The use of the interaction of convex wall jets for ventilation with variable air flow

The most energy efficient ventilation and air-conditioning is variable air flow (VAV) depending on the needs of a room. To avoid broken air circulation by gravitational forces, the most of air diffusers should change geometrical shape and sizes using additionall automation of them. In contrast, high stability of a scheme of air exchange organization with air supply over a working zone by convex wall jets that interact with each other under conditions of variable air flow, is confirmed. This scheme is useful in cases where it is impossible to supply air directly to the working zone. Simulation of the air exchange organization in an exhibition hall of International Exhibition Centre in Kyiv with ventilation at a variable air volume (VAV) in the entire possible range of performance control has been performed. The floor area is 5258 m2, the height is 19 m. The outdoor air-flow at design conditions (100 % load) is 21.667 m3/s (78000 m3/h). The minimum load corresponds to the absence of solar radiation and only some people in the room. The minimum air-flow is 25 % of the design one. The proposal air scheme is single-zonal using 24 diffusers PES-D-8-10/15-0,9 4 m above the floor and air removal from the upper zone. The air distributor have a diameter of a cylindrical surface and an inlet branch pipe of 8 dm (800 mm). There are 10 rows of nozzles at an angle π/12 (15 °) to the horizon on each distributor. The total area of the air outlet on them is equal to 0.9 of the cross-sectional area of the inlet pipes. Due to forces of the vacuum holding of jets on the wall surfaces, the influence of gravitational forces is significantly reduced. This avoids the automation of air distribution devices to stabilize the scheme of air circulation in the room by gravitational forces. It is enough to install valves with actuators on branches of a network of air ducts. Thus, the economic benefit of the system is confirmed both at the stage of installing and during operation.

Improvement of the indoor air environment using phytodesign by phytoncidal plants

The main problem of closed rooms is air pollution with chemical compounds, dust, anthropotoxins and pathogens. Solving this problem with the help of technical and engineering technologies is not always effective, since it requires a lot of time and significant capital investments. The technology of phytodesign by phytoncidal plants is proposed. The purpose of the work is to optimize the air environment by an example of the winter garden in Kiev National University of Construction and Architecture using phytodesign by phytoncidal plants. Objectives of the work: to examine the assortment of plants in the winter garden; to assess whether the number of plants is sufficient for sanitation of the air environment of the premises with an area of ​​930 m2; analyze the shortcomings of the range of phytoncidal plants; to develop proposals for the phytodesign of a winter garden to improve the quality of the air environment. It was found that the existing number of phytoncidal plants (18 pieces) for effective sanitation of the air in the investigated room is insufficient. Their decorative effect is reduced due to some disadvantages of care. It’s one of the reasons for a decrease in the growth of vegetative mass and the production of phytoncides. For effective air sanitation of the area of the investigated room, 310 specimens of large-sized phytoncidal plants are required. To expand the assortment, the following phytoncidal species are offered: Aglaonema, Anthúrium Aspidistra elatior, Begonia Chlorophytum, Dracena marginata, Ficus benjamina Wiandi, Hedera, Kalanchoe, Nolina, Philodendron, Spatifillum, Scindapsus, Sansevieria, Eucevieriaceae, plants of the families Euphorbiaceae, Orchidáceae, Bromeliaceae. Green phytoncidal zones can also be expanded by introducing "green" structures.

