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An analysis on the comparison of low-GWP refrigerants to alternatively use in mobile air-conditioning systems
(Elsevier, 2017) Devecioglu, Atilla G.; Oruc, Vedat
The results of an analysis are discussed in this paper considering R1234yf, R444A and R445A refrigerants having low Global Warming Potential (GWP) which can be used in the mobile air conditioning systems. The evaporation temperatures of -5 degrees C and +5 degrees C while condenser temperatures of 30 degrees C and 60 degrees C were taken for the evaluations of thermodynamic properties of the refrigerants. In the study, electrical power consumption of the system and COP values were calculated considering thermodynamic properties determined for the points in the cycle depending on the assumed system parameters. The system was considered to operate in a steady-state cycle. The pressure loss through evaporator and condenser, and heat transfer amounts through connecting tubes, expansion valve and compressor were neglected for the computations. The computations have pointed out that while cooling capacity of R444A and R445A were higher; their COP values were smaller compared to R1234yf because of their increased consumption of electricity. Although COP of R444A is smaller compared to R1234yf, it may be suggested that R444A can be utilized in air-conditioning systems of heavy vehicles such as busses, trucks, and trains due to its decreased flammability risk by mixture content. (C) 2017 Elsevier Ltd. All rights reserved.
An Approach for the Analysis of Collapse Onset in Elastic Tube Flows
(Springer Heidelberg, 2011) Carpinlioglu, Melda Ozdinc; Oruc, Vedat
An experimental study conducted for the determination of the onset of collapse of an elastic tube of a Starling resistor conveying air is presented herein. The collapse was induced under the action of external pressure p(e) applied to the tube walls. The influence of length L, thickness h, and modulus of elasticity E of the tube on collapse were determined by using a variety of silicone rubber and latex-Penrose tubes. The experiments were conducted under the presence of constant upstream head with the absence of a longitudinal strain of the tube in a range of flow Reynolds number (Re) 16750 < Re < 70280. At each air flow rate Q through the tube, p(e) was increased gradually. The inlet and exit pressures of the tubes p(1) and p(2) were measured. The variation of Q with p(e) was used to determine the onset of collapse. The magnitude of p(e) at the onset of collapse was defined as p(e,c). The visually observed collapse was associated with a flow rate reduction, followed by so-called oscillating and non-oscillating cases. The experimental data at the onset of collapse were expressed in terms of a correlation between Re (h/L) and a non-dimensional pressure parameter defined as (p(e,c) - p(2))/K-p including circumferential bending stiffness of the tube K-p.
Characteristics of Some New Generation Refrigerants with Low GWP
(Elsevier Science Bv, 2015) Devecioglu, Atilla Gencer; Oruc, Vedat
In the present study, a comparison was considered about some characteristics of new generation low GWP value gases most of which are at the trial stage. Hydrofluoro-olefin (HFO) based mixed gases having low GWP value were investigated as alternatives to different four refrigerants used commonly in refrigerating and air conditioning equipments. In the study, R450A, R513A, R1234yf and R1234ze(E) gases were used instead of R134a; DR-33, L40, DR-7 and R448A were used instead of R404A; DR-5 and R447A were used instead of R410A; and N20 and R444B refrigerants were used as alternatives to R22. Refrigerants were compared within their own groups in terms of liquid density and viscosity properties. (C) 2015 The Authors. Published by Elsevier Ltd.
A COMPARATIVE ENERGETIC ANALYSIS FOR SOME LOW-GWP REFRIGERANTS AS R134a REPLACEMENTS IN VARIOUS VAPOR COMPRESSION REFRIGERATION SYSTEMS
(Turkish Soc Thermal Sciences Technology, 2018) Devecioglu, Atilla G.; Oruc, Vedat
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 degrees C) and two condensing temperatures (40 and 55 degrees 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.
