DIGITAL MODELS OF STEADY MODES OF HEAT SUPPLY SYSTEMS BASED ON INVERSE CHARACTERISTICS

Methods and algorithms of digital models for describing and solving the calculation of steady-state hydraulic regimes of heat supply systems, a modified nodal model for calculating the flow distribution,using the method of a new approach to forming a system of equations of nodal heads, in which not direct, but inverse characteristics of passive and active elements of the pipeline network are used. The result of the analysis of the numerical efficiency of the contour and nodal models based on the developed information-graphic system is presented.

Formalization of the problem of analysis of stationary modes of complex heat supply systems

On the basis of a systematic approach, the goals and functional tasks of the analysis of the steadystate hydraulic regime are formalized, as a proven practice of the methodology of decision-making in the field of commissioning and prospective development of complex heat supply systems of megacities. The use of a systematic approach to setting and improving the tasks of mode analysis allowed us to develop and implement an applied information system with an effective analyzing methodology for solving professional problems.

The Effectiveness of Extended Schedules of Heating Regulation at CHP Plants with Decreasing Normative Design Temperature of the Supply Water

The aim of the work is a computational study of the effectiveness of the extended schedules of heating regulation at steam turbine CHPPs with a decrease in the normative design temperature of the supply water. The study was carried out on adequate mathematical models of CHP tur-bines and heat supply systems, considering heat pipelines' actual diameters and lengths. The main energy efficiency indicator is the specific reference fuel consumption for electricity sup-ply, calculated under comparable conditions for the operating modes of turbine plants and the load of the heat supply system. The study took into account the electricity consumption for the drive of network pumps, standard heat losses in heating networks and the electricity generation for the heat consumption of CHPPs. The study results allowed for the first time to determine the integral indicators of the energy efficiency of work during the transition of CHPPs from the normative design ones to the temperature schedules reduced by the temperature of the supply water. At the same time, the calculations revealed the limitations on the parameters of the extended schedules of regulation when transitioning to reduced temperature schedules. The most important results of the work should also be attributed to the determination of the optimal schedules of the temperature of the supply water for different values of the district heating coef-ficient of the CHPP. The results obtained are essential for assessing the efficiency of the transi-tion of heat supply systems to reduced supply water's design temperatures when using modern heating regulation schedules.

Rational Heat Schemes Using Condensing Boilers in Local Heat Supply Systems

Within the framework of this publication, thermal diagrams of autonomous heat supply systems using condensing heat generators are considered. The insignificant Russian experience of using small condensation boilers in residential construction shows that it is often used to simply replace traditional equipment with condensation technology in existing (or traditionally used) heat schemes, for example, with protection of the boiler from “cold return” by recirculating heat carrier or installing a hydraulic regulator. The consequence of this is almost completely lost the effect of the use of condensing boilers. At the same time, even using the heating temperature schedule of quality regulation 80-60°C and applying water heating to the DHW target up to 45°C you can achieve the effect of the boiler operation in the condensation mode, depending on the construction area, up to 75% of the total working time per year, generating about 70% of thermal energy in the annual cycle. However, it must be borne in mind that the efficiency of the condensing boiler is determined by the part of the latent heat of water vapor in the combustion products, which can be obtained with partial condensation. If this part is small, for example, when cooling the flue gases to 50-45°C (on gas), then the efficiency gain is only 1-3%.

Alternative Options for Modernization of Regional Heat Supply Systems: Environmental and Economic Aspects

At present, environmental pollution by fuel combustion products is one of the key problems in the heat supply sector. It affects the entire population of the Earth. The purpose of the research is to substantiate the necessity of ecological upgrading of thermal power facilities in the Irkutsk region and using a part of municipal solid waste as an alternative fuel at thermal power facilities of the Russian Federation. The research shows that the use of the two kinds of fuel (solid biofuel and alternative fuel) can reduce the anthropogenic load. This measure can be a way of energy efficient disposal of accumulated and annually generated production and consumer waste. The transition to alternative fuels can be most efficiently implemented in boiler houses. This is due to lower capital investments in the modernization of boiler houses as compared to the modernization of thermal power plants. The calculations in the article confirm that the implementation of environmental modernization of regional heat supply systems is not economically beneficial for entrepreneurs. The state should supplement the methods of regulation with targeted co-financing of programs for the modernization of thermal power facilities in order to accelerate the processes of modernization of heat supply in the Russian Federation. At the same time, the recipients of support must comply with the established indicators further on.