Experimental studies of burning plant pellets in a domestic boiler

In recent years, biofuels have increasingly been used as fuel in Ukraine. Ukraine is an agro-industrial country with great potential for the production and use of pellets of plant origin. Our country ranks 6th in the world for the production of such biofuels as pellets, but most of them (about 85 %) are exported abroad. This is due to the low demand for pellets in the domestic market. Cereal straw can be used in municipal energy. The amount of straw left after harvest is sufficient for its use as fuel. This biofuel in its composition and calorific value is close to such traditional fuels as wood and peat. Also, raw materials for bio-pellets can be sunflower husks and energy crops. The main objectives of this work are experimental studies of the combustion of different types of agropellets. An experimental installation of a solid fuel boiler with a pellet burner was developed and implemented at the Institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine to study the peculiarities of pellet combustion. With the help of the developed measurement system based on a comb with thermocouples, which is located above the torch in the boiler, the temperature regime in the boiler volume was studied and the peculiarities of the pellet burning process in the burner were determined. As a result of the work, experimental studies of the peculiarities of burning pellets of agricultural origin, namely straw (barley, wheat) and pellets from corn cobs were carried out. On the basis of the constructed graphic dependences the characteristic features of temperature modes of work of a household copper at burning of agropellets were defined. The use of the results is possible in the communal and industrial heat energy, social and budgetary sphere and individual household sector.

An analysis of effectiveness of air heat pump operation dependent on change of external air temperature

Currently, air-to-water heat pumps are more widely used, which due to the high coefficient of performance reduce energy consumption and negative impact on the environment. They decrease the dependency on costs of energy resources. The work is devoted to solving the urgent problem of improving the efficiency of air heat pumps at low temperature of outdoor air in winter. One of the main problems of an air heat pump is the reduction of productivity when the outdoor air temperature decreases in winter. In this paper, the effectiveness of LG Therma V air-to-water heat pump to provide apartments with heating and hot water supply was analyzed. The heat pump is reversive, which can cool or heat a heat carrier. A four-way valve swithes the coolant flows between air exchangers. On the basis of the obtained results, plots of effectivness of the heat pump dependent on outdoor air temperature are built. It is shown that the effectiveness of the heat pump significantly depends not only on the outside temperature but also on the water temperature at the outlet of the heat pump. The use of heat pumps with a high coefficient of performance can significantly reduce energy costs. The most effective are low-temperature heating systems, in which the water temperature does not exceed 45 °C. The example is floor heating, which requires very low temperature of the floor surface – up to 30 °C. At outdoor air temperature not less than milnus 7 °C the heat pump is effective at higher temperature off heat carrier at output – up to 55 °C. To provide the uninterrupted heat supply, an additional air heater is included. It covers heat load during defrosting and very low outdoor air temperature. On the basis of the conducted researches, the directions of the further experimental and field researches are planned.

Analysis of Polish norms on thermal resistance and thermal comfort for underfloor heating

In the paper, there is an analysis of the requirements for the thermal resistance of floors with underfloor heating. It corresponds to the human physiology as much as possible, creates comfortable conditions at a lower temperature of the internal air, reduces the rise of dust by reducing convective flows, allows the use of low-grade heat carriers, especially from secondary and renewable energy resources, does not take up space in the room, minimally affects the interior. However, the temperature of the heating elements is significantly higher than the room temperature. At the same time, the requirements for thermal insulation under the heating elements should be higher than for structures without heating. As the analysis of the regulations in force in Poland has shown, this is not always observed. In many cases, the heat transfer resistance is lower by 42-181 %. The percentage difference in requirements for flooers over aisles in rooms with an air temperature of 16 °C and above is 160%. It will reach 215 %, according to the requirements that will be applied from 2021. In the case of floors over unheated rooms, the percentage difference between the requirements reaches 181 %. By the new norms in 2021, this difference will reach 215 %. Also, the normative limitation on the temperature of the floor surface does not always allow providing the normative level of comfort. In rooms of categories A and B, the surface temperature of the floor must be 20-28 °C. In the case of category C it should not exceed 30 °C. The most favorable conditions are achieved when the floor surface temperature is close to 23.5 °C. PN-EN 1264-4 standard allows the temperature of the floor surface in some rooms up to 33...35 °C. Thus, to ensure energy efficiency and comfort, it is necessary to harmonize the regulations with each other.

