scholarly journals INVESTIGATION OF VARIABLE MODES OF CENTRALIZED HEAT SUPPLY SYSTEMS OPERATION WITH QUALITATIVE AND QUANTITATIVE REGULATION

2019 ◽  
Vol 10 (2) ◽  
pp. 79-91
Author(s):  
T. A Rafalskaya ◽  
A. R Mansurov ◽  
A. R Mansurova
Keyword(s):  
Water Supply ◽  
Flow Rate ◽  
Heat Load ◽  
Heat Supply ◽  
Heat Supply System ◽  
Hot Water ◽  
Constant Flow Rate ◽  
Network Water ◽  
Qualitative And Quantitative ◽  
Hot Water Supply

The combined method of generating electric and heat energy at CHP plants has been and remains the most effective way of fuel saving both in housing and communal services and in industry. In Russia, historically, a qualitative method of regulation has been adopted, which consists in changing the temperature of the fluid depending on the change in the temperature of the outside air at a constant flow rate of the fluid. An analysis of the heat supply schemes of a number of Russian cities revealed that central quality regulation at heat sources has practically ceased everywhere. In modern methods of calculating the qualitative and quantitative regulation, the main load is heating, and the load of hot water is taken into account only by increasing the flow rate of network water and the variable modes of joint operation of heating and hot water systems are not calculated. Thus, at present, there are no methods for calculating the qualitative and quantitative regulation, allowing to fully taking into account the effect of the load of hot water on the operation of heating systems. Therefore, in modern conditions, the previously developed methods and technological methods of controlling the combined heat load are characterized by a decrease in efficiency, and, accordingly, the problem of their optimization arises. For different temperatures of outdoor air, the calculation of variable operating modes of the heat supply system was carried out, which showed that the existing schedules of qualitative and quantitative regulation cannot provide a comfortable temperature condition of the premises. Under the conditions of a connected supply of heat, simply adding up the flows of network water for heating and hot water supply fails to achieve optimal thermal conditions for the premises. Therefore, further improvement of the technology of the central qualitative and quantitative regulation of the heat load taking into account hot water supply is required.

scholarly journals Equations of temperature graphics of a heating point with a two-stage scheme of heat exchangers of hot water supply

2020 ◽  
Vol 208 ◽  
pp. 02001
Author(s):  
Tatyana Rafalskaya
Keyword(s):  
Water Supply ◽  
Air Temperature ◽  
Water Consumption ◽  
Heat Exchangers ◽  
Heat Supply ◽  
Heat Supply System ◽  
Supply System ◽  
Hot Water ◽  
Two Stage ◽  
Hot Water Supply

The temperature of the water returned to the heating network from consumers largely determines the energy efficiency of the heat supply system. It depends on a number of parameters: outside air temperature, hot water supply heaters connection scheme, daily water consumption in the hot water supply system. The calculation of this temperature is usually performed numerically, which makes it difficult to control the modes of the heat supply system. From a practical point of view, a simpler toolkit is needed. In this paper, equations are proposed that allow directly determining the change in the heat output of heat exchangers depending on the outside air temperature and the temperature of the network water returned to the heating network. These equations are obtained on the basis of systematic modeling of variable operating modes of the heat supply system, using the method previously proposed by the author. The operating characteristics of the heat station are taken into account by the coefficients of the equations, for the determination of which the calculation formulas were obtained. The equations used are valid for substations with a two-stage mixed scheme of hot water supply heaters in the mode of maximum water consumption.

