Independent Heating Systems Research Articles

RECONSTRUCTION OF HEATING SYSTEMS IN RESIDENTIAL BUILDINGS WHILE MAINTAINING EXISTING HEAT SOURCES

The purpose of the article is to substantiate the need for real reconstruction of single-pipe vertical centralized heating systems, which are operated in most multi-story residential buildings in Ukraine, into apartment horizontal systems. The paper presents the main design shortcomings of heating systems in residential buildings built in the second half of the 20th century. The feasibility of using horizontal apartment systems is substantiated. For the first time, the heating system was reconstructed during the heating season without displacing residents and without stopping the existing heating system. A technical solution is proposed for supplying heat to apartments from an existing individual heating station with an elevator without its reconstruction. The article presents the results of a number of studies aimed at improving the heating system and determining the indicators of its economic and energy efficiency. Installation work can be carried out selectively in any number of apartments, and "old" and "new" heating systems can operate in parallel. The methodology for the reconstruction of heating systems presented in this paper can be used in the process of post-war restoration of the destroyed infrastructure of the housing stock of Ukraine. Modernizing in-building systems while maintaining the existing heat source is much cheaper than decentralizing heat supply by installing independent heating systems with a gas boiler in each apartment. The main conclusions of the article include that the reconstruction of existing heating systems is an objective necessity, without which the subscriber's influence on his heat consumption is impossible. The modernization described in this article is dictated by all the regulatory deadlines for major repairs of heating systems, which in most cases are more than twice as long.

Hydraulic and thermal stability of independent systems of apartment heating

Introduction. Individual apartment heating has been used in the Russian Federation since 1998. More than two million wall-mounted gas boilers were installed in the apartments of apartment buildings, 99 percent of which are wall-mounted double-circuit convection boilers with atmospheric burners. Their hydraulic and thermal stability is a requirement of the current standards for the design of heating systems. The heat generator of independent heating systems is part of a single circulation circuit; it has its own hydraulic resistance. The circulation of coolant and transfer of thermal energy through the pipelines to heating appliances is performed by the circulation pump. Stability of an independent heating system, in contrast to the centralized one, depends on the regulatory parameters of energy supply (pressure, calorific value of gas, voltage of the electric network).
 Materials and methods. The authors studied the thermal capacity parameters of the gas burner and the circulation pump within the framework of current standards of variable supply of energy resources and their influence on the hydraulic and thermal stability of systems.
 Results. Quantitative results of the studied parameters were obtained. The authors identified the coefficient of heat power generation depending on gas pressure, range of pressure change and flow characteristics of circulation pumps, wall boiler hydraulic resistance, influence of thermostatic valves of heating appliances and the use of antifreezes.
 Conclusion. An independent heating system differs from a centralized one in that a heat generator and a circulation pump are its integral parts. The operating parameters of independent heating systems depend on standard parameters of energy resources supply. Hydraulic resistance does not determine thermal stability. When calculating the hydraulic resistance of the heating circuit, it is necessary to take into account the hydraulic resistance of the gas boiler. Thermal heads on heating appliances and antifreezes in the system of independent apartment heating contradict the concept of hydraulic stability of the heating circuit. Thermal stability of an apartment heating system should be checked taking into account the algorithms of the heat generator performance.

Design and Development of the Novel Electrothermal Wall-Hanging Boiler

Background: With the rapid development of the domestic, independent heating system, the wall-hanging boiler has become the focus of concern for a large number of users. As an independent heat source, it has been widely applied in many places. Objective: Based on many deficiencies emerging from the wall-hanging gas boiler used at present, a novel electrothermal wall-hanging boiler is presented in this paper to realize the family central heating and provide constant temperature water supply system in the meantime. Method: 3D solid model of the wall-hanging boiler was firstly designed by using the software Solidworks, and then, based on ARM intelligent microcontroller, the circuit board production was completed with the corresponding control circuit design to conduct the automatic temperature regulation of the wall-hanging boiler, so as to achieve the desired effect of the constant temperature heating and energy conservation. Results: On the basis of the experiments and the test of sample, the trial operation of the prototype can meet the expected requirements. The greatest innovation of the product is to use a new type of nano semiconductor material and a sort of hydrocyclone mode to enhance the heat exchange in a more full and uniform way, as well as improve the thermal efficiency greatly. Conclusion: Such patent provides an effective theoretical and experimental basis for the diagnosis and fixing of the electrothermal wall-hanging boiler. With the help of the prototyping fabrication and debugging installation, it can be shown that the novel electrothermal wall-hanging boiler will have a very broad application prospect.

