Natural circulation heating systems
The natural circulation heating system became widespread in the pre-war period due to its efficiency, simplicity and reliability. Most often, this type of heating system is used in summer cottages, as well as in country houses due to frequent power outages at such facilities. Such systems are conventionally divided into two types - with bottom and top water supply. To determine with the choice of the type of heating system, it is necessary to consider their differences, characteristics and scope.
Schematic diagram of heating with natural circulation of the coolant
Natural circulation heating systems
17.1.2.2. Drainage system of the eye
The drainage system of the eye consists of the TA, the scleral sinus (Schlemm's canal) and the collector tubules (Fig. 17.6).
TA is a ring-shaped crossbar, thrown over the internal scleral groove. In the section, the TA has the shape of a triangle, the apex of which is attached to the anterior edge of the groove (Schwalbe border ring), and the base to its posterior edge (scleral spur). The trabecular diaphragm consists of three main parts: the uveal trabecula, the corneoscleral trabecula, and the juxta-canalicular tissue. The first two parts have a layered structure. Each layer (10-15 in total) is a plate consisting of collagen fibrils and elastic fibers, covered on both sides by the basement membrane and endothelium. There are holes in the plates, and between the plates there are slots filled with explosives. Yukstakan-lycular layer, consisting of 2-3 layers of fibrocytes and loose fibrous tissue, provides the greatest resistance to the outflow of explosives from the eye. The outer surface of the yukstakan-licular layer is covered with endothelium containing "giant" vacuoles (). The latter are dynamic intracellular tubules, through which the IV passes from the TA to the Schlemm canal.
The Schlemm canal is a circular fissure lined with endothelium and located in the posterior-anterior part of the internal scleral groove (see Fig. 17.4). It is separated from the anterior chamber by TA; the sclera and episclera with venous and arterial vessels are located outside the canal. BB flows from the Schlemm's canal along 20-30 collector tubules into episcleral veins (recipient veins).
Heating systems with top water supply
The heating medium - in this case water - must be heated and supplied to the upper part of the heating system through a pipeline. The pipe used to supply water must have a large diameter compared to the pipes that are responsible for supplying water to the radiator. This is necessary to achieve the greatest resistance to heat exchange. Horizontal pipes should be installed with a minimum slope of one centimeter per fitting meter.
The expansion tank must be installed in the upper part of the system: it will perform the function of receiving steam and excess heat - this is necessary due to the property of water to expand when heated and go into a steam state. The tank must have a drain cock and a cap or valve at the top. After the water is heated, it is distributed through the supply pipe to the risers and radiators.
Advice: if you are going to use a heating system with natural water circulation, remember that radiators must be connected using a diagonal method
After direct heating of the room, the water flows into the boiler through a specialized pipe - the return line. Here it is reheated and the cycle of water movement is repeated. The boiler for heating is located in the lowest part of the system, under the radiators. Usually, these elements are installed in boiler rooms, for which basements are allocated.
The term “circulation” refers to the movement of people through buildings and between buildings and other parts of the constructed environment. Inside buildings, circulation spaces are spaces that are primarily used for circulation, such as entrances, foyers and lobbies, corridors, staircases, landings, etc.
Circulation spaces can be categorized as facilitating horizontal circulation, such as corridors and those that promote vertical circulation, such as stairs and ramps. They can also be limited to specific user groups, for example in buildings used by the public, there may be public circulation areas as well as restricted areas of restricted access. They can be confined spaces such as corridors or open spaces such as atriums and, in some cases, can serve multiple functions.
In architecture, circulation refers to how people move and interact with a building. In public buildings, circulation is essential; Structures such as elevators, escalators, and stairs are often referred to as circulation elements because they are located and designed to optimize the flow of people through a building, sometimes using a core.
In particular, circulation routes are paths that people travel through buildings or to urban areas. Circulation is often referred to as the “space between spaces”, which has a connecting function, but it can be much more. It is a concept that reflects the experience of moving our bodies around a building, three-dimensional and over time.