Equations of Temperature Graphs of Operation Modes of a Heating Station with a Two-Step Scheme of Connection of Hot Water Supply Heaters

2020 ◽  
pp. 29-41
Author(s):  
Т. А. Рафальская
Keyword(s):  
Water Supply ◽  
Water Consumption ◽  
Heat Supply ◽  
Heat Supply System ◽  
Supply System ◽  
Water Supply System ◽  
Hot Water ◽  
Water Heaters ◽  
Hot Water Supply ◽  
Hot Water Supply System

Постановка задачи. Температура обратной воды, возвращаемой в тепловую сеть от потребителей, является важным показателем энергоэффективности системы теплоснабжения. Она зависит от температуры наружного воздуха, схемы присоединения подогревателей горячего водоснабжения, суточного водопотребления в системе горячего водоснабжения. Ее расчет производится на ЭВМ, в основном численными методами. Необходимо получить уравнения, позволяющие напрямую определять температуру сетевой воды после каждой ступени подогревателей и возвращаемой в тепловую сеть. Результаты. Методом моделирования переменных режимов работы системы теплоснабжения получены уравнения температурных графиков работы теплового пункта с двухступенчатой смешанной схемой присоединения подогревателей горячего водоснабжения. Определены зависимости для коэффициентов уравнений температурных графиков после каждой ступени подогревателей горячего водоснабжения. Выводы. Полученные уравнения справедливы для отопительно-бытового графика центрального регулирования, в том числе со срезкой, в режиме максимального водоразбора в системе горячего водоснабжения. Анализ эксплуатационных режимов системы теплоснабжения выявил закономерности, позволяющие прогнозировать температуру обратной сетевой воды в зависимости от наружной температуры и переменного водоразбора в системе горячего водоснабжения. Statement of the problem. The temperature of water returned into a network from the user is an important indicator of the energy efficiency of the heat supply system. It depends on the outdoor temperature, the connection scheme of the hot water heaters, the daily water consumption in the hot water supply system and its calculation is carried out on a computer, mainly by numerical methods. It is necessary to obtain equations that directly determine the temperature of the network water after each stage of the heaters and returned to the heat supply network. Results. By the method of modeling variable modes of operation of the heat supply system, the equations of the temperature schedules of the operation of the heating station with a two-stage scheme for connecting the hot water heaters are obtained. The dependences for the coefficients of the equations of the temperature graphs after each stage of the hot water heaters are determined. Conclusions. The obtained equations are valid for the heating schedule of central regulation, including with a cut, in the maximum water consumption mode in the hot water supply system. An analysis of the operating modes of the heat supply system revealed patterns that makes it possible to predict the temperature of the return network water depending on the outdoor temperature and variable water consumption in the hot water supply system.

scholarly journals ENERGY EFFICIENCY OF COMBINED HEAT SUPPLY SYSTEMS

2021 ◽  
Vol 2 (39) ◽  
pp. 92-97
Author(s):  
R. Klimov ◽  
A. Morozovskaya
Keyword(s):  
Water Supply ◽  
Heat Supply ◽  
Fossil Fuel ◽  
Heat Supply System ◽  
Heat Pumps ◽  
Supply System ◽  
Hot Water ◽  
Solar Collectors ◽  
Hot Water Supply ◽  
Supply Systems

The consumption of energy resources in the world states is constantly growing from year to year. The production of fossil fuels is also increasing, but for various reasons it cannot fully cover the required amount from consumers. One of the most important consumption sectors is heat loads from heating, ventilation and hot water supply of industrial and residential buildings. To cover the thermal loads of heating and hot water supply, the necessary heat carrier is water heated to a certain temperature. The most promising from the point of view of heating water for hot water supply are solar collectors. Hot water for heating needs to be reheated practically throughout the entire heating period. The introduction of heat pumps is promising. When using solar collectors, the heating agent can be reheated in heat pumps. The aim of the study is to develop such a combined heat supply system that uses more renewable energy and as a peak source a fossil fuel boiler (electric energy), as well as a method for calculating this system to determine the optimal composition of equipment and rational modes of its operation. The methodology for calculating heat supply systems combining solar collectors, heat pumps and fossil fuel boilers is presented. The problem of load distribution between the main elements of the combined heat supply system should take into account the probabilistic component. This is due to the fact that with a changing real mode of operation, different thermal load of the equipment can be optimal. This is primarily influenced by the variable heat inputs from solar collectors during the day. According to the above method, it is possible to determine the optimal parameters of the heat supply system for different operating modes, at which the minimum consumption of fossil fuel will be ensured.

