Помощь с рефератом по иностранному языку для ТулГУ, пример оформления

Реферат по дисциплине «Иностранный язык (английский язык)» на тему «Ventilation systems» Contents Introduction 3 1. Fans 4 2. Types of Ventilation Systems 6 2.1 Exhaust Ventilation Systems 7 2.2 Supply Ventilation Systems 7 2.3 Balanced Ventilation Systems 8 2.4 Energy Recovery Systems 9 Conclusion 10 References 11 Introduction Comfortable and healthy living conditions depend on a number of factors. One of the main tasks of housing arrangement is to create an optimal microclimate. Air composition inside a building depends on its ducting. Modern housing provides residents with reliable sound insulation and heat protection. Accommodation is becoming almost fully sealed. However, the air accumulates unwanted, and substances that are sometimes harmful to human health in critical quantities. Therefore, ventilation is definitely necessary. The main function that the system fulfils is maintaining an optimal air composition. Any air purifying or moisturing device does not compensate for the function of ventilation. In this work to make the situation clear, I will study application areas and types of ventilation systems. In addition, I’m going to provide an insight into one of integral parts of some ventilation systems, which is a fan. 1. Fans A fan is a motor-driven device for creating a flow of air or other gas. Fans are used in air conditioning, ventilation and heating systems. They create air flows in steam boilers, cool internal combustion engines, develop thrust in vacuum cleaners and cooling and drying systems, and are used in pneumatic transport systems. Fans are usually electrically driven. Electric fans consist of a set of rotating blades that are housed in a protective housing allowing air to pass through it. The blades are rotated by an electric motor. [1] The history of the fan begins several centuries ago. The first mechanical devices that create a breath of air appeared about 500 BC. The punkah fan was used in India. It was a frame of wood, covered with canvas, which was fixed on the ceiling with ropes. The servants had to swing this gigantic fan to let the breeze freshen the ruler. In the 19th century, attempts were made to mechanize everything (the era of the industrial revolution), and ventilation was not an exception. In 1830, an American James Baron managed to obtain a patent for the fan, which drove an intricate mechanism. Above the head of the vacationer, there was a plate making reciprocating movements. They continued until the previously raised weight was lowered down to the floor. The first ever household fan powered by electricity was created by Thomas Edison. The vane of his fan didn’t survive to this day, but the blackened with time electric motor on a tripod is nothing but a priceless relic of the history of household appliances. Commercial enterprises engaged in the production of electric fans at the end of the 19th century. The first company to manage it was Grocker & Curtis from the US. The desktop fan appearance of that time quickly took the form that it has now. Fans create relatively low overpressure. Blowers and compressors are used instead of fans to create higher pressures. There are several types of fans, such as centrifugal (or radial) and axial fans. The latter type is called a propeller. In a centrifugal fan, air is sucked in parallel to the axis, and exhausted in the radial direction. In an axial fan, the air moves parallel to the axis both in front of the screw and behind it. In addition, there is a cross flow, or tangential, fan. There are several varieties of fans installed on floors, tables, hung from the ceiling or built into a wall. In addition, they are used in electronic systems such as computers to cool the circuits inside. Besides, domestic appliances such as hair dryers and heaters are usually equipped with fans. Fans are used to ventilate the premises, but their use is not limited to supply and exhaust ventilation. They can be used for air supply in industrial lines or, for example, for pneumatic transportation of dry bulk materials. Finally, this device can be used to cool electrical equipment, engines or other machines. An increasing number of manufacturers are starting to produce household appliances with the ability to work offline, when alternative, renewable energy sources are used to power the devices. One of these devices is a fan powered by a solar battery. The basic elements of a solar powered fan have no difference from ordinary devices. The only peculiarity is the source of energy, which is a solar battery. As a rule, this type of fans is of small capacity, which is determined by the ability of solar panels to produce a certain amount of electrical energy. The electric current used to power the fan is obtained by converting solar energy inside the solar cells, which the solar battery is based on. To get the most of the sun light and produce energy, a solar panel is installed in the spot and then connected to the fan mounted as far as 6 to 7 m away. The solar panels used for such fans are detached or integrated (non-detachable). Besides, fans can be powered by large, slow-moving energy sources such as a flowing river. A water wheel and a series of step-down gears or pulleys are bright examples of these sources. Finally, it should be mentioned that fans, together with vents and ventilation equipment, comprise a “ventilation system” in our homes. Such a system helps exchange indoor and outdoor air while saving energy. 