Hot Water Supply System Research Articles

About expediency of changing the connection diagram of hot water supply units

PURPOSE. The article is devoted to an urgent problem for domestic district heating. A widespread situation is considered when consumers from heat supply systems with a closed connection scheme for hot water supply plants are switched to an open heat supply system from a thermal power plant. METHODS. Study of operating modes of operating heat supply systems was performed. Data collection was carried out using an online system for monitoring and commercial accounting of energy resources. Methodology for calculation of compared mode parameters is proposed. RESULTS. Using the example of the existing heat supply system, it is shown that the effect of the measure to switch subscribers of uneconomical boiler houses to heat sources with combined heat and power generation is leveled by legislative restrictions on the development of open heat supply systems, as well as by the regulatory method for determining heat consumption in hot water supply systems. The main technical and economic indicators were selected for comparative analysis of the operation of the centralized heat supply system in conditions of complete switching of hot water supply plants according to an open circuit and in the presence of a certain number of hot water supply plants with a closed connection scheme. CONCLUSION. The period of inefficient operation of the centralized heat supply system was determined and the amount of annual economic damage was calculated, which made it possible to prove the need to bring all schemes for connecting hot water supply plants in one heat supply system to a single type.

Determining the efficiency of local heat recycling wastewater based on a heat exchanger

RELEVANCE. The authors research the potential energy, economic and environmental effects of using local heat recovery from wastewater generated in showers. At the moment in Russia, almost all household wastewater is disposed of in sewer networks without the beneficial use of the heat that they possess. It is important to determine the effect of implementing this method of heat recovery, to identify and analyze the problems that prevent this from being done.THE PURPOSE. The purpose of the work is to determine the potential effect of using local heat recovery from wastewater generated in showers.METHODS. Based on a verified mathematical model of the heat exchanger, the energy effect from the individual use of the shower room is determined. A number of assumptions are applied to the heat consumption structure of an individual building and, based on available data on the average annual heat consumption of residential buildings in Moscow, the economic and environmental effect of energy-saving measures is calculated.RESULTS. Relative savings within the annual heat consumption of a building with a decentralized and centralized hot water supply system were 5,3% and 3,1%, respectively (64 and 37 GCal). Fuel economy amounted to: 9145 toe and 5227 toe for a building with a decentralized and centralized hot water supply system, respectively (14,5 and 8,5 thousand tons of CO2-eq). The payback period for energy-saving measures for the case of a decentralized hot water system based on an instantaneous electric water heater was 1,5 years.CONCLUSION. Local waste heat recovery makes it possible to obtain a significant energy and environmental effect within any locality, but at the moment there are no measures to support consumers implementing energy-saving measures. Currently, this method of heat recovery is of interest only to those consumers whose source of thermal energy for the needs of hot water supply is electricity.

Reservation of the heat supply system with biofuel heat energy sources

The implementation of the reservation of the heat supply system to a populated area was analyzed. It is noted that increasing the reliability of heat supply to consumers is a fundamental task, especially given the current military situation in Ukraine. The solution to this difficulty is considered when reserving heat supply by constructing a backup source of thermal energy using alternative types of fuel. A combined thermal scheme for connecting a hot water heat generator using biofuel to the existing city heat supply system is proposed to increase its reliability and survivability, which ensures the efficiency and reliability of operation of the heat supply system during the heating and summer periods. It is shown the possibility of operating a solid fuel heat generator with its power significantly less than the total heat load of the city's heating supply in several operating modes: during the heating period - for heating the return coolant at the inlet to the existing gas boiler house; in the summer period - for the needs of hot water supply in full; in the event of an emergency shutdown of a gas boiler house in winter - to maintain the viability of the heat supply system. The results of a calculation analysis of the operation of a 5,0 MW biofuel heat generator under different operating modes are presented. Heating the return coolant by 4...5 °C in winter, in addition to saving natural gas, prevents low-temperature corrosion of existing gas boilers. In the event of an emergency lack of natural gas supply, the combustion of wood chips ensures the production of thermal energy at the level of thermal losses of the heating network while maintaining the coolant temperature at least 3 °C at the calculated external air temperature. Thanks to the accumulation of thermal energy at night in the summer period in the volume of heating network pipes as a buffer tank, compensation for peak hot water consumption is provided with the available power of the solid fuel boiler house equal to the average load of the hot water supply system. When implementing a project to back up the heat supply system in Lutsk using a combined thermal scheme for connecting a solid fuel boiler house, an increase in the reliability and viability of the system and natural gas savings of 40,5% during a year of operation were achieved

