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%.     

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.     

A new approach to assess the dependency of extant half-saturation coefficients on maximum process rates and estimate intrinsic coefficients

The Monod equation is often used to describe biological treatment processes and is the foundation for many activated sludge models. The Monod equation includes a “half-saturation coefficient” to describe the effect of substrate limitations on the process rate and it is customary to consider this parameter to be a constant for a given system. The purpose of this study was to develop a methodology, and its use to show that the half-saturation coefficient for denitrification is not constant but is in fact a function of the maximum denitrification rate. A 4-step procedure is developed to investigate the dependency of half-saturation coefficients on the maximum rate and two different models are used to describe this dependency: (a) an empirical linear model and (b) a deterministic model based on Fick's law of diffusion. Both models are proved better for describing denitrification kinetics than assuming a fixed KNO₃$K_{{\text{NO}}_3}$ at low nitrate concentrations. The empirical model is more utilitarian whereas the model based on Fick's law has a fundamental basis that enables the intrinsic KNO₃$K_{{\text{NO}}_3}$ to be estimated. In this study data was analyzed from 56 denitrification rate tests and it was found that the extant KNO₃$K_{{\text{NO}}_3}$ varied between 0.07 mgN/L and 1.47 mgN/L (5th and 95th percentile respectively) with an average of 0.47 mgN/L. In contrast to this, the intrinsic KNO₃$K_{{\text{NO}}_3}$ estimated for the diffusion model was 0.01 mgN/L which indicates that the extant KNO₃$K_{{\text{NO}}_3}$ is greatly influenced by, and mostly describes, diffusion limitations.     

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 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.     

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.     

Experimental study on strength and deformation of plain concrete under triaxial compression after freeze-thaw cycles

The behavior of strength and deformation of plain concrete under triaxial compression after 0, 25, 50 and 75 cycles of freeze-thaw are experimentally studied using the static and dynamic triaxial experimental machine. The compressive strength, strain at the peak of stress and stress–strain relationship under triaxial compression were measured. The failure modes of concrete specimens are also described. The experimental results showed that the triaxial compressive strength decreased as the freeze-thaw cycles were repeated for plain concrete. The influence of the number of freeze-thaw cycles and the stress ratio on the principal compressive stresses_σ3${\sigma }_3$and corresponding strain_ε3${\epsilon }_3$, stress–strain relationship was analyzed. On this basis, the failure criterion of concrete under triaxial compression after freeze-thaw cycles is proposed. It can serve as a reference for the maintenance, design and the life prediction of ocean structures, hydraulic structures, marine structures and offshore platform in cold regions.     

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.     

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.     

Effect of machining on surface roughness of wood

The objective of this study is to evaluate effect of various machining techniques on the surface roughness of beech (Fagus orientalis) and aspen (Populus tremula  ) lumber. Surface characteristics of sawn, planed, and sanded samples of both species were determined employing a stylus type profilometer. Average roughness (_Ra$R_{\mathrm{a}}$), mean peak-to-valley height (_Rz$R_{\mathrm{z}}$), core roughness depth (_Rk$R_{\mathrm{k}}$), reduced peak height (_Rpk$R_{\mathrm{pk}}$), and reduced valley depth (_Rvk$R_{\mathrm{vk}}$) roughness parameters were used to determine surface characteristics of the samples. Based on the results of statistical analysis, measurements taken from the surface in tangential and radial directions of both species did not result in significant difference at a 95% confidence level. However, significant statistical difference was found between surface characteristics of aspen and beech samples, machined with four different ways in both grain orientations. This study suggests that stylus method can be successfully used to evaluate and distinguish variations on the surface of wood, due to grain orientation and planning and sanding. Data generated in this study can be used as a quality control tool for further processes such as finishing or gluing of wood from two species.     

Determination of user profile at city parks: A sample from Turkey

A survey study conducted randomly in the cities of Erzurum, Erzincan and Kars included 360 subjects interviewed face to face. It was aimed to detect the subjective features of the participants such as gender, marital status, age, educational status and income level and the reflections of these features on the city parks. Conclusively, it was determined that those who are male, unmarried, at the age of between 19 and 24, university graduate and with a monthly income of 65–125 USD use the parks in majority. In the statistical analysis, the SPSS software was used and variables were compared. Chi-square (χ²) test was used to determine the independency correlations. According to the analysis, gender and income had no significant effect on the use of city parks, but marital status, age and education status had significant effects at 5% significance levels (*p<0.05$p<0.05$, χ²: 27.805; *p<0.05$p<0.05$, χ²: 44.073; *p<0.05$p<0.05$, χ²: 39.998, respectively).     

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.     

