Реферат на тему «Heating, ventilation, air Conditioning»

Introduction Throughout the history of mankind, along with the problems of providing food, issues related to the creation of comfortable conditions in the home were of paramount importance. At the same time, the dwelling was at the same time a refuge, which made it possible to hide from various dangers. The problems of maintaining certain temperature conditions acquired particular importance after a person began to build special structures for overnight stay and protection from the vagaries of the environment — wigwams, yurts, igloos, wooden and brick houses, as well as castles. It was necessary to maintain a certain temperature in them, mostly different from the ambient temperature, and also, if necessary, ensure the removal of combustion products from the dwelling. As society developed, human requirements for living and working conditions in enclosed spaces became more stringent and specific. Experience was accumulated and generalized, which made it possible to improve both the dwellings themselves and devices for heating / cooling them, for supplying water and removing waste products. Based on the experience of generations, conclusions were made and generalized, which ultimately formed the basis of the first sciences. On the basis of one of them — physics — disciplines have also developed that study the laws of converting heat into work and vice versa, as well as studying the problems of transfer of thermal energy, the flow of gases and liquids. Thus emerged and further developed as independent sciences of thermodynamics, heat transfer, hydraulics and gas dynamics. Ultimately, it was these disciplines that formed the basis of the subject “Heat and gas supply and ventilation with the basics of heat engineering”, which studies the issues of rational organization of heating and hot water supply, laying gas and heat networks, supplying gas to residential and industrial premises, as well as problems of ventilation and air conditioning . As an independent discipline, this branch of science was formed relatively recently. At present, the progress and development of theoretical sciences is accompanied by the improvement of used and designed generators and energy converters, which leads to an increase in their efficiency and a relative reduction in harmful emissions leading to pollution — toxic and thermal — of the environment. The creation and use of new materials and technologies makes it possible to reduce energy losses, speed up construction work and solve emerging environmental problems. For further improvement of heat and gas supply systems, as well as devices for maintaining comfortable conditions in the premises, it is necessary to master the basics of the discipline “Heat and gas supply and ventilation with the basics of heat engineering”.

Chapter 1.Basic definitions, terms

Thermal engineering studies the methods of obtaining, converting, transferring and using heat, as well as the principles of operation and design features of heat and steam generators, machines, apparatus and devices. Heat engineering includes three main parts: technical thermodynamics, heat transfer and heat engines (machines, apparatus and devices). The foundation of heat engineering is technical thermodynamics, which studies the patterns of mutual transformation of thermal and mechanical energy, the processes occurring in gases and vapors, as well as the properties of these bodies under various physical conditions. Basic laws of thermodynamics — the first and second. The first law (a special case of the universal law of conservation and transformation of energy (Helmholtz, 1847), stating that energy does not arise from nothing and does not disappear, but passes from one form to another, says: the heat supplied to the system is spent on changing it internal energy and the work done by it. The second law states that not all of the heat supplied is useful. The degree of use of the supplied heat determines the thermal efficiency. Building thermal physics considers the issues of heat transfer, air permeability and humidity regime (vapor permeability) of the building envelope in connection with the processes of heat and mass transfer due to the action of external climatic factors, internal sources and the operation of heating, ventilation or air conditioning systems. Heating is artificial heating of premises in order to compensate for heat losses in them and maintain a temperature at a given level, determined by the conditions of thermal comfort for people in the room or the requirements of the technological process taking place in it. Ventilation is a word of Latin origin means ventilation, according to construction terminology — natural or artificial controlled air exchange in rooms, ensuring the creation of an air environment in accordance with sanitary and hygienic and technological requirements. Air conditioning is giving the air certain specified parameters or creating and automatically maintaining indoor temperature, relative humidity, cleanliness, composition and speed of movement, air mobility, the most favorable for people’s well-being, conducting technological processes, operating equipment and instruments, storing materials, raw materials , finished products. Heat supply is providing heat with the help of hot water or steam to heat consumers for various purposes. Heat network is a set of devices, including pipes, thermal insulation, building structures, fittings, for transferring a coolant (in the form of hot water or steam) from a source of thermal energy to heat consumers. Sources of thermal energy (heat supply) is a set of devices for generating only thermal (boiler) or electrical and thermal (combined heat and power) energy. The totality of heat energy sources, heat networks and heat consumers represents the heat supply system.

Chapter 2. Overview .Heating, ventilation, and air conditioning (HVAC).