Analysis of operation of heat exchangers of hot water supply system in the scheme of reliable and safe heat supply of residential buildings

The scheme of internal heat supply of residential buildings with independent connection of the heating system to the external heating networks and connection of the heater of the DHW system in a parallel single-stage arrangement, providing reliability of heat supply and the necessary comfort in the premises due to the unrelated regulation of heat supply for heating, ventilation and DHW even in case of fluctuations in water intake, is considered. A mathematical model describing the non-stationary modes of operation of DHW system heaters under the conditions of implementation of this scheme is constructed and investigated. Calculations were carried out using this model, including numerical simulation on a computer using the Monte Carlo method. It is established that in this case, a decrease in the average heat transfer coefficient of the heater of the DHW system due to fluctuations in the flow of mains water following the daily change in water consumption at the DHW can be neglected, since this decrease lies within the usual error of engineering calculation, despite the fact that this coefficient depends on the flow in a nonlinear way, and its growth during the period of increased water intake for DHW does not fully compensate for the decrease during the reduction of water consumption. At the same time, it is proved that with a characteristic number of heat transfer units in a DHW system heater referred to the heated stream, the total amount of heat transferred can decrease quite noticeably, by an amount of 10 to 12 percent; however, with a rational choice of the heater size, such a decrease is within the limits allowed by the applied factors of margin when setting determination of the heat exchange surface.

An Energy and Ecological Assessment of The Prior and Post-Hybrid Renovation State of Multi-Dwelling Building in the Algerian City of Skikda

In the context of Algerian energy and environmental concerns and its aspirations for energy transition, this article examines the pre- and post-state of a multi-family residential building in the city of Skikda, in northern Algeria, utilizing the UBEM reduced-order approach, alongside QGIS, CEA and METEONORM tools. Primarily focusing on the building's solar exposure, energy aspects, and environmental considerations. Six hybrid renovation scenarios were considered then, and assessed for their contribution for energy savings and ecological improvement. The main results revealed that 87% of annual energy requirements were related to heating and hot water, which are supplied by a natural gas system, a source of various types of greenhouse gases, which suggested the use of triple glazing, with or without two selective low-emissivity coatings only, or be combined by changing hot-water supply system to an electric one, alongside the installation of the hybrid PVT panels on the south façade. This triple glazing was joint in another scenario by integrating the same type of panels on the roof alongside a seasonal thermal energy storage system. This latter scenario being the best in terms of energy and ecology, and making the building highly performant in both aspects.

ТЕХНИКО-ЭКОНОМИЧЕСКОЕ ОБОСНОВАНИЕ УСТАНОВКИ СОЛНЕЧНЫХ КОЛЛЕКТОРОВ ДЛЯ ИНДИВИДУАЛЬНЫХ ДОМОВ

The hot water supply system of Perm uses solar energy. The aim of the study was to substantiate the economic efficiency of solar collectors and determine their payback period taking into account climatic conditions, equipment cost and economic criteria. The proposed technical solutions of solar energy using were analyzed and compared with electric heating. During the study, the authors defined the required minimum solar collector area for a household (taking into account the hot water standard for Perm) as a functional dependence of the amount of incoming solar insolation on the amount of using heat energy. We evaluated domestic and imported solar collectors on the required parameters. The value of the reduction in the payment for electric energy was taken as the income for the households. The economic efficiency was calculated based on the forecasted average electricity tariff, taking into account inflation from 2 to 16 %. The payback of a solar hot water heating system depends primarily on the cost of purchase, installation of equipment and on the discount rate. The practical significance is to substantiate the economic efficiency of solar collectors for consumers. The methodology and results of the study can be used in private residential construction and in justification of the use of alternative energy sources for Russian regions with low insolation.