Energy efficient optimization of heat supply system for oil therminal

In the context of the need to develop the transport infrastructure of Ukraine and to diversify sources of energy carriers supply to the country, including oil and oil products, the problem of the development of oil terminals arises. This work is devoted to the optimization of the structure of heat supply to oil terminals. In this sense it is relevant. The object of research is the heat supply systems of an oil terminal. At the same time, the subject of research is the energy efficiency of heat supply systems for oil terminals using water vapor and high-temperature organic heat carriers. The following research methods were used: an analytical review of information sources, a technical and economic analysis with the necessary substantiating calculations. As a result of the studies, the possibility of using high-temperature organic heat carriers for organizing heat supply to oil terminals has been shown. The advantage in the efficiency, environmental friendliness and reliability of systems with high-temperature organic heat carriers versus systems using water vapor as a heat carrier is shown. On-site heating networks in the oil terminal are recommended. The main advantages are that the heat losses in them have been reduced and the reliability of the system has increased. The cost estimation of capital investments of the compared variants of the heat supply system arrangement is carried out. The centralized heat supply systems have greater equipment cost compared with the decentralized ones. The operating cost for decentralized systems is also lower due to a decrease in specific fuel and electricity consumption. The materials obtained as a result of the research can be used as recommendations for the design of heat supply systems for oil terminals using high-temperature organic heat carriers.

Air distribution in convex wall jets for ventilation with a constant air flow

The scheme of air exchange organization using air supply above a working zone by convex wall jets that interact with each other has been substantiated. This scheme is advisable in cases where it is impossible to supply air directly to the working zone. It provides optimal microclimate parameters with minimal recirculation of polluted air from the upper zone. Simulation of the air exchange organization in an exhibition hall in International Exhibition Centre in Kyiv with ventilation at a constant air volume (CAV) has been performed. The floor area is 5258 m2, the height is 19 m, the minimum outdoor air flow is 21.667 m3/s (78000 m3/h). The current design scheme of air exchange organization is zonal. General air exchange is 43.3333 m3/s (156000 m3/h). Recirculation is accepted 50 %. The air flow supplied in the upper and middle zones is, respectively, 22.5 m3/s (81000 m3/h) and 20.833 m3/s (75000 m3/h). Inlet air has temperature 291.65 K (18.5 °C). It is supplied downward by twisted jets. There are 65 Trox VDL-AHLD-E3/800/0/0/0/RAL 9010 air diffusers with a diameter of 800 mm. The proposed scheme is single-zonal using 24 diffusers PES-D-8-10/15-0,9 4 m above the floor and air removal from the upper zone. This scheme allows halving the air exchange to the minimum outdoor air without recirculation. The air temperature should be decreased by 3.3 K to 288.35 K (15.2 °С). The number of air-conditioners is decreased twice. The calculated consumption of cold decreased by 65.58 W/m2 or 29 %, the calculated consumption of heat for the second heating – by 7.17 W/m2 or 18 %. Saving of capital investments in prices of February 2020 is 792.16 UAH/m2 or 55 %, and decrease of operating costs for the cooling period is 6.61 UAH/m2 or 15 %. Thus, the system is economically beneficial from the beginning of its installation. In the future, its operation will be simulated in a mode with a variable flow rate.

Energy efficient modernization of KVG and TGV boilers

At present, the district heating systems of Ukrainian cities are in a critical state. They need significant modernization. This especially applies to very important components of district heating systems – heating water boilers. Unsatisfactory condition of boilers is mainly due to the obsolescence of basic equipment, including boilers. The operating time of them exceeds the passport lifetime. There ia a lack of modern automation, especially in terms of controlling operating modes. Nominal power of them exceeds the real heat loads. The range of hot water boilers used is not large. These are low-power boilers of the series NDIST, "Universal", "Energiia", "Fakel" and others, medium-power boilers of the series TVG and KVG and high-power boilers of series PTVM and KVGM. According to their prevalence, special attention should be paid to boilers of the series TVG and KVG. The series are installed on quarter boiler houses. The boilers of these series have an efficient design of the furnace volume and an optimized design of the convective part. Nevertheless, in terms of automation, gas supply and air supply systems, they no longer meet today's requirements. They are outdated comparing to the achieved level of technical solutions. The article discusses the main shortcomings of the design of boilers: insufficient durability of the gas collector in the hearth burner, small diameter of the pipes of the convective part and the use of fireclay materials in the setting of the burners. The first two shortcomings were overcome by the developers by the increase in the diameter of the pipes of convective packages and the modernization of MPIG-3 hearth burners. The third shortcoming should be overcomed by replacing the setting with a modern one during off-season repairs. Reserves for improving the energy efficiency of boilers of these series are found. To do this, it is necessary to install additional convective heating surfaces (economizers or air-heaters), replace the setting and equip the boilers with a modern automation system with cascading the burners. It allows improving efficiency up to 94...95 % and environmental performance according to the modern requirements.

