Exergoeconomic analysis and optimization of a solar-assisted heating system for residential buildings

In this study, an exergoeconomic model was developed for analysis and optimization of solar heating systems with residential buildings. The optimum collector area (_Ac$A_{\mathrm{c}}$) and storage volume (V$V$) for solar-assisted heating system in the Elaz??, Turkey (38.7^°N)$(38.7^{°}\mathrm{N})$, weather conditions were obtained using MATLAB optimization toolbox. The energy and exergy losses in each of the components of a solar heating system with seasonal storage were also determined. The results showed that the exergy loss and total cost increased with increasing per house collector area for the trapeze and cylindirical tanks. It was found that the total cost of the cylindrical tank system was higher than that of the other trapeze tank system. The exergy loss at the cylindrical tank was 19.8%, while the exergy loss at the trapeze tank was 8.3%.     

Scale model study of airflow performance in a ceiling slot-ventilated enclosure: Non-isothermal condition

Scale-model study of a non-isothermal ceiling slot-ventilated enclosure was investigated in both airspeed and thermal fields. Results of airflow pattern, centerline velocity and centerline temperature decay, velocity and temperature profile, airflow boundary layer and thermal boundary layer growth, floor velocity, and floor temperature difference were analyzed to establish semi-empirical prediction equations. Results also compared with previous researches to validate the physical behavior of air-jet. Data of centerline velocity decay showed similar airflow characteristics as isothermal air-jet with Archimedes number (Ar)<0.004$(\mathit{Ar})<0.004$, which performed as pseudo-isothermal airflow. Air-jet fell on entry with Ar>0.018$\mathit{Ar}>0.018$. A single circulation airflow existed at 0.004<Ar<0.011$0.004<\mathit{Ar}<0.011$ and two-circulation airflow occurred at 0.011<Ar<0.018$0.011<\mathit{Ar}<0.018$. The centerline velocity decay was fitted well as similar form of an isothermal condition. The centerline temperature decay was fitted well as the form of centerline velocity decay in both ceiling and floor regions. Both the velocity and temperature profiles agreed with results obtained from literature. Both airflow boundary layer and thermal boundary layer growths increased with traveling distance of air-jet. Maximum floor velocity and floor temperature difference were fitted well with different parameters. Analysis of airflow performance in a non-isothermal condition makes progress in predicting air quality inside the enclosures and guides the design concepts of ventilation system for an indoor environment.     

Impacts of some building passive design parameters on heating demand for a cold region

In this study, the impact of passive design parameters such as building shape and orientation position on heating demand has been theoretically investigated. Therefore, a transient heat transfer problem in the building envelope with insulation and without insulation is solved by using the finite difference method. The considered buildings are placed on the ground with the azimuth angles from 0^°$0^{°}$ to 90^°${90}^{°}$. The heat loss per unit area of the buildings is computed by hour–hour and the yearly energy consumption of the buildings is also determined in the simulation model. The climatic data of Elazigˇ (38.4^°N)$(38.4^{°}\mathrm{N})$, a city located in a cold region of Turkey, are considered for the analysis. It is shown that buildings with a square shape have more advantages, and the most suitable orientation angles are 0^°$0^{°}$ and 80^°${80}^{°}$ for buildings having shape factors (the ratio of building length to building depth ) 2/1 and 1/2, respectively.     

The impact of urban street layout on local atmospheric environment

The investigation was carried out to reveal the impact of urban street layout on local atmospheric environment through computational fluid dynamics (CFD) numerical simulations using standard k$k$–ε$\epsilon$ turbulence model. Different street canyon configurations are considered and the flow regimes summarized according to the aspect ratio of the leeward building height and the street width H1/W$H1/W$ and the aspect ratio of the leeward building height and the windward building height H1/H2$H1/H2$. Three regimes are defined to denote the vortices and characteristics of pollutant dispersion in street canyons according to the parameters H1/W$H1/W$ and H1/H2$H1/H2$. It is found that the pollutant transport and diffusion is strongly dependent upon the type of flow regime inside the canyon and exchange between canyon and the above roof air. The study indicated that there is a strong influence of the street layout on the wind field and the pollutant dispersion in the street canyon mainly depends on the vortex structure in the canyon. The results are validated against an extensive wind tunnel experimental (Meroney and Rafailidis) [Journal of Wind Engineering and Industrial Aerodynamics, 1996;62:37–56; http://www.mi.uni-hamburg.de] and the simulated results concluded by Sini [Atmospheric Environment 1996;30:2659–77] and Sang [Atmospheric Environment 2002;36:1137–45].     