Метод совершенствования планирования и управления технологическими процессами воздухообеспечения угольных шахт

Introduction. Management methods in complex technical systems of the mining and processing complex are currently considered as the main tool for improving the planning and management of technological processes in coal mines. In this regard, there is a need to develop an apparatus that allows research and design of methods on a unified basis. Methodology and research methods. During theoretical studies, methods of mathematical statistics and graph theory were used. The apparatus of mathematical logic, set theory and Gomori algorithms and their modifications were used. Discussion of research results. The article presents the results of research to develop a method for improving the planning and control of technological processes of air supply in coal mines. It has been established that the assessment and analysis of methods for improving the planning and control of technological processes of air supply (ATS) in coal mines are becoming increasingly relevant in connection with the modernization of mining production in the Russian Federation. Conclusion. Based on the research carried out, theoretical and practical problems were set and solved, an analysis of the patterns of TPV was carried out to improve the safety and prevent emergency situations of TPV in coal mines. Methods for calculating and analyzing safety for the variable structure of the system and its multifunctional states have been improved, allowing for the selection of optimal TPV parameters and performing calculations to ensure trouble-free operation of the TPV. The research results can be used to set the structure and control technological processes of air supply in coal mines. Conclusions on the article. The article presents the results of TPV studies conducted in coal mines. A method has been developed for analyzing and assessing components for controlling the air supply system of hot water supply, where its use allows for a comprehensive analysis and assessment of emergency situations of hot water supply. The research results can be useful when carrying out mining operations at all enterprises where air supply is necessary.

Modernization of local heat distribution stations of city heat supply system

The PURPOSE of this work is to develop technical solutions to increase the efficiency of functioning of centralized urban heating systems by modernizing local heat distribution stations. The article considers the issues of functioning of district heating systems with open water intake. The work presents technical solutions that increase the efficiency of the local heat distribution station with a hot water supply unit. A technological scheme has been developed, the selection of equipment has been made. The feasibility of using the developed technical solutions is confirmed by technical, economic and investment indicators. The objectivity of determining the technical and economic effect of the modernization of the local heat distribution station is ensured by comparing the obtained indicators of the modernized and similar facilities.METHODS. To fulfill the objectives of the study, the following methods were applied: full-scale tests on a real object; processing of experimental data using application programs; feasibility study in the municipal heat power industry.THE RESULTS show an improvement in the technical and economic performance of the heating and hot water supply system of an apartment building in Yoshkar-Ola city: reduced network water consumption by 36–39%; temperature drop in the return pipeline was 13.5%; the heat content of hot water has been reduced to 0.168 Gcal/m3 (normative heat content is 0.145 Gcal/m3), the required circulation was ensured in all risers of the hot water supply system. The total losses from October 2021 to September 2022 are 3486,4 Gcal or 11.4% of heat supplied to consumers, which is less than 13% set by the tariff. Compared to a similar house without a regulation depending on the outside air temperature, the consumption of thermal energy during the heating season is reduced by 80 Gcal (10.9%).CONCLUSION. The new scheme of a local heat distribution station has been proposed, including the regulation of domestic hot water (DHW) recirculation, as well as the installation of a hydroelevator with weather regulation. The developed technical solution is relevant for district heating systems with open water intake. For the first time, an experimental study of the effect of the joint installation of the following equipment was carried out: a pump and a control valve on the DHW recirculation line before the recirculation mixing unit with the return pipeline of the heating system; hydraulic elevator with weather regulation. The results of the study can be used in the feasibility study of similar circuit solutions for the modernization of DHW systems. Operating experience has shown that the application of the developed technological scheme of local heat distribution station has positive effects: reduction of network water consumption, temperature in the return pipeline and heat losses; improvement of circulation in all risers of the DHW system; reduction of thermal energy consumption during the period of the “lower” cutoff of the temperature graph; curbing the growth of tariffs for thermal energy.

A water heater that adjusts its temperature based on solar energy

The calculation method for a water distributor of a constant cross section uniformly perforated along the height for a multilayer stratified thermal storage tank used in solar heating and hot water supply systems was developed. The advantages of using self-regulating stratification water heat accumulators in solar heat supply systems are considered. It is shown that the use of stratification for short-term and long-term thermal accumulation leads to an increase in the use of solar heat by 15-20% compared to batteries with completely mixing water. In hot water systems, these batteries can provide earlier preparation of hot water with the required temperature for consumers. Based on the analysis of world experience in the development of water heat accumulator designs using temperature stratified water and the stability of the stratified flow of coolant in the accumulator volume, a new, self-regulating, water accumulator design has been proposed.

