The need to maintain a high temperature of the coolant for hot water supply during the transition period of the year leads to large heat losses, and this is a significant drawback of high-quality central regulation of heat release. The purpose of the study is to substantiate the effectiveness of the transition to a combined quantitative and qualitative method of regulating heat release. The paper proposes the implementation of a combined quantitative and qualitative regulation, in which the release of heat is regulated by changing the temperature of the heat carrier before the cut-off temperature of the temperature graph, and after the cut-off, the transition to quantitative central regulation is carried out. The work shows that the need for such regulation is an organic need for centralized heat supply systems (СНSs) in connection with the thermal modernization of buildings and their equipment with automated IНPs. The low-temperature schedule of heat release, provided that the CНSs boilers are equipped with condensation heat exchangers, makes it possible to significantly increase the efficiency of heat generators and СНSs as a whole.

Ensuring optimal hydraulic and thermal regimes in district heating systems (DHS) in the regulation of heat supply is an important factor in improving the energy and economic efficiency of DHS. In addition, high efficiency of the HS system is a factor that can ensure the preservation of its vital functions. Solving the problem of increasing the energy efficiency of the heat supply system is a complex problem that requires changes at all stages of heat transformation: in the energy source, heating networks and subscriber heating systems of heat consumers. The purpose of this study is to identify the impact of heat dissipation control processes in district heating systems on their energy and economic efficiency, provide recommendations for improving control processes taking into account modern challenges and regulatory requirements, analyze heat dissipation temperature schedules and select the optimal temperature schedule. It is shown that the optimal is the combined quantitative and qualitative regulation of heat release, which should be carried out both at the energy source and at consumers. The paper considers the possibility of using combined control systems in the existing district heating systems of Ukrainian cities. It is shown that the achievement of high energy efficiency is possible only with the introduction of automatic individual heating points with weather control and pressure drop regulators at the inlet to the buildings in the subscriber heating systems. Calculations of the amount of heat consumption reduction of centralized heat supply systems with the introduction of optimal control systems are performed.

The reason for the ambiguous assessment of high-temperature modes of heat release is the influence of the heat carrier temperature in the return pipeline on the work efficiency and thermodynamic efficiency of heat sources in centralized heat supply systems (CSTs). Non-productive heat losses due to heat losses with waste gases.The purpose of the research is to substantiate the feasibility of implementing the utilization of the heat of combustion products in a condensing heat exchanger-utilizer.The results of the calculations confirm that a significant reduction in heat loss with waste gases and a corresponding increase in the efficiency of the unit can be achieved if the temperature of the waste gases after the heat exchanger is reduced below the dew point. Without the introduction of condensing boilers or condensing heat exchangers-utilizers and without changing the method of regulation, the transition to a low-temperature heat release schedule will only lead to a deterioration of the overall efficiency of the heat supply system.

Heat supply regulation should ensure high energy efficiency of district heating systems (DHS) in general, reducing the specific indicators of heat production and release and maintaining the normalized thermal regime of the premises with any changes in outdoor temperature, insolation, infiltration and heat. Usually the processes of central regulation of DHS at heat sources and heat consumers are considered separately: not only technically but also organizationally. In this regard, the proposal for joint consideration of central and local regulation of heat supply is relevant and useful. The proposed solutions can increase the efficiency of existing DHS at the stage of transition to modern options for their implementation, in which heat control units are located at the entrance to individual apartments, and thus, the degree of regulation of DHS as close as possible to autonomous heating systems. The purpose of the study is to comprehensively consider the impact of individual stages of heat supply on the overall efficiency of DHS. The most common in domestic DHS is a method of high-quality central control of heat supply by changing the temperature of the coolant in the pipelines of thermal networks at the outlet of heat sources. However, this method has a significant disadvantage - it is inefficient regulation during the period of cutting the temperature schedule with a joint load on heating and hot water. Working during this period leads to significant overheating in premises and unproductive heat loss. Unproductive heat losses because of inadequate regulation when lowering the heat release schedule reach up to 18% of the heat potential of the fuel used. The introduction of a combined quantitative and qualitative regulation is proposed, in which, up to the cutoff temperature of the temperature schedule, the heat release is controlled by changing the temperature of the coolant, and after the cutoff, the transition to quantitative central regulation is carried out. Practical recommendations for the implementation of such regulation have been developed. Combined central regulation ensures the possibility of providing hot water supply services throughout the entire heating period, avoids hydraulic and thermal deregulation of systems and ensures optimal conditions for the operation of heat generators, reduced energy consumption and a significant increase in the overall efficiency of the DHS. Key words: heat supply, centralized systems, energy saving, efficiency, heat load regulation

The paper presents the results of studies aimed to increase the efficiency of centralized heating networks by improving heat supply control at the plant and at the local level. With this in view, we considered issues of choosing the optimal heat supply schedule and its influence on the efficiency of heat generation, transportation and use, as well as the influence of the heat carrier temperature on heat losses at the corner of the temperature curve. We also studied the influence of the heat carrier temperature in the return pipe of heating networks on the operation of heat generators by using various control methods. Another issue considered in the course of the study was the issue of ensuring the hydraulic and thermal stability of heating networks and heating systems connected to them by using the combined control method. The methodology of the study was based on the analysis of heat balance equations for the steady-state operation of a complex including a heating network and a building’s heating system. As a result, we obtained relationships that make it possible to determine the variation in the heat carrier flow rate and temperature depending on the heat load, as well as the reduction in energy consumption for heat carrier transportation. Recommendations were developed for the introduction of combined heat load control. A scheme for the reconstruction of central heat stations is proposed. The scientific and practical results of the study can be used to prevent significant heat losses, ensure optimal operation of heating networks, heat generators, and heating systems, reduce energy consumption, and increase the overall efficiency of centralized heating networks.