Energy efficiency of buildings in the cities of Ukraine under the conditions of sustainable development of centralized heat supply systems

In the current economic situation in Ukraine, the operation of heat supply systems occurs at a reduced temperature of circuit water. The increased temperature graph of 95/70 °C due to the high cost of fuel is impractical. The experience of such countries as Denmark, Germany, Finland, Sweden and Holland with developed centralized heat supply indicates the need for the first-class equipment of an individual heating point (IHP) of a building with an automatic control system, and then the transition to technology with a reduced temperature graph is carried out. Therefore, the modernization of heat supply systems in Ukraine aimed at the use of a reduced temperature graph will require a transition to closed independent heating systems, to qualitative and quantitative regulation and to automation of consumer IHP systems. A lot of district heating systems in Poland also require modernization to meet the requirements of the European Directive EED 2018/2002. This paper presents the results of numerical study of the influence of design and operating parameters of the heat supply network on the choice of the optimal temperature and flow- rate of circuit water of a distric heating system (DHS).

The enhanced plate heat exchanger for systems of housing and communal services

The problem of intensification of thermal processes and the process of heat exchange in a plate heat exchanger of the HHN02 type is considered. A comparison is made of two types of heat exchangers - shell-and-tube and plate. The formulas for calculating heat transfer and heat transfer coefficients are presented. The analysis of theoretical studies on the intensification of heat transfer in a plate heat exchanger with a corrugated surface of the plates is carried out. A full-scale experiment was carried out on a specially designed semi-industrial stand “Independent heating system of a residential building”. It has been found that the use of a corrugated surface is capable of providing a high value of the heat transfer coefficient. It has thus confirmed the advantages of the plate heat exchanger in comparison with the shell-and-tube.

A field investigation on the winter thermal comfort of residents in rural houses at different latitudes of northeast severe cold regions, China

The severely cold regions of Northeast have a colder climate and large latitude span in China. Scholars should pay more attention to the creation of a comfortable indoor thermal environment in winter. In order to understand indoor thermal environments and residents’ thermal comfort statuses in areas at different latitudes, a field survey was conducted in three areas: Harbin (45°N), Changchun (43°N) and Shenyang (41°N). On-site environmental parameter measurements and a subjective questionnaire were conducted simultaneously. Then, the relation between operative temperature and building energy consumption was explored. The results showed that the neutral operative temperature is the highest in Harbin (16.8 °C), followed by Changchun (16.4 °C) and Shenyang (16.0 °C), which are all higher than the measured temperatures. For these regions, 90% of the acceptable temperature ranges are 14.6–19.1 °C, 14.4–18.6 °C and 13.9–18.2 °C, respectively. The expected operative temperatures are 18.6 °C, 17.8 °C and 17.3 °C higher than the neutral temperature, respectively. This reveals that as the latitude increases, the neutral temperature, the upper and lower limits of the acceptable range and the expected temperature are all increased. For different ages, the youth have a higher requirement in terms of thermal comfort, followed by the middle-aged and elderly groups. Compare to males, females feel colder under the same operative temperature. Due to the independent heating system in rural houses, adjusting the heat supply, instead of clothing, is the main adaptive behavior. Regarding building energy consumption, as the latitude declines, the influence of changes in operative temperature increases. If both the regional neutral temperature and zoning heating mode are adopted, energy consumption further decreases. These findings provide a reference for the development of an evaluation standard for indoor thermal environments and an energy-saving design for rural houses in the northeast severe cold regions of China.