2. Types of Ventilation Systems Earlier, natural ventilation was to let fresh outdoor air in. However, nowadays, this type of ventilation has a number of disadvantages, such as inability to be applied for homes that are properly air sealed for energy efficiency or to provide adequate moisture control. [5] Most of our houses have natural ventilation. This means that the air comes from the street into the building by itself, without any special equipment or artificial injection. The air usually enters houses through cracks and small holes in walls and windows, as well as through open doors. Then, it goes through an air extraction system located in kitchens and bathrooms. Indoor air is drawn through it into the ventilation shaft, rises up it and is ejected through the roof. It should be mentioned that natural ventilation rate in our homes is unpredictable and uncontrollable. It usually depends on inside airtightness, outdoor temperatures, wind, and other factors, such as air pollutant or tightly sealing. In this case, spot ventilation can be useful in order for natural ventilation to become more effective. There are some advantages of spot ventilation. First, it removes indoor air pollutants. Besides, it eliminates moisture at its source. Finally, this type of ventilation utilizes localized exhaust fans. Nevertheless, a whole-house ventilation strategy is needed for people to meet ventilation needs in their homes. All ventilation systems can be grouped in four types, such as exhaust, supply, balanced, and heat-recovery ventilation systems. To choose the right variant, it is important to define the climate and the needs of the structure. In cold climate, an exhaust ventilation type is preferable, because they are less likely to draw moist air into the home. In contrast, warm climate is suitable for supply ventilation. Balanced ventilation systems can be applied for both cold and warm climates. However, their disadvantage is their installation, which is more expensive. As for heat-recovery ventilation, it exchanges indoor air with outdoor air. 2.1 Exhaust Ventilation Systems Exhaust ventilation systems is based on depressurizing the building. In this case, a fan creates lower pressure in the house, pulling air out of the premises. These systems remove exhaust air from rooms where there are sources of pollution. The equipment and characteristics of the exhaust ventilation system vary depending on the purpose of the object. They work successfully in production, warehouses, kitchens and smoking rooms. As a rule, the fan is connected to ducts from several rooms. Installation of passive vents is needed to let fresh air in. Nevertheless, it may lead to less efficiency because of larger pressure differences needed for them to work properly. Spot ventilation systems are preferred in cases where the working process is accompanied by a point release of hazardous and harmful substances to people in the room. When the harmful substances concentration is high enough, spot exhaust ventilation systems allow to achieve better sanitary and hygienic conditions. Such systems are more efficient than general exchange ventilation, which does not provide the necessary degree of air purification. The simplest form of spot ventilation is represented by exhaust fans installed in the bathroom. One of the drawbacks of the exhaust ventilation system is that it can let pollutants together with fresh air into the house. For example, while supplying fresh outdoor air, it can draw harmful substances, such as radon and its varieties, dust from an attic, fumes from an underground garage, or flue gases from a fireplace. Exhaust ventilation systems can also increase heating and cooling costs compared to energy recovery systems because they do not regulate or remove moisture from the make-up air before it enters the home. 2.2 Supply Ventilation Systems Supply ventilation systems work by creating additional pressure in the building. They use a fan to force outside air into the room while air leaks out of the building through holes in the building’s bulk. Like exhaust ventilation systems, installation of supply ventilation systems is relatively simple and inexpensive. For supply and exhaust ventilation systems, equipment is used, which is very compact, and takes up little space when it is installed. Ventilation systems have a block design, so easy to transport and install. Typically, this system has a fan and duct system