Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2013Scopus SJRQ1/r/bayburt/12485
  An experimental exergetic comparison of four different heat pump systems working at same conditions: As air to air, air to water, water to water and water to air

  Çakir, Uǧur; Çomakli, Kemal; Çomakli, Ömer; Karsli, Süleyman

  In this study, we designed a multifunctional heat pump system using just one scroll compressor and which can be run in four different modes, namely air to air, air to water, water to water and water to air, in order to make an experimental energetic and exergetic performance comparison. Experimental system consists of two condensers and two evaporators and uses R22 as working fluid. One of the evaporators and condensers uses water and the others use air as heat source/sink. Heating capacities of four heat pump types are equal to each other. It is realized by adjusting the mass flow rate and temperature level of external fluid of condenser. Results show that the heat pump unit which has the maximum COP (coefficient of performance) value is water to air type with 3.94 and followed by water to water type with 3.73, air to air type with 3.54 and air to water type with 3.40. Ranking of four heat pump types with respect to their mean exergy efficiency is as follows; water to air type with 30.23%, air to air type with 30.22%, air to water type with 24.77% and water to water type with 24.01%. Exergy destruction rates of the systems were investigated in this study and the results revealed that the heat pump type which has the maximum exergy destruction is air to air type with 2.93kW. The second highest one is air to water type with 2.84kW. The third highest one is water to air type with 2.64kW and last one is water to water type with 2.55kW. It is understood that the temperature of the evaporator external fluid affects the exergetic efficiency of the system more than the mass flow rate. In contrast to the previous, the dominant parameter which has more important effect on the exergy destruction of the heat pump unit is the mass flow rate of evaporator external fluid.

  AtıfScopus55·WoS46

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• MakaleAçık Erişim2013Scopus SJRQ2/r/bayburt/12251
  Experimental research of dynamic instabilities in the presence of coiled wire inserts on two-phase flow

  Omeroglu, Gokhan; Comakli, Omer; Karagoz, Sendogan; Sahin, Bayram

  The aim of this study is to experimentally investigate the effect of the coiled wire insertions on dynamic instabilities and to compare the results with the smooth tube for forced convection boiling. The experiments were conducted in a circular tube, and water was used as the working fluid. Two different pitch ratios (H / D = 2.77 and 5.55) of coiled wire with circular cross-sections were utilised. The constant heat flux boundary condition was applied to the outer side of the test tube, and the constant exit restriction was used at the tube outlet. The mass flow rate changed from 110 to 20 g/s in order to obtain a detailed idea about the density wave and pressure drop oscillations, and the range of the inlet temperature was 15-35°C. The changes in pressure drop, inlet temperature, amplitude, and the period with mass flow rate are presented. For each configuration, it is seen that density wave and pressure drop oscillations occur at all inlet temperatures. Analyses show that the decrease in the mass flow rate and inlet temperature causes the amplitude and the period of the density wave and the pressure drop oscillations to decrease separately.

  AtıfScopus2·WoS1·OpenAlex4

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• MakaleYalnız künye2012Scopus SJRQ2/r/bayburt/14030
  Forced convective two phase flow analysis in a circular tube equipped with twisted tapes

  Omeroglu, Gokhan; Comakli, Omer; Karagoz, Sendogan; Manay, Eyuphan

  In forced convection boiling systems, it is important to know the dynamic behavior for understanding and predicting the local and global stability of the system. Besides this, the instability phenomenon in the industrial processes in which two phase flow takes part becomes more of an issue. So, the mechanisms of instabilities and the ways of decreasing the stabilities are of interest of the researchers for a long time. In this study, the effects of pitch ratio, inlet temperature and the mass flow rate on two phase flow instabilities in a horizontal circular tube are investigated. The experiments are conducted under constant system pressure, and a constant heat input of 24 kW is applied to the outer surface of the circular test pipe having constant exit restriction. The results of two different pitch ratios are also compared with the smooth tube. For all investigated cases, the results are evaluated in terms of pressure drop type and density wave type oscillations. The time dependent measurements of top wall temperature, bottom wall temperature, inlet pressure and mass flow rate variations are also presented. The boundaries of the oscillations are found for both twisted tape and smooth channel. It is found that the unstable region of the flow extends while the distance between boundaries increases. It is observed that the system is more stable in the case of the lowest pitch ratio, and the increase of the pitch ratio causes system to be less stable. By the decrease of the inlet temperature, the single phase liquid region extends in the test tube and thus the system becomes more stable.

  İncele
• MakaleYalnız künye2012Scopus SJRQ3/r/bayburt/14026
  The prediction of heat transfer and fluid characteristics for equilateral triangular bodies in tandem arrangement by artificial neural networks

  Manay, Eyüphan; Güneş, Sibel; Akçadirci, Esra; Özceyhan, Veysel; Çakir, Ǔur; Çomakli, Ömer

  The objective of this study is to investigate the effect of the spacing between equilateral dual triangular bodies symmetrically placed into the channel axis under steady state conditions on heat transfer and fluid characteristics by using artificial neural networks (ANN). The Back Propagation (BP) training algorithm was applied to train the model. The successful application proved that ANN model can be used for predicting the Nusselt number and skin friction coefficient as a convenient and effective method. The distribution of local Nusselt number, skin friction coefficient along the channel wall and overall enhancement ratio of all investigated cases are presented.

  AtıfScopus5

  İncele
• MakaleYalnız künye2010Scopus SJRQ3/r/bayburt/14520
  ANALYSIS OF HEAT PUMPS WITH ZEOTROPIC REFRIGERANT MIXTURES BY TAGUCHI METHOD

  Comakli, Omer; Comakli, Kemal; Ozdemir, Nesrin; Yilmaz, Mehmet

  The goal of this work is to determine the optimum set of parameters by using the Taguchi method in vapour compression heat pump systems. The experimental apparatus consist of an air-to-liquid vapor compression heat pump, a water cooled condenser, a forced air evaporator, an electrical air and water heaters, and various measuring elements and other auxiliary equipments. Refrigerants R22, R407C, and five of their binary mixtures which contain about 0%, 25%, 50%, 75%, and 100% mass fractions of R407C were tested. To determine the effect of the chosen parameters on the system and optimum working conditions, an experimental design method suggested by Genichi Taguchi was used. The most effective parameters are found to be the condenser water mass flow rate for the coefficient of performance and to be condenser water inlet temperature for the exergetic efficiency.

  AtıfWoS6

  İncele
• Derleme MakaleYalnız künye2010Scopus SJRQ1/r/bayburt/14018
  Energy production, consumption, policies and recent developments in Turkey

  Toklu, E.; Güney, M.S.; Işik, M.; Comakli, O.; Kaygusuz, K.

  Many factors to be appropriately addressed in moving towards energy sustainability in Turkey are examined. These include harnessing sustainable energy sources, utilizing sustainable energy carriers, increasing efficiency, reducing environmental impact and improving socioeconomic acceptability. The latter factor includes community involvement and social acceptability, economic affordability and equity, lifestyles, land use and aesthetics. On the other hand, Turkey, with its young population and growing energy demand per person, its fast growing urbanization, and its economic development, has been one of the fast growing power markets of the world for the last two decades. Turkey is heavily dependent on expensive imported energy resources that place a big burden on the economy and air pollution is becoming a great environmental concern in the country. In this regard, renewable energy resources appear to be the one of the most efficient and effective solutions for clean and sustainable energy development in Turkey. Turkey's geographical location has several advantages for extensive use of most of these renewable energy sources. This article presents a review of the potential and utilization of the energy sources in Turkey.

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  AtıfScopus79·WoS68·OpenAlex99

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