2.1.Heating, ventilation, and air conditioning (HVAC) is the use of various

technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. «Refrigeration» is sometimes added to the field’s abbreviation as HVAC&R or HVACR, or «ventilation» is dropped, as in HACR (as in the designation of HACR-rated circuit breakers). HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels, and senior living facilities; medium to large industrial and office buildings such as skyscrapers and hospitals; vehicles such as cars, trains, airplanes, ships and submarines; and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors. Ventilating or ventilation (the «V» in HVAC) is the process of exchanging or replacing air in any space to provide high indoor air quality which involves temperature control, oxygen replenishment, and removal of moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases. Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, and prevents stagnation of the interior air. Methods for ventilating a building are divided into mechanical/forced and natural types. The three major functions of heating, ventilation, and air conditioning are interrelated, especially with the need to provide thermal comfort and acceptable indoor air quality within reasonable installation, operation, and maintenance costs. HVAC systems can be used in both domestic and commercial environments. HVAC systems can provide ventilation, and maintain pressure relationships between spaces. The means of air delivery and removal from spaces is known as room air distribution.

2.2.Goals and objectives

The HVAC system is an important component in the development of industrial and administrative buildings, as well as pools where safe and comfortable conditions in terms of temperature and humidity are maintained with the help of outside air supply. It is an indispensable attribute of modern smart home. The main tasks of management microclimate (HVAC) is: • creation and maintenance of a microclimate comfortable for humans, plants, animals or material objects (equipment, works of art, etc.) within a building or structure; • saving energy spent on creating and maintaining a microclimate. It could be like living quartersand saloncar,spacecraftor other building or premises. Microclimate control is carried out using the following engineering systems: warm floor (electrica land water), radiators, fancoils, systems conditioning And ventilation,humidifiers And air dryers,ionizersetc. Therefore, for an integrated climate control system (“climate control”), it becomes necessary to ensure the coordinated management of all these devices. With the smooth operation of the microclimate control system, various elements of engineering systems should not conflict with each other within a given room or structure. When properly configured, the devices behave differently in different situations: with open and closed windows, in the presence or absence of people in the room, at different times of the day and days of the week (weekends and holidays / weekdays), depending on tariff changes for energy carriers, etc. In addition, in a modern building it is possible to remotely control the climate throughInternetorcellular telephone, or withcomputerdispatcher.

Chapter 3.Heating Systems

Depending on your geography, special consideration should be given to heating your new home. Important items to consider are energy costs, air quality and safety. Since it’s a costly installation to any new home it makes good economic sense to look carefully at energy efficiency. Heating alone can account for more than 40% of your household energy costs, for larger homes and families, it’s as high as 65%. The first thing you should do is find out how much heat will be required to adequately and efficiently heat your new home. The heating requirements or «heating load» (as industry professionals say) of a house depends on climate, size, and style of house; insulation levels; air tightness; amount of useful solar energy Source: www.thehousedesigners.com 79 through windows; amount of heat given off by lights and appliances; thermostat setting; and other operational factors. Together, these factors determine how much heat must be put into your home by the heating system over the annual heating season. To make it simple, this number (usually measured as BTU per year), should be determined by a competent heating contractor because it involves measuring the house (windows included), checking insulation levels, maybe even doing a blower door test, and running calculations to determine how much heat will be needed in the specific climate you live in. Once this is determined, it is up to you to decide the preferred heating system for your home and what you want it to run on. Oil, gas, wood and propane are a few options.

3.1.Types of Heat

Basically there are two ways in which you can have your home heated: radiant or convective heat. Radiant heaters heat the object rather than the air surrounding it, while convection heaters fill a room with warm air by transferring heat from one object to another using moving air or water. The design of your interior home will have a great impact on which form of heat is best for your home. For homes with large open spaces, open stairwells and high ceilings, radiant heaters work best, because they ensure that you and your family are warmed, not the open space surrounding you. If your home has lots of enclosed and well insulated rooms than convective heat, is the heat for you, because it’s very easy to control once you’ve had your home properly zoned. Central Heating vs. Space Heating. Before you decide whether you want central heating or space heating, you need to figure out which areas of your home you want to heat, how large the rooms are and how long you need to heat the rooms for. By creating zones in your home, you give yourself the flexibility to heat each zone individually, which is the key to energy efficiency. Whether you choose to use space heaters or a zone central heating system, both systems are preferred over using a whole house central heating system, because that system will heat every room in your home regardless of whether you using them or not.