A new stable finite volume method for predicting thermal performance of a whole building

Discretised governing equations involving only temperatures and heat fluxes at both surfaces of a solid wall layer were obtained by combining a new stable finite volume scheme for the two inner nodes of the wall layer with the surface diffusion equations (discretised by third order equations). The finite volume scheme for the inner nodes of the layer is proved to be stable with its truncation error being O(Δx⁴,Δx²Δt²)$O(\mathrm{\Delta }{x}^4,\mathrm{\Delta }{x}^2\mathrm{\Delta }{t}^2)$. A special analytical solution for a solid wall was used to evaluate different schemes for the inner nodes, showing that the new proposed scheme performs better than all other schemes for time steps of 3600 and 600 s. Finally, this scheme was used to simulate a whole house and the predicted zonal air temperature, and surface temperatures agreed well with measured values.     

Bond performance of polystyrene aggregate concrete (PAC) reinforced with glass-fibre-reinforced polymer (GFRP) bars

This paper concerns the bond performance of GFRP bars in polystyrene aggregate concrete (PAC) by the proposed concentric pullout test. Identical specimens reinforced with mild steel bars were used for comparison. The bond performance including the mode of failure and bond strength was studied with varying polystyrene aggregate content, concrete strength, embedment length, shape and surface treatment of the bars. Empirical formulae were developed for the estimation of development length on the basis of the pullout test results. The bond development length (_ld)$(l_{\mathrm{d}})$ determined according to ACI Building Code was used for comparison.     

Interaction between the mixing and displacement modes in a naturally ventilated enclosure

Experiments are carried out to study for the first time interactive phenomena in buoyancy-induced natural ventilation in a full-scale enclosure with upper and lower openings on one of the sidewalls. The interaction between the mixing and the displacement ventilation modes is revealed by opening the lower vent to different heights while the upper vent is kept fully open. Both the transient process and steady state interaction are explored. Measurements include temperature differences between inside and outside and air velocity through the upper opening. The level of the neutral plane at the upper vent, defined here as the plane separating between inflow and outflow, decreases with R^*$R^{*}$, the ratio between the opening heights (and areas) of the lower and upper vents. Experiments show that when 0*<0.27$0<R^{*}<0.27$ the mixing and displacement modes interact through a new combined ventilation mode. For 0.53*?1$0.53<R^{*}?1$, the displacement mode dominates whereas in the intermediate range, 0.27?R^*?0.53$0.27?R^{*}?0.53$, either the combined or the pure displacement mode takes place. The experiments are in qualitative agreement with a previous theoretical model.     

A field study on determination of preferences for windows in office environments

We aimed to determine the preferences for windows in office spaces and discover the underlying reasons which may affect design decisions. We conducted a field study on office buildings in Izmir–Turkiye. The research findings indicated that majority of users (48.6%; n=107$n=107$) have preferred firstly window-wall, which has the largest window area, secondly horizontal window (35%; n=77$n=77$) and thirdly square window types (10.9%; n=24$n=24$) for their own workspaces. Although having equal surface areas in the preference scale, square-shaped windows have been preferred much more than the rectangular and round shaped ones and horizontal shaped windows than the vertical ones. The window type, gender, quality of office job and quality of view created significant differences in determining prior factors behind window preferences.     

Structural characteristics of Hagia Sophia: I—A finite element formulation for static analysis

The historic Hagia Sophia in Istanbul, which held the record as the world's largest domed building for some 800 years, is analysed with a finite element formulation, including the effects of thickness shear deformations and the term z/R$z/R$, to understand its structural behaviour under the action of static loading. The structure, including all essential elements of the system, is modelled by using the same curved trapezoidal finite element with 40 degrees of freedom. Its structural behaviour and its structural load carrying system are demonstrated and the results are compared with those obtained earlier and also with those observed at the structure.     

Evaluation of surface characteristics of laminated flooring

In this study, surface characteristics of commercially manufactured laminated flooring were evaluated. The surface roughness of samples consisting of high-density fiberboard (HDF) base and melamine resin saturated paper overlay was investigated. Here, 10 cm×10 cm samples of two types of panels were used for the experiments. A fine stylus technique was employed for the measurements. Three roughness parameters, namely average roughness (_Ra$R_{\mathrm{a}}$), mean peak to valley height (_Rz$R_{\mathrm{z}}$), and maximum roughness (_Rmax$R_{\max }$) were considered to determine roughness of the flooring panels. It was found that statistically significant difference existed between two types of samples as well as values taken along and across the sandmarks of the HDF and overlaid panels. Average _Ra$R_{\mathrm{a}}$, _Rz$R_{\mathrm{z}}$, and _Rmax$R_{\max }$ values for HDF were found as 2.73, 26.04, and 27.27 μm, respectively. Overlaid samples resulted in 15.6%, 26.0%, and 21.0% lower values of above parameters than those of HDF panels.     

