M. Sivrioglu

Parametric study of natural convection heat transfer from horizontal rectangular fin arrays

Abstract A systematic theoretical investigation of the effects of fin spacing, fin height, fin length and temperature difference between fin and surroundings on the free convection heat transfer from horizontal fin arrays was carried out. The three-dimensional elliptic governing equations were solved using a finite volume based computational fluid dynamics (CFD) code. Preliminary simulations were made for cases reported in the literature. After obtaining a good agreement with results from the literature a large number of runs were performed for a detailed parametric study. It has been shown that it is not possible to obtain optimum performance in terms of overall heat transfer by only concentrating on one or two parameters. The interactions among all the design parameters must be considered. Results are presented in graphical form together with optimum values and correlations, and compared with available experimental data from the literature.

Numerical analysis of Grashof number, Reynolds number and inclination effects on mixed convection heat transfer in rectangular channels

Abstract Mixed convection heat transfer in rectangular channels has been investigated computationally under various operating conditions. The lower surface of the channel is subjected to a uniform heat flux, sidewalls are insulated and adiabatic, and the upper surface is exposed to the surrounding fluid. Solutions were obtained for Pr=0.7, inclination angles 0° ≤ θ ≤ 90°, Reynolds numbers 50 ≤ Re ≤ 1000, and modified Grashof numbers Gr = 7.0×10 5 to 4.0×10 6 . The three-dimensional elliptic governing equations were solved using a finite volume based computational fluid dynamics (CFD) code. From a parametric study, local Nusselt number distributions were obtained and effects of channel inclination, surface heat flux and Reynolds number on the onset of instability were investigated. Results obtained from the simulations are compared with the literature and a parallel conducted experimental study, from which a good agreement was observed. The onset of instability was found to move upstream for increasing Grashof number. On the other hand, onset of instability was delayed for increasing Reynolds number and increasing inclination angle.

Transient heat conduction with uniform heat generation in a slab subjected to convection and radiation cooling

A finite difference scheme with fourth order Runge-Kutta method is employed to determine the unsteady state temperature distribution in a plane slab with uniform heat generation. The plane slab is insulated on one face and subjected to convective and radiative cooling at the other face. The plane slab has a uniform initial temperature and the ambient environment as well as the fluid temperatures are assumed to be constant. Heat conduction is considered to be one dimensional. Results are presented in dimensionless charts over a wide range of parameters.ZusammenfassungZur Ermittlung der instationären Temperaturverteilung in einer Platte mit gleichförmiger Wärmeerzeugung wird ein Differenzverfahren vierter Ordnung nach Runge-Kutta angewendet. Die ebene Platte ist einseitig isoliert und wird auf der anderen Seite durch Konvektion und Abstrahlung gekühlt. Zu Beginn befindet sich die Platte gleichförmig auf einer bestimmten Anfangstemperatur, die Temperaturen der umgebenden Objekte sowie des Fluids sind ebenfalls konstant. Der Wärmeleitungsvorgang sei eindimensional. Die Ergebnisse sind in dimensionsloser Form für einen weiten Parameterbereich in Diagrammform dargestellt.

Exergy analysis of a vacuum tube solar collector system having indirect working principle

In this study, the energy and exergy analysis of a hot water preparation system, which is a boiler assisted vacuum tube solar collector, has been conducted. The obtained data were compared with reported results in the literature related to direct operating principle system. Average energy and exergy efficiencies of the experimental system were founded 12% and 0.3%, respectively. The average energy and exergy efficiencies of the vacuum tube solar collectors were founded 13.6% and 1.3%. Energy and exergy efficiencies of the vacuum tube solar collectors, which have indirect operating principle, are lower than direct system working with solar collectors. Maximum exergy loss has occurred in the vacuum tube solar collectors and followed it boiler and pump, respectively.

Data on energy, exergy analysis and optimisation for a sugar factory ☆

A huge amount of energy is consumed during sugar production in the food industry. The large amount of steam used and the power of the turbine power plant are key factors. This makes energy and exergy analysis important in sugar factories. The data given in the following paper are related to input and output information of the paper entitled Energy – exergy analysis and optimisation of a model sugar factory in Turkey by Taner and Sivrioglu (2015) [1]. Factory total energy efficiency and exergy efficiency are found to be ηenT=72.2% and ηexT=37.4%, respectively, and according to these results, the total energy quality ∅T=0.64. These results indicate higher efficiency than similar studies (Vuckovic et al., 2014; Pellegrini and Oliviera Junior, 2011; Deshmukh et al., 2013; Palacios-Bereche et al., 2015) [2], [3], [4], [5]. This study can be a model for these similar factories by Taner and Sivrioglu (2015) [1].