Thermal insulation applications on the exterior facades of buildings have been the subject of numerous studies from the past to the present. Some of these studies focus on the cost reduction effect of insulation, while others emphasize its ecological benefits. In this study, multi-objective optimization, the objectives of which are minimum cost and minimum CO₂ emission, has been carried out with the NSGA-II method. In emission calculations, in addition to fuel-related emissions, the carbon footprint of all materials comprising the wall has also been included. The multi-objective optimization study examined four design variables: wall thickness, wall material (light concrete, reinforced concrete, and brick), insulation material (expanded polystyrene, extruded polystyrene, mineral wool, and polyurethane foam), and heating source (natural gas, electricity, fuel oil). Analyses have been carried out for four cities (Osmaniye, Bursa, Isparta, and Erzurum), which are located in different climatic regions, and considering solar radiation effects. An existing building has been taken as the base case scenario, and the study has determined the improvements in the total cost and the amount of CO₂ released into the environment when the appropriate insulation material, insulation thickness, wall material, and heating source identified in the multi-objective optimization study have been used. At the cost-oriented optimum point in the study, the most suitable insulation material was found to be expanded polystyrene, the most suitable wall material was brick, and the most suitable heating source was natural gas. In the CO₂-oriented optimum, in contrast to the cost-oriented approach, optimal results have been obtained when light concrete was selected as the wall material.

In this study, the performance of organic Rankine cycle (ORC), which produces electrical energy, was examined by using a geothermal resource with a temperature of 145°C. The fluids used in the system were determined as dry type fluids, and R142b, R227ea, R245fa, R600, and R600a were preferred as a working fluid. Within the scope of this study, energy and exergy analysis of the system was performed for different evaporator pressures (1000–2000 kPa). With the help of these analyses, the performances of the cycle elements were examined and the first and second law efficiencies of the system were compared for different refrigerants. Considering the selection of refrigerant, and evaporator pressure within the scope of this study, the first and second law efficiencies of the cycle have enhanced maximum of 4.86% and 19.78%, respectively.

This paper investigates the factors affecting the optimum insulation thickness and its pay-back period, such as heating and cooling energy requirements of building, lifetime, present worth factor, costs of insulation material and installation, costs of energy sources for heating and cooling, heating and cooling system efficiencies, and solar radiation. For this purpose, by considering two cities characterizing the hot and cold climatic conditions, the optimum insulation thickness and its pay-back period have been calculated and a detailed parametric analysis has been carried out. To achieve practical results, the ranges of the parameters considered in the study include the values typically reported in the literature. The variations in the optimum insulation thickness and the pay-back period with all parameters are presented in graphical form. Finally, order of importance and contribution ratios of the examined parameters on the optimum insulation thickness are determined with the help of Taguchi method. It is found that heating degree-days is the most efficient parameter on the optimum insulation thickness with an impact ratio of 27.33% of the total effect while the least efficient parameter is the efficiency of heating system with an impact ratio of 3.21%.

Automobile radiator which is one of the vital components used for engine cooling in vehicles is expected to provide higher thermal performance without changing the exterior dimensions of the radiator with the development of engine technology. This situation necessitates changes in both design and operating parameters in the currently used radiator. In the present study, all fundamental parameters affecting the thermal and hydraulic performance of an automobile radiator are evaluated and optimized with statistical methods. Optimization study is carried out using Taguchi and ANOVA methods for two specified objective functions (heat transfer and pressure drop). The order of importance and impact rates for each design and operating parameter, the best and worst working conditions in terms of both target functions are determined. Air velocity, air inlet temperature, coolant inlet temperature, and fin pitch are found to be the most effective parameters on the heat transfer with a contribution ratio of 88%. The best and worst working conditions are obtained for the heat transfer and under these working conditions, they are calculated as 43.68 kW and 1.63 kW, respectively. When the system is examined in terms of the pressure drop, the results show that the coolant flowrate and tube height have a great impact with a contribution ratio of 67.04% and 32.06%, respectively. Lastly, the maximum and minimum pressure drop within the studied operating condition range is determined as 20.68 kPa and 0.12 kPa, respectively.

An optimization study on thermal insulation applied to building exteriors has been performed in this research. Solar radiation has been considered while obtaining optimum insulation thicknesses for various directions. Analyses have been conducted not only for the cardinal directions (south, north, west, and east) but also for the intermediate directions (southeast, northeast, northwest, and southwest). Solar radiation received by vertical walls and cooling and heating degree day values have been computed according to directions. This research examines the most suitable insulation thicknesses for different seasonal usage scenarios, considering cooling, heating, and annual energy demands. Variations in energy cost savings, savings rates, payback periods, seasonal energy demands, and optimum insulation thicknesses for various wall orientations have been presented. Additionally, correlations providing the total cost based on the applied insulation thickness for each direction and various building usage scenarios have been determined. The results indicate that incoming solar radiation varies from 52.08 W/m² to 111.82 W/m² across different wall orientations, while energy cost savings range from 23.48 USD/m² to 24.56 USD/m², with savings rates between 69.8% and 70.3%. Payback periods range from 5.94 to 6.05 years. Depending on the wall orientation, optimum insulation thicknesses vary between 4.52 and 5.02 cm for heating, 1.56 and 2.09 cm for cooling, and 5.92 and 6.08 cm for annual energy requirements. The heating energy demands ranged from 54.8 MJ/m² to 58.38 MJ/m², while the cooling energy demands varied between 10.91 MJ/m² and 12.08 MJ/m², depending on the wall orientation. It has been concluded that the ideal insulation thicknesses for meeting cooling, heating, and annual energy demands vary depending on the wall orientation and the building’s use purpose.