Arif Ozbek

Estimation of human heat loss in five Mediterranean regions

This study investigates the effects of seasonal weather differences on the human bodys heat losses in the Mediterranean region of Turkey. The provinces of Adana, Antakya, Osmaniye, Mersin and Antalya were chosen for the research, and monthly atmospheric temperatures, relative humidity, wind speed and atmospheric pressure data from 2007 were used. In all these provinces, radiative, convective and evaporative heat losses from the human body based on skin surface and respiration were analyzed from meteorological data by using the heat balance equation. According to the results, the rate of radiative, convective and evaporative heat losses from the human body varies considerably from season to season. In all the provinces, 90% of heat loss was caused by heat transfer from the skin, with the remaining 10% taking place through respiration. Furthermore, radiative and convective heat loss through the skin reached the highest values in the winter months at approximately between 110 and 140W/m(2), with the lowest values coming in the summer months at roughly 30-50W/m(2).

Analysis of alumina/water nanofluid in thermally developing region of a circular tube

Analysis of Al2O3/water nanofluid flow in thermally developing region of a circular tube is the subject of present numerical study. In order to consider the hydrodynamically fully developed condition in the tube, a fully developed velocity profile is defined in the inlet section of tube. Three-dimensional computations are performed for a wide variety of nanoparticle concentrations (1 ≤ γ ≤ 10%). On the other hand, for examination of nanoparticle size, effects on the thermal characteristics, two different particle sizes of dp = 25 and 75 nm are applied. The resulting governing equations are solved numerically by means of the finite volume method. For enhanced visualization, different results are presented in thermally developing region. It is obtained that suspending the Al2O3 nanoparticles in pure water increases the thermal boundary layer growing rate. In addition, an increase on the heat transfer rate is observed in thermal boundary layer using the Al2O3 nanoparticles in which this enhancement varies as a function of nanoparticle size and nanoparticle volume concentration. However, it is found that the role of nanoparticle volume concentration on the thermal characteristics such as thermal boundary layer growing rate, temperature gradient, and heat transfer enhancement is significantly important comparing to the nanoparticle size.

Investigation of wind power density at different heights in the Gelibolu peninsula of Turkey

ABSTRACT This study aims to determine the wind characteristics and wind power potential of the Gelibolu peninsula in the Çanakkale region of Turkey. For this purpose, hourly average wind data observed at the Gelibolu meteorological station were used. The Weibull probability density functions and Weibull parameters of time-series of wind speed, mean wind speed, and mean wind power potential were determined for different heights as 10, 20, 30, 40, and 50 m. According to the results obtained at 10- and 50-m heights above the ground level, the annual wind speed varied from 6.85 to 8.58 m/s in this region, respectively. The annual wind power potential of the site was determined as 407 and 800 W/m2 for 10- and 50-m heights, respectively. These results indicate that the investigated site has a reasonable wind power potential for generating electricity.

Effect of atmospheric temperature on exergy efficiency and destruction of a typical residential split air conditioning system

This work presents an experimental investigation on energy and exergy performance characteristics of a typical residential split air conditioning system. Analyses are performed for different atmospheric temperatures. On the basis of experimental data coefficient of performances (COP), exergy efficiencies (ψ) and exergy destructions (Ėxdest) of whole system and its each subunits are evaluated. The results also demonstrate that the atmospheric temperature (Tatm) rise affects the system performance as well as its performance of components substantially. The values of Ėxdest in the compressor and capillary tube increase with an increase of Tatm but the values of Ėxdest in the condenser and evaporator decrease with an increase of Tatm. When Tatm is risen from 20°C to 46°C; it is determined that power consumption (Ẇcomp) and Ėxdest of the air conditioning system are enhanced by 47.1% and 24.5%, respectively, but ψ is reduced by 38.8%.

Yoğunlaştırılmış Güneş Enerjisi Teknolojisi ve Yatırım Maliyetlerinin Küresel Değerlendirilmesi

Bugunlerde dunya, gunes enerjisi gibi konvensiyonel olmayan enerji kaynaklarina dogru egilim gostermektedir. Diger enerji kaynaklariyla karsilastirildiginda gunes enerjisinin en onemli avantaji, herhangi bir cevresel kirlilik olusturmamasidir. Bu calismada, yogunlastirilmis gunes enerjisi teknolojisinin (YGE) dunyadaki mevcut durumu, gelisimi, gelecekteki durumu ve uygulamalari sunulmustur. Parabolik oluk, fresnel aynalari, gunes kuleleri ve parabolik canak adi verilen dort ana teknolojiden olusan yogunlastirilmis gunes enerjisi teknolojisi yatirim maliyetleri acisindan degerlendirilmistir. Sonucta, dunyadaki toplam yenilenebilir kurulu guc kapasitesi icerisinde yogunlastirilmis gunes enerjisi kurulu kapasite oraninin halen %1’in altinda kaldigi; ancak gun gectikce bu oranin arttigi gozlenmektedir. Buna ilaveten, YGE’nin diger yenilenebilir teknolojilere kiyasla nispeten dusuk maliyetli isil depolama avantajina sahip oldugu gorulmektedir