• Energy Research

Pumping equipment consumes about 20 % of the electrical energy produced by humankind. A significant, even drastic, reduction in the weight and size indicators of pumping equipment leads to a decrease in the cost price and, therefore, competitiveness of such products in the market. Simultaneously, it makes it possible to use more valuable and high-quality construction materials and technologies that improve the reliability of equipment and its energy efficiency, which in turn is a clear step in solving many UN Sustainable Development Goals (SDGs). According to the research results, it was proved that by increasing the frequency of the drive, it is possible to reduce the mass and size indicators of the submersible pump for the needs of the critical infrastructure sector by reducing the number of stages. Mainly, the amplitudes of oscillations near the rotation frequency are 12–22 % and do not exceed 35 % of the gaps in the seals, as required by the available international standards to ensure the guaranteed vibration reliability of the pump. Overall, using a bearingless support design will significantly increase the reliability of the developed pump.

The heating processes of private residential buildings demand substantial fuel and energy resources and contribute to global warming, necessitating the transition to energy-efficient and eco-friendly heating. This study aims to develop a methodological approach for selecting cost-optimal strategies for household heating systems by assessing the environmental impacts and cost-effectiveness of available options of fossil fuels and renewable energy used in the residential sector during a heating season while ensuring homes’ greening and energy efficiency. The research extends the existing methodology by considering climatic zones and their ambient air temperature fluctuations during a heating season, household energy efficiency, various energy carriers used for heating, household running and capital costs for heating, multi-zone electricity tariffs, and prospects of heating automation, aiding policymakers in shaping residential heating choices. Tested on a typical Ukrainian household, the approach contributes to sectoral policy improvement by creating energy-efficient and decarbonization strategies for housing stock, with potential application in other countries. The results show that the most cost-optimal options for heating in Ukraine are firewood and natural gas use under the current energy policy. Based on the findings, the study suggests recommendations within Ukraine’s regional context and carbon neutrality goals. They provide a transition to renewables (wood pellets and heat pumps) by developing a market infrastructure for servicing boiler equipment and logistics for biofuel supply, state economic support to local boiler equipment manufacturers, and partial reimbursement of investments in pellet boilers and heat pumps for households, electricity tariff adjustments, etc.

Purpose. Improving the methodology for determining the recirculation power of low and medium specific speed centrifugal pumps in order to determine ways to increase their energy efficiency. Methodology. A numerical simulation based on the physical nature of the phenomena of recirculation power, conducted using the ANSYS CFX software. findings. The dynamics of changes in the integral parameters of the operational process of a centrifugal pump D2000­100­2 at flow rates that deviate from optimal (Qopt) are investigated and presented. Based on the results of the numerical simulation, the values of the theoretical head of the impeller, as well as the head at its outlet, taking into account and excluding recirculation, are determined. Due to the difference in the obtained head values, the value of the power losses for recirculation and their part in the balance of hydraulic losses are determined. Based on the simulation results of the operational process of the centrifugal pump D2000­100­2, it is shown that part of the recirculation losses in the flow rate range (0.7–0.4)·Qopt is 25–30 % of the total hydraulic losses, while in the flow rate range (0.3–0.1)·Qopt it increases to 44 %. originality. Further development of the method for determining the recirculation power which is based on the results of numerical simulation of three­dimensional fluid flow in the flowing part of the centrifugal pump, taking into account the circulation vortex processes at the outlet of the impeller. Practical value. Definition of the recirculation power in the power balance of hydraulic losses at the pump design stage. Taking account of the influence of the design parameters of the impeller on the value of recirculation.