Calculation of geometric dimensions and hydrodynamic characteristics of venturi pipes of a self-draining solar circuit

This research paper provides an increase in the energy efficiency and reliability of self-draining solar plants by optimizing their hydrodimatic operating modes. Based on this goal, the objectives of the study were to analyze the existing methods of protecting solar collectors of water heating and hot water supply systems from freezing and to identify the most promising methods. Also, the identification of the regularities of the hydrodynamics of a self-draining solar circuit.

Possibility of utilizing waste activated sludge as a renewable energy source

This paper gives results of a study of biofuel granules made from a waste activated sludge of wastewater treatment. A novel method to enhance waste activated sludge dewaterability with untreated and calcined water treatment sludge of thermal power plants is proposed, and the potential reuse of dewatered sludge as biofuel is evaluated. The water treatment sludge destroyed membrane, resulting in the release of intracellular water by converting bound water into free water, thus enhancing sludge dewaterability. Biofuel granules can be used for technological needs, electricity generation and in heating and hot water supply systems at industrial and domestic facilities. Biofuel granule is a renewable energy that can substituted low grade coal from biomass sources.

Study on the optimization of heat loss during operation of air source heat pump based on entransy theory

Existing research on the analysis heat pump operation generally focuses on the efficiency of doing work while ignores heat loss in the transfer process. Hence, heat pumps are often studied based on theory of minimum entropy production. However, this theory is rarely applied to optimizing heat transfer process with?out heat work conversion. Taking the air source heat pump hot water supply sys?tem of a hotel building as an example, this paper simulates the heat production, power and COP of the air source heat pump during operation based on the the?ory of entransy and entransy dissipation proposed by Professor Zengyuan Guo. The findings show that heat pump operates best at inlet water temperatures of 293 K and 298 K, with a COP of 4.8. In the water at a temperature of 298 K, water temperature can be adjusted by the function of heating capacity between 30 kW and 40 kW to minimize the system?s entransy dissipation, where the system?s unit power consumption reaches its minimum at 9 kW, corresponding to an entransy dissipation of 245.4 kJK. This study provides a good research idea to optimize the thermal power conversion process using the theory of entransy and entransy dissipation.

Development of solar water heater collector with less hydraulic resistance

In this article analysis of ways and methods to improve the efficiency of existing structures of the solar water heater collector in the article. The practical significance of the research results is explained by the fact that the solar water heater collector developed for hot water supply systems is proposed to use a collector circuit with low hydraulic resistance, which allows you to reduce the hydraulic resistance coefficient in the heat transfer water pipe relative to the integrated pipe absorber, without reducing the heat transfer coefficient.

Occurrence of Legionella sp. bacteria in hot water systems in hospitals and nursing homes in the Świętokrzyskie Province of south-eastern Poland.

The occurrence of bacteria of the genus Legionella sp. in hot water supply systems in buildings is a real threat to human health, especially for patients in hospitals and residents of nursing homes. The aim of the study was determination of the degree of colonization of hot water systems in hospitals and nursing homes in the Świętokrzyskie Province in south-east Poland. Between 2014 - 2018, samples were collected from hot water systems in 30 hospitals and 32 nursing homes in order to determine the degree of contamination. 631 samples collected of the bacteria Legionella sp were analyzed. Excessive contamination (≥ 100CFU/100 ml) with the bacteria Legionella sp. was detected in 12.12% (n=71) of samples. Contamination was significantly more frequently detected in samples from hot water systems in nursing homes, compared to hospitals (16.48% vs. 10.37%). Above-standard contamination of hot water systems with Legionella sp. bacteria occurred in 34.43% of the facilities, and was more frequent in hospitals (41.38%) than in the nursing homes (28.13%). In 21.3% of the facilities, contamination was detected many times during the study period. Excessive contamination of hot water systems with Legionella sp. bacteria in the examined facilities was a common phenomenon. The presence of the pathogen in the installations of these facilities may constitute a considerable health hazard for patients and residents.