The size of circulation spaces can be influenced by factors such as type of use, number of people using them, direction of travel, intersecting flows, etc. In complex buildings such as hospitals or traffic exchanges, signage or other forms of return route, assistance may be required people in movement to places of circulation.
Some circulation spaces can have very specific uses, such as moving goods or evacuating. According to Approved Document B "Fire Safety", the circulation space (regarding fire safety):
The space (including the sheltered staircase) is primarily used as a means of access between the room and the exit from a building or department. Where the secured staircase is a staircase that unloads through an end exit to a safe location (including any exit passage between the rung of the staircase and the end exit) that is suitably covered by a fire retardant structure. A compartment is a building or part of a building consisting of one or more rooms, spaces or floors constructed to prevent the spread of fire to another part of the same building or an adjacent building or from another part of a building.
Approved Document B establishes a number of design requirements for the circulation spaces in which they are used for exit. Other requirements for circulation locations are specified in Approved Document K, Fall, Impact and Impact Protection, and Approved Document M, Access to and Use of Buildings.
Circulation Components Although every space a person can receive or occupy is part of a building's circulation system, when we talk about circulation, we usually do not try to explain where each person can go. Instead, we often zoom in on the main routes of most users.
To simplify further, architects usually divide their thinking into different types of circulation, which overlap each other and the overall planning. The type and extent of these units depends on the project, but may include:
direction of movement: horizontal or vertical; type of use: public or private, in front of the house or behind the house; frequency of use: general or emergency; and also the time of use: morning, afternoon, evening, continuous. Each of these types of treatment will require a different architectural consideration. Movement can be fast or slow, mechanical or manual, carried out in the dark or fully lit, crowded or individual. Trails can be leisurely and winding, or narrow and straight.
Of these types of handling, direction and use are often critical to the layout of a building.
Direction: Horizontal circulation can include corridors, atria, pathways, recordings, and exits. It is also affected by the placement of furniture or other objects in space, such as columns, trees, or topographic changes. This is why architects usually create furniture as part of conceptual design, because it is critically related to flow, function and space feel.
Vertical circulation is how people move up and down a building, so it includes things like stairs, elevators, ramps, stairs and escalators that allow us to move from one level to the next.
Usage: Public appeal is the areas of the building that are most widely and readily accessible. In this view, circulation is often duplicated with other functions such as the lobby, atrium or gallery, and is enhanced to a high level of architectural quality. Key issues related to visibility, crowd movement and clear escape routes are important.
The private circulation explains the more intimate movements within the building, or the uglier ones that require a certain amount of privacy. In the home, this can be the back door, in a large building, in the back of the house, in offices, or in storage areas.
Replication Design There are two rules of thumb when designing a circulation. The main routes of circulation should:
be clear and unobstructed;
follow the shortest distance between two points. The reason for these two rules of thumb is pretty obvious: people want to be able to move around a building with ease and efficiency, without feeling or loss.
But, once you get these rules in order, you can break them down. Sometimes, for architectural reasons, you want to interrupt the direct circulation path with a piece of furniture or a level change in order to detect a change in place, make people slow down, or provide a focal point. Likewise, circulation does not have to follow the shortest distance between two points. Rather, it can account for the sequence of spaces, thresholds, and atmospheres that occur as you move, preparing you to move from one location to the next. Circulation can be choreographed to add architectural interest.
In this way, circulation is also inextricably linked with the Program or with what activity another key Architectural concept occurs, which we will talk about in this series.
Efficiency and Location of Circulation Space Circulation space is sometimes viewed as wasted space, adding unnecessary area and cost to the project. As a result, word efficiency often goes hand in hand with circulation.
For example, commercial office buildings and apartment buildings tend to minimize the amount of circulating space and return that space to rented space or living quarters that can be rented and therefore profitable. In these cases, where buildings are often tall, vertical circulation is often designed as a core in the center of the building, with densely packed staircases and elevators, and short corridors at each level leading from that core to individual apartments or offices.
