The performance of Photovoltaic/Thermal (PV/T) systems is critically dependent on effective heat removal, a challenge exacerbated in high-ambient temperature regions such as Baghdad, Iraq. Conventional PV/T cooling methods often struggle to maintain low PV operating temperatures while simultaneously recovering thermal energy efficiently. This study introduces and validates a novel dual-stage hybrid cooling architecture for PV/T collectors. The innovative core of this system is a primary internal cooling mechanism: an embedded, pumpless Enhanced Heat Pipe (EHP) closed loop. Utilizing a highly conductive nanoparticle-enhanced working fluid, the EHP system is positioned directly beneath the PV cells to facilitate rapid waste heat absorption. This heat is then passively transferred to a secondary external water-cooling circuit for thermal recovery. Experimental validation in the arid climate of Baghdad demonstrated that the EHP dual-stage system significantly mitigated thermal degradation, achieving a peak relative electrical power enhancement of 35.7% compared to a conventional uncooled PV module. This enhancement corresponds to a maximum net power gain (Delta P) of 67.2 W, restoring the absolute electrical efficiency of the panel to 16.9% under peak irradiance. Crucially, by recovering waste heat, the system reached a peak overall energy efficiency (thermal and electrical combined) of 92.1%. Furthermore, a transient Simscape model was validated with high accuracy (RMSEPmax = 2.84 W; RMSETpv = 1.29 degrees C), confirming the system's performance predictability. The results confirm that the EHP-integrated dual-stage design provides a highly responsive, scalable, and effective strategy for maximizing cogeneration performance in demanding environments.

This article discusses the applications of the smoothed particle hydrodynamics (SPH) methods to propose adaptations for compressible flow problems, particularly with discontinuities: shock tube, cavitation shock tube, and shock-bubble interaction. The formulations and their parameters are obtained to solve both single-phase and multi-phase flows effectively. The effects of the variation of artificial viscosity, variation of thermal conductivity, and particle shifting on interfacial problems are examined. The model parameters are tuned to avoid spurious oscillations while reducing numerical dissipation. It is determined that a minimum artificial viscosity constant between 0.1 and 0.5 is required for a stable interface with lower dissipation. Likewise, the minimum artificial thermal conductivity is set to 0 in order to efficiently mitigate energy discontinuities and minimize the wall heating effect. Moreover, it is noted that the integration of artificial viscosity and thermal conductivity with particle shifting does not enhance computational accuracy. The local grid refinement improves interface resolution accuracy in the shock-bubble problem, demonstrating strong accordance with experimental data in the literature while minimizing computational cost, particularly at interfaces characterized by high density and pressure ratios. This paper examines various formulations for density and momentum equations to address the adverse effects of single and multi-phase flow problems with discontinuities. Previous research can address these multiphase problems with density ratios of up to one hundred, whereas the suggested continuity-based density formulation and pressure difference-based momentum equation provide superior performance and stability for density ratios of sixteen thousand.

Laser powder bed fusion (L-PBF) fabricates components by melting layers of metal powder. Consequently, it has the potential to induce interparticle air gaps or generate unpredictable stresses. As such, understanding temperature distribution and predicting the melt pool based on process parameters are essential. While numerous numerical studies in the literature aim to determine these parameters, these numerical estimation methods often demand extensive computational time and powerful processors. This study introduces a new analytical model and a solution method, offering a significantly faster and more precise solution compared to numerical approaches. Furthermore, the developed model allows the identification of liquid and solid phase regions within the part during production, along with insights into the phase region changes over time. Eigenfunction expansion, separation of variables, and variable transformation methods were employed in the analytical solution of the model equations. Results obtained from this method have been validated by experimental studies available in the literature. By utilizing the derived solution function, the L-PBF process was parametrically investigated, revealing temperature distributions and melt pool geometries. The parametric study focused on the laser power, spot size, and powder layer thicknesses as variable parameters. The study determined that a 50 W increase in laser power raises the maximum melt pool temperature by an average of 800 K, and laser power has been identified as the most influential parameter affecting temperature distribution and melt pool geometry.

The conventional fuel used to produce electrical energy and the burning of the conventional fuel causes global warming. Also, there is a depletion of these fuel and hence there is a need of alternative fuels. The biodiesel is a renewable fuel and it is a sustainable fuel. The biodiesel can be derived from waste cooking oil (WCO) as it increases the commercial value of the WCO. The biodiesel has lower oxidation stability and hence onion oil which has good anti oxidation value was added with WCO biodiesel. The engine tests were carried with WCO biodiesel added with onion oil shows that the addition of onion oil improves the thermal efficiency and improvement in cylinder pressure and heat release rate. We conclude that the onion oil can be used as additive to the WCO biodiesel.

