Pressure drop in pipes can be calculated by using the Darcy-Weisbach formula. In order to use this formula, the Darcy friction factor should be known. The best approximation to the Darcy friction factor for turbulent flow is given by the Colebrook-White equation. This equation can only be solved by numerical root finding methods. There are several other approximate correlations to the Darcy friction factor with some relative error compared to the Colebrook-White equation. It was found that in some of these correlations, the percentage error is so small that they can be used directly in place of the Colebrook equation. In this study, a review of several friction factor correlations is performed. Relative error of these correlations is re-evaluated against the Reynolds number for a different value of relative pipe roughness. Also statistical analyses will be given for each correlation.

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In this study, a numerical analysis of the inward solidification of phase change material inside spherical capsule is carried out. The spherical capsule that is subjected to convection from the outside surface initially is not at its melting temperature. The control volume approach and temperature transforming method are applied to solve the dimensionless energy equation. The model solution results are validated through a comparison with published experimental data for similar case and it shows a considerably good agreement. The analysis results show that the larger diameter spherical capsules have significantly greater solidification time compared to those with smaller diameters of spherical capsules. In addition, the entropy generation inside spherical capsule is analyzed. It is found that the entropy generation increases with increasing sphere capsule diameter, attains a maximum and then decreases. Ó 2016 Faculty of Engineering, Ain Shams University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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This work investigates the solidification of phase change material (PCM) embedded with metal foam (MF) in a spherical capsule which its outer layer is exposed to convective heat transfer. The one-dimensional energy equation is resolved by performing finite volume method accompanied with temperature transforming technique. Four separate scenarios are developed for different porosity value of MF in order to analyze the thermal behavior of composite PCM with MF. The numerical model is validated by experimental data taken from the literature and substantially good agreement is demonstrated. The results show that at the case where the porosity ε =0.92, the elapsed time for complete solidification is decreases by 88% compared to the case without MF (ε =1.0).

Bu çalışmada, boruları düşey konumda olan gövde boru tipi bir ısı değiştiricide, borular içinde 23°C sıcaklıkta ergiyebilen faz değişim malzemesi bulunan bir sistem ele alınmıştır. Isı transfer akışkanı olan hava sisteme fan aracılığıyla sağlanmıştır. Bu çalışmada öncelikle faz değişim malzemeli ısı değiştiricinin tasarımına ilişkin sayısal bir yöntem geliştirilmiş ve elde edilen sonuçlar daha önce yapılan analitik yöntemin sonuçları ile karşılaştırılmıştır. Daha sonra, faz değişim malzemeli ısı değiştiricinin hacmi sabit tutulmuş ve sistem üzerinde parametrik bir çalışma yapılmıştır. Boru aralığı değişimi, hava debisi (fan hızı) değişimi ve faz değişim malzemesi değişken parametreler olarak ele alınmıştır. Boru sayısı akışa dik yönde iki kat arttığında toplam ergime zamanı tüm dört aralık durumu için ortalama olarak %38 oranında azalmıştır.