In contrast to this method, when all circulations are centrally located and often hidden, the circulation can be expressed externally and shown from the facade or inside the building. Even in small buildings such as homes, circulation areas such as stairs can become architectural features of the home.
An example of this method is the Center Pompidou in Paris, designed in high-tech style by Richard Rogers and Renzo Piano. Here you can see translucent escalators with red undersides sweeping through the exposed facade of the building, the ever-changing movements of people that make the building real and active in the square.
Representation of circulation Circulation is often presented using diagrams with arrows showing the “flow” of people or the proposed openness of spaces. You can use different colors or line types to describe different movements - check out our Pinterest contact board for ideas.
Although a critical part of design, circulation is often not represented directly in the final set of architectural drawings - it is in the white space and gaps between structural elements. However, there are some cases where it is necessary to indicate exit paths, for example in the design of a public building, where the routes that people will go out to get out of the building in the event of a fire must be clear to be assessed in relation to the Building Code.
Circulation and Building Code In New Zealand, circulation is mainly governed by the New Zealand Building Code Compliance Act D1: Access Routes, which you can download here. This document sets out performance standards for a range of circulation elements, including stairs and landings, corridors, doors, handrails, balustrades, ramps, and stairs.
While at the School of Architecture your design projects may not require you to check the days to comply with the code, this document can be a good place to start at least the slope of your staircase that looks vaguely legal and understand how wide the corridors need to be to make it easier different types of movement are two aspects of your project that will be obvious to critics who study your plans and sections of the project.
Tags: Architectural design Architectural element stubs
Heating systems with bottom water supply
A system in which the heating medium is supplied from below is usually used for heating houses where there is no attic space or access to it is closed. The main difference between the presented heating system is that the pipes are laid under the radiators. There is also an expansion tank, which is installed in the upper level of the system; usually utility rooms are used for this. If, at the same time, there is no circulation of water in the heating system, which should occur naturally, then it is created by force.
Forced circulation heating systems
A standard forced circulation heating system operates using the same connection methods. The difference is that due to the long length of this system or the absence of natural conditions, it is necessary to include a pump in the system to create a slope of the pipes. The circulation pump is mounted to the main pipe - this helps to increase the life of the heating system. The use of a pump helps not only to increase the heating efficiency, but also to reduce the number of lines. A forced circulation system has the ability to heat not just several rooms, but even a house with several floors.
Forced circulation heating systems
In order to produce high-quality work of this type of system, you need a continuous power supply. Installation of a pump for circulation in the heating system is required in order to create forced circulation of water in a closed loop. In this type of system, the pump is the central component among the equipment.It should be noted that the circulation pump may not differ in significant performance: its power is only needed to direct the liquid into the supply pipe. The same pressure pushes the water in the opposite direction, since the system is closed.
The circulation pump is necessary to ensure the smooth operation of the heating system, therefore, it must fully correspond to the system in which the installation is carried out. Due to its functionality, this type of pump can be widely used in a wide variety of pipelines.
Circulation of liquid in the heating system
Any heating system is designed to transfer heat generated by a fuel generator to various rooms that require heating. A heating system, in essence, is an interconnected set of certain devices and elements that provide air heating to the required temperature of various kinds of premises and maintain it in the initially specified parameters for a designated time period.
Heating system classification
The main components of all kinds of heating systems are, first of all, a heat generator, a suitable heat pipe, and, of course, certain heating devices. A heat carrier is an environment whose main task is to transfer heat from an installed heat generator to existing heating devices. The heat carrier can be air, steam or liquid.
Forced and natural circulation of fluid
Naturally, for this reason, there was a classification of heating systems, according to their specific types of coolant. For heating country houses, owners, as a rule, prefer liquid heating systems. There are two types of coolants for them: ordinary water or special non-freezing liquids, the so-called antifreezes.