The effects of atmospheric exposure on the fracture properties of polymer concrete

In this experiment the effect of atmospheric exposure of epoxy and fiber-reinforced epoxy polymer concrete was investigated to evaluate its fracture properties, such as stress intensity factor, _KIc,$K_{\mathrm{Ic}},$ and fracture energy, _Gf$G_{\mathrm{f}}$. The deterioration and structural performance of polymer concrete were investigated in a real situation of exposure during a year period and compared the same formulation in laboratory conditions. The relationship between year period, exposure time and load-bearing capacity of deteriorated polymer concrete is studied and fracture mechanics of the specimens are discussed. From the tests results and discussion it is clear that the material studied, polymer concrete, suffers a high deterioration when subjected to aggressive environments.     

Numerical analysis of the street canyon thermal conductance to improve urban design and climate

Built environment is increasingly dependent on the scientific knowledge which integrates urban design and climate. In the work presented here, the canyon thermal conductance which quantifies the heat transported outside of a canyon street, is analyzed to improve on understanding of how to accomplish this integration. A two-dimensional, steady, k$k$–ε$\epsilon$ turbulence model is used to study the influence of a windward heated wall on the air flow circulation in a street canyon with building height-to-street width ratio (aspect ratio) from 0.7 to 1.5. The numerical results presented here suggest that the air flow regime is strongly affected by buoyancy and three configurations are predicted: (I) and (II) with high Froude numbers (≈10¹$\approx {10}^1$) result in one or two stable counter-rotating vortices, with an intenser upper vortex; air flow regime (III), with low Froude numbers (≈10^-1$\approx {10}^{-1}$), is dominated by the lower vortex whose intensity is enhanced by a strong upward current close to the heated surface confining the upper vortex to a strict leeward zone of the canyon. Transitional Froude numbers are found as a function of canyon aspect ratio for transitions between regimes. The relevance of the results for urban design are quantified and analyzed in terms of canyon thermal conductance. The main conclusion is that, for one vortex skimming air flow regime, the canyon thermal conductance linearly increases with wind intensity, being larger streets more exposed to thermal losses. Multiple vortices in the air flow regime significantly decrease the canyon thermal conductance and, therefore, narrow streets provide protection from heat losses on windy and cloudy days and nights.     

Statistical models for traffic noise at signalized intersections

A total of 14,235 noise levels measurements were utilized in developing statistical models that have the capability to predict different noise levels including: equivalent, maximum, or minimum noise level in terms of parameters affecting each level. Different parameters expected to have an effect on noise levels were collected. These parameters included traffic volume, composition of traffic, traffic speed, horn using effect, number of lanes, width of lanes, approach width, road slope, and pavement surface texture. The parameters affecting each noise level were selected based on simple correlation matrices, scatter plots, and statistical t$t$-test. Different forms of models were evaluated for each noise level. The best model describing the relationship between each noise level and parameters affecting it are presented in this paper. The reliability of the nonlinear developed models were judged based on coefficient of multiple determination (R²$R^2$), the significance of each variable at α$\alpha$-level of 0.05, and the standard error of the estimates. While the reliability of linear developed models were judged based on the general linear regression tests represented by F$F$-value and t$t$-value in addition to the coefficient of multiple determination (R²$R^2$), the significance of each variable at α$\alpha$-level of 0.05, and the standard error of the estimates.     

A simple method to assess the quenching effectiveness of fire suppressants

A screening concept is suggested for evaluating the effectiveness of fluids to thermally suppress fires. It is based on measuring a fluid's ability to inhibit (or quench) the temperature rise of a material that is rapidly heated. The experimental design is similar to the transient hot wire technique, in which the evolution of the average material temperature is recorded for a given input power, and internal temperature gradients in the material are minimized. A gold wire (100 μm long and 5 μm diameter) is used as the surface which heats the fluid. The wire temperature response due to a power pulse provides a measure of the effectiveness of the fluid to suppress thermally the temperature increase. The results indicate that the “quenching effectiveness”, QE=(_Tmax−_T∞)/(_Tmax,ref−_T∞)$\mathit{QE}=(T_{\max }-T_{\infty })/(T_{\max ,\mathit{ref}}-T_{\infty })$, correlates with the ratio of the fluid thermal conductivity to that of the wire, k_fluid/k_solid, using different Nusselt numbers (representing both conduction and natural convection) for the liquids or gases. The concept developed here could be included in a more comprehensive screening protocol, which would assess the thermal potential of candidate fire suppressants.