Моdern heat and steam supply systems of industrial enterprises using deep utilization of the technological steam energy potential

Steam supply systems of industrial enterprises, as a type of heat supply system, are a large consumer of primary energy in national energy balances. In turn, due to the specificity of thermodynamic steam processes, steam supply systems of industrial enterprises in practice have significant unused potential of secondary energy resources (SEP). Modern steam supply systems should be built exclusively when evaluating their exergetic efficiency, which will make it possible to evaluate the effectiveness of such systems grossly in all elements of the life cycle of the project: energy, economic, ecological and even social. The article shows modernized thermal schemes of steam supply systems, for which it is possible to achieve additional electrical power at the level of 135-250 kW/(kg/s) when devices with a relative internal efficiency of up to 60-70 % are operating. In combination with an increase in the percentage of condensate return and the utilization of secondary energy resources (SRP), the increase in energy efficiency of the system is 2-4 %, and the absolute value of exergetic efficiency is 16-22 %, taking into account the exergetic efficiency of the boiler unit. Low-potential "tail" consumers: the heating system, the hot water supply system - increase the exergy efficiency of the steam supply system of an industrial enterprise by 0.2-0.6 % in the case of joining on the steam side of secondary boiling. Any processes of generating electrical energy are associated with obtaining a significant amount of thermal energy, and must be accompanied by its utilization; enterprises that use steam as an energy carrier (the same applies to energy enterprises such as thermal power plants and nuclear power plants) for the deep utilization of hydroelectric power plants must have thermal energy consumers in their composition, which can act as communal household consumers (if they exist), as well as new technological consumers of thermal energy.

Determination of the circulation flow rate in the calculation of internal hot water supply networks

Calculations of internal ring networks of buildings have always been, are and will be an urgent task. The schemes of internal hot water supply systems change, the number of floors of buildings changes, the location of heating points from which hot water begins its journey to the consumer changes, the definition of water consumption changes, and finally the calculations themselves change, but it is undoubtedly the calculation methods for centralised hot water supply systems that are a key part of creating reliable and economical hot water supply networks in buildings. Modern methods consist of three different calculations: the supply part of the system, the circulation part with the determination of pressure losses in the entire system, and the thermal disinfection mode of the system. The circulation flow rate methodology widely used in Ukraine is based on a 1985 regulatory document and borrowed part of the calculation from the 1992 Polish regulations. As a result, questions arise that are not answered in the DBN. In terms of determining the heat losses of individual sections of the hot water system, not everything is perfect either. A building is designed for a lifespan of 50 years or more with daily, round-the-clock use of heat energy, and the heat consumption for preparation and transportation of hot water is the largest in the building and requires a detailed calculation. The DBN "Internal Water Supply and Sewerage" provides two figures for all cases: 11 and 7 W/m (specific heat losses by pipes of the internal hot water supply network). The calculated surface temperature of the pipes in different parts of the network varies, the air temperature in the premises through which the pipes pass varies, and the diameters of the pipes in certain areas change, but the two figures remain unchanged. Moreover, it is recommended that, regardless of the insulation material used for pipe insulation, the insulation thickness should be at least 10 mm. This may have been appropriate in 1985, when there were no computer programs for calculations and fewer thermal insulation materials, but now it is 2023 and the situation is completely different. The article, after analysing the regulatory documents, proposes a methodology for determining the circulation flow rate and calculating the hot water supply network in the mode of passing this flow rate.

Strategies for integral rehabilitation and improvement of the energy efficiency of Lagos Park building in Madrid

As a primary goal, Inadequate energy consumption and outdated construction systems are causing financial losses for homeowners. Spain’s failure to meet European guidelines on CO2 emissions highlights the urgent need to address the energy inefficiency of buildings, responsible for 40% of such emissions. This article presents a comprehensive refurbishment project undertaken in the Lagos Park residential building in Madrid. The paper offers a detailed analysis of common building issues related to excessive humidity in the surrounding areas and deficiencies in the energy performance of the building envelope, including facades and roofs. Precise measures for achieving compliance with the Spanish Technical Building Code (CTE), as well as enhancing energy efficiency and functionality, are explained through the renovation of the building envelopes. The study also encompasses improvements made to the domestic hot water supply systems and the air-conditioning system, which contribute to the building’s attainment of an optimal energy rating (energy Class A). The extensive renovation undertaken in the complex has transformed Lagos Park homes into “zero energy consumption” residences. The strategies employed, ranging from electrical appliances to the house’s structural design, are all geared towards maximizing energy usage efficiency, resulting in significantly reduced monthly electricity bills by 65%–75%.

