Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2019/r/gumushane/15122
  Natural convection in an enclosure with a pair of discrete heat sources

  Saglam, Mehmet; Sarper, Bugra; Aydin, Orhan

  An experimental and numerical study is carried out to investigate natural convection cooling characteristics of discrete heat sources in a rectangular enclosure. One of the sidewalls of the enclosure is heated by a pair of identical discrete heat sources, whereas the other sidewall is maintained at a constant temperature. The effect of the heat dissipation ratio of the heat sources on buoyancy-induced flow and heat transfer characteristics is investigated. Experimental studies are performed for a constant value of the modified Rayleigh number (Ra = 7.7 × 105) and three different values of the heat dissipation ratio (rh = q1 = q2 = 0.5, 1 and 2), whereas numerical studies cover the range of 104to 5 × 106 for the modified Rayleigh number and different values of the heat dissipation ratios between 0.25 and 2. In the experimental study, qualitative flow visualization studies are carried out as well as temperature measurements. In the numerical study, a commercial computational fluid dynamics code in ANSYS Fluent is used. The variations of the surface temperatures, the hot spot temperature, and the mean Nusselt number with the modified Rayleigh number and the heat dissipation ratio are obtained. Results are presented in terms of streamlines, isotherms, and heat lines.

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• MakaleYalnız künye2014/r/gumushane/15494
  Exergetic analysis of using the gaseous fuels in spark ignition engines

  Sezer, Ismet; Bilgin, Atilla

  This paper aims to investigate the use of alternative gaseous fuels in spark ignition engines via an exergy analysis. A quasi-dimensional two-zone thermodynamic cycle model is used for this purpose. The intake and exhaust processes are computed by a simple approximation method, and the processes (that is, compression, combustion, and expansion) are simulated in detail. The turbulent flame propagation process is used for the combustion simulation. The second law of thermodynamics is applied to the cycle model to perform the exergy analysis. The exergy transfers associated with heat, work, and exhaust; the irreversibilities, thermomechanical exergy, fuel chemical exergy, and total exergy have been computed in the exergy analysis. A distribution of the fuel exergy, the energy-based (the first law) efficiency, and the exergetic (the second law) efficiency were also calculated during the exergy analysis. Thus, the effects of using natural gas and liquefied petroleum gas on the exergetic terms and the efficiencies are investigated. The results of the study show that investigated alternative gaseous fuels have affected the variations in the exergy transfers, irreversibilities, and efficiencies. The gaseous fuels are suitable from the exergy point of view because of the lessened exergy destruction rate, but they suffer from the engine performance reduction.

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