In this study, a numerical model is developed to analyze the thermal behavior of a panel type (PCP) aluminum radiator used for space heating. The developed model is applied for a slice of the radiator and convection and radiation effects are included in the calculations. The effects of backside vents, radiator cap and its openings are investigated. The model accuracy tests were carried out in the test chamber located in the Thermal Sciences Laboratory of the Department of Mechanical Engineering, Faculty of Engineering, Gazi University, using the test results carried out according to TS EN 442 standard on the market equivalent of the analyzed radiator. The test chamber was equipped according to ANSI/ASHRAE-138 standard and converted to TS EN 442 radiator test. The results of the numerical analysis show that 600-800-1100-1400 W thermal power can be obtained for temperature differences of 30-40-50-60°C using the radiator under investigation and the heat transfer coefficient of the radiator was found to be between 5-8 W/m2 K on average. The openings at the back of the radiator enhance the radiator power by approximately 6,7%. Radiator cap reduces the radiator power of the radiator by about 10%. The open air vent of the radiator cap increases the power by 1.4%. The effect of this is limited.

This study aims to develop a computational fluid dynamics (CFD) analysis model to be used in the nose optimization at hypersonic speeds and to validate the model. While creating the analysis model, standard hyperballistic-1 (HB-1) geometry, whose tests were made in the wind tunnel, was used. Base equation used in the study is compressible real gas Navier-Stokes equations. Generated structured grids were analyzed in METACOMP CFD++. During the model validation, aerodynamic coefficients obtained from the CFD analysis were compared with the wind tunnel test results for HB-1. Comparing CFD results and wind tunnel data for axial force coefficient indicated that CFD analysis estimates this coefficient 5

This paper, concerned with the low and ultra-low-temperature district heating goals of several countries for decarbonization, reveals the temperature mismatch between existing heating and cooling equipment and the thermal supply. The industry and the energy sector aim to resolve this conflict by total electrification with renewables and heat pumps for temperature peaking and, or equipment oversizing. This study shows that both measures defeat the purposes of decarbonization and quantify the carbon dioxide responsibility in embodiments and during operation according to exergy destructions. It has been concluded that widely available but with low exergy waste and solar energy resources can be mobilized for decarbonization in the building sector only with temperature-compatible heating and cooling terminal units minimizing the temperature mismatches. In this respect, a new panel radiator with heat pipe technology, which can satisfy indoor thermal loads with supply temperatures as low as 35 degrees C (95 degrees F) and sensible cooling loads as high as 19 degrees C (292 K, 66.4 degrees F) with little oversizing, is introduced. Test results from the ASHRAE Standard 138 are discussed.

This study was built on the basis of experimental results from a simple refrigeration system using R134a as a refrigerant. Based on the real dimensions of the system and the experimental results, Ansys fluent software was used to simulate the system to prepare the system to introduce the nanoparticles theoretically. Since the nanoparticle preparation process is expensive, this research presents a simple, easy, and inexpensive method for the preparation process based on, distilled water, ammonia, copper nitrate, and cerium nitrate to synthesize seven types of nanoparticles as a single oxide and as a mixture from two different oxides The results of preparing using X-ray diffraction and scanning electron microscopy confirmed that the particles were spherical in shape, with suitable average diameters ranging between 78.95 nm, 79.9 nm, 44.15 nm and 63.3 nm for copper oxide, cerium oxide, the first mixture, and the second mixture respectively. The theoretical study confirmed that both copper oxide, cerium oxide, and the mixture consisting of both improved the performance of the refrigeration system and reduced energy consumption. Moreover using the numerical equations available in the literature to calculate the thermophysical properties proved an improvement in these properties with an increase in the nanoparticle concentration when mixed with R134a.

The fact that the energy produced by renewable sources cannot be consumed instantaneously has brought energy storage systems to the fore. Due to its low cost and ease of use, the thermally integrated pumped thermal energy storage (TI-PTES) system is widely used. In this study, unlike the literature, the Kaline cycle with TI-PTES system was investigated thermodynamically. In the system analysis, heat pump, evaporator and hot tank temperatures were selected as variable parameters and their effects on system performance were examined. The results showed that the system efficiency increases with the increase in evaporator temperature but the increase in hot tank temperature significantly reduces the system efficiency.