Liquid heating systems differ, in turn, by the way the coolant moves inside them and are divided into two types:
- With natural, or in other words, gravitational circulation;
- And also with forced circulation, providing for the presence of a pump.
Water heating system with natural circulation of liquid
In the case of heating systems, the work of which is carried out due to gravitational circulation, water or antifreeze moves through the system due to the formation of a natural hydrostatic head resulting from the difference in temperature parameters in different parts of the system.
However, to be more precise, the reason is not so much the temperature difference as the difference in the densities of these liquids. After all, everyone knows that the density of a hot liquid is somewhat higher than the density of a cooled one, in other words, hot water or antifreezes are lighter than cold ones.
In essence, an exact analogy with warm air is obtained, the hot liquid rises upward, while the cold one naturally descends down the heating system. And the second important point, on which the gravitational circulation of the liquid in the heating system depends, is the difference in heights formed in different parts of the system.
Principle of operation
The process of operation of such a heating system is as follows: the coolant, heating up in the heating boiler (1), enters the main supply riser (2), into a thick vertical pipe, rising, floats up. The rise, as noted earlier, occurs due to the resulting temperature difference. In addition, the hot coolant displaces, "pushing" the liquid that has had time to cool, returning to the boiler.
The main riser, its top, is connected to the expansion tank (9) with the branches of the pipeline (7) connected to it, consisting of pipes that are mounted at a slight slope.According to these pipes, the hot coolant rushes into heating devices, radiators (4), from which it follows in a return line directed back to the boiler, which, by the way, is also installed at a certain slope.
Then the movement is repeated, forming a cycle. As the fluid moves through the system, heat is released into the room, as a result of which it cools down, as a result of which it moves down the system even more rapidly.
Application area
The speed of movement of the coolant in the system depends on the difference in its temperatures in the pipes of the return line and the main riser, and, of course, on the difference in height. Naturally, the hottest liquid is located immediately after the supply riser, therefore, the air is heated there more intensively.
Rooms with pipes, into which the coolant is supplied, which has already cooled down, warm up much worse. Hence, we can conclude that heating systems operating on the principles of natural circulation of liquid are not the best variation for large cottages. It is not recommended to install them in buildings with an area of 100 m2, they will definitely not be able to warm up some rooms.
But this is the best option for houses with a smaller area, it is great for excellent heating. The indisputable advantages of this heating system include:
- Ease of design
- Easy installation
- Self-sufficiency, expressed by non-volatility.
Their electrical independence is recognized as the key advantage of these systems. After all, they are able to work even in the absence of power supply in the presence of a heat generator that does not require electricity for operation, which is not difficult to find. For this reason, the choice of a heating system with gravitational circulation of water for compact country houses is obvious, and almost indisputable.
However, it is not without its drawbacks. To normalize the operation of such a heating system, it is necessary to take care of the sufficiency of the circulating pressure, which helps the coolant to overcome the resistance arising in the system. This can be achieved by increasing the diameter of the pipes, and by providing for piping with elementary circuit configurations.
In modern housing construction, such systems are much less used, they are used less and less. The reason for this is the unattractive thick pipes laid along the walls with a slope, which certainly many do not like. After all, they extremely limit the implementation of architectural and design ideas for the interior of buildings, the layout of its premises.
In addition, these systems make thermal regulation difficult, and practically do not lend themselves to it. And they also impose significant restrictions on the use of many modern materials.
Water heating system with artificial circulation of liquid
Heating systems with forced circulation of the coolant are devoid of the above disadvantages.
Distinctive characteristics
Their distinctive feature lies in the fact that the liquid moves due to the functioning of the circulation pump installed in the return line. This location of the pump avoids contact with the hottest water.
The circulating pump used in the system eliminates the use of thick pipes, usually half an inch, creating a large slope in the system. This helps to reduce the cost of materials and simplify the design.
Now they produce compact silent circulation pumps. It is recommended to purchase units that automatically change their capacity, depending on the conditions. They are very economical, they work at full capacity only when necessary, using less energy.