Development of low-pressure electric steam heater

The study was devoted to solving the issue of creating new electric heating devices that can be used in autonomous heat supply systems. The issues were resolved by developing an original low-pressure electric steam heater. The study was aimed at improving the efficiency of heat supply systems for buildings and structures. Given the current trends in the global striving for energy conservation, it cannot be fully realized without the introduction of high-tech and low-energy-consuming electrical equipment. As a result of theoretical studies of a heat pipe with an electric heater, a design of an electrovacuum heating element has been developed. The low-pressure electric steam heater can be used in heat supply systems of autonomous users. Thermal energy transfer is currently accompanied by substantial energy losses since the heat carrier has to pass considerable distances. Switching of the facility to the heating plant is impossible in some cases because of technical problems or significant material costs for laying pipelines. As a result of the study, the dependence of heating the heat pipe at various volumes of the heat carrier and mass of the pipe itself was established. When a certain mass is reached, the temperature of the heating surfaces can reach 70 °C which is considered acceptable. The experimental data obtained have made it possible to develop an electric heater of new generation with a fundamentally new design of the heating element. It combines the efficiency of an electric spiral and comfortable warmth from a traditional radiator. This heater is an explosion and fire-safe and can be integrated into the Smart Home system

Hybrid Carbon Dioxide Heat Pump for the Multifamily Residential Buildings in the Heat Supply System Based on CHP

The work is devoted to centralized heat supply systems based on CHP plants and the use with them heat pumps (HP) on carbon dioxide as refrigerant. Heat pumps are used in heat supply systems for buildings and use the heat of the outside air and, at the same time, the heat of the return network water (WWR) as a source of low-grade heat (LHP). The aim of the study is to develop a structural diagram of such a heat pump, where the outside air is heated by a heat exchanger installed in the return water line of the heating system, to develop a hydraulic circuit of a heat pump taking into account the law of regulation of the building heating system, to develop an algorithm for controlling the operating modes of the so-called balancing heat exchanger installed after gas cooler and internal heat exchanger of the heat pump. The most significant results were the hydraulic circuit of the heat pump, the aerodynamic circuit of the air supply path to the heat pump evaporator, the balancing heat exchanger control system, taking into account the requirement to ensure the operation of the control valve in a single-phase flow. The significance of the results obtained consisted in obtaining the dependences between the CO temperature graph and the parameters of the thermodynamic cycle of the heat pump, which ensured the operation of the control valve of the heat pump in a single-phase environment.

INDICATORS THERMAL AND HYDRAULIC MODES OF DISTRIBUTION HEAT NETWORKS

The task of heat supply systems is to ensure the quality of services at a minimum cost in the production and transportation of thermal energy. Because the distribution heat networks of district and district systems are characterized by significant branching and significantly longer lengths of heat pipelines compared to the main sections of heating networks, reducing heat loss in these elements of the heating system significantly affects the overall efficiency of district heating. The amount of heat loss depends on the method of laying networks and the diameter of heat pipes, thermal insulation parameters and temperature of the coolant and the environment. Based on the formulas for determining the specific pressure losses to overcome the friction forces obtained from the generalization of these projects of central heating systems of a number of residential districts of Kharkiv, calculated dependences for determining heat losses by supply and return pipelines of the main branches of the heating network. Estimates of accuracy of use of the offered formulas are carried out. The aim of the work is to determine the specific pressure losses for the main branches of heating distribution networks on the basis of generalization of design data for heat supply systems of building groups and clarification of formulas for calculating heat losses by pipelines of central heating distribution system. Based on the generalization of projects for the heating network of residential neighborhoods in Kharkiv, a formula for calculating the specific pressure loss during water movement in the pipelines of the main branches of the heating network depending on the heat load of buildings connected to the branch. Formulas for calculation of heat losses by supply and return pipelines of the main branches of a heating network of the residential district are offered. A comparison of the accuracy of calculations using the proposed formulas with existing methods for determining heat loss in branched heat supply networks, which showed the possibility of using formulas in preliminary assessments of the thermal state of networks.

ENERGY EFFICIENT SOLAR HEAT SUPPLY SYSTEMS FOR BUILDINGS AND STRUCTURES

Today, the energy sector of Ukraine requires significant consumption of traditional energy sources (oil, gas, coal, nuclear energy). However, their use is associated with a number of difficulties, including thermal, chemical, and radioactive contamination of the environment and the exhaustion of their reserves. The paper is devoted to solving the actual problem of improving the efficiency of solar heat supply systems with solar collectors. An analysis of the potential of solar energy and existing solar heat supply systems is presented. The advantages and disadvantages of various solar collector designs and methods of their research are analyzed. The analysis of the main directions for improving the efficiency of solar collectors and solar heat supply systems, in general, is presented. An improved solar heat supply system with the proposed design of a solar collector is obtained and its temperature characteristics are established depending on the intensity of solar energy intake.

TECHNIQUE FOR DESIGNING ENGINEERING SYSTEMS WHEN OPERATING ON A LOW-POTENTIAL ENERGY SOURCE

Statement of the problem. To develop a design methodology for air conditioning and heat supply systems operating for a long period on the basis of a vertical geothermal well. Results. A description and procedure of the proposed design methodology for calculating the main parameters of air conditioning and heat supply systems are given.Conclusions. As a result of the study, a methodology for designing air conditioning and heat supply systems based on a low-potential energy source (NIE) was proposed. It allows you to calculate the required number of geothermal wells as accurately as possible, taking into account the technological features of the operation of engineering systems, which allows you to minimize the amount of capital and operational investments for the installation of heat pump equipment and its components.