This study was built on the basis of an experimental study that was carried out on a simple refrigeration system that works with R134a as a refrigerant, and based on the real dimensions of the system and the experimental results, the Ansys fluent software was used to simulate the system to prepare the system to introduce the nanoparticles theoretically. Since the nanoparticles preparation process is expensive, this research presents a simple, easy, and inexpensive method for the preparation process based on the following materials, distilled water, ammonia, copper nitrate, and cerium nitrate to synthesize seven types of nanoparticles as a single oxide and as a mixture from two different oxides The results of preparing using X-Ray Diffraction and Scanning Electron Microscopy proved that particles of samples were spherical in shape, with suitable average diameter ranging between 78.95, 79.9, 44.15 and 63.3 nm for both copper oxide, cerium oxide, first mixture, and second mixture, respectively, the theoretical study confirmed that both copper oxide, cerium oxide, and the mixture consisting of both improved the performance of the refrigeration system and reduced energy consumption.

It is necessary to understand the efficiency of the filters, which are the most important part of the ventilation systems, in order to hinder the spreading of the Covid-19 virus. In this article, a model was created using theoretical solutions developed for single fiber efficiency and with this created model, the previous theoretical data were confirmed. Then, the theoretical data in the model created with the experimental data were compared. Also, factors such as fiber diameter, particle diameter, or flow velocity affecting single fiber efficiency were changed and the effects of these parameters were investigated. As a result of this investigation, it was seen that, as the Peclet number increased, the single fiber efficiency decreased, and the efficiency of the single fiber increased when the particle diameter increased. Finally, when the solidity, which can be considered as the fiber density in the filter, increased, the single fiber efficiency increased along with it. When solidity was increased from 0.011 to 0.03, single fiber efficiency increases from 0.023 to 0.0269. That is, there was an increase of approximately 16.9 %.

Most studies report that dispersing nanoparticles into refrigerants and lubricating oils leads to performance improvements in refrigeration systems, due to improvements in the thermal physics properties of a pure refrigerant, which leads to reduced energy consumption. Using nanoparticles in a refrigeration system is associated with many difficulties, such as the cost of preparing and obtaining a stable and homogeneous mixture with less agglomeration and sedimentation. Most current studies focus on the use of metals, metal oxides, and a hybrid of oxides as nanoparticles in refrigeration systems. In this research, nanoparticles were prepared in an inexpensive and easy way as a single oxide and as a mixture consisting of copper and cerium oxides. The results of nanoparticle preparation using X-ray diffraction and scanning electron microscopy prove that the particles of the samples were spherical in shape, with suitable average diameters ranging from 78.95 nm, 79.9 nm, 44.15 nm and 63.3 nm for copper oxide, cerium oxide, the first mixture, and the second mixture, respectively. Cerium oxide has not been used in a refrigeration system; this study preferred the implementation of a theoretical study using Ansys Fluent software to verify the possibility of improving the performance of the refrigeration system. The results confirmed that copper oxide enhanced the coefficient of performance of the refrigeration system by 25 %, and cerium oxide succeeded in improving the performance of the. system by a lesser value. The mixture containing a higher percentage of copper oxide yielded better results.

The optimisation of PV/T flat-plate water collector groups depending on the variable values of mass flow rate, tube diameter, tube spacing and number of collectors was made based on exergy efficiency. Two different hydronic configurations, namely, series and series-parallel connection arrangements were investigated. An analytical model was developed to obtain exergy efficiencies. The results showed that when all other parameters were kept constant, the total exergy gain for any operating condition was higher at the series connected collector arrangement than at the series-parallel one.

Processing with the selective laser melting method requires estimation of the operating parameters because the process is very fast and the production cost is high. Numerical methods used in parameter estimation require high computation times and powerful processors. With the analytical model and solution method developed in this study, it has been possible to obtain a much faster and exact solution compared to numerical methods. In addition, the developed model makes it possible to determine the liquid and solid phase regions formed in the part during production and gives information about the change of the phase regions according to time. The methods of Eigen function expansion, separation of variables, and change of variables were used in the analytical solution of model equations. The results obtained with this method have been confirmed by experimental studies in the literature. By using the obtained solution function, the SLM process was parametrically examined, temperature distributions and melt pool geometries were determined. Laser power, laser spot size and powder layer thicknesses were selected as variable parameters in the parametric study. The results showed that laser power is the most effective parameter both in the formation of the melt pool geometry and in the temperature distribution. Accordingly, for 250 watts of laser power, the maximum temperature in the part is obtained as 6600 K and the size of the melt pool is estimated as 85 µm, 125 µm and 544 µm in x, y and z directions, respectively.