Scope of application
Such heating systems are convenient, first of all, for buildings of any complexity, because the liquid is able to move in them rather quickly, supplying the whole house with heat evenly. At the same time, thermal management can be made quite flexible, differentiated by room.
In addition, they leave room for any architectural and design delights. Branches of the wiring are made with pipes of small diameters, which are easily hidden in the monolith of walls and floors. That allows you to create unusual designs, such as warm floors.
Lack of systems, related to the type of forced circulation, one - their electrical dependence.
Coolant delivery methods
So, it has been found that heating systems differ in the way the coolant moves inside them and are pumping or gravitational. Next, it is worth paying attention to how they differ in the method of delivering liquid to heating devices.
There are two wiring schemes:
- Single pipe
- Two-pipe.
Both types of wiring can be used equally for natural and forced circulation systems.
One-pipe branch
Cheapness is one of the advantages of one-pipe wiring. Indeed, in this case, the consumption of pipes, shaped and connecting products is less than with two-pipe branching. Its main advantage is the presence of heating devices with thermal independence. They allow flexible temperature control in individual rooms.
And its disadvantages are related:
- With the difficulty, and often the impossibility, without additional costs, to create optimal control of the required temperature regime in heated rooms.
- With the need to purchase expensive heating devices with greater heat transfer.
Two-pipe wiring
Two-pipe wiring provides for the sequential passage of fluid through all devices, while giving each device part of the heat. Moreover, each subsequent unit will be slightly colder than the previous one. In order to maintain the necessary heat transfer, the dimensions of each subsequent device must be larger than the previous one.
With two-pipe wiring, each heater separately receives a heating agent from a common line. All devices are completely independent from each other, because the liquid is supplied at the same temperature. The cooled liquid is also discharged to the return line from each radiator separately.
Choosing a circulation pump for a heating system
In order to select a circulation pump for a heating system, it is necessary to make appropriate calculations. Please note that during an hour, this element will run three times more water than its total volume in the system. Thus, the total volume of a suitable amount of liquid is on average 10 liters per 1 kilowatt of heating boiler output. The required pump model for the heating system and its power are determined by the pressure-flow parameters. The head must be equal to the hydraulic resistance of the heating system.
Circulation pump
Typically, the head velocity of the liquid in systems with forced circulation is quite low, which gives the right to judge the low loss of hydraulic resistance, which usually does not exceed 2 meters. The exact resistance is not easy to calculate, so the performance of the circulation pump is determined at the midpoint. In order to calculate the productivity, the dimensions of the area of the heating object and the power that the source of electricity possesses are also taken into account. It should be remembered that a pump is only needed in a forced circulation system; a natural circulation system does not need it.
EcoloLife.ru
In rivers and other flowing bodies of water, water is constantly being mixed, capturing its entire thickness.In slowly flowing and stagnant bodies of water, such as lakes, reservoirs, ponds, oxbows, etc., the main role in mixing water passes to wind waves and vertical circulation.
The most superficial layer of water mixes wind waves. Despite the fact that this layer is thin, the wind significantly increases the rate of gas exchange between water and the atmosphere.
Mixing layers in sufficiently deep bodies of water - vertical convection,
or circulation
- can occur only in one case: when the density of surface water becomes greater than or equal to the density of water in the underlying layers. Since in fresh water bodies the density is a linear function of temperature, one can say another way: vertical circulation occurs when the temperature of the overlying water becomes lower than or equal to the temperature of its underlying water. However, there is a significant limitation: fresh water has a maximum density at 4 ° C (more precisely, 3.98 ° C). Therefore, when the water temperature drops below 4 ° C, the density of the water decreases again. Consequently, the bottom layers cannot have a temperature below 4 ° C (at least until the overlying ones freeze).
Since the main source of heat is the Sun, in summer the surface layers have a higher temperature, i.e., less density than the bottom ones.