Effect on the thermodynamic performance using N20 and R444B refrigerants instead of R22 in a vapor compression refrigeration system
(Gazi Univ, Fac Engineering Architecture, 2016) Oruc, Vedat; Devecioglu, Atilla Gencer
In this study, the energy and exergy parameters were theoretically investigated for a vapor compression refrigeration system for which N20 and L20 (R444B) refrigerants were used instead of R22. The comparison of the energy parameters was carried out for different evaporation temperatures (-15 degrees C, -10 degrees C, -5 degrees C, 0 degrees C) and condensing temperatures (30 degrees C, 40 degrees C, 50 degrees C) under the same operating conditions. The coefficients of performance (COP) were seen to be in the same order of magnitude for three refrigerants, but the highest COP value was obtained with R22 case. It was seen that the equipments which will use N20 or R444B should have larger condenser surface areas compared to devices operating with R22. It was also determined that the exergetic efficiency of R22 was higher among the investigated refrigerants.
Energy and exergy analyses of a solar air heater with wire mesh-covered absorber plate
(Inderscience Enterprises Ltd, 2018) Devecioglu, Atilla G.; Oruc, Vedat; Tuncer, Zafer
Thermodynamic analysis on a novel design of solar air heater (SAH) having absorber plate covered with copper wire mesh was presented in this study. The newly-designed collector was tested for various air flow rates and tilt angles of the collector. The study was carried out for mass flow rates of 0.030 kg/s and 0.055 kg/s as well as collector tilt angles of 25 degrees and 35 degrees. Thermal efficiency, thermo-hydraulic efficiency and exergetic efficiency were computed by using experimental data. The results indicated that temperature at the outlet of collector, useful heat amount and pressure loss through collector were increased for higher mass flow rate and smaller collector tilt angle. Thermal efficiency of collectors was in the range of 34-82%, thermo-hydraulic efficiency was 25-66% and exergetic efficiency was 3.70-9.65% depending on the studied case. It may be suggested that greater mass flow rate and the lower tilt angle can lead to remarkable improvements in thermal and exergetic efficiencies of SAH with wire mesh on its absorber plate.
Enhancement of Energy Parameters for Refrigerants Used instead of R22 by Arranging Capillary Tube Length
(Asce-Amer Soc Civil Engineers, 2017) Devecioglu, Atilla G.; Oruc, Vedat
The capillary tube is used in most air-conditioning systems due to its low cost and not requiring sensitivity. In this study, the improvement of energy parameters was examined by adjusting the length of capillary tubes as well as using alternative refrigerants for an air conditioner operating with R22. The cooling capacity, coefficient of performance (COP), and electricity consumption results as well as pressure and temperature measurements in the system were investigated for the available length of capillary tube in the unit and shorter lengths (i.e.,cutting 20 and 40cm from the original length, respectively) with R422D and R417A refrigerants at ambient temperatures of 25-45 degrees C. Evaporator inlet pressure and evaporation temperature increased as a result of decreasing the capillary tube length. According to the results of study, the most suitable capillary tube length may be suggested as 80cm, which developed an increase in COP by about 0.9-2.8% compared to the original capillary tube length for studied ambient temperatures using R422D and R417A. (C) 2016 American Society of Civil Engineers.
THE EXPERIMENTAL COMPARISON OF ENVIRONMENTAL IMPACTS OF SOME HFC'S USED INSTEAD OF HCFC-22
(Turkish Soc Thermal Sciences Technology, 2016) Devecioglu, Atilla G.; Oruc, Vedat
In this study, the TEWI values for R417A and R424A refrigerants instead of HCFC-22 gas which don't deplete ozone layer were calculated and then compared. For a split type air conditioning equipment, the energy consumption amounts were experimentally determined for the three different refrigerants at an average ambient temperature of 38 degrees C. The annual energy consumption that is the cooling requirement was evaluated for the specific operating hours in May-September period. As a result of calculations, direct impact of R424A with the higher GWP value was also higher. It was found that although energy consumptions for both R424A and R417A were less than that for R22 by 10%, their TEWI values were to be higher with 2 to 4% because of their greater GWP magnitudes.
Experimental comparison of the energy parameters of HFCs used as alternatives to HCFC-22 in split type air conditioners
(Elsevier Sci Ltd, 2016) Oruc, Vedat; Devecioglu, Atilla G.; Berk, Ugur; Vural, Ibrahim
The R22 refrigerant widely used in refrigerating and air conditioning devices is invariably released to the atmosphere due to reasons such as breakdown and/or translocation. As the sales of new devices operating with R22 are decreasing gradually, refrigerants of such available devices should be changed with the ones that are not depleting the ozone layer. In this paper, the amount of consumed energy, cooling capacity and COP values of R417A, R422A, R422D and R424A, which can be used as alternatives to R22, were determined experimentally for a split type air conditioning device at the ambient temperatures of 35, 38 and 41 degrees C. Basically, COP values of all HFC refrigerants were found to be smaller than that of R22. It was noted that the most suitable refrigerating fluid was R424A, which can be used instead of R22, since the COP of R424A was smaller than that of R22 by 2.5% only at an ambient temperature of 41 degrees C. (C) 2016 Elsevier Ltd and International Institute of Refrigeration. All rights reserved.
Improvement of energy parameters using R442A and R453A in a refrigeration system operating with R404A
(Pergamon-Elsevier Science Ltd, 2018) Oruc, Vedat; Devecioglu, Atilla G.; Ender, Sertac
In this study, R404A having high GWP (global warming potential) was experimentally compared with R442A and R453A refrigerants which have low GWP. The alternatives refrigerants of R442A and R453A were directly tested without performing a constructional modification in the refrigeration system. Three different evaporation temperature (-6, -3 and 0 degrees C) and three condenser temperature (35, 40, 45 degrees C) cases were investigated in the experimental work. Power consumption of compressor was highest for R404A while it was the lowest for R453A at three condenser temperatures. The measurements presented that cooling capacity amounts of R442A and R453A were greater by 1-8% than that of R404A. In comparison with R404A, COP (coefficient of performance) value was better by 5-12% using R442A and it was substantially improved by about 10-14% for the case of R453A refrigerant. The volumetric efficiency values were obtained as the highest for R453A at the covered experimental cases. The mass flow rate and quality of refrigerant at evaporator inlet were also reduced as a result of using considered alternatives refrigerants. (C) 2017 Elsevier Ltd. All rights reserved.
Improvement on the energy performance of a refrigeration system adapting a plate-type heat exchanger and low-GWP refrigerants as alternatives to R134a
(Pergamon-Elsevier Science Ltd, 2018) Devecioglu, Atilla G.; Oruc, Vedat
This study is directed to propose a method for enhancing the energy parameters of the refrigeration systems operating with R134a which generally presents low performance of the units. Hence, R134a was experimentally compared with HFO-based refrigerants of R1234yf and R1234ze(E) having low-GWP. Additionally, plate-type liquid to suction heat exchanger (LSHX) was utilized in order to determine its effect on the system's energy performances. The evaporation temperatures were -9, -4.5 and 0 degrees C while the condenser temperatures were 40, 45, and 50 degrees C in the experimental work. The cooling capacity and power consumption of R1234ze(E) were noticed lower, however its COP was higher compared to R1234yf. It was also figured out that COP of the system with LSHX using R1234ze(E) was better about by 3% than that without LSHX which operated with R134a. The results of the present study indicated that the presence of LSHX caused improved COP and lower power consumption of the refrigeration system. (C) 2018 Elsevier Ltd. All rights reserved.
The influence of plate-type heat exchanger on energy efficiency and environmental effects of the air-conditioners using R453A as a substitute for R22
(Pergamon-Elsevier Science Ltd, 2017) Devecioglu, Atilla G.; Oruc, Vedat
It is well-known from previous investigations that energy parameters of the systems, which operate using directly alternative refrigerants, have poorer energy parameters compared with R22. The cooling capacity amounts are also desired to be kept constant while changing the refrigerant of the systems originally designed and constructed to work with R22. In order to achieve this aim, the performance of R453A refrigerant was investigated by coupling a plate-type liquid to suction heat exchanger for an air conditioner operating with R22. Therefore, smaller discharge pressure of the compressor, decreased electricity consumption, and enhanced cooling capacity amounts were intended in this study. The results indicated lower TEWI amounts as well as improved both exergetic and energetic parameters as a result of using R453A as an alternative to R22 with the presence of a plate-type liquid to suction heat exchanger in the system. (C) 2016 Elsevier Ltd. All rights reserved.
Suppression of asymmetric flow behavior downstream of two side-by-side circular cylinders with a splitter plate in shallow water
(Elsevier Sci Ltd, 2013) Oruc, Vedat; Akar, M. Atakan; Akilli, Huseyin; Sahin, Besir
The flow downstream of a pair of circular cylinder in a side-by-side arrangement normal to the free stream is known to exhibit intermittently bistable structure for the range of G/D = 1.2-2.2 where G is the center-to-center distance between the cylinders and D is the diameter of the cylinder. Eventually, the wake downstream of one of the two cylinders can be wider or narrower than the one downstream of the other cylinder depending on the direction of gap-flow deflection. In the present study, such an asymmetric flow behavior downstream of two side-by-side cylinders, which were vertically located in shallow water, was passively controlled with a splitter plate with a length of L (1 <= L/D <= 5). The center of splitter plate was just coincided with the mid-height of the gap between centers of the cylinders. The investigations were carried out in a water channel using dye visualization and particle image velocimetry, PIV for qualitative and quantitative measurements, respectively. The diameter of the cylinder, D was 40 mm while the depth of water was 20 mm so that the shallow flow condition was provided through the experiments. The Reynolds number, Re based on D was 5000 and the cylinder's center to center spacing to the cylinder diameter ratio (G/D) was equal to 1.25. The results demonstrated that the deflection of the wake and thereby the bistability of the wake was considerably prevented with the presence of the splitter plate for L/D >= 3 which resulted in two well symmetric, stable wakes having approximately the same order of magnitudes of vortex shedding frequencies around the cylinders. (C) 2012 Elsevier Ltd. All rights reserved.
The thermodynamic and environmental analysis of a variable speed R404A refrigeration system using R455A
(Elsevier, 2024) Devecioglu, Atilla G.; Oruc, Vedat
The suitability of drop-in application of low-GWP refrigerant R455A in a R404A refrigeration system is experimentally investigated in this paper comparing energy performance and environmental impacts (i.e., CO2 emissions) of the system. The evaporation temperatures are -5, 0 and + 5 degrees C while condensation temperatures are 30, 40 and 50 degrees C in the test conditions. Besides, the compressor speed is adjusted for three cases as 40, 45 and 50 Hz. The behaviours of COP, exergy efficiency and total equivalent warming impact (TEWI) are determined depending on evaporation and condensation temperatures as well as compressor speed. The results demonstrate that although cooling capacity of R404A is higher, COP of R455A is computed to be better than R404A about by 4.3 % (on average) for all covered cases. The exergy efficiency of R455A is also found to be higher compared to R404A. The COP and exergy efficiency values are reduced, TEWI enhances as compressor speed increases for both R404A and R455A. Additionally, an empirical expression (valid within about +/- 5 % and independent of variable parameters such as refrigerant type, compressor speed as well as evaporation and condensation temperatures) is proposed for the relationship between nondimensional parameters COP and compression ratio. Furthermore, the amount of TEWI is verified to be lower for R455A than R404A, hence the studied alternative blend can be preferred due to the environmentally friendly characteristic. It can be suggested referring to the obtained results that R455A can be directly used in a R404A refrigeration system due to improved thermodynamic performance and diminished CO2 emissions.
Thermodynamic performance of air conditioners working with R417A and R424A as alternatives to R22
(Elsevier Sci Ltd, 2015) Oruc, Vedat; Devecioglu, Atilla G.
The energy and exergy parameters of R417A and R424A gases which can be used instead of R22 were experimentally investigated for a split-type air conditioner. Although GWP amounts of the available alternative refrigerants are higher compared to R22, their ODP values are zero. The experiments were accomplished for three different ambient temperature values of 25 degrees C, 30 degrees C and 35 degrees C. The covered test conditions were carried out for steady-state case while keeping the inside medium temperature at constant temperature of 22 degrees C. The cooling capacity, COP, exergy destruction of components in the unit (i.e., compressor, condenser, evaporator, and expansion device), exergetic efficiency and some other parameters of the system were determined. COP values for the refrigerants of R417A and R424A were noted to be smaller compared to R22. Similarly, both isentropic efficiency of the compressor and exergetic efficiency of the system were higher for R22. The use of R424A will be more suitable rather than R417A since COP values of R417A are lower about 5 -16% compared to R424A. The COP value of R22 is greater than that of R417A and R424A by amounts of 17-23% and 4-18%, respectively. At the greater evaporation temperatures (0 degrees C to +5 degrees C as in the air-conditioners) it can be stated that R424A is more preferable than R417A as an alternative refrigerant to R22. (C) 2015 Elsevier Ltd and IIR. All rights reserved.

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