Determination of Corrosion Rate in Galvanized Pipes in Centralized Hot Water Supply Systems

To counteract possible corrosion, steel pipes are coated with a protective layer of zinc with a thickness of 20 to 85 microns, depending on the requirements of regulatory documentation. It is proven that hot-deposited zinc can effectively protect steel surfaces for 20 to 120 years. However, in centralized hot water supply (CHWS) systems, the period of protective action can decrease to two to three years, with further damage to the zinc layer and the appearance of fistulas. In order to counteract adverse factors, it is necessary to take into account the operating mode and design features of the system, the properties of the coating, and the environment in which the pipes operate. In this article, the main attention is paid to the study of the behavior of zinc coating. The protective properties and corrosion rate of zinc coating in tap water were evaluated. It was established that the protective effect of zinc is effectively manifested in the ratio of the protected area to the unprotected, as SZn/SFe ≥ 9:1. The influence of iron-containing sediment, when it accumulates in the pipes of a CHWS system, on the corrosion rate of the zinc coating was studied. It was also noted that the corrosion rates of the new zinc coating and uncoated steel pipe measured in short-term tests differed slightly.

INCREASING THE EFFICIENCY OF HEAT PUMP USING CIRCULATING WATER OF POWER PLANTS

In the article analytical studies of the efficiency of heat pumps in the thermal schemes of thermal and nuclear power plants for centralized heating and hot water supply systems taking into account the climatic conditions of Ukraine have been carried out. This task meets the objectives of energy saving and reduces emissions of harmful substances into the environment. The main focus is on improving the efficiency of the heat pump power supply system, which integrates an alternative energy source. An analysis of the exergy parameters of heat pump cycles has been performed, which have made it possible to establish that the most efficient working fluid of the cycle is freon R152a, at which the highest heat pump conversion coefficient and the lowest compressor power indicator are achieved. Ways and methods leading to reduction to underproduction of the electricity by turbine of of power plant and to increasation of the efficiency of a steam turbine cycle are proposed. It is shown that the efficiency of the system is most affected by losses in the evaporator, so the efficiency of this element of the heat pump should be given the most attention when using the energy of circulating water. An additional aspect of the novelty of the proposed method lies in the possibility of further optimization of the technical and economic parameters of the power system. A methodology based on the use of the exergy method of analysis to substantiate the conditions for the rational use of heat pumps for power plants in the utilization of low-grade heat of circulating water for cooling the turbine condensers is proposed, which can be considered as innovative way. Results open the further prospects for the development of heat pump heat supplyhas been proposed.

Sustainable solutions for healthcare facilities: examining the viability of solar energy systems

The healthcare sector is responsible for a significant portion of global carbon dioxide emissions, accounting for approximately 5% of the total. As energy demand in the sector continues to rise, sustainable solutions are urgently needed. Hospitals and healthcare facilities require a range of engineering services, including heat ventilation and air conditioning systems, hot and domestic water supply systems, and backup electricity systems. These energy-intensive services offer an excellent opportunity to integrate renewable energy sources and reduce the carbon footprint of healthcare facilities. This study presents a case study of a hospital located in the Gulf Cooperation Council (GCC) that utilizes a solar-collected water-heated system. The research aims to investigate the impact of adding multi-solar collector and photovoltaic systems to healthcare facilities, analyze the system’s thermodynamic efficiency in terms of energy and exergy, assess its technical and economic viability, and gauge the adoption rate of solar systems by healthcare technical departments. The results demonstrate that the solar thermal system provides around 12% of the total energy needed for the hot water system, while the solar PV system contributes approximately 29.6% of the total load for the HVAC system. This study explores the potential of using solar energy systems in healthcare facilities in the GCC region, analyzing their technical, thermodynamic, and economic viability. It promotes the adoption of solar systems in GCC and Middle East healthcare facilities and identifies research gaps related to solar systems implementation in healthcare facilities in the GCC. The study highlights the potential benefits of solar energy systems in terms of energy efficiency, cost savings, and environmental sustainability, with implications for healthcare facilities in the region and beyond. By utilizing renewable energy in healthcare facilities, the sector can reduce its carbon footprint and contribute to a more sustainable future.