Feasibility study for the use of variable air volume systems for office buildings

The main factor contributing to greenhouse gas emissions is the building up of the surrounding area. Studies have shown that buildings globally consume 30-40 % of energy use and release 40-50 % of global carbon dioxide emissions. Among all systems in houses, heating, ventilation and air conditioning (HVAC) systems are by far the most energy intensive. They consume approximately 50 % of the total energy demand of buildings. However, the systems are some of the most important systems in today's buildings. The number of these systems that are being installed has increased dramatically over the past few years. This is mainly due to the increasing demands for thermal energy, comfort and climate change. This paper presents a feasibility and ecology study between two ventilation or air-conditioning systems: constant air volume (CAV) and variable air volume (VAV). One of the purposes of this work is to determine the energy costs for each of the systems. An air conditioning system that saves operating costs usually requires a large initial investment. In this case, engineers must decide whether it is worth paying the additional upfront costs for a system that has lower operating costs. Despite the low attractiveness from the point of view of the investor, the VAV systems reduce the amount of greenhouse gas emissions and the amount of energy resources for servicing the commercial sector. Such system have less metal consumption. Thus, the cost of metal processing is also reduced. The results of this study can contribute to the future selection of ventilation systems, as well as contribute to the design and improvement of the systems under study. Energy saving is one of the main reasons why VAV systems are very popular today for the design of ventilation and air conditioning systems for office buildings and in many industries abroad. With these systems, the volume of transported air is reduced as soon as the operating load falls below the maximum projected load. The calculation of emissions of harmful substances into the environment was made while ensuring the operation of CAV and VAV systems.

Experimental research of electrical characteristics combined solar-electric air heater

The development and improvement of solar equipment is a necessary step in the development of solar heating systems. One of the ways to develop solar air heaters is to use new materials for the production of solar absorbers. This expands the possibility of using nozzle and capillary-porous materials in contrast to liquid solar collectors. Development and research of air heating systems with equipment made of modern textile materials is relevant. For the manufacture of absorbers it is advisable to use textile materials. This will reduce the cost of solar collectors, as well as reduce their weight and capital costs. The absorber meets requirements for both solar thermal collectors and electric heaters: high absorption capacity of solar radiation; developed heat transfer surface; relevant physical properties: low mass, resistance to ultraviolet radiation, thermal resistance, low cost for cheaper solar system; sufficient electrical resistance. A combined solar-electric air heater has been developed, which combines two main elements of any solar system – a solar heat collector and an additional heat source, the absorber of which is made of carbon graphite knitted fabric. This reduces its cost and mass and allows them to be used on existing heating facilities without the construction of bulky supporting structures to accommodate solar fields. The combined solar-electric air heater can be used as an independent heat generator for heat supply systems. To use the proposed solar-electric air heater, it is necessary to heat its absorber with an electric current, so the material from which it is made must be electrically conductive, but have sufficient electrical resistance. The use of carbon-graphite knitted fabric allows the use the direct heating of the solar energy absorber by electric current due to the corresponding electrical characteristics. This article presents the results of an experimental study of the electrical resistivity of carbon-graphite knitted fabric. These studies allow determining the electrical power of the device regardless of the size of the device. The research results presented in the article can be used only for a certain type of carbon graphite knitted fabric.