scholarly journals Analysis of procedures for heating, ventilation and air conditioning for transfer to low-temperature heat supply

2019 ◽  
pp. 8-8
Author(s):  
Stanislav Chicherin
Keyword(s):  
Water Supply ◽  
Heat Supply ◽  
Heating System ◽  
Heat Energy ◽  
Hot Water ◽  
Heat Consumption ◽  
High Quality ◽  
Hot Water Supply ◽  
Supply Systems ◽  
Selection Of

Introduction. Renovation of housing stock supposes construction of new buildings, where the main utilities consuming heat energy will be heating and hot water supply (HWS) systems. Under such conditions the task of heat consumption reduction by transfer to low-temperature and use of the associated procedures is relevant. Materials and Methods. Research was performed on the basis of residential and administration buildings designed within the whole Russia, the facilities were selected based on the year of putting into operation and their purpose. The source of data concerning buildings became documents included into the scope of the design and detailed documentation: plans, drawings and explanatory notes. As meeting the demands of hot water supply makes the main contribution to daily nonuniformities of heat energy consumption, the attention was paid to equipment of hot water supply systems. For calculations, the commercial product of Microsoft Office Excel 2010 was used. Results. During selection of roof boiler house as a source of heat supply increase in consumption of equivalent fuel in relation to the variant of connection to heat power plant operating on solid fuel by 187,314 tons of fuel oil equivalent is possible. General refusal from power-and-heat generation complicates operation of large district heat supply systems. The design parameters of coolant in building heating system differ from project to project: from 95/70 °С, used everywhere till the beginning of the XXI century, up to 90/65 °С corresponding to existing practice of designing or 80/60 °С as at the facility in Sevastopol. Reduction of design temperatures by 5 % is insufficient to decrease general heat consumption of the building. Reduction of heat consumption is explained by selection of advanced materials for pipeline heat insulation. Use of automation diagrams for heat points on the basis of regulator ECL Comfort 310 contributes to improvement of hydraulic control for heating systems, however, concealed automation results in violation of high-quality mode for heat network control and decrease of coolant parameters on adjacent (often non-automated) consumers. Conclusions. Supplement of central high-quality control by local constant temperature/variable flow control at individual heat unit and installation of temperature controllers on heating radiators with mechanical thermostatic head have potential for reduction of the heat energy volume used ineffectively. Increase in level of controllability for heating system together with cheaper and responsive automation systems are basic conditions for increase in quality of heat supply in future.

scholarly journals Energy efficiency of multi-apartment residential houses with individual heat supply

2020 ◽  
Vol 212 ◽  
pp. 01011
Author(s):  
Vladimir Melnikov ◽  
Uladzimir Navaseltsau ◽  
Dzina Navaseltsava
Keyword(s):  
Water Supply ◽  
Flow Rate ◽  
Thermal Energy ◽  
Water System ◽  
Hot Water ◽  
Water Supply Systems ◽  
Hydraulic Systems ◽  
Circulation Mode ◽  
Hot Water Supply ◽  
Internal Networks

Centralized hot water systems widely used in Russia and Belarus are characterized by a considerable length and branching which inevitably leads to increased heat losses and to an unstable hydraulic system. The operation of the domestic hot water system in the circulation mode can be characterized by several parameters; one of which is the specific ratio of the cost of thermal energy for heating a cubic meter of hot water. The parameter is often regulated by law in Russia; exceeding this parameter is considered as administrative violation. The aim of the research is to determine the design and actual costs of thermal energy for hot water supply (hot water heating) and their comparison, analysis of the data obtained. The methodology for determining the design and real costs of thermal energy for hot water supply was to study the operation of the hot water supply system of a residential 144-apartment 9-storey building. The research showed that the actual circulating flow rate is much less than the calculated circulating flow rate. The authors note that in order to optimize the standard for heating a cubic meter of water it is necessary to observe the calculated circulation modes. This will require stabilization of the hydraulic systems of both the external and internal networks which is a difficult but feasible task. The research results are supposed to be taken into account when setting up existing hot water supply systems.