In reservoirs of high and temperate latitudes and in mountain reservoirs of low latitudes, the surface temperature during the year crosses the line of 4 ° C. This results in the following processes (Fig. 1.18):
1. In autumn, the density of water increases due to a decrease in the surface temperature and becomes greater than the density of the underlying layers that have warmed up over the summer. Therefore, the surface water sinks, and the bottom water rises. As a result, due to the small size of fresh water bodies, the density is quickly equalized throughout the entire water column from the surface to the bottom. The uniform density of water allows any disturbances of water (for example, wind waves) to spread throughout its entire thickness, which additionally increases the mixing of water during this period of the year.
2. With a further decrease in air temperature (below 4 ° C), the density of the surface layers decreases and becomes lower than the density of the underlying layers, this prevents vertical circulation. Therefore, the temperature of the deep layers remains higher, close to 4 °, while the surface layers continue to cool down to the formation of ice.
3. In spring the ice melts and the temperature of the water on the surface rises, its density increases and becomes the same from the surface to the bottom. This allows any water disturbances to spread throughout the entire thickness, which is why vertical mixing also occurs in spring.
4. A further increase in the temperature of the surface layer of water leads to a decrease in its density in comparison with the underlying, heating less. IN
Fig. 1.18.
Vertical circulation in fresh water bodies of high and temperate latitudes
(explanation in the text).
as a result, a thermocline is formed that separates epilimnion
(surface water layer) and hypolimnion
(bottom, with denser water). The difference in water density prevents vertical convection, including due to wind.
Thus, during the year, the reservoir goes through 4 hydrological stages:
1. Autumn homothermy.
2. Winter stratification.
3. Spring homothermy.
4. Summer stratification.
Intensive mixing of water and enrichment of the bottom layers with oxygen occurs during periods of homothermy (autumn and spring). During the periods of stratification in the bottom layers, only photosynthesis is a source of oxygen. Due to the low transparency of water in fresh water bodies (and in winter and due to a decrease in the sanctification under the ice and low temperatures), the supply of oxygen from photosynthesis does not compensate for its consumption.And in the absence of other sources of oxygen, with a sufficiently high oxygen consumption (usually due to bacterial oxidation of organic matter in the soil) and a small volume of hypolimnion, death may occur.
As we move to higher latitudes and higher into the mountains, summer becomes shorter, and the period of summer stratification decreases. With a very short summer, the periods of autumn and spring homothermy merge into one. With a further drop in air temperature, the periods of homothermy are shortened, the freezing of reservoirs occurs to a greater depth, and in the limit, instead of a reservoir, a glacier appears.
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Circulation pump installation: what should you pay attention to?
To install the circulation pump yourself, use the following recommendations:
- to extend the operating life of the entire system, install a filter in front of the circulation pump to purify the liquid. the filter must be installed on the suction pipe;
- do not choose a circulation pump for the heating system with a higher power and capacity than required. Otherwise, there is a risk of encountering additional unpleasant noise during its operation;
- Never turn on the pump before filling the heating main with water and removing air from it, this can lead to equipment failure;
- install the pump in an area as close as possible to the expansion tank;
- when installing a pump in a closed heating system, if possible, install a pump on the return. This is due to the fact that this section of the line has the lowest temperature.
Installation of a circulation pump
Advice: before starting the heating system, flush it with water to remove various foreign particles. Do not forget that even a short-term idle operation of the circulation pump in the absence of liquid in the system may result in the failure of the pump itself and other elements of the system.
Almost all circulating pumps on the modern market are equipped with communication with automatic control of boilers for heating. This function provides owners with the ability to regulate the air temperature in the heated facility by changing the speed of water movement in the heating system. In order to take into account the level of heat consumption in the premises, special meters are installed, thanks to which the heat losses arising from the wear of the mains are controlled. The heating circuit itself is not subject to any changes.
You can get acquainted with the method of installing the circulation pump yourself by watching the video:
