The article presents the results of a study aiming to select the optimal source of heat for a newly designed single-family home. Commercial software was used to compare heating and ventilation systems involving a bituminous coal boiler, a condensing gas boiler, a biomass boiler, a heat pump with water and glycol as heat transfer media. The effectiveness of natural ventilation, mechanical ventilation with a ground-coupled heat exchanger, and solar heater panels for water heating were evaluated. The analysis was based on the annual demand for useful energy, final energy, and non-renewable primary energy in view of the pollution output of the evaluated heating systems. The analysis revealed that the heat pump with water and glycol was the optimal solution. However, the performance of the heat pump in real-life conditions was below its maximum theoretical efficiency. The biomass boiler contributed to the highest reduction in pollutant emissions (according to Intergovernmental Panel on Climate Change Change guidelines, carbon dioxide emissions have zero value), but it was characterized by the highest demand for final energy. Mechanical ventilation with heat recovery was required in all analyzed systems to achieve optimal results. The introduction of mechanical ventilation decreased the demand for final energy by 10% to around 40% relative to the corresponding heating systems with natural ventilation.

Energy-saving ventilation systems are designed to improve the energy efficiency of buildings. Low energy efficiency in buildings poses a considerable problem that needs to be addressed. Mechanical ventilation with heat recovery has gained increased popularity in recent years. Mechanical ventilation has numerous advantages, including easy adjustment and control, high indoor air quality and elimination of indoor pollutants. Mixing ventilation is the most popular type of mechanical ventilation, in particular in residential buildings. Unsteady ventilation is a type of mixing ventilation that involves stronger mixing effects and smaller vertical temperature gradients to improve indoor air quality (IAQ) and minimize energy consumption. This study examines the possibility of controlling and modifying Coanda effect hysteresis (CEH) to generate unsteady flow and simulate the conditions of unsteady mixing ventilation. The experiment was performed on a self-designed test bench at the University of Warmia and Mazury in Olsztyn. It demonstrated that an auxiliary nozzle can be applied at the diffuser outlet to control CEH and the angles at which the air jet becomes attached to and separated from the flat plate positioned directly behind the nozzle. The study proposes an innovative mixing ventilation system that relies on CEH. The potential of the discussed concept has not been recognized or deployed in practice to date. This is the first study to confirm that an auxiliary nozzle by the diffuser outlet can be operated in both injection and suction mode to control CEH. In the future, the results can be used to design a new type of nozzles for unsteady ventilation systems that are based on CEH control.

In the present study, the real-world performance of a ground-to-air heat exchanger (GAHE) was analyzed in the Polish climate which is characterized by warm summers and cold winters. The heat exchanger’s performance was monitored over a period of three years (2017 to 2019), and real-world conditions were compared with a Typical Meteorological Year (TMY). The aim of the study was to assess the exchanger’s energy-efficiency potential in various ventilation scenarios in a single-family home under variable real-world conditions, rather than to simply determine its heating and cooling capacity. The analyzed single-family home was a modern, single-story building with a usable floor area of 115 m². The building’s thermal insulation and airtightness met stringent energy-efficiency standards. Energy consumption in a building equipped with a natural ventilation system was compared with three other scenarios: ventilation coupled with a GAHE, mechanical ventilation with heat recovery and a high-efficiency heat exchanger (HE), and mechanical ventilation with heat recovery coupled with a GAHE. Sensible heating and cooling loads were calculated based on standard ISO 13790:2008, and latent heating and cooling loads were also included in the energy balance. During the year, the GAHE generated around 257.6 W of heating energy per hour and 124.7 W of cooling energy per hour. Presented results can be used to select the optimal HVAC system scenarios for engineering projects as well as private investors.

As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. In the experiment, the Reynolds number ranged from 16,192 to 42,240. A fixed geometry diffuser (Witoszyński nozzle) with a height of 0.60 m, width of 0.02 m and outlet velocity of 11.33–29.57 m/s was used. A plate with a length of 1.00 m and a variable inclination angle was installed at the diffuser outlet. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0° and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90° in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface. The study demonstrated that for a turbulent jet, pressure distribution on a flat plate is determined not only by the plate’s inclination angle, but also by the direction of its rotation.

Numerous classrooms at the University of Warmia and Mazury in Olsztyn, built in the years 1960–1980, require deep modernization to implement the idea of the green university there. The paper presents an energy analysis of possible scenarios of modernization of a selected lecture hall and an indication of the optimal variant in terms of the user’s thermal comfort. The conditions of the room were experimentally measured. Authors compared the energy effects of typical thermorenovation activities, such as increased thermal resistance of external walls (reduction of the primary energy (EP) demand by about 45%), with more advanced measures, such as replacement of natural ventilation with mechanical with heat recovery (indicated in the course of numerical studies as necessary for health and comfort of users). The authors also compared the effectiveness of the heat network and individual sources that could be implemented in the building. The heat pump, in combination with photovoltaic panels, turned out to be optimal (reduction of the EP by 97%, utility energy by 69%). As the problem of modernizing facilities to a similar standard is also faced by many campuses, school facilities, and assembly rooms in Central and Eastern Europe, the presented results can be a reference point for similar activities in other locations.