Natural minerals like calcite, clay, kaolin and dolomite are used as fillers up to 15 wt % in productions of rigid polyurethane foams to reduce production costs and enhance the fire resistance. In general, only filler additions do not significantly enhance the fire resistance of the foams. Therefore, different flame retardant materials are added together with the fillers. In this study, effects of 10 wt % nanoclay/5 wt % an intumescent flame retardant additions on combustion behaviour of rigid polyurethane foam were investigated by cone calorimeter tests. Heat release rate, total heat released, ignition time, smoke production and carbon monoxide emissions of neat and nanoclay/intumescent flame retardant filled polyurethane foams were examined. The experimental results showed that 10 wt % nanoclay/5 wt % the intumescent flame retardant addition significantly improved the fire resistance.

The first reinforced concrete spatial structures date from 1920. These types of structures faded near 1970’s because of the high costs in formwork and labor work, but also from calculations difficulties. The technological evolution of formworks, as well as the advance of software industry for civil engineering, has helped to reach new levels of expertise during the structural design process. The scope of this analytical study is the use of structural openings to create new lighter, sustainable and architectural forms of structures, and using algorithms for form finding process. The paper includes structure cyclic analysis due to finding the appropriate position and geometrical form of the openings considering stresses, deformations and boundary conditions of specific cases. Optimizations are made using advanced optimization algorithms of form finding and topological optimization (ATOM – Abaqus Topology Optimization Module ®) and FEM for static analysis. Based on the analysis data of the examples presented on this paper with the use of advanced software, we conclude that spatial shells in 21-st century should be considered as the next engineering challenge in conjunction to architectural trends for free, irregular and diverse forms. In this article a theoretical study of the issue is made, including data from examples of optimization of shells with advanced algorithms using step by step sensitivity analysis. As a result of all data taken from the optimizations is concluded that using latest optimization algorithms, sensitivity analysis sums up to 40 % less stressed structures, and up to 30-40% lighter ones by creating structural openings.

This study presents a numerical investigation of volume fraction effect of water based hybrid CuO-SiO2 nanofluid in a horizontal tube on thermal performance. Uniform heat flux was applied onto the outer surface of the test tube. Fully developed turbulent flow was ensured with adjusting solution domain. k-epsilon turbulent model was chosen to simulate turbulent flow, and analyses were implemented for Reynolds number ranging from 10,000 to 50,000. The nanofluid flow was assumed as single phase, and properties of nanoparticles and water are concerned as independent in temperature. Thermo-physical properties of nanofluid were calculated with commonly used equations and correlations in literature. Nanoparticle volume fractions in water were employed as 5, 4, 3, and 2% in which each volume fraction is different value of CuO and SiO2. As a result, since CuO is more effective thermal properties than SiO2, it is observed that greater volume fraction of CuO than SiO2 shows better heat transfer performance. Moreover, the highest Nusselt number is obtained for 1%CuO-4%SiO2 water based nanofluid for Reynolds number of 50,000. However, due to better hydraulic properties of SiO2 than CuO, the higher volume fraction of SiO2 compared to CuO, the higher thermo-hydraulic performance was obtained.

The present study investigates buckling in functionally graded material (FGM) beams when exposed to a temperature rise. The proposed FGM beams have arbitrary edge supports that are modeled by rotational and translational springs. The mechanical properties are assumed to vary continuously across the thickness direction according to a simple four-parameter power law. To obtain the critical value of temperature, the governing equilibrium equations are extracted based on Timoshenko beam theory, using the assumption of Von-Karman nonlinearity for the physical neutral surface concept. The equations are further solved by Fourier series expansion via Stokes’ transformation technique. Numerical examples are provided to demonstrate the accuracy and reliability of the proposed method. The influence of two models of metal-ceramic distribution across the thickness (symmetrical and unsymmetrical ones) on the response of the beam in thermal buckling of FG beam is investigated. It is observed that, the critical buckling temperature rises more for symmetrical model of FGM beam with respected to unsymmetrical one. Also, increasing the translational and rotational spring coefficient makes the beam stiffer; consequently, the critical buckling temperature is increased.

In this study, increasing the efficiency of liquid fuelled smoke tube boilers used for domestic heating was researched. In this context, turbulators with conical geometries placed to smoke tubes of boiler and effects on flame structure and heat transfer were investigated numerically. Calculations were carried out at two dimensional axisymmetric conditions and Fluent was used as the computational fluid dynamics software. In all cases, the standard k-e model was used for modeling the turbulent flow and the species transport model was used for modeling the combustion. Based on the results of these turbulators were evaluated for each condition. Besides, temperature and stream function distribution and pressure drop were investigated according to the arrangement of turbulators and which number of turbulator would be the most appropriate at boilers was discussed. Increasing the number of turbulators from zero to three decreased the exhaust temperatures 15 K from 365 K to 350 K, and consequently the efficiency of the boiler was increased. Yet the turbulators inserted into smoke tube increased the pressure losses insignificantly from 20 to 23.5 Pa.