3.2.Types of Heating Systems

All climate-control devices or systems have three basic components: a source of warmed or cooled air, a means of distributing the air to the rooms being heated or cooled, and a control used to regulate the system (e.g. thermostat). A variety of technologies are available for heating your house: • In a central heating system a furnace or boiler consumes the fuel (e.g. gas, oil, or electricity) that powers it. As fuel is burned, pipes take hot water to radiators. You get hot water at the same time as heating, depending on how you set the controls. • Electric heat pumps remove heat from outdoor air, ground, surface water or the earth and move heat from one place to another. They can also be used as air conditioners when the weather is warm. The thermostat will also include controls for air conditioning. • Radiant skirting board heaters are long, metal units with electrical elements inside. They are sometimes the only source of heat in a house, or they can be an extra heating device in cooler rooms. • Radiant ceiling or floor systems are installed in floors, ceilings or (occasionally) walls. They warm objects in much the same way as the sun does. • In hydronic heating a boiler warms the circulating water and hot water flows through tubes under the floor or through units that are similar to skirting board heaters. They can also be installed in ceilings. They are sometimes used under concrete in driveways to keep snow and ice from accumulating. • Portable space heaters are either freestanding or attached to a wall and work with electricity, gas or kerosene. Their area cannot be qualified as heated living space.

Chapter 4.Ventilation

Ventilation – the exchange of indoor air with outdoor air – is important to reduce indoor moisture, odours, and other pollutants. Contaminants such as volatile organic compounds, and radon (that may cause health problems) can accumulate in poorly ventilated homes. Excess moisture needs to be removed before high humidity levels lead to physical damage to the home. There are three main types of ventilation: • Natural ventilation which is uncontrolled air movement through cracks and small holes (infiltration) and through vents such as doors and windows. The disadvantage of this is that it is uncontrollable. • Spot ventilation which means using localised fans in the rooms where contaminant substances are generated (for example kitchen extractor fans and bath fans). • Whole-house ventilation is a system that works thanks to fan and duct systems to exhaust stale air and supply fresh air to the house. Whole-house ventilation systems are usually classified as exhaust ventilation when the air is forced out of the house, supply ventilation if it is forced inside and balanced ventilation if the same amount of air is forced inside and outside the house.

Сhapter 5. Air Conditioning

Air conditioning is the process of altering the properties of air (primarily temperature and humidity) to more comfortable conditions, typically with the aim of distributing the conditioned air to an occupied space to improve thermal comfort and indoor air quality. In common use, an air conditioner is a device that lowers the air temperature. The cooling is typically achieved through a refrigeration cycle, but sometimes evaporation or free cooling is used. Air conditioning systems can also be made based on desiccants. In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, cooling, humidification, cleaning, ventilation, or air movement). However, in construction, such a complete system of heating, ventilation, and air conditioning is referred to as HVAC. The basic concept behind air conditioning is said to have been applied in ancient Egypt, where reeds were hung in windows and were moistened with trickling water. The evaporation of water cooled the air blowing through the window. This process also made the air more humid, which can be beneficial in a dry desert climate. In Ancient Rome, water from aqueducts was circulated through the walls of certain houses to cool them. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool buildings during the hot season.http://en.wikipedia.org/wiki/Air_conditioning — cite_note-3 Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1902 by American inventor Willis Carrier. The introduction of residential air conditioning in the 1920s helped enable the great migration to the Sun Belt in the United States. Air-conditioning is the bringing of air in a building to a desired temperature, purity, and humidity throughout the year to maintain healthy Air conditioning units outside a building Window unit inside a room 90 and comfortable atmosphere. Air-conditioning may be divided into two main sections: one for the processing of materials in industry, the other for human comfort. Air-conditioning provides the following services: 1. Filtration of the air both in winter and summer to remove dust. 2. Circulation of the air at low velocity and with proper diffusion to prevent draughts and maintain a uniform temperature and humidity at all parts of the inhabited space. 3. Introduction of enough fresh air from the outside atmosphere. 4. Heating of the air in winter. 5. Cooling of the air in summer below the outside atmosphere. 6. Humidify the air in winter to a relative humidity of at least 20-25 per cent. 7. Dehumidify the air in summer to a relative humidity not exceeding 55 per cent.

Conclusion

Russia belongs to the countries with a high level of heat supply centralization. The energy, environmental and technical advantage of district heating over autonomous in the conditions of a monopoly of state ownership was considered a priori. Autonomous and individual heat supply of individual houses was taken out of the scope of energy and developed according to the residual principle. In the district heating system, CHPPs are widely used — enterprises for the combined generation of electricity and heat. Technologically, CHPPs are focused on the priority of power supply, the heat produced by the process is in demand to a greater extent in the cold season, and discharged into the environment — in the warm season. It is far from always possible to harmonize the modes of production of heat and electric energy with the modes of their consumption. Nevertheless, the high level of large-scale power generation predetermined “technological independence” and even a certain export potential of the country, which cannot be said about small-scale thermal power generation. Low prices for fuel resources, economically unjustified price of thermal energy did not contribute to the development of «small» boiler building technologies. Heat supply is an important industry in our life. It brings warmth to our home, provides coziness and comfort, as well as hot water supply, which is necessary every day in the modern world. Modern heat supply systems significantly save resources, are more convenient to use, meet sanitary and hygienic requirements, are smaller in size and look more aesthetically pleasing.

References

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