In this study, a mathematical model is developed for determining the process parameters used in the manufacturing process of powder materials with selective laser melting method. Although the studies carried out to date cover detailed modeling studies including three-dimensional and time-dependent situations, obtaining quite different approaches from experimental results has led to the idea that a change should be made in the construction of the mathematical problem. Therefore, different from other studies and for the first time, the Eigen-function expansion method was used in the analytical solution of the selective laser melting thermal model. The developed mathematical model includes the steady-state solution with the appropriate boundary conditions of the 2-D non-homogeneous heat equation. The mathematical model was first solved analytically with the Eigen-function expansion method, and the function obtained as a result of the solution was introduced into the MATLAB software. The parametric study was performed numerically over laser power, laser spot size and powder bed thickness. With the developed model, the solution was converged in 30 s and 11.5% more accurate with respect to experimental results were obtained in width, 29% in depth and 3% in temperature as compared to other analytical models exist in the literature.

The main objective of this study is to determine the optimum insulation thickness of residential buildings in Turkey, under the influence of cooling and heating loads by life cycle cost analysis (LCCA). Five-storey apartment building with an Area/Volume ratio (A/V) of 0.40 m(-1)and 10-storey apartment building with an A/V ratio of 0.32 m(-1)are taken as reference buildings. The annual energy needs are calculated according to TS 825 standard for heating and TS EN ISO 13790 standard for cooling. Natural gas is used for heating and electricity is used for cooling. LCCA based on the total cost approach is performed for 30 years. Optimum insulation thicknesses (U-values) based on climate regions are calculated between 10.5 cm and 17.3 cm (0.30-0.19 W/m(2)K) for wall, 17.5 cm and 26.8 cm (0.24-0.16 W/m(2)K) for ceiling, 6.0 cm and 9.8 cm (0.49-0.32 W/m(2)K) for floor. When compared with the limit values specified in TS 825, it has been determined that the energy savings provided by an insulated building using optimum insulation thicknesses vary between 12.9% and 21.5% according to the region. As a result, it is concluded that the limit U-values should be revised for all regions specified in the TS 825.

The main objective of this study is to determine the optimum insulation thickness of residential buildings in Turkey, under the influence of cooling loads by life cycle cost analysis (LCCA) and to specify the Degree Day (DG) regions that the cooling load should also be included in the calculations in the TS 825 "Heat Insulation Rules in Buildings" standard. A 5-storey apartment building with an Area/Volume ratio (A/V) of 0,40 m(-1) is taken as a reference building. The annual energy requirements of the reference building for cooling loads are calculated according to TS EN ISO 13790 standard. Life-cycle cost analysis based on the total cost approach is performed for a period of 30 years. Optimum insulation thicknesses based on climate zones are calculated between 0 cm and 4 cm for wall, 0 cm and 7,5 cm for ceiling, 0 cm and 2,7 cm for floor. As a result, it has been determined that cooling load should be included in the optimum insulation thickness calculations in the DG1 and DG2 regions specified in the TS 825 standard It is concluded that the cooling loads don't affect the optimum insulation thickness in DG3 and DG4 regions where the cooler climate is more effective than DG1 and DG2 regions.

Bu çalışmanın amacı, Türkiye’deki konut tipi binalar için soğutma yükü etkisi altında optimum yalıtım kalınlığının (U-değerlerini) ömür maliyet analizi yapılarak belirlenmesi ve elde edilen sonuçlara göre TS 825 “Binalarda Isı Yalıtım Kuralları” standardında soğutma yükünün de hesaplamalara katılması gereken Derece Gün (DG) bölgelerinin tespit edilmesidir. Alan/Hacim (A/V) oranı 0,40 m-1 olan 5 katlı bir apartman binası referans bina olarak alınmıştır. Binaların yıllık enerji ihtiyaçları, TS EN ISO 13790 standardına göre hesaplanmıştır. Toplam maliyeti temel alan ömür maliyet analizi 30 yıllık bir kullanım ömrü için yapılmıştır. Optimum yalıtım kalınlıkları iklim bölgelerine göre; cephe için 0 cm ile 4 cm, tavan için 0 cm ile 7,5 cm, taban için 0 ile 2,3 cm arasında hesaplanmıştır. Sonuç olarak, TS 825 standardında belirtilen DG1 ve DG2 bölgelerinde soğutma yükünün optimum yalıtım kalınlığı hesaplarına dahil edilmesi gerektiği belirlenmiştir. DG1 ve DG2 bölgelerine göre daha soğuk iklim şartlarının etkili olduğu DG3 ve DG4 bölgelerinde soğutma yükünün optimum yalıtım kalınlığını etkilemediği sonucuna varılmıştır.