A numerical study was performed of natural laminar convective heat transfer to its concentrated triangular enclosure around a horizontal circular cylinder. The air-filled enclosure kept the inner and outer cylinders at uniform temperatures. The Boussinesq density approximation to the momentum problem and the control volume approach iteratively resolved the governing equations to explain buoyancy. CFD results show that the velocity behavior increases by increasing Ra, so the stream lines becomes more sluggish and less uniform behavior and vortices gets less circulated pattern. The rotation angle ? has significant effect on vortices, at 90o gives the higher range of velocity zones of free convection with higher range. The thermal boundary layer seems to be larger in rr=0.455 as compared with rr=0.345 and decreases by increasing ?. The larger variation of isotherms and thermal boundary layer appears at lower ? because the higher heat transfer rate occurs at higher ? and becomes maximum at 90o. Eight correlations of average Nusselt number have been deduced as a function of Rayleigh number for the taken values of aspect ratio and enclosure angles of rotation and inclination.
The objective of this study to estimate the Radiation Use Efficiency under effect of three levels of nitrogen (N1 = 80 Kg N ha-1, N2 =120 Kg N ha-1, and N3=160 Kg N ha-1) for a set of maize hybrids include (Gloria, Market, Cruze and Draxma) in two different seasons in spring and fall of 2017 in Qlyasn-Sulaimani. The experiment was conducted using split plot design with three replicates . The results revealed higher intensity of PAR in autumn season than that of spring (15.672 and 10.555)MJm-2d-1 respectively that led to higher RUE in autumn revealing (4.311,3.546, and 4.702)g MJ-1 m-2 under the effect of (N1,N2, and N3) respectively, while the results of the autumn were higher (5.237, 4.681, and 6.019) g MJ-1 m-2 under the same levels of nitrogen fertilization, the highest application of nitrogen was more effective in autumn. The RGR and the rate of total dry matter accumulation were higher in autumn season displaying positive performance of studied maize hybrids to the higher intercepted of solar energy as well higher temperature.
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