Simultaneous satisfaction of both thermal and visual comfort in buildings may be a challenging task. Therefore, this paper suggests a comprehensive framework for the building energy optimization process integrating computational fluid dynamics (CFD) daylight simulations. A building energy simulation tool, IDA Indoor Climate and Energy (IDA-ICE), was coupled with three open-source tools including GenOpt, OpenFOAM, and Radiance. In the optimization phase, several design variables i.e., building envelope properties, fenestration parameters, and Heating, Ventilation and Air-Conditioning (HVAC) system set points, were selected to minimize the total building energy use and simultaneously improve thermal and visual comfort. Two different scenarios were investigated for retrofitting of a generic office building located in Oslo, Norway. In the first scenario a constant air volume (CAV) ventilation system with a local radiator in each zone was used, while an all-air system equipped with a demand control ventilation (DCV) was applied in the second scenario. Findings showed that, compared to the reference design, significant reduction of total building energy use, around 77% and 79% in the first and second scenarios, was achieved respectively, and thermal and visual comfort conditions were also improved considerably. However, the overall thermal and visual comfort satisfactions were higher when all-air system was applied.

The present study investigates experimental cooling from the ceiling using phase change materials (PCMs) in Yazd, a city characterized by a hot and dry climate. A one-fourth scale model of a real room, measuring 4 m × 3 m × 3 m, was employed for the analysis. To evaluate system performance and the impact of PCM on energy consumption reduction, three configurations were considered: a simple PCM system, a PCM system with a fan (PCM-F), and a PCM system with a mini cooler (PCM-C). Additionally, to assess the influence of window configurations on ventilation, temperature, and comfort conditions within the model, three scenarios were examined: two open windows, one open window, and no windows. The economic analysis compared the two systems with the fan and mini cooler against a full mechanical cooling system without PCMs. Furthermore, CO₂ emissions and environmental impacts associated with the systems were also evaluated. The results indicate that the presence of PCMs in the ceiling, due to heat absorption during phase change, leads to a temperature reduction of 5 to 10 °C in the ceiling and a 3.2 °C reduction in the average room temperature compared to the scenario without PCMs. The findings demonstrate that ceiling cooling with PCMs significantly contributes to energy consumption reduction during peak hours of cooling demand. Specifically, the PCM-F system results in a 92% reduction, and the PCM-C system leads to a 71% reduction in total cost compared to the reference mechanical cooling system. Additionally, the PCM-F system achieves approximately a 36% reduction, and the PCM-C system results in a 34% reduction in environmental impact relative to the reference full mechanical cooling system.

The widespread use of journal bearings in rotating machinery has intensified the need to optimize their operational performance. A key determinant of bearing efficiency lies in the lubricant film thickness between the rotor and bearing surface. Recent studies demonstrate that strategically engineered surface textures can effectively modulate film thickness and enhance both static and dynamic characteristics of bearing. This investigation specifically examines how cubic, cylindrical, and semi-ellipsoidal texture geometries at varying depths influence the performance of noncircular two-lobe bearings. Through finite element analysis, the study evaluates critical performance parameters including load capacity, rotor attitude angle, critical mass threshold, and whirl frequency ratio to establish texture–depth relationships with system stability and operational efficiency. The analysis reveals that texturing the maximum pressure zone in lobe 2 significantly enhances bearing performance, with semi-ellipsoidal, cylindrical and cubic geometries, respectively. Also, the results demonstrate that texture geometry and depth significantly influence two-lobe bearing performance. Optimal enhancements in load capacity, whirl frequency reduction, and critical rotor mass occur at texture depths below the bearings clearance space width, with performance peaking before gradually declining as depth increases further. Notably, texture application in low-pressure or cavitation regions generally yields diminished or even counterproductive effects. The findings demonstrate that cubic textures provide optimal bearing performance across all depth ranges, with cylindrical and semi-ellipsoidal geometries ranking second and third, respectively, in comparative analysis.

This paper investigates a hybrid ventilation control method for a mixed-mode office landscape in a cold climate, i.e. Norway. The mixed-mode building utilizes a hybrid ventilation system that combines natural ventilation through automatic window opening with a balanced mechanical ventilation system controlled by demand control ventilation (DCV) method. For natural ventilation, the windows consist of two parts: the upper part which is openable and the lower part that is not openable and equipped with external solar shading. From a control point of view, the article elaborates a control algorithm for the proposed hybrid ventilation based on various parameters including outdoor air temperature, indoor air temperature, CO₂ level, maximum air change per hour (ACH), operation schedules, and heating/cooling setpoints. The simulation results obtained from the hybrid ventilation and mechanical ventilation cases are compared based on thermal comfort, CO₂ level, and energy savings. The primary results show that the proposed hybrid ventilation control method can satisfy the thermal comfort and CO₂ level requirements while reducing the energy use for fan and ventilation cooling by approximately 55% and 45%, respectively. While the impact on energy consumption for space and ventilation heating is negligible.

The Climate House at Tøyen in Oslo is a nearly Zero Emission Building (nZEB) designed for exhibitions and educational purposes. It operates with a hybrid ventilation system, where natural ventilation via operable windows serves as the primary strategy, supplemented by mechanical ventilation when natural ventilation alone cannot maintain acceptable indoor thermal comfort and air quality. However, monitoring and analysis indicate that the current ventilation system underperforms, particularly during the winter season, resulting in suboptimal thermal comfort and reduced energy efficiency. This study aims to investigate whether optimized hybrid ventilation control strategies can be beneficial in nZEB buildings in cold climates, both under current and future conditions. A new control strategy was tested using IDA-ICE 5.0 simulations, prioritizing mechanical ventilation while using natural ventilation as a supplement. Results show a 13% energy reduction compared to full mechanical ventilation, with improved thermal comfort and compliance with indoor air quality standards. When tested under future climate scenarios (RCP 2.6, 4.5, and 8.6), the strategy yields energy savings of 19%–21% by 2050 and up to 30% by 2100. However, under extreme heat conditions in 2100, the system may struggle with overheating, indicating the need for higher airflow rates and extended night ventilation. Overall, the findings suggest that, with adaptive control, hybrid ventilation is a promising solution for improving energy efficiency in low-energy buildings in cold climates—even as temperatures rise.