmiştir. Sistemde sadece kompresör yağı değiştirilmiştir. R22 ile çalışırken mineral yağ kullanılırken R442A ile yapılan çalışmalarda sentetik polyol ester (POE) yağ kullanılmıştır. Deneyler aynı çalışma şartları altında üç farklı çevre sıcaklığı (25°C, 30°C, 35°C) için tekrarlanmıştır. Deneyler sonucunda soğutucu akışkanlara ait kütlesel debi, soğutma kapasitesi, COP ve sıkıştırma oranı tespit edilmiştir. Tespit edilen bu enerji parametrelerinin mukayesesi yapılmıştır. Sonuçlarda R22’nin soğutma kapasitesi ve soğutma performans katsayısı R442A’ya göre bir miktar yüksek tespit edilmiştir. R22’nin elektrik tüketimi ise R442A’dan düşük tespit edilmiştir. Ozon yok etme potansiyeli sıfır olan ve R22’nin enerji parametrelerine yakın değerlere sahip R442A’nın orta vadede R22 yerine iklimlendirme sistemlerinde kullanılabilecek uygun bir soğutucu akışkan olduğu söylenebilir.
On the satisfaction of EU F-Gas regulation using R455A as an alternative to R404A in refrigeration systems
(Elsevier, 2022) Devecioğlu, Atilla G.; Oruç, Vedat
The aim of this study is to investigate the possibilities for satisfying F-Gas regulation of European Union (EU) using R455A with low-global warming potential (GWP) in refrigeration systems. Hence an experimental work was conducted for energy analysis of a refrigeration system constructed to operate with R404A. The studied evaporation temperatures were -5 and + 5 degrees C while the condenser temperatures were 35 and 55 degrees C. It was determined that COP values of R455A were higher about by 13.7% compared to R404A. The results of the present investigation point out that R455A is suitable to use in refrigeration systems due to better energy performance. It is possible to use R455A in refrigeration systems after 2022 with respect to the EU regulation 517/2014. (C) 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Smart and Sustainable Developments in Materials, Manufacturing and Energy Engineering.
Passive control of flow structures around a circular cylinder by using screen
(Elsevier, 2012) Oruç, Vedat
he results of PIV measurements are presented in this paper for the water flow downstream of a circular cylinder surrounded with a screen (meshed outer control element) which had a streamlined shape. The diameter of cylinder, D was 50 mm and the Reynolds number based on the cylinder diameter was 5200. The characteristic length of the control element, L was tested for different cases so that the values of L/D were 2, 2.4, 2.8 and 3.2 in the experiments. It was noted that a forced reattachment of the shear layers separated from the cylinder was achieved by setting up the screen around the cylinder. As a consequence, the formation of vortical flow pattern was suppressed and turbulence statistics of the flow such as the intensity of turbulence, Reynolds shear stress, and turbulent kinetic energy were drastically diminished in comparison to the bare cylinder case. It was also found that the variable parameter of L/D did not dominantly influence the characteristics of the distribution of turbulence statistics along streamwise and transverse directions, however, the turbulence level decreased slightly for a smaller case of L/D.
PIV measurements on the passive control of flow past a circular cylinder
(Elsevier, 2016) Oruç, Vedat; Akıllı, Hüseyin; Şahin, Beşir
The passive control of water flow downstream of a circular cylinder with 50 mm diameter is experimentally investigated in this study using particle image velocimetry (PIV) technique. The experiments were carried out for three different Reynolds number (based on cylinder diameter) values of 3350, 6850 and 10,200. The flow structure was substantially vortical with large-scale downstream of the bare cylinder due to strong interactions of the shear layers separating from the cylinder surface. For the passive controlling of flow, a drop-shaped mesh surrounding the cylinder was used to suppress the formation of Karman vortex street in the wake region of the cylinder. Time averaged flow structures such as velocity distribution, vorticity, streamline topology, Reynolds shear stress and turbulent kinetic energy were referred for interpreting the experimental results. The spectral analysis of the measured velocity data was also performed to have information about the vortex shedding frequency of the unsteady flow in the cylinder wake. It was confirmed that flow was successfully controlled by paying attention to the absence of large-scale vortical flow structure (although small-scale vortices, which were not strong compared to the former one, were still present in the shear layers) as well as elongation in vorticity layers, attenuation in both Reynolds shear stress and turbulent kinetic energy distributions related to the fluctuating velocity components measured in the wake region.
Retrofitting of R-22 Air-conditioning system with R1234ze(E)
(Springer International Publishing Ag, 2020) Devecioğlu, Atilla G.; Oruç, Vedat
In this study, the effect on energy parameters and total equivalent warming impact (TEWI) using R1234ze(E) as a substitute for R22 in an air-conditioning device was investigated. The R22 system was retrofitted with R1234ze(E) changing compressor oil. The experimental data was obtained for three different ambient temperatures (30, 35 and 40 degrees C). It was seen that the power consumption of R1234ze(E) was smaller than that of R22 about by 41%. Although the cooling capacity of R1234ze(E) was 50% lower, its coefficient of performance (COP) was reduced only by 5% compared to R22. Furthermore, refrigerant charging amount of R1234ze(E) was smaller by 16% than R22. The results indicated that TEWI value of R1234ze(E) was lower than that of R22 by 65% due to small GWP (global warming potential) value and proper COP of the alternative refrigerant tested in the study. Hence, it can be expressed that R1234ze(E) can be used in air-conditioners of small capacity as an alternative to R22.
Soğutma sistemlerinde R454C kullanılmasının deneysel incelenmesi
(Gazi Üniversitesi, 2023) Devecioğlu, Atilla G.; Oruç, Vedat
Bu çalışmanın amacı, yüksek GWP değerine sahip R404A soğutucu akışkanı yerine hidrofloroolefin/hidroflorokarbon (HFO/HFC) karışımı düşük GWP değerine sahip R454C soğutucu akışkanın kullanılmasının incelenmesidir. Deneysel çalışmada iki farklı buharlaşma sıcaklığı (-4°C ve +4°C) ve iki farklı yoğuşma sıcaklığı (30°C ve 50°C) kullanılmıştır. Her iki kondenser sıcaklığında R404A’nın elektrik tüketimi R454C’den yüksek tespit edilmiştir. Ayrıca R454C’nin COP değeri R404A’dan ortalama %10 fazla tespit edilmiştir. R454C’nin kullanılmasıyla, sistemde dolaşan kütlesel debi değerinde azalma olmuştur. R454C’nin güç tüketimi R404A’dan ortalama %15 daha düşüktür. Alternatif karışımın kompresör çıkış sıcaklıkları R404A’dan yüksek olmakla birlikte R454C’nin çalışma koşulları için uygun olduğu görülmüştür. Hesaplanan TEWI değeriyle, R454C kullanılmasıyla CO2 emisyonlarında önemli azalmalar olmuştur. R454C’nin ekserji verimi R404A’dan yaklaşık %10-%15 daha yüksek bulunmuştur. Sistemde hiçbir değişiklik yapılmadan R404A’ya alternatif olarak R454C kullanılması mümkün olabilecektir.

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