Numerical investigation of smoke exhaust mechanism in a gymnasium under fire scenarios

The Fire Dynamics Simulator code is used to investigate the smoke filling process in a large building. Initially, the model is used to simulate the smoke descending process in an atrium under fire scenarios. By comparing with experimental data, reasonable model constants of _Cs$C_{\mathrm{s}}$ and _Prt${\mathit{Pr}}_{\mathrm{t}}$ are determined for simulating smoke movement in buildings with large space. The performance of different smoke exhaust methods in a real gymnasium is then studied. Smoke filling processes are investigated under different natural and enhanced smoke exhaust methods. Simulated results show that natural smoke exhaust method is preferred when the smoke exhaust vents are located at the ceiling of the gymnasium. On the other hand, when the smoke exhaust vents are located on the walls of the gymnasium, enhanced smoke exhaust methods are preferred. In addition, the influence of ceiling temperature in the gymnasium on the smoke spreading process is presented in this paper. Results indicate that high ceiling temperature slows down the so-called smoke ceiling jet moving horizontally at the ceiling, whereas low ceiling temperature accelerates such smoke ceiling jets.     

Physical characterization of particulate matter and ambient meteorological parameters at different indoor–outdoor locations in Singapore

The paper reviews the exposure to fine and coarse particles in different indoor and outdoor locations. The methodology involves measuring the particulate matter at different indoor and outdoor locations. The locations included a major expressway (high traffic volume), a minor road, and naturally and mechanically ventilated indoor spaces. It was observed that significant concentrations of fine particles were found at the expressway as compared to the normal road and naturally ventilated space. However, larger size particles were found to be higher in number density (count per litre) and mass concentration at the minor road and naturally ventilated space at close proximity to the minor road. In the mechanically ventilated space the particles above 1 μm size were negligible both in count and mass. A linear relation was established between the particle mass (PM₁₀) and particle count (r²=0.5564$r^2=0.5564$, n=60$n=60$). Denser particulate matter was found at naturally ventilated indoor spaces in the evenings. Indoor–outdoor ratio (I/O) for the naturally ventilated space is observed to be closer to unity as in the case of mechanically ventilated space with 0.46. A higher I/O ratio is observed in the evening as compared to morning for the naturally ventilated space. Better correlation was observed between fine and coarse mode particles at the expressway as compared to the minor road.     

Assessment of the microclimatic and human comfort conditions in a complex urban environment: Modelling and measurements

Several complex thermal indices (e.g. Predicted Mean Vote and Physiological Equivalent Temperature) were developed in the last decades to describe and quantify the thermal environment of humans and the energy fluxes between body and environment. Compared to open spaces/landscapes the complex surface structure of urban areas creates an environment with special microclimatic characteristics, which have a dominant effect on the energy balance of the human body. In this study, outdoor thermal comfort conditions are examined through two field-surveys in Szeged, a South-Hungarian city (population 160,000). The intensity of radiation fluxes is dependent on several factors, such as surface structure and housing density. Since our sample area is located in a heavily built-up city centre, radiation fluxes are mainly influenced by narrow streets and several 20–30-year-old (20–30 m tall) trees. Special emphasis is given to the human-biometeorological assessment of the microclimate of complex urban environments through the application of the thermal index PET. The analysis is carried out by the utilization of the RayMan model. Firstly, bioclimatic conditions of sites located close to each other but shaded differently by buildings and plants are compared. The results show that differences in the PET index amongst these places can be as high as 15–20 ^°C${}^{°}\mathrm{C}$ due to the different irradiation. Secondly, the investigation of different modelled environments by RayMan (only buildings, buildings+trees$\mathrm{buildings}+\mathrm{trees}$ and only trees) shows significant alterations in the human comfort sensation between the situations.     

The effects of thermal modification on crystalline structure of cellulose in soft and hardwood

In this study the crystallinity and estimations of relative triclinic (I_α) and monoclinic (I_β) structure content of cellulose isolated from heated spruce (Picea orientalis) and beech (Fagus orientalis) wood samples were determined by using Fourier Transform Infrared (FT-IR) spectrometry. Heat treatment was applied on the test samples in an oven at three different temperatures (150, 180 and 200 °C) and two different durations (6 and 10 h) under atmospheric pressure. It was determined that crystallinity of cellulose in wood samples increased with thermal modification. The results indicate that the changes in crystallinity of cellulose in wood samples related to not only temperature but also time during thermal modification. _Iα/_Iβ$I_{\alpha }/I_{\beta }$ ratio of cellulose in spruce and beech wood samples changed with thermal modification, but it was established that monoclinic structure was dominant in cellulose crystalline structure. It was designated that the crystalline structure of cellulose in spruce wood samples affected from thermal modification more than in beech wood samples.