scholarly journals Reliable and safe heat supply of residential buildings using wastewater after heaters for hot water supply

2019 ◽  
Vol 12 (2) ◽  
pp. 120-125
Author(s):  
O. D. Samarin
Keyword(s):  
Water Supply ◽  
Heat Supply ◽  
Power Plants ◽  
Residential Buildings ◽  
Thermal Power ◽  
Break Point ◽  
Hot Water ◽  
Outdoor Temperature ◽  
Capital Costs ◽  
Hot Water Supply

A modified scheme of heat supply of residential buildings with dependent connection to external heating networks is considered, providing reliability of heat supply and the necessary comfort in the premises due to mixing in some of wastewater after hot water supply (DHW) heaters at an outdoor temperature exceeding the break point of the temperature graph. The main equations describing the dependence of the water temperature in the supply line on the outside air temperature are analyzed, and a review of possible ways of regulating the heat supply and preventing "overflows" near the beginning and the end of the heating period is carried out, taking into account the requirements of the current regulatory documents of the Russian Federation. Calculations are made to determine the required proportion in the mixture for water consumption after the heaters of hot water supply in the conditions of the application of the scheme of connection of buildings to the heating network. The analysis of obtained results is given, and conclusions are drawn concerning expediency of application of the considered scheme. It is established that, from the power point of view, mixing of wastewater after heaters of DHW in the calculated quantity will allow to provide reliability of heat supply of the main group of residential buildings and safety of activity of people at high temperatures of outside air. It is shown that, at the same time, that the higher the current outdoor temperature, the greater the share of wastewater in the mixture, with the above dependence close to linear, and its numerical coefficients associated only with the calculated outdoor temperature in the construction area for the cold season. It is noted that the introduction of the proposed scheme is possible with a minimum reconstruction of existing units and structures without significant capital costs, and also gives a system-wide effect in the form of increased electricity generation in thermal power plants on thermal consumption.

Reliable and safe heat supply of residential buildings in transitional conditions with independent connection of the heating system

2021 ◽  
Vol 14 (1) ◽  
pp. 27-33
Author(s):  
O. D. Samarin
Keyword(s):  
Water Supply ◽  
Heat Exchangers ◽  
Heat Supply ◽  
Residential Buildings ◽  
Structural Characteristics ◽  
Heating System ◽  
Hot Water ◽  
Heat Output ◽  
Outdoor Air ◽  
Hot Water Supply

The arrangement for heat supply of residential buildings with indirect connection to external heating systems is considered, providing reliability of heat input and required comfort in case of cold snaps after the official end of the heating season or before its beginning by supplying water from the return main of the heating system downstream the hot water supply heat exchangers. The calculations have been made to determine the amount of the main components of heat balance of a residential building on an example of one of standard projects being currently used in the climatic conditions of Moscow, subject to the structural characteristics of the building and its occupancy level. It is established that the actual heat output of the heating system when using the system of chilled water downstream the hot water supply heat exchangers as a heat source enables to main-tain an indoor temperature required for safe living conditions with the average daily outdoor air temperature above +2°C, the heat gain from solar radiation being moderate. It is proven that, tak-ing into account the thermal stability of the enclosing structures, the daily flow rate fluctuations do not significantly affect the stability of the temperature conditions of residential buildings or the comfort of their indoor microclimate at high outdoor air temperatures. It is noted that, in terms of reliability of heat supply of the main group of residential buildings and ensuring the life safety, the proposed arrangement is not inferior to the standard two-stage arrangement of connection of DHW heat exchangers with restriction of the total consumption of delivery water and with the associated regulation of heat supply for DHW, heating and ventilation. It is shown that the use of this arrangement involves virtually no extra costs, provides hydraulic resistance of the heating system and ensures a system-wide effect in the form of higher electricity generation at thermal consumption when using cogeneration.