introducing fresh air into one, but preferably into several rooms that are most occupied by residents (e.g. bedrooms, living rooms, or kitchens). This system may include adjustable window or wall vents in other rooms. Supply and exhaust ventilation systems allow better control of the air entering the room compared to exhaust ventilation systems. Depending on the performanceб the supply and exhaust systems can be used for: • apartments, offices, separate buildings, cottages; • health facilities; • conference rooms, cafes, restaurants, sales areas, studios, libraries, classrooms, swimming pools; • factory premises, laboratories; • industrial and agricultural enterprises. Supply ventilation systems are not suitable for working in cold climates because of possible moisture problems. 2.3 Balanced Ventilation Systems Being designed and installed properly, balanced ventilation systems introduce fresh outside air and exhaust polluted inside air in almost equal quantities. As a rule, such a system is equipped with two fans and two duct systems. An appropriate placement of supply and exhaust fans contributes to a good distribution of fresh air. A typical supply and exhaust (balanced) ventilation system is designed to supply fresh air to bedrooms and to those common areas where people are used to spend the most time. It also exhausts air from areas where moisture and pollutants are most likely to appear, such as kitchens, bathrooms or laundries. Supply and exhaust ventilation systems are suitable for all climatic zones. However, since they require two duct systems and two fans, they tend to be more expensive to install. 2.4 Energy Recovery Systems Fundamentally, this system is an air exchange between rooms and the street. Energy recovery means heat exchange of air flows inside a ceramic element, due to the transfer of stored energy to the incoming air from the outgoing flow. That is, the air going outside delivers its heat to the air going into the house, which allows the air to remain fresh and warm. The outgoing flow, on the contrary, cools down, making the system as a whole energy-saving. Energy recovery ventilation systems are usually more expensive than other ventilation systems. To save on the cost of installation, many of them are used together with the existing duct system. Sophisticated systems are not only more expensive to install, but also they are often more maintenance intensive and consume more electricity. However, most homes recovering and using all the energy in the exhaust air probably won’t need the extra cost. In addition, these types of ventilation systems are still not very common, because only a few contractors have sufficient technical expertise and experience to install them. [3] Conclusion To sum up, fans are mechanical or power-driven devices designed to move air through the ducts of air conditioning and ventilation systems, as well as for direct air supply to the room or air exhaustion from the room and creating the necessary pressure balance. These machines have been used for many centuries. There are centrifugal (or radial), axial and cross flow (tangential) fans. Fans can be installed on floors, tables, hung from the ceiling or built into a wall. As a power source, solar panels or large, slow-moving energy sources are traditionally used. One of the application areas of fans is a ventilation system. Most premises are naturally vented. However, depending on the climate, various types of spot ventilation are more effective. There are four groups of ventilation systems, such as exhaust, supply, balanced, and heat-recovery ventilation systems. To choose the right variant, it is important to define the climate and the needs of the structure. In cold climate, an exhaust ventilation type is preferable, because they are less likely to draw moist air into the home. In contrast, warm climate is suitable for supply ventilation. Balanced ventilation systems can be applied for both cold and warm climates. However, their disadvantage is their installation, which is more expensive. As for heat-recovery ventilation, it exchanges indoor air with outdoor air. References 1. Fan (machine) [Electronic resource] – Access mode: https://en.wikipedia.org/wiki/Fan_(machine) – Date of access: 17.12.2019. 2. Gupta, N. C. Comprehensive HVAC System Design: A Handbook on Practical Approach to Air Conditioning, Heating and Ventilation / N. C. Gupta. – London : MV Learning, 2016. 3. Kreider, J. F. Handbook of Heating, Ventilation, and Air Conditioning (Handbook Series for Mechanical Engineering) / J. F. Kreider. – Boca Raton : CRC Press, 2000. 4. Rutkowski, H. Manual D — Residential Duct Systems / H. Rutkowski. – Air Conditioning Contractors of America, 2016. 5. Types of Ventilation Systems [Electronic resource] – Access mode: https://www.hometips.com/how-it-works/ventilation-systems-exhaust.html – Date of access: 17.12.2019. 6. Ultimate Guide to Home Repair and Improvement. – Creative Homeowner Press Publisher, 2016.