Optimization of the Parameters of the Heat Network Under a Reduced Temperature Schedule

The economic and environmental problems of Ukraine lead to decrease the water temperature in heat supply systems. Increasing the cost of fuel made it inappropriate to schedule temperature 95/70. To switch to a lower temperature schedule, at first it is necessary to ensure the automation of the regulation of individual heat points. Only after that it is possible to use reduced temperature schedules. This is confirmed by the successful experience of countries where central heating is widely used: Denmark, Germany, Finland, Sweden, Holland, etc. Modernization of the heat supply systems of Ukraine should go through transition to independent heating systems with qualitative and quantitative regulation, after which the temperature schedule can be reduced to appropriate values. A numerical study of the optimal temperature and water flow in the heat network depending on the design and operating parameters has been carried out. In addition, the results of field studies of the heating characteristics of residential buildings and administrative buildings, the heat supply of which is carried out from two big sources of Kharkov, were used. The entropy production in the heat supply system is numerically determined depending on the design and operating parameters. As a result of the computational experiment, when using entropy production as an optimization criterion, the parameters of the reduced temperature schedule of the heat supply system for the conditions of Kharkiv were determined and substantiated. The results of the numerical study show that the parameters of the heat network at maximum heat load and outdoor air temperature (-25 °C) are as follows: the temperature of the supply network water is 76.7 °C; heat carrier flow rate is 5.7 kg/s, velocityis 0.73 m/s, specific pressure loss is 85.3 Pa/m, specific consumption of electric power to transport the heat carrier is 0.81 W/m, specific heat loss is 33.8 W/m.

EQUALIZATION OF HEAT-TRANSFER AGENT TEMPERATURE EXPANSION IN HEATING SYSTEM WITH THE USE OF REGULATING AND SAFETY VALVES

The scheme of equalization of heat-transfer agent temperature expansion in independent heating system without temperature tank is viewed. To equalize heat-transfer agent temperature expansion regulating and safety valves are used in this scheme instead of temperature tank. The valves provide heat supply and heat rejection in- and out of heating system. The proposed scheme permits to equalize heat-transfer agent temperature expansion in heating systems with a large amount of heattransfer agent and with minimal capital cost.

Caesium oven design and R&D for the SPIDER beam source

In the ITER neutral beam injectors caesium will be used in the negative ion source to enhance the ion yield, by lowering the surface work function, and to reduce the co-extracted electrons. Fresh Cs has to be deposited almost continuously inside the plasma source and its injection is obtained by means of Cs ovens.Three independent Cs ovens have been integrated in the SPIDER (Source for Production of Ion of Deuterium Extracted from Rf plasma) beam source (BS). Since the entire BS is in-vacuum, a completely new design of the Cs ovens was required, assuring their vacuum and high temperature compatibility, and remote operation. They feature an ON–OFF valve and two independent heating systems to control the Cs evaporation and to avoid vapour condensing on the injection duct, by controlling the temperature. A Cs level indicator to measure the quantity of liquid caesium inside the reservoir, based on the electric resistance variation of an electrode, is proposed for the first time and a proof of concept is given.The oven design and the R&D activity on the level measurement system are presented.

Highly enhanced migration in Pt‐catalyst‐assisted MOVPE InN by controlling the catalyst temperature

AbstractThis paper reports on the catalyst‐assisted metal‐organic vapor phase epitaxy (CA‐MOVPE) growth of InN with an independent control of catalyst temperature. When the catalyst temperature is increased above the growth temperature of InN, the grain size becomes large and full width at half maximum (FWHM) of X‐ray rocking curve (XRC) is drastically decreased The migration of precursors is highly enhanced and the crystal quality is improved by CA‐MOVPE with an independent heating system of the catalyst. This CA‐MOVPE system will open the possibility of the growth of high‐quality InN and In containing alloys especially with the higher In content (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Supply and Demand of a Forest Biomass in Application to the Region of South-East Finland

In Finland it is estimated that forest biomass will be the main source of bioenergy when meeting the national target: 38% renewable from total energy consumption by 2020. This target must become concrete for regional and local level participators of a forest industry and actions should take place in large combined heat and power generation (CHP) plants, district heating plants and independent heating systems. In energy production replacing fossil fuels with renewa-ble energy is reasonable in many cases. However, there are usually doubts about the availability and security of supply of forest biomass. The aim of this study is to introduce a systematical method for analyzing the availability and demand of forest biomass in regional and local level. This study introduces an objective method for analyzing local possibilities on where and how much the use of forest biomass could be increased. By replacing use of fossil fuels with renewable and domestic energy sources carbon dioxide (CO2) emissions and dependency on imported fossil fuels can be reduced. Utilization of biomass creates also local employment on energy sector.