Simulation Study of a Novel Solar Thermal Seasonal Heat Storage System Based on Stable Supercooled PCM for Space Heating and Domestic Hot Water Supply of Single Family Houses

2019 ◽  
Vol 887 ◽  
pp. 650-658
Author(s):  
Christoph Moser ◽  
Gerald Englmair ◽  
Hermann Schranzhofer ◽  
Andreas Heinz
Keyword(s):  
Water Supply ◽  
Latent Heat ◽  
Heat Supply ◽  
Heat Storage ◽  
Hot Water ◽  
Solar Thermal ◽  
Space Heating ◽  
Single Family ◽  
Domestic Hot Water ◽  
Hot Water Supply

A TRNSYS model of a novel PCM heat storage, utilizing stable supercooling of Sodium Acetate Trihydrate (SAT), is presented. To achieve high solar fractions in heat supply of single family houses, the necessary integration of big water volumes is challenging. To evaluate its functionality, a system model of a solar thermal combisystem for space heating and domestic hot water supply for dynamic system simulation was built. The key component is a PCM volume for long term heat storage. While conventional heat storage concepts with SAT release the latent heat a few degrees below the melting temperature, with the concept of stable supercooling latent heat can be stored for long periods of time at ambient temperature. This allows the design of a partly loss-free storage. Solar fractions were evaluated for simulation runs with two building variations. Annual specific space heating demands of 15 and 30 kWh/(m2a) and a domestic hot water demand of a typical single family house were considered. A sensitivity analysis on solar fractions of domestic heat supply was performed by variation of the collector field and the PCM volume. While the increase of the PCM volume from 4.5 m3 to 9 m3 shows moderate effects in all simulation runs, an increase of the collector area has substantial effects on the share of solar heat on the total energy demand of the building.

Selection of Hot Water Supply Metering Devices for Residential Buildings

2015 ◽  
Vol 725-726 ◽  
pp. 1267-1272 ◽  
Author(s):  
Viktor Pukhkal ◽  
Boris Jurmanov
Keyword(s):  
Water Supply ◽  
Flow Rate ◽  
Water Consumption ◽  
Residential Buildings ◽  
Residential Building ◽  
Hot Water ◽  
Water Supply Systems ◽  
Hot Water Supply ◽  
Selection Of ◽  
Water Meter

Experimental measurements of actual hot water consumption in residential building have been performed. It was established that distribution of hot water for domestic needs has random character and constitutes non-stationary process. It was proposed for hot water supply systems calculation to employ “rated mode of water consumption”. Rated mode is a simplified mathematical description of entire ordered collection of hourly consumptions anticipated during rated period of hot water supply system operation. Most precise description of water consumption rated mode may be obtained with coefficient of general hourly discontinuity at 98% coverage. Selection of hot water metering devices for residential house requires that operating flow rate of water meter should correspond by maximum to residential building water consumption parameters. Methods of calculation of daily water volumes passing through water meter at flow rates lower than transient flow rate value for the specified device were proposed.

scholarly journals Improving a heat supply system by increasing the efficiency of the heat pump unit

2022 ◽  
Vol 2150 (1) ◽  
pp. 012033
Author(s):  
P V Rotov ◽  
R A Gafurov
Keyword(s):  
Heat Pump ◽  
Heat Supply ◽  
Operating Time ◽  
Heat Supply System ◽  
Supply System ◽  
Hot Water ◽  
Water Supply Systems ◽  
Network Water ◽  
Heat Pump Unit ◽  
Supply Systems

Abstract The reliability and efficiency of the operation of district heating systems is largely determined by the efficiency of preparation of heating network water. In open heat supply systems, make-up water, among other things, compensates for the water intake in hot water supply systems. A number of technologies have been developed that increase the efficiency of an open heat supply system by reducing the water consumption in the supply pipeline of the heating network, increasing the operating time of the heat pump, and increasing the specific generation of electricity for heat consumption at the CHP plant due to additional cooling of the network water in the return pipe of the heating network.

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