Efficiency Analysis of Independent and Centralized Heating Systems for Residential Buildings in Northern Italy

The primary energy consumption in residential buildings is determined by the envelope thermal characteristics, air change, outside climatic data, users’ behaviour and the adopted heating system and its control. The new Italian regulations strongly suggest the installation of centralized boilers in renovated buildings with more than four apartments. This work aims to investigate the differences in primary energy consumption and efficiency among several independent and centralized heating systems installed in Northern Italy. The analysis is carried out through the following approach: firstly building heating loads are evaluated using the software TRNSYS® and, then, heating system performances are estimated through a simplified model based on the European Standard EN 15316. Several heating systems have been analyzed, evaluating: independent and centralized configurations, condensing and traditional boilers, radiator and radiant floor emitters and solar plant integration. The heating systems are applied to four buildings dating back to 2010, 2006, 1960s and 1930s. All the combinations of heating systems and buildings are analyzed in detail, evaluating efficiency and primary energy consumption. In most of the cases the choice between centralized and independent heating systems has minor effects on primary energy consumption, less than 3%: the introduction of condensing technology and the integration with solar heating plant can reduce energy consumption by 11% and 29%, respectively.

Legionella waterline colonization: detection of Legionella species in domestic, hotel and hospital hot water systems

An evaluation was made of the prevalence of Legionella species in hot water distribution systems in the city of Bologna (Italy) and their possible association with bacterial contamination (total counts and Pseudomonadaceae) and the chemical characteristics of the water (pH, Ca, Mg, Fe, Mn, Cu, Zn and Total Organic Carbon, TOC). A total of 137 hot water samples were analysed: 59 from the same number of private apartments, 46 from 11 hotels and 32 from five hospitals, all using the same water supply. Legionella species were detected in 40.0% of the distribution systems, L. pneumophila in 33.3%. The highest colonization was found in the hot water systems of hospitals (93.7% of samples positive for L. pneumophila, geometric mean: 2.4 x 10(3) CFU l(-1)), followed by the hotels (60.9%, geometric mean: 127.3 CFU l(-1)) and the apartments with centralized heating (41.9%, geometric mean: 30.5 CFU l(-1)). The apartments with independent heating systems showed a lower level of colonization (3.6% for Legionella species), with no evidence of L. pneumophila. Correlation analysis suggests that copper exerts an inhibiting action, while the TOC tends to favour the development of L. pneumophila. No statistically significant association was seen with Pseudomonadaceae, which were found at lower water temperatures than legionellae and in individual distribution points rather than in the whole network. The water recirculation system used by centralized boilers enhances the spreading of legionellae throughout the whole network, both in terms of the number of colonized sites and in terms of CFU count. Differences in Legionella colonization between types of buildings are not due to a variation in water supply but to other factors. Besides the importance of water recirculation, the study demonstrates the inhibiting action of copper and the favourable action of TOC on the development of L. pneumophila.

Efficiency gains in Danish district heating. Is there anything to learn from benchmarking?

Facing a market structure of independent heating systems and cost-of-service regulation the regulator considers ways to create incentives for increasing efficiency in heat production. One way is to implement benchmark regulation. The aim of this paper is twofold: (1) To investigate the potential for increasing productivity in Danish district heating production and (2) to examine whether benchmarking has a role to play. Using data envelopment analysis our analyses show that by assuming variable returns to scale a potential exists to reduce production costs by 5–27% depending on the portfolio of inputs and outputs included in the model. Further, our analyses show that the ranking of producers is much dependent on the combination of inputs and outputs included in the model. Therefore, great care should be taken when deciding on the appropriate model to be used when implementing benchmarking as a regulatory mean.

Improved supercritical fluid chromatography-ion mobility spectrometry interface

This article describes the construction and performance of a restrictor . heater for interfacing an ion mobility detector IMD to a supercritical fluid chromatograph. In this interface design, an independent heating system controlled . the temperature of the supercritical fluid chromatography SFC column restrictor up to 3258C. The performance of this direct SFC)IMD interface was evaluated by separating and detecting test compounds that do not contain chromophore groups and cannot be detected by UVrvisible detection methods. Polydimethylsilicone .PDMS oligomers with molecular weights larger than 4000 amu were efficiently separated and detected when the restrictor was heated to 3258C. Overall detector sensitivity and chromatographic resolution were improved with the novel interface. Q 1999 John Wiley & Sons, Inc. J Micro Sep 11: 251)257, 1999